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QMetaMethod 类

QMetaMethod class provides meta-data about a member function. 更多...

头： #include <QMetaMethod>
qmake: QT += core

公共类型

enum Access { Private, Protected, Public }
enum MethodType { Method, Signal, Slot, Constructor }

公共函数

Access access () const
bool invoke (QObject * object , Qt::ConnectionType connectionType , QGenericReturnArgument returnValue , QGenericArgument val0 = QGenericArgument( Q_NULLPTR ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument()) const
bool invoke (QObject * object , QGenericReturnArgument returnValue , QGenericArgument val0 = QGenericArgument( Q_NULLPTR ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument()) const
bool invoke (QObject * object , Qt::ConnectionType connectionType , QGenericArgument val0 = QGenericArgument( Q_NULLPTR ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument()) const
bool invoke (QObject * object , QGenericArgument val0 = QGenericArgument( Q_NULLPTR ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument()) const
bool invokeOnGadget (void * gadget , QGenericReturnArgument returnValue , QGenericArgument val0 = QGenericArgument( Q_NULLPTR ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument()) const
bool invokeOnGadget (void * gadget , QGenericArgument val0 = QGenericArgument( Q_NULLPTR ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument()) const
bool isValid () const
int methodIndex () const
QByteArray methodSignature () const
MethodType methodType () const
QByteArray name () const
int parameterCount () const
QList<QByteArray> parameterNames () const
int parameterType (int index ) const
QList<QByteArray> parameterTypes () const
int returnType () const
int revision () const
const char * tag () const
const char * typeName () const

静态公共成员

QMetaMethod fromSignal (PointerToMemberFunction signal )
bool operator!= (const QMetaMethod & m1 , const QMetaMethod & m2 )
bool operator== (const QMetaMethod & m1 , const QMetaMethod & m2 )

宏

Q_METAMETHOD_INVOKE_MAX_ARGS

详细描述

QMetaMethod class provides meta-data about a member function.

A QMetaMethod has a methodType (), a methodSignature (), a list of parameterTypes () 和 parameterNames (), a return typeName (), a tag (), and an access () specifier. You can use invoke () to invoke the method on an arbitrary QObject .

另请参阅 QMetaObject , QMetaEnum , QMetaProperty ，和 Qt 的特性系统 .

成员类型文档编制

enum QMetaMethod:: Access

This enum describes the access level of a method, following the conventions used in C++.

常量 值
QMetaMethod::Private 0
QMetaMethod::Protected 1
QMetaMethod::Public 2

enum QMetaMethod:: MethodType

常量 值 描述
QMetaMethod::Method 0 函数是纯成员函数。
QMetaMethod::Signal 1 函数是信号。
QMetaMethod::Slot 2 函数是槽。
QMetaMethod::Constructor 3 函数是构造函数。

成员函数文档编制

Access QMetaMethod:: access () const

Returns the access specification of this method (private, protected, or public).

注意： Signals are always public, but you should regard that as an implementation detail. It is almost always a bad idea to emit a signal from outside its class.

另请参阅 methodType ().

[static] QMetaMethod QMetaMethod:: fromSignal ( PointerToMemberFunction signal )

返回的元方法相当于给定 signal ，或无效 QMetaMethod if signal 不是类的信号。

范例： 

QMetaMethod destroyedSignal = QMetaMethod::fromSignal(&QObject::destroyed);

该函数在 Qt 5.0 引入。

bool QMetaMethod:: invoke ( QObject * object , Qt::ConnectionType connectionType , QGenericReturnArgument returnValue , QGenericArgument val0 = QGenericArgument( Q_NULLPTR ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument()) const

Invokes this method on the object object 。返回 true 若成员可以被援引。返回 false 若没有这样的成员或参数不匹配。

The invocation can be either synchronous or asynchronous, depending on the connectionType :

  • 若 connectionType is Qt::DirectConnection ，成员将被立即援引。
  • 若 connectionType is Qt::QueuedConnection ， QEvent will be posted and the member is invoked as soon as the application enters the main event loop.
  • 若 connectionType is Qt::AutoConnection , the member is invoked synchronously if object lives in the same thread as the caller; otherwise it will invoke the member asynchronously.

