playing with imp_implementationWithBlock

imp.m

//
//  imp.m
//  imp
//
//  Copyright (c) 2012 Matt Rajca. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <objc/runtime.h>

@interface Person : NSObject

- (void)sayHello;

@end


@implementation Person

- (void)sayHello {
	NSLog(@"hello");
}

@end


int main(int argc, const char *argv[])
{
	@autoreleasepool {
		Person *person = [[Person alloc] init];
		[person sayHello];
		
		IMP a = imp_implementationWithBlock(^{
			NSLog(@"hello again");
		});
		
		class_replaceMethod([Person class], @selector(sayHello), a, NULL);
		
		[person sayHello];
	}
	
	return 0;
}