path: root/src/qml/qml/qqmllist.cpp

/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtQml module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
** Qt Foundation. The licenses are as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-2.0.html and
** https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qqmllist.h"
#include "qqmllist_p.h"
#include "qqmlengine_p.h"
#include "qqmlproperty_p.h"

QT_BEGIN_NAMESPACE

QQmlListReferencePrivate::QQmlListReferencePrivate()
: propertyType(-1), refCount(1)
{
}

QQmlListReference QQmlListReferencePrivate::init(const QQmlListProperty<QObject> &prop, int propType, QQmlEngine *engine)
{
    QQmlListReference rv;

    if (!prop.object) return rv;

    QQmlEnginePrivate *p = engine?QQmlEnginePrivate::get(engine):0;

    int listType = p?p->listType(propType):QQmlMetaType::listType(propType);
    if (listType == -1) return rv;

    rv.d = new QQmlListReferencePrivate;
    rv.d->object = prop.object;
    rv.d->elementType = QQmlPropertyPrivate::rawMetaObjectForType(p, listType);
    rv.d->property = prop;
    rv.d->propertyType = propType;

    return rv;
}

void QQmlListReferencePrivate::addref()
{
    Q_ASSERT(refCount > 0);
    ++refCount;
}

void QQmlListReferencePrivate::release()
{
    Q_ASSERT(refCount > 0);
    --refCount;
    if (!refCount)
        delete this;
}

/*!
\class QQmlListReference
\since 5.0
\inmodule QtQml
\brief The QQmlListReference class allows the manipulation of QQmlListProperty properties.

QQmlListReference allows C++ programs to read from, and assign values to a QML list property in a
simple and type-safe way.  A QQmlListReference can be created by passing an object and property
name or through a QQmlProperty instance.  These two are equivalent:

\code
QQmlListReference ref1(object, "children");

QQmlProperty ref2(object, "children");
QQmlListReference ref2 = qvariant_cast<QQmlListReference>(ref2.read());
\endcode

Not all QML list properties support all operations.  A set of methods, canAppend(), canAt(), canClear() and
canCount() allow programs to query whether an operation is supported on a given property.

QML list properties are type-safe.  Only QObject's that derive from the correct base class can be assigned to
the list.  The listElementType() method can be used to query the QMetaObject of the QObject type supported.
Attempting to add objects of the incorrect type to a list property will fail.

Like with normal lists, when accessing a list element by index, it is the callers responsibility to ensure
that it does not request an out of range element using the count() method before calling at().

The \l {Qt Quick 1} version of this class is named QDeclarativeListReference.
*/

/*!
Constructs an invalid instance.
*/
QQmlListReference::QQmlListReference()
: d(0)
{
}

/*!
Constructs a QQmlListReference for \a object's \a property.  If \a property is not a list
property, an invalid QQmlListReference is created.  If \a object is destroyed after
the reference is constructed, it will automatically become invalid.  That is, it is safe to hold
QQmlListReference instances even after \a object is deleted.

Passing \a engine is required to access some QML created list properties.  If in doubt, and an engine
is available, pass it.
*/
QQmlListReference::QQmlListReference(QObject *object, const char *property, QQmlEngine *engine)
: d(0)
{
    if (!object || !property) return;

    QQmlPropertyData local;
    QQmlPropertyData *data =
        QQmlPropertyCache::property(engine, object, QLatin1String(property), 0, local);

    if (!data || !data->isQList()) return;

    QQmlEnginePrivate *p = engine?QQmlEnginePrivate::get(engine):0;

    int listType = p?p->listType(data->propType()):QQmlMetaType::listType(data->propType());
    if (listType == -1) return;

    d = new QQmlListReferencePrivate;
    d->object = object;
    d->elementType = p?p->rawMetaObjectForType(listType):QQmlMetaType::qmlType(listType)->baseMetaObject();
    d->propertyType = data->propType();

    void *args[] = { &d->property, 0 };
    QMetaObject::metacall(object, QMetaObject::ReadProperty, data->coreIndex(), args);
}

/*! \internal */
QQmlListReference::QQmlListReference(const QQmlListReference &o)
: d(o.d)
{
    if (d) d->addref();
}

/*! \internal */
QQmlListReference &QQmlListReference::operator=(const QQmlListReference &o)
{
    if (o.d) o.d->addref();
    if (d) d->release();
    d = o.d;
    return *this;
}

/*! \internal */
QQmlListReference::~QQmlListReference()
{
    if (d) d->release();
}

/*!
Returns true if the instance refers to a valid list property, otherwise false.
*/
bool QQmlListReference::isValid() const
{
    return d && d->object;
}

/*!
Returns the list property's object.  Returns 0 if the reference is invalid.
*/
QObject *QQmlListReference::object() const
{
    if (isValid()) return d->object;
    else return 0;
}

/*!
Returns the QMetaObject for the elements stored in the list property.  Returns 0 if the reference
is invalid.

The QMetaObject can be used ahead of time to determine whether a given instance can be added
to a list.
*/
const QMetaObject *QQmlListReference::listElementType() const
{
    if (isValid()) return d->elementType.metaObject();
    else return 0;
}

/*!
Returns true if the list property can be appended to, otherwise false.  Returns false if the
reference is invalid.

\sa append()
*/
bool QQmlListReference::canAppend() const
{
    return (isValid() && d->property.append);
}

/*!
Returns true if the list property can queried by index, otherwise false.  Returns false if the
reference is invalid.

