// Copyright (C) 2020 The Qt Company Ltd. // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only /*! \class QVector \inmodule QtCore \brief QVector is an alias for QList. Please see the QList documentation for details. */ /*! \class QList \inmodule QtCore \brief The QList class is a template class that provides a dynamic array. \ingroup tools \ingroup shared \reentrant QList\ is one of Qt's generic \l{container classes}. It stores its items in adjacent memory locations and provides fast index-based access. QVector\ used to be a different class in Qt 5, but is now a simple alias to QList. QList\ and QVarLengthArray\ provide similar APIs and functionality. They are often interchangeable, but there are performance consequences. Here is an overview of use cases: \list \li QList should be your default first choice. \li QVarLengthArray provides an array that reserves space on the stack, but can dynamically grow onto the heap if required. It's good to use for short lived containers that are usually small. \li If you need a real linked list, which guarantees \l{Algorithmic Complexity}{constant time} insertions mid-list and uses iterators to items rather than indexes, use std::list. \endlist \note QList and QVarLengthArray both guarantee C-compatible array layout. \note QList in Qt 5 did not always have a C-compatible array layout and we often recommended to use QVector instead for more predictable performance. This is not the case in Qt 6 anymore, where both classes now share an implementation and can be used interchangeably. Here's an example of a QList that stores integers and a QList that stores QString values: \snippet code/src_corelib_tools_qlist.cpp 0 QList stores its items in an array of continuous memory. Typically, lists are created with an initial size. For example, the following code constructs a QList with 200 elements: \snippet code/src_corelib_tools_qlist.cpp 1 The elements are automatically initialized with a \l{default-constructed value}. If you want to initialize the list with a different value, pass that value as the second argument to the constructor: \snippet code/src_corelib_tools_qlist.cpp 2 You can also call fill() at any time to fill the list with a value. QList uses 0-based indexes, just like C++ arrays. To access the item at a particular index position, you can use operator[](). On non-const lists, operator[]() returns a reference to the item that can be used on the left side of an assignment: \snippet code/src_corelib_tools_qlist.cpp 3 For read-only access, an alternative syntax is to use at(): \snippet code/src_corelib_tools_qlist.cpp 4 at() can be faster than operator[](), because it never causes a \l{deep copy} to occur. Another way to access the data stored in a QList is to call data(). The function returns a pointer to the first item in the list. You can use the pointer to directly access and modify the elements stored in the list. The pointer is also useful if you need to pass a QList to a function that accepts a plain C++ array. If you want to find all occurrences of a particular value in a list, use indexOf() or lastIndexOf(). The former searches forward starting from a given index position, the latter searches backward. Both return the index of the matching item if they found one; otherwise, they return -1. For example: \snippet code/src_corelib_tools_qlist.cpp 5 If you simply want to check whether a list contains a particular value, use contains(). If you want to find out how many times a particular value occurs in the list, use count(). QList provides these basic functions to add, move, and remove items: insert(), replace(), remove(), prepend(), append(). With the exception of append(), prepend() and replace(), these functions can be slow (\l{linear time}) for large lists, because they require moving many items in the list by one position in memory. If you want a container class that provides fast insertion/removal in the middle, use std::list instead. Unlike plain C++ arrays, QLists can be resized at any time by calling resize(). If the new size is larger than the old size, QList might need to reallocate the whole list. QList tries to reduce the number of reallocations by preallocating up to twice as much memory as the actual data needs. If you're building a QList gradually and know in advance approximately how many elements it will contain, you can call reserve(), asking QList to preallocate a certain amount of memory. You can also call capacity() to find out how much memory the QList actually has allocated. Note that using non-const operators and functions can cause QList to do a deep copy of the data, due to \l{implicit sharing}. QList's value type must be an \l{assignable data type}. This covers most data types that are commonly used, but the compiler won't let you, for example, store a QWidget as a value; instead, store a QWidget *. A few functions have additional requirements; for example, indexOf() and lastIndexOf() expect the value type to support \c operator==(). These requirements are documented on a per-function basis. For iterating over the items, see \l {Iterating over Containers}. In addition to QList, Qt also provides QVarLengthArray, a very low-level class with little functionality that is optimized for speed. \section2 More Information