swizzling class for oBj-c

swizzler.m

//
//  Swizzler.m
//  ZombieFarm
//
//  Created by Stephen Altamirano on 8/16/12.
//  Copyright (c) 2012 playforge. All rights reserved.
//

#import <objc/runtime.h>
#import "Swizzler.h"

// hidden class
@interface SwizzleState : NSObject
- (id)initWithMethod:(Method)m implementation:(IMP)i;
- (void)revert;
@end

@implementation SwizzleState
{
    Method originalMethod;
    IMP originalImplementation;
}

- (id)initWithMethod:(Method)m implementation:(IMP)i
{
    if (self = [super init])
    {
        originalMethod = m;
        originalImplementation = i;
    }
    return self;
}

- (void)revert
{
    method_setImplementation(originalMethod, originalImplementation);
}
@end


@implementation Swizzler
{
    NSMutableArray* history;
}

- (void)replaceClassMethod:(SEL)action
                  forClass:(Class)target
                 fromClass:(Class)source
{
    Method originalMethod = class_getClassMethod(target, action);
    IMP originalImplementation = method_getImplementation(originalMethod);

    Method replacementMethod = class_getClassMethod(source, action);
    IMP replacementImplementation = method_getImplementation(replacementMethod);

    method_setImplementation(originalMethod, replacementImplementation);

    SwizzleState* state = [[SwizzleState alloc] initWithMethod:originalMethod
                                                 implementation:originalImplementation];

    [history addObject:[state autorelease]];

}

- (void)replaceInstanceMethod:(SEL)action
                     forClass:(Class)target
                    fromClass:(Class)source
{
    Method originalMethod = class_getInstanceMethod(target, action);
    IMP originalImplementation = method_getImplementation(originalMethod);

    Method replacementMethod = class_getInstanceMethod(source, action);
    IMP replacementImplementation = method_getImplementation(replacementMethod);

    method_setImplementation(originalMethod, replacementImplementation);

    SwizzleState* state = [[SwizzleState alloc] initWithMethod:originalMethod
                                                 implementation:originalImplementation];

    [history addObject:[state autorelease]];
}

- (void)undoReplacements
{
    SwizzleState* state;
    for (int i = [history count] - 1, l = 0; i >= l; i--)
    {
        state = [history objectAtIndex:i];
        [state revert];
    }
    [history removeAllObjects];
}

- (void)dealloc
{
    [self undoReplacements];
    [history release];
}

@end