Re: Forwarding to Super
Re: Forwarding to Super
- Subject: Re: Forwarding to Super
- From: Herr Witten <email@hidden>
- Date: Sun, 4 Jul 2004 13:57:32 -0400
On 4 Jul 2004, at 3:57, John Randolph wrote:
>
The thing I have to wonder here, is why you want to break
>
encapsulation and message super from *outside* the class in question?
Sometimes encapsulation is not well thought out, so workarounds are
needed.
I have included a more complete implementation, which handles
structures as return types and has other changes:
//
// SuperProxy.h
//
// Michael Witten on Thur 1 July 2004 43470 85
// Copyright (c) 2004 Michael Witten. All rights reserved.
// NOTE: You may reuse this code as long as the copyright remains
intact.
@interface SuperProxy : NSObject
{
id _theTarget;
Class _theClass;
Class _theSuperclass;
BOOL _isObject;
}
+ (id)superProxyWithTarget: (id)theTarget;
- (id)initWithTarget: (id)theTarget;
@end
//
// SuperProxy.m
//
// Michael Witten on Thur 1 July 2004 43470 85
// Copyright (c) 2004 Michael Witten. All rights reserved.
// NOTE: You may reuse this code as long as the copyright remains
intact.
#import "SuperProxy.h"
#import <objc/objc-runtime.h>
static Method _method;
static IMP _method_imp_old;
id _imp_proxy(id theReceiver, SEL theSelector, ...)
{
struct objc_super superContext;
superContext.receiver = theReceiver;
superContext.class = [theReceiver superclass];
void* args = __builtin_apply_args();
void* ptr = &superContext;
memmove((int*)args + 1, &ptr, sizeof(int*));
_method->method_imp = _method_imp_old;
__builtin_return(__builtin_apply((void(*)())objc_msgSendSuper, args,
method_getSizeOfArguments(_method)));
}
void _imp_proxy_stret(void* stretAddr, id theReceiver, SEL theSelector,
...)
{
struct objc_super superContext;
superContext.receiver = theReceiver;
superContext.class = [theReceiver superclass];
void* args = __builtin_apply_args();
void* ptr = &superContext;
memmove((int*)args + 2, &ptr, sizeof(int*));
_method->method_imp = _method_imp_old;
__builtin_apply((void(*)())objc_msgSendSuper_stret, args,
method_getSizeOfArguments(_method));
}
@implementation SuperProxy
+ (id)superProxyWithTarget: (id)theTarget
{
return [[[[SuperProxy alloc] initWithTarget: theTarget] retain]
autorelease];
}
- (id)initWithTarget: (id)theTarget
{
self = [super init];
if (self)
{
_theTarget = [theTarget retain];
_theClass = [_theTarget class];
_theSuperclass = [_theTarget superclass];
_isObject = [_theTarget isMemberOfClass: _theClass];
}
return self;
}
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
{
return [_theSuperclass instanceMethodSignatureForSelector: aSelector];
}
- (void)forwardInvocation:(NSInvocation *)anInvocation
{
SEL theSelector = [anInvocation selector];
_method = (_isObject) ? class_getInstanceMethod(_theClass,
theSelector) : class_getClassMethod(_theClass, theSelector);
_method_imp_old = _method->method_imp;
const char* type = [[anInvocation methodSignature] methodReturnType];
switch (type[0])
{
case _C_ARY_B:
case _C_UNION_B:
case _C_STRUCT_B:
_method->method_imp = (IMP)_imp_proxy_stret;
break;
default:
_method->method_imp = _imp_proxy;
break;
}
[anInvocation invokeWithTarget: _theTarget];
}
- (void)dealloc
{
[_theTarget release];
[super dealloc];
}
@end
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