on Using Qt Containers For a detailed discussion comparing Qt containers with each other and with STL containers, see \l {Understand the Qt Containers}. \section1 Maximum size and out-of-memory conditions The maximum size of QList depends on the architecture. Most 64-bit systems can allocate more than 2 GB of memory, with a typical limit of 2^63 bytes. The actual value also depends on the overhead required for managing the data block. As a result, you can expect the maximum size of 2 GB minus overhead on 32-bit platforms, and 2^63 bytes minus overhead on 64-bit platforms. The number of elements that can be stored in a QList is this maximum size divided by the size of a stored element. When memory allocation fails, QList uses the \l Q_CHECK_PTR macro, which throws a \c std::bad_alloc exception if the application is being compiled with exception support. If exceptions are disabled, then running out of memory is undefined behavior. Note that the operating system may impose further limits on applications holding a lot of allocated memory, especially large, contiguous blocks. Such considerations, the configuration of such behavior or any mitigation are outside the scope of the Qt API. */ /*! \fn template QList QList::mid(qsizetype pos, qsizetype length = -1) const Returns a sub-list which contains elements from this list, starting at position \a pos. If \a length is -1 (the default), all elements after \a pos are included; otherwise \a length elements (or all remaining elements if there are less than \a length elements) are included. */ /*! \fn template QList QList::first(qsizetype n) const \since 6.0 Returns a sub-list that contains the first \a n elements of this list. \note The behavior is undefined when \a n < 0 or \a n > size(). \sa last(), sliced() */ /*! \fn template QList QList::last(qsizetype n) const \since 6.0 Returns a sub-list that contains the last \a n elements of this list. \note The behavior is undefined when \a n < 0 or \a n > size(). \sa first(), sliced() */ /*! \fn template QList QList::sliced(qsizetype pos, qsizetype n) const \since 6.0 Returns a sub-list that contains \a n elements of this list, starting at position \a pos. \note The behavior is undefined when \a pos < 0, \a n < 0, or \a pos + \a n > size(). \sa first(), last() */ /*! \fn template QList QList::sliced(qsizetype pos) const \since 6.0 \overload Returns a sub-list that contains the elements of this list starting at position \a pos and extending to its end. \note The behavior is undefined when \a pos < 0 or \a pos > size(). \sa first(), last() */ /*! \fn template QList::QList() Constructs an empty list. \sa resize() */ /*! \fn template QList::QList(QList &&other) Move-constructs a QList instance, making it point at the same object that \a other was pointing to. \since 5.2 */ /*! \fn template QList::QList(qsizetype size) Constructs a list with an initial size of \a size elements. The elements are initialized with a \l{default-constructed value}. \sa resize() */ /*! \fn template QList::QList(qsizetype size, Qt::Initialization) \since 6.8 Constructs a list with an initial size of \a size elements. QList will make an attempt at \b{not initializing} the elements. //! [qlist-uninitialized-strategy] Specifically: \list \li if \c{T} has a constructor that accepts \c{Qt::Uninitialized}, that constructor will be used to initialize the elements; \li otherwise, each element is default constructed. For trivially constructible types (such as \c{int}, \c{float}, etc.) this is equivalent to not initializing them. \endlist //! [qlist-uninitialized-strategy] \sa resizeForOverwrite() */ /*! \fn template QList::QList(qsizetype size, parameter_type value) Constructs a list with an initial size of \a size elements. Each element is initialized with \a value. \sa resize(), fill() */ /*! \fn template QList::QList(const QList &other) Constructs a copy of \a other. This operation takes \l{Algorithmic Complexity}{constant time}, because QList is \l{implicitly shared}. This makes returning a QList from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), and that takes \l{Algorithmic Complexity}{linear time}. \sa operator=() */ /*! \fn template QList::QList(std::initializer_list args) \since 4.8 Constructs a list from the std::initializer_list given by \a args. */ /*! \fn template template ::if_input_iterator = true> QList::QList(InputIterator first, InputIterator last) \since 5.14 Constructs a list with the contents in the iterator range [\a first, \a last). \note This constructor only participates in overload resolution if \c InputIterator meets the requirements of a \l {https://en.cppreference.com/w/cpp/named_req/InputIterator} {LegacyInputIterator}. The value type of \c InputIterator must be convertible to \c T. */ /*! \fn template QList::~QList() Destroys the list. */ /*! \fn template QList &QList::operator=(const QList &other) Assigns \a other to this list and returns a reference to this list. */ /*! \fn template QList &QList::operator=(QList &&other) Move-assigns \a other to this QList instance. \since 5.2 */ /*! \fn template QList &QList::operator=(std::initializer_list args) \since 5.14 Assigns the collection of values in \a args to this QList instance. */ /*! \fn template void QList::swap(QList &other) \since 4.8 Swaps list \a other with this list. This operation is very fast and never fails. */ /*! \fn template void QList::swapItemsAt(qsizetype i, qsizetype j) Exchange the item at index position \a i with the item at index position \a j. This function assumes that both \a i and \a j are at least 0 but less than size(). To avoid failure, test that both \a i and \a j are at least 0 and less than size(). */ /*! \fn template bool QList::operator==(const QList &other) const Returns \c true if \a other is equal to this list; otherwise returns \c false. Two lists are considered equal if they contain the same values in the same order. This function requires the value type to have an implementation of \c operator==(). \sa operator!