Up
Authors
- Richard Frith-Macdonald (
richard@brainstorm.co.uk
)
-
- Andrew Kachites McCallum (
mccallum@gnu.ai.mit.edu
)
-
Version: 1.67
Date: 2005/11/06 13:53:39
Copyright: (C) 1998,2003 Free Software Foundation, Inc.
- Declared in:
- Foundation/NSInvocation.h
Availability: OpenStep
The NSInvocation
class implements a mechanism of constructing messages (as NSInvocation
instances), sending these to other objects, and handling the returned values.
An NSInvocation
object may contain a target object to which a message can be sent, or may send the message to an arbitrary object.
Each message consists of a selector for that method and an argument list. Once the message has been sent, the invocation will contain a return value whose contents may be copied out of it.
The target, selector, and arguments of an instance be constructed dynamically, providing a great deal of power/flexibility.
The sending of the message to the target object (using the -invoke
or -invokeWithTarget:
method) can be done at any time, but a standard use of this is by the [NSObject -forwardInvocation:]
method which is called whenever a method is not implemented by the class of the object to which it was sent.
Related to the class are two convenience macros... NS_MESSAGE()
and NS_INVOCATION()
... to allow easy construction of invocations with all the arguments set up.
Instance Variables
Method summary
+ (
NSInvocation*)
invocationWithMethodSignature: (
NSMethodSignature*)_signature;
Availability: OpenStep
Returns an invocation instance which can be used to send messages to a target object using the described signature.
You must set the target and selector (using
-setTarget:
and -setSelector:) before you attempt to use the invocation.
Raises an NSInvalidArgumentException if the signature is
nil
.
- (BOOL)
argumentsRetained;
Availability: OpenStep
Returns a flag to indicate whether object arguments of the invocation (including its target) are retained by the invocation.
- (void)
getArgument: (void*)buffer
atIndex: (int)index;
Availability: OpenStep
Copies the argument identified by index into the memory location specified by the buffer argument.
An index of zero is the target object, an index of one is the selector, so the actual method arguments start at index 2.
- (void)
getReturnValue: (void*)buffer;
Availability: OpenStep
Copies the invocations return value to the location pointed to by
buffer if a return value has been set (see the
-setReturnValue:
method).
If there isn't a return value then this method raises an exception.
- (void)
invoke;
Availability: OpenStep
Sends the message encapsulated in the invocation to its target.
- (void)
invokeWithTarget: (id)anObject;
Availability: OpenStep
Sends the message encapsulated in the invocation to anObject.
- (
NSMethodSignature*)
methodSignature;
Availability: OpenStep
Returns the method signature of the invocation.
- (void)
retainArguments;
Availability: OpenStep
Instructs the invocation to retain its object arguments (including the target). The default is not to retain them.
- (void)
retainArgumentsIncludingTarget: (BOOL)retainTargetFlag;
Availability: Not in OpenStep/MacOS-X, Base 1.11.1
Similar to -[NSInvocation retainArguments], but allows the sender to explicitly control whether the target is retained as well. Retaining the target is sometimes not desirable (such as in NSUndoManager), as retain loops could result.
- (SEL)
selector;
Availability: OpenStep
Returns the selector of the invocation (the argument at index 1)
- (void)
setArgument: (void*)buffer
atIndex: (int)index;
Availability: OpenStep
Sets the argument identified by
index from the memory location specified by the
buffer argument.
Using an
index of 0 is equivalent to calling
-setTarget:
and using an argument of 1 is equivalent to
-setSelector:
Proper arguments start at
index 2.
NB. Unlike
-setTarget:
and
-setSelector:
the value of
buffer must be
a pointer to the argument to be set in the invocation.
If
-retainArguments
was called, then any object argument set in the receiver is retained by it.
- (void)
setReturnValue: (void*)buffer;
Availability: OpenStep
Sets the return value of the invocation to the item that buffer points to.
