Using NSProxy to perform operation on main thread easily

JTMainQueueProxy.h

//
//  JTMainQueueProxy.h
//
//  Created by James Tang on 02/10/2011.
//

#import <Foundation/Foundation.h>

@interface JTMainQueueProxy : NSProxy {
    id _proxiedTarget;
}

+ (id)proxy;
- (id)prepareInvocationWithTarget:(id)target;

@end

JTMainQueueProxy.m

//
//  JTMainQueueProxy.m
//
//  Created by James Tang on 02/10/2011.
//

#import "JTMainQueueProxy.h"

@implementation JTMainQueueProxy

- (id)init {
    return self;
}

- (void)dealloc {
    [_proxiedTarget release];
    [super dealloc];
}

#pragma mark Instance method

- (id)prepareInvocationWithTarget:(id)target {
    [_proxiedTarget autorelease], _proxiedTarget = nil;
    _proxiedTarget = [target retain];
    return self;
}

#pragma mark NSProxy

- (void)forwardInvocation:(NSInvocation *)invocation {
    [invocation setTarget:_proxiedTarget];
    [invocation performSelectorOnMainThread:@selector(invoke) withObject:nil waitUntilDone:YES];
}

- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel {
    return [_proxiedTarget methodSignatureForSelector:sel];
}

#pragma mark Class Methods

+ (id)proxy {
    JTMainQueueProxy *proxy = [[JTMainQueueProxy alloc] init];
    return [proxy autorelease];
}

@end