=() */ /*! \fn template bool QList::operator!=(const QList &other) const Returns \c true if \a other is not equal to this list; otherwise returns \c false. Two lists are considered equal if they contain the same values in the same order. This function requires the value type to have an implementation of \c operator==(). \sa operator==() */ /*! \fn template bool QList::operator<(const QList &other) const \since 5.6 Returns \c true if this list is \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare} {lexically less than} \a other; otherwise returns \c false. This function requires the value type to have an implementation of \c operator<(). */ /*! \fn template bool QList::operator<=(const QList &other) const \since 5.6 Returns \c true if this list is \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare} {lexically less than or equal to} \a other; otherwise returns \c false. This function requires the value type to have an implementation of \c operator<(). */ /*! \fn template bool QList::operator>(const QList &other) const \since 5.6 Returns \c true if this list is \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare} {lexically greater than} \a other; otherwise returns \c false. This function requires the value type to have an implementation of \c operator<(). */ /*! \fn template bool QList::operator>=(const QList &other) const \since 5.6 Returns \c true if this list is \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare} {lexically greater than or equal to} \a other; otherwise returns \c false. This function requires the value type to have an implementation of \c operator<(). */ /*! \fn template size_t qHash(const QList &key, size_t seed = 0) \since 5.6 \relates QList Returns the hash value for \a key, using \a seed to seed the calculation. This function requires qHash() to be overloaded for the value type \c T. */ /*! \fn template qsizetype QList::size() const Returns the number of items in the list. \sa isEmpty(), resize() */ /*! \fn template bool QList::isEmpty() const Returns \c true if the list has size 0; otherwise returns \c false. \sa size(), resize() */ /*! \fn template void QList::resize(qsizetype size) \fn template void QList::resize(qsizetype size, parameter_type c) \since 6.0 Sets the size of the list to \a size. If \a size is greater than the current size, elements are added to the end; the new elements are initialized with either a \l{default-constructed value} or \a c. If \a size is less than the current size, elements are removed from the end. If this list is not shared, the capacity() is preserved. Use squeeze() to shed excess capacity. \note In Qt versions prior to 5.7 (for QVector; QList lacked a resize() until 6.0), this function released the memory used by the list instead of preserving the capacity. \sa size() */ /*! \fn template void QList::resizeForOverwrite(qsizetype size) \since 6.8 Sets the size of the list to \a size. If \a size is less than the current size, elements are removed from the end. If \a size is greater than the current size, elements are added to the end; QList will make an attempt at \b{not initializing} these new elements. \include qlist.qdoc qlist-uninitialized-strategy */ /*! \fn template qsizetype QList::capacity() const Returns the maximum number of items that can be stored in the list without forcing a reallocation. The sole purpose of this function is to provide a means of fine tuning QList's memory usage. In general, you will rarely ever need to call this function. If you want to know how many items are in the list, call size(). \note a statically allocated list will report a capacity of 0, even if it's not empty. \warning The free space position in the allocated memory block is undefined. In other words, you should not assume that the free memory is always located at the end of the list. You can call reserve() to ensure that there is enough space at the end. \sa reserve(), squeeze() */ /*! \fn template void QList::reserve(qsizetype size) Attempts to allocate memory for at least \a size elements. If you know in advance how large the list will be, you should call this function to prevent reallocations and memory fragmentation. If you resize the list often, you are also likely to get better performance. If in doubt about how much space shall be needed, it is usually better to use an upper bound as \a size, or a high estimate of the most likely size, if a strict upper bound would be much bigger than this. If \a size is an underestimate, the list will grow as needed once the reserved size is exceeded, which may