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Diffstat (limited to 'src/qml/doc/src/cppintegration/data.qdoc')
| -rw-r--r-- | src/qml/doc/src/cppintegration/data.qdoc | 90 |
1 files changed, 4 insertions, 86 deletions
diff --git a/src/qml/doc/src/cppintegration/data.qdoc b/src/qml/doc/src/cppintegration/data.qdoc index e564edb943..2822f4acee 100644 --- a/src/qml/doc/src/cppintegration/data.qdoc +++ b/src/qml/doc/src/cppintegration/data.qdoc @@ -92,7 +92,7 @@ when passed from C++ to QML and vice-versa: \li QVector2D, QVector3D, QVector4D \li \l vector2d, \l vector3d, \l vector4d \row - \li Enums declared with Q_ENUM() or Q_ENUMS() + \li Enums declared with Q_ENUM() \li \l enumeration \endtable @@ -306,97 +306,15 @@ calling its \l {QDateTime::}{time()} method. \section2 Sequence Type to JavaScript Array -Certain C++ sequence types are supported transparently in QML to behave like -JavaScript \c Array types. - -In particular, QML currently supports: -\list - \li \c {QList<int>} - \li \c {QList<qreal>} - \li \c {QList<bool>} - \li \c {QList<QString>} and \c{QStringList} - \li \c {QVector<QString>} - \li \c {std::vector<QString>} - \li \c {QList<QUrl>} - \li \c {QVector<QUrl>} - \li \c {std::vector<QUrl>} - \li \c {QVector<int>} - \li \c {QVector<qreal>} - \li \c {QVector<bool>} - \li \c {std::vector<int>} - \li \c {std::vector<qreal>} - \li \c {std::vector<bool>} -\endlist - -and all registered QList, QVector, QQueue, QStack, QSet, std::list, -std::vector that contain a type marked with \l Q_DECLARE_METATYPE. - -These sequence types are implemented directly in terms of the underlying C++ -sequence. There are two ways in which such sequences can be exposed to QML: -as a Q_PROPERTY of the given sequence type; or as the return type of a -Q_INVOKABLE method. There are some differences in the way these are -implemented, which are important to note. - -If the sequence is exposed as a Q_PROPERTY, accessing any value in the -sequence by index will cause the sequence data to be read from the QObject's -property, then a read to occur. Similarly, modifying any value in the -sequence will cause the sequence data to be read, and then the modification -will be performed and the modified sequence will be written back to the -QObject's property. - -If the sequence is returned from a Q_INVOKABLE function, access and mutation -is much cheaper, as no QObject property read or write occurs; instead, the -C++ sequence data is accessed and modified directly. - -In both the Q_PROPERTY and return from Q_INVOKABLE cases, the elements -of a std::vector are copied. This copying may be an expensive operation, -so std::vector should be used judiciously. +See \l{QML Sequence Types} for a general description of sequence types. The +\l{Qt QML QML Types}{QtQml module} contains a few sequence types +you may want to use. You can also create a list-like data structure by constructing a QJSValue using QJSEngine::newArray(). Such a JavaScript array does not need any conversion when passing it between QML and C++. See \l{QJSValue#Working With Arrays} for details on how to manipulate JavaScript arrays from C++. -Other sequence types are not supported transparently, and instead an -instance of any other sequence type will be passed between QML and C++ as an -opaque QVariantList. - -\b {Important Note:} There are some minor differences between the -semantics of such sequence Array types and default JavaScript Array types -which result from the use of a C++ storage type in the implementation. In -particular, deleting an element from an Array will result in a -default-constructed value replacing that element, rather than an Undefined -value. Similarly, setting the length property of the Array to a value larger -than its current value will result in the Array being padded out to the -specified length with default-constructed elements rather than Undefined -elements. Finally, the Qt container classes support signed (rather than -unsigned) integer indexes; thus, attempting to access any index greater -than INT_MAX will fail. - -The default-constructed values for each sequence type are as follows: -\table -\row \li QList<int> \li integer value 0 -\row \li QList<qreal> \li real value 0.0 -\row \li QList<bool> \li boolean value \c {false} -\row \li QList<QString> and QStringList \li empty QString -\row \li QVector<QString> \li empty QString -\row \li std::vector<QString> \li empty QString -\row \li QList<QUrl> \li empty QUrl -\row \li QVector<QUrl> \li empty QUrl -\row \li std::vector<QUrl> \li empty QUrl -\row \li QVector<int> \li integer value 0 -\row \li QVector<qreal> \li real value 0.0 -\row \li QVector<bool> \li boolean value \c {false} -\row \li std::vector<int> \li integer value 0 -\row \li std::vector<qreal> \li real value 0.0 -\row \li std::vector<bool> \li boolean value \c {false} -\endtable - -If you wish to remove elements from a sequence rather than simply replace -them with default constructed values, do not use the indexed delete operator -("delete sequence[i]") but instead use the \c {splice} function -("sequence.splice(startIndex, deleteCount)"). - \section2 QByteArray to JavaScript ArrayBuffer The QML engine provides automatic type conversion between QByteArray values and |