\sa at()
*/
bool QQmlListReference::canAt() const
{
    return (isValid() && d->property.at);
}

/*!
Returns true if the list property can be cleared, otherwise false.  Returns false if the
reference is invalid.

\sa clear()
*/
bool QQmlListReference::canClear() const
{
    return (isValid() && d->property.clear);
}

/*!
Returns true if the list property can be queried for its element count, otherwise false.
Returns false if the reference is invalid.

\sa count()
*/
bool QQmlListReference::canCount() const
{
    return (isValid() && d->property.count);
}

/*!
    Return true if at(), count(), append() and clear() are implemented, so you can manipulate
    the list.

\sa isReadable(), at(), count(), append(), clear()
*/
bool QQmlListReference::isManipulable() const
{
    return (isValid()
            && d->property.append
            && d->property.count
            && d->property.at
            && d->property.clear);
}


/*!
    Return true if at() and count() are implemented, so you can access the elements.

\sa isManipulable(), at(), count()
*/
bool QQmlListReference::isReadable() const
{
    return (isValid() && d->property.count && d->property.at);
}

/*!
Appends \a object to the list.  Returns true if the operation succeeded, otherwise false.

\sa canAppend()
*/
bool QQmlListReference::append(QObject *object) const
{
    if (!canAppend()) return false;

    if (object && !QQmlMetaObject::canConvert(object, d->elementType))
        return false;

    d->property.append(&d->property, object);

    return true;
}

/*!
Returns the list element at \a index, or 0 if the operation failed.

\sa canAt()
*/
QObject *QQmlListReference::at(int index) const
{
    if (!canAt()) return 0;

    return d->property.at(&d->property, index);
}

/*!
Clears the list.  Returns true if the operation succeeded, otherwise false.

\sa canClear()
*/
bool QQmlListReference::clear() const
{
    if (!canClear()) return false;

    d->property.clear(&d->property);

    return true;
}

/*!
Returns the number of objects in the list, or 0 if the operation failed.
*/
int QQmlListReference::count() const
{
    if (!canCount()) return 0;

    return d->property.count(&d->property);
}

/*!
\class QQmlListProperty
\since 5.0
\inmodule QtQml
\brief The QQmlListProperty class allows applications to expose list-like
properties of QObject-derived classes to QML.

QML has many list properties, where more than one object value can be assigned.
The use of a list property from QML looks like this:

\code
FruitBasket {
    fruit: [
        Apple {},
        Orange{},
        Banana{}
    ]
}
\endcode

The QQmlListProperty encapsulates a group of function pointers that represent the
set of actions QML can perform on the list - adding items, retrieving items and
clearing the list.  In the future, additional operations may be supported.  All
list properties must implement the append operation, but the rest are optional.

To provide a list property, a C++ class must implement the operation callbacks,
and then return an appropriate QQmlListProperty value from the property getter.
List properties should have no setter.  In the example above, the Q_PROPERTY()
declarative will look like this:

\code
Q_PROPERTY(QQmlListProperty<Fruit> fruit READ fruit);
\endcode

QML list properties are type-safe - in this case \c {Fruit} is a QObject type that
\c {Apple}, \c {Orange} and \c {Banana} all derive from.

The \l {Qt Quick 1} version of this class is named QDeclarativeListProperty.

\sa {Extending QML - Object and List Property Types Example}

*/

/*!
\fn QQmlListProperty::QQmlListProperty()
\internal
*/

/*!
\fn QQmlListProperty::QQmlListProperty(QObject *object, QList<T *> &list)

Convenience constructor for making a QQmlListProperty value from an existing
QList \a list.  The \a list reference must remain valid for as long as \a object
exists.  \a object must be provided.

Generally this constructor should not be used in production code, as a
writable QList violates QML's memory management rules.  However, this constructor
can be very useful while prototyping.
*/

/*!
\fn QQmlListProperty::QQmlListProperty(QObject *object, void *data,
                                    CountFunction count, AtFunction at)

Construct a readonly QQmlListProperty from a set of operation functions
\a count and \a at. An opaque \a data handle may be passed which can be
accessed from within the operation functions.  The list property
remains valid while \a object exists.
*/

/*!
\fn QQmlListProperty::QQmlListProperty(QObject *object, void *data, AppendFunction append,
                                     CountFunction count, AtFunction at,
                                     ClearFunction clear)

Construct a QQmlListProperty from a set of operation functions \a append,
\a count, \a at, and \a clear.  An opaque \a data handle may be passed which
can be accessed from within the operation functions.  The list property
remains valid while \a object exists.

Null pointers can be passed for any function. If any null pointers are passed in, the list
will be neither designable nor alterable by the debugger. It is recommended to provide valid
pointers for all functions.
*/

/*!
\typedef QQmlListProperty::AppendFunction

Synonym for \c {void (*)(QQmlListProperty<T> *property, T *value)}.

Append the \a value to the list \a property.
*/

/*!
\typedef QQmlListProperty::CountFunction

Synonym for \c {int (*)(QQmlListProperty<T> *property)}.

Return the number of elements in the list \a property.
*/

/*!
\fn bool QQmlListProperty::operator==(const QQmlListProperty &other) const

Returns true if this QQmlListProperty is equal to \a other, otherwise false.
*/

/*!
\typedef QQmlListProperty::AtFunction

Synonym for \c {T *(*)(QQmlListProperty<T> *property, int index)}.

Return the element at position \a index in the list \a property.
*/

/*!
\typedef QQmlListProperty::ClearFunction

Synonym for \c {void (*)(QQmlListProperty<T> *property)}.

Clear the list \a property.
*/

QT_END_NAMESPACE