lead to a larger allocation than your best overestimate would have and will slow the operation that triggers it. \warning reserve() reserves memory but does not change the size of the list. Accessing data beyond the current end of the list is undefined behavior. If you need to access memory beyond the current end of the list, use resize(). \sa squeeze(), capacity(), resize() */ /*! \fn template void QList::squeeze() Releases any memory not required to store the items. The sole purpose of this function is to provide a means of fine tuning QList's memory usage. In general, you will rarely ever need to call this function. \sa reserve(), capacity() */ /*! \fn template void QList::detach() \internal */ /*! \fn template bool QList::isDetached() const \internal */ /*! \fn template void QList::setSharable(bool sharable) \internal */ /*! \fn template bool QList::isSharedWith(const QList &other) const \internal */ /*! \fn template T *QList::data() Returns a pointer to the data stored in the list. The pointer can be used to access and modify the items in the list. Example: \snippet code/src_corelib_tools_qlist.cpp 6 \warning The pointer is invalidated on detachment or when the QList is modified. This function is mostly useful to pass a list to a function that accepts a plain C++ array. \sa constData(), operator[]() */ /*! \fn template const T *QList::data() const \overload */ /*! \fn template const T *QList::constData() const Returns a const pointer to the data stored in the list. The pointer can be used to access the items in the list. \warning The pointer is invalidated on detachment or when the QList is modified. This function is mostly useful to pass a list to a function that accepts a plain C++ array. \sa data(), operator[]() */ /*! \fn template void QList::clear() Removes all the elements from the list. If this list is not shared, the capacity() is preserved. Use squeeze() to shed excess capacity. \note In Qt versions prior to 5.7 (for QVector) and 6.0 (for QList), this function released the memory used by the list instead of preserving the capacity. \sa resize(), squeeze() */ /*! \fn template const T &QList::at(qsizetype i) const Returns the item at index position \a i in the list. \a i must be a valid index position in the list (i.e., 0 <= \a i < size()). \sa value(), operator[]() */ /*! \fn template T &QList::operator[](qsizetype i) Returns the item at index position \a i as a modifiable reference. \a i must be a valid index position in the list (i.e., 0 <= \a i < size()). Note that using non-const operators can cause QList to do a deep copy. \sa at(), value() */ /*! \fn template const T &QList::operator[](qsizetype i) const \overload Same as at(\a i). */ /*! \fn template void QList::append(parameter_type value) Inserts \a value at the end of the list. Example: \snippet code/src_corelib_tools_qlist.cpp 7 This is the same as calling resize(size() + 1) and assigning \a value to the new last element in the list. This operation is relatively fast, because QList typically allocates more memory than necessary, so it can grow without reallocating the entire list each time. \sa operator<<(), prepend(), insert() */ /*! \fn template void QList::append(rvalue_ref value) \since 5.6 \overload Example: \snippet code/src_corelib_tools_qlist.cpp move-append */ /*! \fn template void QList::append(const QList &value) \overload \since 5.5 Appends the items of the \a value list to this list. \sa operator<<(), operator+=() */ /*! \fn template void QList::append(QList &&value) \overload \since 6.0 Moves the items of the \a value list to the end of this list. \sa operator<<(), operator+=() */ /*! \fn template void QList::prepend(parameter_type value) \fn template void QList::prepend(rvalue_ref value) Inserts \a value at the beginning of the list. Example: \snippet code/src_corelib_tools_qlist.cpp 8 This is the same as list.insert(0, \a value). Normally this operation is relatively fast (amortized \l{constant time}). QList is able to allocate extra memory at the beginning of the list data and grow in that direction without reallocating or moving the data on each operation. However if you want a container class with a guarantee of \l{constant time} prepend, use std::list instead, but prefer QList otherwise. \sa append(), insert() */ /*! \fn template template T &QList::emplaceBack(Args&&... args) \fn template template T &QList::emplace_back(Args&&... args) Adds a new element to the end for the container. This new element is constructed in-place using \a args as the arguments for its construction. Returns a reference to the new element. Example: \snippet code/src_corelib_tools_qlist.cpp emplace-back It is also possible to access a newly created object by using returned reference: \snippet code/src_corelib_tools_qlist.cpp emplace-back-ref This is the same as list.emplace(list.size(), \a args). \sa emplace */ /*! \fn template void QList::insert(qsizetype i, parameter_type value) \fn template void QList::insert(qsizetype i, rvalue_ref value) Inserts \a value at index position \a i in the list. If \a i is 0, the value is prepended to the list. If \a i is size(), the value is appended to the list. Example: \snippet code/src_corelib_tools_qlist.cpp 9 For large lists, this operation can be slow (\l{linear time}), because