- (void)
setSelector: (SEL)aSelector;
Availability: OpenStep
Sets the selector for the invocation.
- (void)
setTarget: (id)anObject;
Availability: OpenStep
Sets the target object for the invocation.
If
-retainArguments
was called, then the target is retained.
- (id)
target;
Availability: OpenStep
Returns the target object of the invocation.
- (BOOL)
targetRetained;
Availability: Not in OpenStep/MacOS-X, Base 1.11.1
Returns YES
if target has been retained yet, NO
otherwise.
Instance Variables for NSInvocation Class
@protected BOOL _argsRetained;
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
@protected void* _cframe;
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
@protected void* _dummy;
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
@protected NSArgumentInfo* _info;
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
@protected unsigned int _numArgs;
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
@protected void* _retval;
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
@protected SEL _selector;
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
@protected BOOL _sendToSuper;
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
@protected NSMethodSignature* _sig;
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
@protected id _target;
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
@protected BOOL _targetRetained;
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
@protected BOOL _validReturn;
Warning the underscore at the start of the name of this instance variable indicates that, even though it is not technically private, it is intended for internal use within the package, and you should not use the variable in other code.
- Declared in:
- Foundation/NSInvocation.h
Availability: Base 0.0.0
Provides some minor extensions and some utility methods to aid integration of NSInvocation
with the Objective-C runtime.
Method summary
- (id)
initWithArgframe: (arglist_t)frame
selector: (SEL)aSelector;
Availability: Base 0.0.0
Internal use.
Initialises the receiver with a known selector and argument list as supplied to the forward:: method by the ObjectiveC runtime when it is unable to locate an implementation for the selector in a class.
- (id)
initWithMethodSignature: (
NSMethodSignature*)aSignature;
Availability: Base 0.0.0
This is a designated initialiser for the class.
Subclasses
should override this method.
Initialised an invocation instance which can be used to send messages to a target object using
aSignature.
You must set the target and selector (using
-setTarget:
and -setSelector:) before you attempt to use the invocation.
Raises an NSInvalidArgumentException if
aSignature is
nil
.
- (id)
initWithSelector: (SEL)aSelector;
Availability: Base 0.0.0
Tries to produce a method signature based on
aSelector and uses that to initialise self by calling the
-initWithMethodSignature:
method.
If the argument type of
aSelector cannot be determined, this releases self and returns
nil
.
- (id)
initWithTarget: (id)anObject
selector: (SEL)aSelector
,...;
Availability: Base 0.0.0
Initialises the receiver with the specified target, selector, and a variable number of arguments.
- (void*)
returnFrame: (arglist_t)argFrame;
Availability: Base 0.0.0
Internal use.
Provides a return frame that the ObjectiveC runtime can use to return the result of an invocation to a calling function.
- (BOOL)
sendsToSuper;
Availability: Base 0.0.0
- (void)
setSendsToSuper: (BOOL)flag;
Availability: Base 0.0.0
Sets the flag to tell the invocation that it should actually invoke a method in the superclass of the target rather than the method of the target itself.
This extension permits an invocation to act like a regular method call sent to super in the method of a class.
- Declared in:
- Foundation/NSInvocation.h
Availability: OpenStep
These methods are for internal use only... not public API
They are used by the
NS_INVOCATION()
and
NS_MESSAGE()
macros to help create invocations.
Method summary
+ (id)
_newProxyForInvocation: (id)target;
Availability: OpenStep
Warning the underscore at the start of the name of this method indicates that it is private, for internal use only, and you should not use the method in your code.
+ (id)
_newProxyForMessage: (id)target;
Availability: OpenStep
Warning the underscore at the start of the name of this method indicates that it is private, for internal use only, and you should not use the method in your code.
+ (
NSInvocation*)
_returnInvocationAndDestroyProxy: (id)proxy;
Availability: OpenStep
Warning the underscore at the start of the name of this method indicates that it is private, for internal use only, and you should not use the method in your code.
Up