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/** Implementation of NSProtocolChecker for GNUStep
Copyright (C) 1995 Free Software Foundation, Inc.
Original by: Mike Kienenberger
Date: Jun 1998
Written: Richard Frith-Macdonald
Date: April 2004
This file is part of the GNUstep Base Library.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free
Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110 USA.
<title>NSProtocolChecker class reference</title>
$Date$ $Revision$
*/
#import "common.h"
#define EXPOSE_NSProtocolChecker_IVARS 1
#import "Foundation/NSProtocolChecker.h"
#import "Foundation/NSException.h"
#import "Foundation/NSInvocation.h"
#import "Foundation/NSMethodSignature.h"
#include <objc/Protocol.h>
/**
* The NSProtocolChecker and NSProxy classes provide message filtering and
* forwarding capabilities. If you wish to ensure at runtime that a given
* object will only be sent messages in a certain protocol, you create an
* <code>NSProtocolChecker</code> instance with the protocol and the object as
* arguments-
<example>
id versatileObject = [[ClassWithManyMethods alloc] init];
id narrowObject = [NSProtocolChecker protocolCheckerWithTarget: versatileObject
protocol: @protocol(SomeSpecificProtocol)];
return narrowObject;
</example>
* This is often used in conjunction with distributed objects to expose only a
* subset of an objects methods to remote processes
*/
@implementation NSProtocolChecker
/**
* Allocates and initializes an NSProtocolChecker instance by calling
* -initWithTarget:protocol:<br />
* Autoreleases and returns the new instance.
*/
+ (id) protocolCheckerWithTarget: (NSObject*)anObject
protocol: (Protocol*)aProtocol
{
return AUTORELEASE([[NSProtocolChecker alloc] initWithTarget: anObject
protocol: aProtocol]);
}
- (void) dealloc
{
DESTROY(_myTarget);
[super dealloc];
}
- (const char *) _protocolTypeForSelector: (SEL)aSel
{
struct objc_method_description desc;
desc = GSProtocolGetMethodDescriptionRecursive(_myProtocol, aSel, YES, YES);
if (desc.name == NULL && desc.types == NULL)
{
desc = GSProtocolGetMethodDescriptionRecursive(_myProtocol, aSel, YES, NO);
}
return desc.types;
}
/**
* Forwards any message to the delegate if the method is declared in
* the checker's protocol; otherwise raises an
* <code>NSInvalidArgumentException</code>.
*/
- (void) forwardInvocation: (NSInvocation*)anInvocation
{
const char *type;
if ([self _protocolTypeForSelector: [anInvocation selector]] == NULL)
{
if (GSObjCIsInstance(_myTarget))
{
[NSException raise: NSInvalidArgumentException
format: @"<%s -%@> not declared",
protocol_getName(_myProtocol),
NSStringFromSelector([anInvocation selector])];
}
else
{
[NSException raise: NSInvalidArgumentException
format: @"<%s +%@> not declared",
protocol_getName(_myProtocol),
NSStringFromSelector([anInvocation selector])];
}
}
[anInvocation invokeWithTarget: _myTarget];
/*
* If the method returns 'self' (ie the target object) replace the
* returned value with the protocol checker.
*/
type = [[anInvocation methodSignature] methodReturnType];
if (GSSelectorTypesMatch(type, @encode(id)))
{
id buf;
[anInvocation getReturnValue: &buf];
if (buf == _myTarget)
{
buf = self;
[anInvocation setReturnValue: &buf];
}
}
}
- (id) init
{
self = [self initWithTarget: nil protocol: nil];
return self;
}
/**
* 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 any method
* in the protocol returns anObject, the checker will replace the returned
* value with itself rather than the target object.<br />
* Returns the new instance.
*/
- (id) initWithTarget: (NSObject*)anObject protocol: (Protocol*)aProtocol
{
_myProtocol = aProtocol;
ASSIGN(_myTarget, anObject);
return self;
}
- (NSMethodSignature*) methodSignatureForSelector: (SEL)aSelector
{
if (_myProtocol != nil)
{
const char *types = [self _protocolTypeForSelector: aSelector];
if (types == NULL)
{
return nil;
}
return [NSMethodSignature signatureWithObjCTypes: types];
}
return [super methodSignatureForSelector: aSelector];
}
/**
* Returns the protocol object the checker uses to verify whether a
* given message should be forwarded to its delegate.
*/
- (Protocol*) protocol
{
return _myProtocol;
}
/**
* Returns the target of the NSProtocolChecker.
*/
- (NSObject*) target
{
return _myTarget;
}
@end
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