The return value of this method call is placed in returnValue . If the invocation is asynchronous, the return value cannot be evaluated. You can pass up to ten arguments ( val0 , val1 , val2 , val3 , val4 , val5 , val6 , val7 , val8 ，和 val9 ) to this method call.

QGenericArgument and QGenericReturnArgument are internal helper classes. Because signals and slots can be dynamically invoked, you must enclose the arguments using the Q_ARG () 和 Q_RETURN_ARG () macros. Q_ARG () takes a type name and a const reference of that type; Q_RETURN_ARG () takes a type name and a non-const reference.

To asynchronously invoke the animateClick() slot on a QPushButton : 

int methodIndex = pushButton->metaObject()->indexOfMethod("animateClick()");
QMetaMethod method = metaObject->method(methodIndex);
method.invoke(pushButton, Qt::QueuedConnection);

With asynchronous method invocations, the parameters must be of types that are known to Qt's meta-object system, because Qt needs to copy the arguments to store them in an event behind the scenes. If you try to use a queued connection and get the error message 

QMetaMethod::invoke: Unable to handle unregistered datatype 'MyType'

call qRegisterMetaType () to register the data type before you call QMetaMethod::invoke().

要同步援引 compute(QString, int, double) slot on some arbitrary object obj retrieve its return value: 

QString retVal;
QByteArray normalizedSignature = QMetaObject::normalizedSignature("compute(QString, int, double)");
int methodIndex = obj->metaObject()->indexOfMethod(normalizedSignature);
QMetaMethod method = obj->metaObject()->method(methodIndex);
method.invoke(obj,
              Qt::DirectConnection,
              Q_RETURN_ARG(QString, retVal),
              Q_ARG(QString, "sqrt"),
              Q_ARG(int, 42),
              Q_ARG(double, 9.7));

QMetaObject::normalizedSignature () is used here to ensure that the format of the signature is what invoke() expects. E.g. extra whitespace is removed.

If the "compute" slot does not take exactly one QString , one int and one double in the specified order, the call will fail.

警告： this method will not test the validity of the arguments: object must be an instance of the class of the QMetaObject of which this QMetaMethod has been constructed with. The arguments must have the same type as the ones expected by the method, else, the behaviour is undefined.

另请参阅 Q_ARG (), Q_RETURN_ARG (), qRegisterMetaType ()，和 QMetaObject::invokeMethod ().

bool QMetaMethod:: invoke ( QObject * object , QGenericReturnArgument returnValue , QGenericArgument val0 = QGenericArgument( Q_NULLPTR ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument()) const

此函数重载 invoke ().

This overload always invokes this method using the connection type Qt::AutoConnection .

bool QMetaMethod:: invoke ( QObject * object , Qt::ConnectionType connectionType , QGenericArgument val0 = QGenericArgument( Q_NULLPTR ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument()) const

此函数重载 invoke ().

此重载可以被使用，若对成员的返回值不感兴趣。

bool QMetaMethod:: invoke ( QObject * object , QGenericArgument val0 = QGenericArgument( Q_NULLPTR ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument()) const

此函数重载 invoke ().

This overload invokes this method using the connection type Qt::AutoConnection and ignores return values.

bool QMetaMethod:: invokeOnGadget ( void * gadget , QGenericReturnArgument returnValue , QGenericArgument val0 = QGenericArgument( Q_NULLPTR ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument()) const

Invokes this method on a Q_GADGET 。返回 true 若成员可以被援引。返回 false 若没有这样的成员或参数不匹配。

The pointer gadget must point to an instance of the gadget class.

The invocation is always synchronous.

The return value of this method call is placed in returnValue . You can pass up to ten arguments ( val0 , val1 , val2 , val3 , val4 , val5 , val6 , val7 , val8 ，和 val9 ) to this method call.

警告： this method will not test the validity of the arguments: gadget must be an instance of the class of the QMetaObject of which this QMetaMethod has been constructed with. The arguments must have the same type as the ones expected by the method, else, the behavior is undefined.