it requires moving all the items at indexes \a i and above by one position further in memory. If you want a container class that provides a fast insert() function, use std::list instead. \sa append(), prepend(), remove() */ /*! \fn template void QList::insert(qsizetype i, qsizetype count, parameter_type value) \overload Inserts \a count copies of \a value at index position \a i in the list. Example: \snippet code/src_corelib_tools_qlist.cpp 10 */ /*! \fn template QList::iterator QList::insert(const_iterator before, parameter_type value) \fn template QList::iterator QList::insert(const_iterator before, rvalue_ref value) \overload Inserts \a value in front of the item pointed to by the iterator \a before. Returns an iterator pointing at the inserted item. */ /*! \fn template QList::iterator QList::insert(const_iterator before, qsizetype count, parameter_type value) Inserts \a count copies of \a value in front of the item pointed to by the iterator \a before. Returns an iterator pointing at the first of the inserted items. */ /*! \fn template template QList::iterator QList::emplace(qsizetype i, Args&&... args) Extends the container by inserting a new element at position \a i. This new element is constructed in-place using \a args as the arguments for its construction. Returns an iterator to the new element. Example: \snippet code/src_corelib_tools_qlist.cpp emplace \note It is guaranteed that the element will be created in place at the beginning, but after that it might be copied or moved to the right position. \sa emplaceBack */ /*! \fn template void QList::replace(qsizetype i, parameter_type value) \fn template void QList::replace(qsizetype i, rvalue_ref value) Replaces the item at index position \a i with \a value. \a i must be a valid index position in the list (i.e., 0 <= \a i < size()). \sa operator[](), remove() */ /*! \fn template void QList::remove(qsizetype i, qsizetype n = 1) Removes \a n elements from the list, starting at index position \a i. //! [shrinking-erase] Element removal will preserve the list's capacity and not reduce the amount of allocated memory. To shed extra capacity and free as much memory as possible, call squeeze(). //! [shrinking-erase] //! [iterator-invalidation-erase] \note When QList is not \l{implicitly shared}, this function only invalidates iterators at or after the specified position. //! [iterator-invalidation-erase] \sa insert(), replace(), fill() */ /*! \fn template void QList::removeAt(qsizetype i) \since 5.2 Removes the element at index position \a i. Equivalent to \code remove(i); \endcode \include qlist.qdoc shrinking-erase \include qlist.qdoc iterator-invalidation-erase \sa remove() */ /*! \fn template template qsizetype QList::removeAll(const AT &t) \since 5.4 Removes all elements that compare equal to \a t from the list. Returns the number of elements removed, if any. \include qlist.qdoc shrinking-erase \sa removeOne() */ /*! \fn template template bool QList::removeOne(const AT &t) \since 5.4 Removes the first element that compares equal to \a t from the list. Returns whether an element was, in fact, removed. \include qlist.qdoc shrinking-erase \sa removeAll() */ /*! \fn template template qsizetype QList::removeIf(Predicate pred) \since 6.1 Removes all elements for which the predicate \a pred returns true from the list. Returns the number of elements removed, if any. \sa removeAll() */ /*! \fn template qsizetype QList::length() const \since 5.2 Same as size() and count(). \sa size(), count() */ /*! \fn template T QList::takeAt(qsizetype i) \since 5.2 Removes the element at index position \a i and returns it. Equivalent to \code T t = at(i); remove(i); return t; \endcode \include qlist.qdoc iterator-invalidation-erase \sa takeFirst(), takeLast() */ /*! \fn template void QList::move(qsizetype from, qsizetype to) \since 5.6 Moves the item at index position \a from to index position \a to. */ /*! \fn template void QList::removeFirst() \since 5.1 Removes the first item in the list. Calling this function is equivalent to calling remove(0). The list must not be empty. If the list can be empty, call isEmpty() before calling this function. \include qlist.qdoc shrinking-erase \sa remove(), takeFirst(), isEmpty() */ /*! \fn template void QList::removeLast() \since 5.1 Removes the last item in the list. Calling this function is equivalent to calling remove(size() - 1). The list must not be empty. If the list can be empty, call isEmpty() before calling this function. \include qlist.qdoc shrinking-erase \sa remove(), takeLast(), removeFirst(), isEmpty() */ /*! \fn template T QList::takeFirst() \since 5.1 Removes the first item in the list and returns it. This function assumes the list is not empty. To avoid failure, call isEmpty() before calling this function. \sa takeLast(), removeFirst() */ /*! \fn template T QList::takeLast() \since 5.1 Removes the last item in the list and returns it. This function assumes the list is not empty. To avoid failure, call isEmpty() before calling this function. If you don't use the return value, removeLast() is more efficient. \sa takeFirst(), removeLast() */ /*! \fn template template QList::iterator QList::emplace(const_iterator before, Args&&... args) \overload Creates a new element in front of the item pointed to