iOS代理重定向消息forwardInvocation

&＃64;interface NSInvocation : NSObject {
&＃64;private__strong void *_frame;__strong void *_retdata;id _signature;id _container;uint8_t _retainedArgs;uint8_t _reserved[15];
}&＃43; (NSInvocation *)invocationWithMethodSignature:(NSMethodSignature *)sig;- (NSMethodSignature *)methodSignature;- (void)retainArguments;
- (BOOL)argumentsRetained;- (id)target;
- (void)setTarget:(id)target;- (SEL)selector;
- (void)setSelector:(SEL)selector;- (void)getReturnValue:(void *)retLoc;
- (void)setReturnValue:(void *)retLoc;- (void)getArgument:(void *)argumentLocation atIndex:(NSInteger)idx;
- (void)setArgument:(void *)argumentLocation atIndex:(NSInteger)idx;- (void)invoke;
- (void)invokeWithTarget:(id)target;&＃64;end

NS_ROOT_CLASS
&＃64;interface NSProxy {Class isa;
}&＃43; (id)alloc;
&＃43; (id)allocWithZone:(NSZone *)zone NS_AUTOMATED_REFCOUNT_UNAVAILABLE;
&＃43; (Class)class;- (void)forwardInvocation:(NSInvocation *)invocation;
- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel;
- (void)dealloc;
- (void)finalize;
- (NSString *)description;
- (NSString *)debugDescription;
&＃43; (BOOL)respondsToSelector:(SEL)aSelector;- (BOOL)allowsWeakReference NS_UNAVAILABLE;
- (BOOL)retainWeakReference NS_UNAVAILABLE;// - (id)forwardingTargetForSelector:(SEL)aSelector;&＃64;end

#import
#include &＃64;interface TargetProxy : NSProxy {id realObject1;id realObject2;
}- (id)initWithTarget1:(id)t1 target2:(id)t2;&＃64;end&＃64;implementation TargetProxy- (id)initWithTarget1:(id)t1 target2:(id)t2 {realObject1 &＃61; [t1 retain];realObject2 &＃61; [t2 retain];return self;
}- (void)dealloc {[realObject1 release];[realObject2 release];[super dealloc];
}// The compiler knows the types at the call site but unfortunately doesn&＃39;t
// leave them around for us to use, so we must poke around and find the types
// so that the invocation can be initialized from the stack frame.// Here, we ask the two real objects, realObject1 first, for their method
// signatures, since we&＃39;ll be forwarding the message to one or the other
// of them in -forwardInvocation:. If realObject1 returns a non-nil
// method signature, we use that, so in effect it has priority.
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector {NSMethodSignature *sig;sig &＃61; [realObject1 methodSignatureForSelector:aSelector];if (sig) return sig;sig &＃61; [realObject2 methodSignatureForSelector:aSelector];return sig;
}// Invoke the invocation on whichever real object had a signature for it.
- (void)forwardInvocation:(NSInvocation *)invocation {id target &＃61; [realObject1 methodSignatureForSelector:[invocation selector]] ? realObject1 : realObject2;[invocation invokeWithTarget:target];
}// Override some of NSProxy&＃39;s implementations to forward them...
- (BOOL)respondsToSelector:(SEL)aSelector {if ([realObject1 respondsToSelector:aSelector]) return YES;if ([realObject2 respondsToSelector:aSelector]) return YES;return NO;
}&＃64;endint main(int argc, const char *argv[]) {NSAutoreleasePool *pool &＃61; [[NSAutoreleasePool alloc] init];// Create an empty mutable string, which will be one of the// real objects for the proxy.NSMutableString *string &＃61; [[NSMutableString alloc] init];// Create an empty mutable array, which will be the other// real object for the proxy.NSMutableArray *array &＃61; [[NSMutableArray alloc] init];// Create a proxy to wrap the real objects. This is rather// artificial for the purposes of this example -- you&＃39;d rarely// have a single proxy covering two objects. But it is possible.id proxy &＃61; [[TargetProxy alloc] initWithTarget1:string target2:array];// Note that we can&＃39;t use appendFormat:, because vararg methods// cannot be forwarded![proxy appendString:&＃64;"This "];[proxy appendString:&＃64;"is "];[proxy addObject:string];[proxy appendString:&＃64;"a "];[proxy appendString:&＃64;"test!"];NSLog(&＃64;"count should be 1, it is: %d", [proxy count]);if ([[proxy objectAtIndex:0] isEqualToString:&＃64;"This is a test!"]) {NSLog(&＃64;"Appending successful.", proxy);} else {NSLog(&＃64;"Appending failed, got: &＃39;%&＃64;&＃39;", proxy);}NSLog(&＃64;"Example finished without errors.");[pool release];return 0;
}