KTextTemplate
Generic type support
KTextTemplate offers powerful support for using any type or container in a QVariant as part of the Context. Qt introspection based on Q_PROPERTY is the most convenient way to access properties on QObject derived type or types decorated with the Q_GADGET
macro. However, sometimes it is necessary to use classes which do can't have Q_PROPERTY macros (perhaps because they are defined in third-party headers) and where it would not be practical to create QObject/Q_GADGET
wrappers around all related classes.
In such cases the metatype can be registered with KTextTemplate and an introspection method can be written.
There are several necessary steps and consequences.
- The type must be registered as a QMetaType with
Q_DECLARE_METATYPE
. Note that this is not needed for QObject derived types. - All containers are supported. (See Generic container support)
- The
KTEXTTEMPLATE_BEGIN_LOOKUP
andKTEXTTEMPLATE_END_LOOKUP
macros help to define the introspection of the type. Between them is the definition of a method with the signatureQVariant getProperty(const Type &object, const QString &property)
. - KTextTemplate::registerMetaType must be called at some point in the program before attempting to use the type in a Context.
- The Context is created and used as normal.
Generic container support
KTextTemplate supports most Qt and STL containers by default if they are registered with the QMetaType system as shown in Generic type support. Where a container does not have built in support it can easily be added (See Third party containers).
The following containers have built in support:
- QList<T>
- QList<T>
- QSet<T>
- QLinkedList<T>
- QStack<T>
- QQueue<T>
- std::vector<T>
- std::deque<T>
- std::list<T>
- QHash<QString, T>
- QHash<qint16, T>
- QHash<qint32, T>
- QHash<qint64, T>
- QHash<quint16, T>
- QHash<quint32, T>
- QHash<quint64, T>
- QMap<QString, T>
- QMap<qint16, T>
- QMap<qint32, T>
- QMap<qint64, T>
- QMap<quint16, T>
- QMap<quint32, T>
- QMap<quint64, T>
- std::map<QString, T>
- std::map<qint16, T>
- std::map<qint32, T>
- std::map<qint64, T>
- std::map<quint16, T>
- std::map<quint32, T>
- std::map<quint64, T>
where T is one of
- bool
- qint16
- qint32
- qint64
- quint16
- quint32
- quint64
- float
- double
- QVariant
- QString
- QDateTime
- A pointer to a type which inherits QObject
- Any type registered with KTextTemplate::registerMetaType
- Any supported container
Note that QSet<T> is an exception and will only work with types for which qHash(T)
is defined. This means that QSet<QVariant> is not possible for example.
Note also that containers of pointers to QObject derived types can be stored in containers, and they do not need to be explicitly registered with KTextTemplate. Where the class has sufficient Q_PROPERTY
s defined, the introspection method described above with KTEXTTEMPLATE_BEGIN_LOOKUP
and KTEXTTEMPLATE_END_LOOKUP
is also not necessary. Note also that any type or container can be used through a Q_PROPERTY
.
- See also
- The regroup tag
The output would be something like
<h1>Tennis</h1> <h2>Smithfield Tennis Club</h2> <ul> <li>Alice, 21</li> <li>Bob, 22</li> </ul> <h2>Greenore Lawn Tennis and Fitness Club</h2> <ul> <li>Charlie, 23</li> <li>David, 24</li> <li>Elaine, 25</li> <li>Frank, 26</li> </ul> <h1>Basketball</h1> <h2>Sandyford Basketball Club</h2> <ul> <li>Gilian, 27</li> <li>Henry, 28</li> </ul>
Of course, it is possible to use containers of pointers to concrete QObject subclasses, such as QSet<PersonObject*> and std::vector<SportsClub*> too.
Because any supported container can also be used as a contained type, nested containers such as QList<QList<PersonObject*>>
are also supported.
Note that if a type is registered with KTextTemplate::registerMetaType, built in containers of that type do not also need to be registered. Third party containers do need to be registered however (See Third party containers)
Third party containers
To support another, non-built in container it is necessary to use some macros to register it with KTextTemplate.
For a sequential container, Q_DECLARE_SEQUENTIAL_CONTAINER_METATYPE
, and Q_DECLARE_ASSOCIATIVE_CONTAINER_METATYPE
are needed.
- See also
- Variable lookups
For associative containers Q_DECLARE_ASSOCIATIVE_CONTAINER_METATYPE
is needed.
Smart Pointers
Shared pointer types containing a custom type should be introspected as normal using KTEXTTEMPLATE_BEGIN_LOOKUP
and KTEXTTEMPLATE_END_LOOKUP
Note that if only shared pointers to the type is in your introspectable API you only need to define the property access for the shared pointer. In the case above, there is no need to use Q_DECLARE_METATYPE
or KTEXTTEMPLATE_BEGIN_LOOKUP
with Person
or Person*
.
This is of course true of any smart pointer:
QSharedPointers containing QObject derived types get special treatment.
QObjects are automatically introspected for their Q_PROPERTY
s (See Custom objects).
If you have QSharedPointer<PersonObject> where PersonObject
is derived from QObject it will be automatically introspected just like a QObject* is without requiring the KTEXTTEMPLATE_BEGIN_LOOKUP
and KTEXTTEMPLATE_END_LOOKUP
macros, the Q_DECLARE_METATYPE
macro, or registration with the KTextTemplate metatype system. All of the access registration is handled by Qt.
The same technique can be used to support QObject derived types in third party shared pointers, but that requires an extra macro, Q_DECLARE_SMART_POINTER_METATYPE
.
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