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QMetaMethod Class Reference

[ QtCore module]

The QMetaMethod class provides meta-data about a member 函数。 更多...

类型

方法

详细描述

The QMetaMethod class provides meta-data about a member 函数。

A QMetaMethod has a methodType (), a signature (), 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 .

A method will only be registered with the meta-object system if it is a slot, a signal, or declared with the Q_INVOKABLE macro. Constructors can also be registered with Q_INVOKABLE .

类型文档编制

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

QMetaMethod.MethodType

常量 值 描述
QMetaMethod.Method 0 The function is a plain member function.
QMetaMethod.Signal 1 The function is a signal.
QMetaMethod.Slot 2 The function is a slot.
QMetaMethod.Constructor 3 The function is a constructor.

方法文档编制

QMetaMethod.__init__ ( self )

QMetaMethod.__init__ ( self , QMetaMethod )

Access QMetaMethod.access ( self )

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

Signals are always protected, meaning that you can only emit them from the class or from a subclass.

另请参阅 methodType ().

object QMetaMethod.invoke ( self , QObject   object , Qt.ConnectionType   connectionType , QGenericReturnArgument   returnValue , QGenericArgument   value0  = QGenericArgument(0,0), QGenericArgument   value1  = QGenericArgument(0,0), QGenericArgument   value2  = QGenericArgument(0,0), QGenericArgument   value3  = QGenericArgument(0,0), QGenericArgument   value4  = QGenericArgument(0,0), QGenericArgument   value5  = QGenericArgument(0,0), QGenericArgument   value6  = QGenericArgument(0,0), QGenericArgument   value7  = QGenericArgument(0,0), QGenericArgument   value8  = QGenericArgument(0,0), QGenericArgument   value9  = QGenericArgument(0,0))

Invokes this method on the object object . Returns true if the member could be invoked. Returns false if there is no such member or the parameters did not match.

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

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 () 到 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 = 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 (), and QMetaObject.invokeMethod ().

object QMetaMethod.invoke ( self , QObject   object , QGenericReturnArgument   returnValue , QGenericArgument   value0  = QGenericArgument(0,0), QGenericArgument   value1  = QGenericArgument(0,0), QGenericArgument   value2  = QGenericArgument(0,0), QGenericArgument   value3  = QGenericArgument(0,0), QGenericArgument   value4  = QGenericArgument(0,0), QGenericArgument   value5  = QGenericArgument(0,0), QGenericArgument   value6  = QGenericArgument(0,0), QGenericArgument   value7  = QGenericArgument(0,0), QGenericArgument   value8  = QGenericArgument(0,0), QGenericArgument   value9  = QGenericArgument(0,0))

此函数重载 invoke ().

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

object QMetaMethod.invoke ( self , QObject   object , Qt.ConnectionType   connectionType , QGenericArgument   value0  = QGenericArgument(0,0), QGenericArgument   value1  = QGenericArgument(0,0), QGenericArgument   value2  = QGenericArgument(0,0), QGenericArgument   value3  = QGenericArgument(0,0), QGenericArgument   value4  = QGenericArgument(0,0), QGenericArgument   value5  = QGenericArgument(0,0), QGenericArgument   value6  = QGenericArgument(0,0), QGenericArgument   value7  = QGenericArgument(0,0), QGenericArgument   value8  = QGenericArgument(0,0), QGenericArgument   value9  = QGenericArgument(0,0))

此函数重载 invoke ().

This overload can be used if the return value of the member is of no interest.

object QMetaMethod.invoke ( self , QObject   object , QGenericArgument   value0  = QGenericArgument(0,0), QGenericArgument   value1  = QGenericArgument(0,0), QGenericArgument   value2  = QGenericArgument(0,0), QGenericArgument   value3  = QGenericArgument(0,0), QGenericArgument   value4  = QGenericArgument(0,0), QGenericArgument   value5  = QGenericArgument(0,0), QGenericArgument   value6  = QGenericArgument(0,0), QGenericArgument   value7  = QGenericArgument(0,0), QGenericArgument   value8  = QGenericArgument(0,0), QGenericArgument   value9  = QGenericArgument(0,0))

此函数重载 invoke ().

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

int QMetaMethod.methodIndex ( self )

Returns this method's index.

该函数在 Qt 4.6 引入。

MethodType QMetaMethod.methodType ( self )

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

另请参阅 access ().

list-of-QByteArray QMetaMethod.parameterNames ( self )

Returns a list of parameter names.

另请参阅 parameterTypes () 和 signature ().

list-of-QByteArray QMetaMethod.parameterTypes ( self )

Returns a list of parameter types.

另请参阅 parameterNames () 和 signature ().

str QMetaMethod.signature ( self )

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

另请参阅 parameterTypes () 和 parameterNames ().

str QMetaMethod.tag ( self )

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: 

 #define THISISTESTTAG // tag text
 ...
 private slots:
     THISISTESTTAG void testFunc();

and the information can be accessed by using: 

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

For the moment, moc doesn't support any special 标签。

str QMetaMethod.typeName ( self )

Returns the return type of this method, or an empty string if the return type is void .

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