by the iterator \a before. This new element is constructed in-place using \a args as the arguments for its construction. Returns an iterator to the new element. */ /*! \fn template QList &QList::fill(parameter_type value, qsizetype size = -1) Assigns \a value to all items in the list. If \a size is different from -1 (the default), the list is resized to \a size beforehand. Example: \snippet code/src_corelib_tools_qlist.cpp 11 \sa resize() */ /*! \fn template template qsizetype QList::indexOf(const AT &value, qsizetype from = 0) const Returns the index position of the first occurrence of \a value in the list, searching forward from index position \a from. Returns -1 if no item matched. Example: \snippet code/src_corelib_tools_qlist.cpp 12 This function requires the value type to have an implementation of \c operator==(). \sa lastIndexOf(), contains() */ /*! \fn template template qsizetype QList::lastIndexOf(const AT &value, qsizetype from = -1) const Returns the index position of the last occurrence of the value \a value in the list, searching backward from index position \a from. If \a from is -1 (the default), the search starts at the last item. Returns -1 if no item matched. Example: \snippet code/src_corelib_tools_qlist.cpp 13 This function requires the value type to have an implementation of \c operator==(). \sa indexOf() */ /*! \fn template template bool QList::contains(const AT &value) const Returns \c true if the list contains an occurrence of \a value; otherwise returns \c false. This function requires the value type to have an implementation of \c operator==(). \sa indexOf(), count() */ /*! \fn template bool QList::startsWith(parameter_type value) const \since 4.5 Returns \c true if this list is not empty and its first item is equal to \a value; otherwise returns \c false. \sa isEmpty(), first() */ /*! \fn template bool QList::endsWith(parameter_type value) const \since 4.5 Returns \c true if this list is not empty and its last item is equal to \a value; otherwise returns \c false. \sa isEmpty(), last() */ /*! \fn template template qsizetype QList::count(const AT &value) const Returns the number of occurrences of \a value in the list. This function requires the value type to have an implementation of \c operator==(). \sa contains(), indexOf() */ /*! \fn template qsizetype QList::count() const \overload Same as size(). */ /*! \fn template QList::iterator QList::begin() Returns an \l{STL-style iterators}{STL-style iterator} pointing to the first item in the list. //! [iterator-invalidation-func-desc] \warning The returned iterator is invalidated on detachment or when the QList is modified. //! [iterator-invalidation-func-desc] \sa constBegin(), end() */ /*! \fn template QList::const_iterator QList::begin() const \overload */ /*! \fn template QList::const_iterator QList::cbegin() const \since 5.0 Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the first item in the list. \include qlist.qdoc iterator-invalidation-func-desc \sa begin(), cend() */ /*! \fn template QList::const_iterator QList::constBegin() const Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the first item in the list. \include qlist.qdoc iterator-invalidation-func-desc \sa begin(), constEnd() */ /*! \fn template QList::iterator QList::end() Returns an \l{STL-style iterators}{STL-style iterator} pointing just after the last item in the list. \include qlist.qdoc iterator-invalidation-func-desc \sa begin(), constEnd() */ /*! \fn template QList::const_iterator QList::end() const \overload */ /*! \fn template QList::const_iterator QList::cend() const \since 5.0 Returns a const \l{STL-style iterators}{STL-style iterator} pointing just after the last item in the list. \include qlist.qdoc iterator-invalidation-func-desc \sa cbegin(), end() */ /*! \fn template QList::const_iterator QList::constEnd() const Returns a const \l{STL-style iterators}{STL-style iterator} pointing just after the last item in the list. \include qlist.qdoc iterator-invalidation-func-desc \sa constBegin(), end() */ /*! \fn template QList::reverse_iterator QList::rbegin() \since 5.6 Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing to the first item in the list, in reverse order. \include qlist.qdoc iterator-invalidation-func-desc \sa begin(), crbegin(), rend() */ /*! \fn template QList::const_reverse_iterator QList::rbegin() const \since 5.6 \overload */ /*! \fn template QList::const_reverse_iterator QList::crbegin() const \since 5.6 Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing to the first item in the list, in reverse order. \include qlist.qdoc iterator-invalidation-func-desc \sa begin(), rbegin(), rend() */ /*! \fn template QList::reverse_iterator QList::rend() \since 5.6 Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing just after the last item in the list, in reverse order. \include qlist.qdoc iterator-invalidation-func-desc \sa end(), crend(), rbegin() */ /*! \fn template QList::const_reverse_iterator QList::rend() const \since 5.6 \overload */ /*! \fn template QList::const_reverse_iterator QList::crend() const \since 5.6 Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing just after the last item in the list, in reverse order. \include qlist.qdoc iterator-invalidation-func-desc \sa end(), rend(), rbegin() */ /*! \fn template QList::iterator QList::erase(const_iterator pos) Removes the item pointed to by the iterator \a pos from the list, and returns an iterator to the next item in the list (which may be end()). \include qlist.qdoc shrinking-erase \include qlist.qdoc iterator-invalidation-erase \sa insert(), remove() */ /*! \fn template QList::iterator QList::erase(const_iterator begin, const_iterator end) \overload Removes all the items from \a begin up to (but not including) \a end. Returns an iterator to the same item that \a end referred to before the call. \include qlist.qdoc shrinking-erase \include qlist.qdoc iterator-invalidation-erase */ /*! \fn template T& QList::first() Returns a reference to the first item in the list. This function assumes that the list isn't empty. \sa last(), isEmpty(), constFirst() */ /*! \fn template const T& QList::first() const \overload */ /*! \fn template const T& QList::constFirst() const \since 5.6 Returns a const reference to the first item in the list. This function assumes that the list isn't empty. \sa constLast(), isEmpty(), first() */ /*! \fn template T& QList::last() Returns a reference to the last item in the list. This function assumes that the list isn't empty. \sa first(), isEmpty(), constLast() */ /*! \fn template const T& QList::last() const \overload */ /*! \fn template const T& QList::constLast() const \since 5.6 Returns a const reference to the last item in the list. This function assumes that the list isn't empty. \sa constFirst(), isEmpty(), last() */ /*! \fn template T QList::value(qsizetype i) const Returns the value at index position \a i in the list. If the index \a i is out of bounds, the function returns a \l{default-constructed value}. If you are certain that \a i is within bounds, you can use at() instead, which is slightly faster. \sa at(), operator[]() */ /*! \fn template T QList::value(qsizetype i, parameter_type defaultValue) const \overload If the index \a i is out of bounds, the function returns \a defaultValue. */ /*! \fn template void QList::push_back(parameter_type value) This function is provided for STL compatibility. It is equivalent to append(\a value). */ /*! \fn template void QList::push_back(rvalue_ref value) \since 5.6 \overload */ /*! \fn template void QList::push_front(parameter_type value) \fn template void QList::push_front(rvalue_ref value) This function is provided for STL compatibility. It is equivalent to prepend(\a value). */ /*! \fn template void QList::pop_front() This function is provided for STL compatibility. It is equivalent to removeFirst(). */ /*! \fn template void QList::pop_back() This function is provided for STL compatibility. It is equivalent to removeLast(). */ /*! \fn template T& QList::front() This function is provided for STL compatibility. It is equivalent to first(). */ /*! \fn template QList::const_reference QList::front() const \overload */ /*! \fn template QList::reference QList::back() This function is provided for STL compatibility. It is equivalent to last(). */ /*! \fn template QList::const_reference QList::back() const \overload */ /*! \fn template void QList::shrink_to_fit() \since 5.10 This function is provided for STL compatibility. It is equivalent to squeeze(). */ /*! \fn template bool QList::empty() const This function is provided for STL compatibility. It is equivalent to isEmpty(), returning \c true if the list is empty; otherwise returns \c false. */ /*! \fn template qsizetype QList::max_size() \since 6.8 This function is provided for STL compatibility. It returns the maximum number of elements that the list can theoretically hold. In practice, the number can be much smaller, limited by the amount of memory available to the system. */ /*! \fn template QList &QList::operator+=(const QList &other) Appends the items of the \a other list to this list and returns a reference to this list. \sa operator+(), append() */ /*! \fn template QList &QList::operator+=(QList &&other) \since 6.0 \overload \sa operator+(), append() */ /*! \fn template void QList::operator+=(parameter_type value) \overload Appends \a value to the list. \sa append(), operator<<() */ /*! \fn template void QList::operator+=(rvalue_ref value) \since 5.11 \overload \sa append(), operator<<() */ /*! \fn template QList QList::operator+(const QList &other) const & \fn template QList QList::operator+(const QList &other) && \fn template QList QList::operator+(QList &&other) const & \fn template QList QList::operator+(QList &&other) && Returns a list that contains all the items in this list followed by all the items in the \a other list. \sa operator+=() */ /*! \fn template QList &QList::operator<<(parameter_type value) Appends \a value to the list and returns a reference to this list. \sa append(), operator+=() */ /*! \fn template QList &QList::operator<<(rvalue_ref value) \since 5.11 \overload \sa append(), operator+=() */ /*! \fn template QList &QList::operator<<(const QList &other) Appends \a other to the list and returns a reference to the list. */ /*! \fn template QList &QList::operator<<(QList &&other) \since 6.0 \overload */ /*! \class QList::iterator \inmodule QtCore \brief Provides an STL-style non-const iterator for QList and QStack. QList provides both \l{STL-style iterators} and \l{Java-style