NSProtocolChecker

Inherits From:
NSObject

Declared In:
Foundation/NSProtocolChecker.h

Class Description

The NSProtocolChecker class defines an object that restricts the messages that can be sent to another object (referred to as the checker's delegate). This can be particularly useful when an object with many methods, only a few of which ought to be remotely accessible, is made available using the Distributed Objects system.

A protocol checker acts as a kind of proxy; when it receives a message that is in its designated protocool, it forwards the message to its delegate, and consequently appears to be the delegate itself. However, when it receives a message not in its protocol, it raises an NSInvalidArgumentException exception to indicate that th emessage isn't allowed, whether or not th edelegate implements the method.

Typically, an object that is to be distributed (yet must restrict messages) creates an NSProtocolChecker for itself and returns the checker rather than returning itself in response to any messages. The object might also register the checker as the root object of an NSConnection.

The object should be careful about vending references to self; the protocol checker will convert a return value of self to indicate the checker rather than the object for any messages that were forwarded by the checker, but direct references to the object (by passing the checker) could be passed around by other objects.

Method Types

Creating a checker

+ protocolCheckerWithTarget:protocol:
- initWithTarget:protocol:

Reimplemented NSObject methods

- forwardInvocation:
- methodDescriptionForSelector:

Getting information

- protocol
- target

Class Methods

protocolCheckerWithTarget:protocol:

+ (id)protocolCheckerWithTarget:(NSObject *)anObject protocol:(Protocol *)aProtocol

Allocates and initializes an NSProtocolChecker instance that will forward any messages in the aProtocol protocol to anObject, its delegate. Thus, the checker can be vended in lieu of anObject to restrict the messages that can be sent to anObject. Returns the new instance.

Instance Methods

forwardInvocation:

- (void)forwardInvocation:(NSInvocation *)anInvocation

Forwards any message to the delegate if the method is declared in the checker's protocol; otherwise raises an NSInvalidArgumentException.

initWithTarget:protocol:

- (id)initWithTarget:(NSObject *)anObject protocol:(Protocol *)aProtocol

Initializes a newly allocated NSProtocolChecker instance that will forward any messages in the aProtocol protocol to anObject, its delegate. Thus, the checker can be vended in lieu of anObject to restrict the messages that can be sent to anObject. If anObject is allowed to be freed or dereferenced by clients, the free method should be included in aProtocol. Returns the new instance.