该函数在 Qt 5.5 引入。

另请参阅 Q_ARG (), Q_RETURN_ARG (), qRegisterMetaType ()，和 QMetaObject::invokeMethod ().

bool QMetaMethod:: invokeOnGadget ( void * gadget , QGenericArgument val0 = QGenericArgument( Q_NULLPTR ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument()) const

这是重载函数。

This overload invokes this method for a gadget and ignores return values.

该函数在 Qt 5.5 引入。

bool QMetaMethod:: isValid () const

返回 true if this method is valid (can be introspected and invoked), otherwise returns false .

该函数在 Qt 5.0 引入。

int QMetaMethod:: methodIndex () const

Returns this method's index.

该函数在 Qt 4.6 引入。

QByteArray QMetaMethod:: methodSignature () const

Returns the signature of this method (e.g., setValue(double) ).

该函数在 Qt 5.0 引入。

另请参阅 parameterTypes () 和 parameterNames ().

MethodType QMetaMethod:: methodType () const

Returns the type of this method (signal, slot, or method).

另请参阅 access ().

QByteArray QMetaMethod:: name () const

Returns the name of this method.

该函数在 Qt 5.0 引入。

另请参阅 methodSignature () 和 parameterCount ().

int QMetaMethod:: parameterCount () const

Returns the number of parameters of this method.

该函数在 Qt 5.0 引入。

另请参阅 parameterType () 和 parameterNames ().

QList < QByteArray > QMetaMethod:: parameterNames () const

Returns a list of parameter names.

另请参阅 parameterTypes () 和 methodSignature ().

int QMetaMethod:: parameterType ( int index ) const

Returns the type of the parameter at the given index .

The return value is one of the types that are registered with QMetaType ，或 QMetaType::UnknownType if the type is not registered.

该函数在 Qt 5.0 引入。

另请参阅 parameterCount (), returnType ()，和 QMetaType .

QList < QByteArray > QMetaMethod:: parameterTypes () const

Returns a list of parameter types.

另请参阅 parameterNames () 和 methodSignature ().

int QMetaMethod:: returnType () const

Returns the return type of this method.

The return value is one of the types that are registered with QMetaType ，或 QMetaType::UnknownType if the type is not registered.

该函数在 Qt 5.0 引入。

另请参阅 parameterType (), QMetaType ，和 typeName ().

int QMetaMethod:: revision () const

Returns the method revision if one was specified by Q_REVISION , otherwise returns 0.

该函数在 Qt 5.1 引入。

const char *QMetaMethod:: tag () const

Returns the tag associated with this method.

Tags are special macros recognized by moc that make it possible to add extra information about a method.

Tag information can be added in the following way in the function declaration: 

// In the class MainWindow declaration
#ifndef Q_MOC_RUN
// define the tag text as empty, so the compiler doesn't see it
#  define MY_CUSTOM_TAG
#endif
...
private slots:
    MY_CUSTOM_TAG void testFunc();

and the information can be accessed by using: 

MainWindow win;
win.show();
int functionIndex = win.metaObject()->indexOfSlot("testFunc()");
QMetaMethod mm = win.metaObject()->method(functionIndex);
qDebug() << mm.tag(); // prints MY_CUSTOM_TAG

For the moment, moc will extract and record all tags, but it will not handle any of them specially. You can use the tags to annotate your methods differently, and treat them according to the specific needs of your application.

注意： Since Qt 5.0, moc expands preprocessor macros, so it is necessary to surround the definition with #ifndef Q_MOC_RUN , as shown in the example above. This was not required in Qt 4. The code as shown above works with Qt 4 too.

const char *QMetaMethod:: typeName () const

Returns the return type name of this method.

另请参阅 returnType () 和 QMetaType::type ().

相关非成员

bool operator!= (const QMetaMethod & m1 , const QMetaMethod & m2 )

这是重载函数。

返回 true if method m1 is not equal to method m2 ，否则返回 false .

该函数在 Qt 5.0 引入。

bool operator== (const QMetaMethod & m1 , const QMetaMethod & m2 )

这是重载函数。

返回 true if method m1 is equal to method m2 ，否则返回 false .

该函数在 Qt 5.0 引入。

宏文档编制

Q_METAMETHOD_INVOKE_MAX_ARGS

Equals maximum number of arguments available for execution of the method via QMetaMethod::invoke ()