iterators}. //! [iterator-invalidation-class-desc] \warning Iterators on implicitly shared containers do not work exactly like STL-iterators. You should avoid copying a container while iterators are active on that container. For more information, read \l{Implicit sharing iterator problem}. \warning Iterators are invalidated when QList is modified. Consider that all iterators are invalidated by default. Exceptions to this rule are explicitly documented. //! [iterator-invalidation-class-desc] \sa QList::begin(), QList::end(), QList::const_iterator, QMutableListIterator */ /*! \class QList::const_iterator \inmodule QtCore \brief Provides an STL-style const iterator for QList and QStack. QList provides both \l{STL-style iterators} and \l{Java-style iterators}. \include qlist.qdoc iterator-invalidation-class-desc \sa QList::constBegin(), QList::constEnd(), QList::iterator, QListIterator */ /*! \typedef QList::reverse_iterator \since 5.6 The QList::reverse_iterator typedef provides an STL-style non-const reverse iterator for QList. \include qlist.qdoc iterator-invalidation-class-desc \sa QList::rbegin(), QList::rend(), QList::const_reverse_iterator, QList::iterator */ /*! \typedef QList::const_reverse_iterator \since 5.6 The QList::const_reverse_iterator typedef provides an STL-style const reverse iterator for QList. \include qlist.qdoc iterator-invalidation-class-desc \sa QList::rbegin(), QList::rend(), QList::reverse_iterator, QList::const_iterator */ /*! \typedef QList::Iterator Qt-style synonym for QList::iterator. */ /*! \typedef QList::ConstIterator Qt-style synonym for QList::const_iterator. */ /*! \typedef QList::const_pointer Provided for STL compatibility. */ /*! \typedef QList::const_reference Provided for STL compatibility. */ /*! \typedef QList::difference_type Provided for STL compatibility. */ /*! \typedef QList::pointer Provided for STL compatibility. */ /*! \typedef QList::reference Provided for STL compatibility. */ /*! \typedef QList::size_type Provided for STL compatibility. */ /*! \typedef QList::value_type Provided for STL compatibility. */ /*! \typedef QList::parameter_type */ /*! \typedef QList::rvalue_ref */ /*! \fn template QList QList::toList() const \fn template QList QList::toVector() const \deprecated A no-op in Qt 6. Provided for backwards compatibility with Qt 5, where QList and QVector where two different types. Returns this list. */ /*! \fn template QList QList::fromList(const QList &list) \fn template QList QList::fromVector(const QList &list) \deprecated A no-op in Qt 6. Provided for backwards compatibility with Qt 5, where QList and QVector were two different types. Returns this list. */ /*! \fn template QDataStream &operator<<(QDataStream &out, const QList &list) \relates QList Writes the list \a list to stream \a out. This function requires the value type to implement \c operator<<(). \sa{Serializing Qt Data Types}{Format of the QDataStream operators} */ /*! \fn template QDataStream &operator>>(QDataStream &in, QList &list) \relates QList Reads a list from stream \a in into \a list. This function requires the value type to implement \c operator>>(). \sa{Serializing Qt Data Types}{Format of the QDataStream operators} */ /*! \fn template qsizetype erase(QList &list, const AT &t) \relates QList \since 6.1 Removes all elements that compare equal to \a t from the list \a list. Returns the number of elements removed, if any. \note Unlike QList::removeAll, \a t is not allowed to be a reference to an element inside \a list. If you cannot be sure that this is not the case, take a copy of \a t and call this function with the copy. \sa QList::removeAll(), erase_if */ /*! \fn template qsizetype erase_if(QList &list, Predicate pred) \relates QList \since 6.1 Removes all elements for which the predicate \a pred returns true from the list \a list. Returns the number of elements removed, if any. \sa erase */ /*! \fn template QList& QList::assign(qsizetype n, parameter_type t) \since 6.6 Replaces the contents of this list with \a n copies of \a t. The size of this list will be equal to \a n. This function will only allocate memory if \a n exceeds the capacity of the list or this list is shared. */ /*! \fn template template ::if_input_iterator> QList& QList::assign(InputIterator first, InputIterator last) \since 6.6 Replaces the contents of this list with a copy of the elements in the iterator range [\a first, \a last). The size of this list will be equal to the number of elements in the range [\a first, \a last). This function will only allocate memory if the number of elements in the range exceeds the capacity of this list or this list is shared. \note This function overload only participates in overload resolution if \c InputIterator meets the requirements of a \l {https://en.cppreference.com/w/cpp/named_req/InputIterator} {LegacyInputIterator}. \note The behavior is undefined if either argument is an iterator into *this. */ /*! \fn template QList& QList::assign(std::initializer_list l) \since 6.6 Replaces the contents of this list with a copy of the elements of \a l. The size of this list will be equal to the number of elements in \a l. This function only allocates memory if the number of elements in \a l exceeds the capacity of this list or this list is shared. */