(iOS) Swizzling Image Example

NSObject+Swizzling.h

#import <Foundation/Foundation.h>

@interface NSObject (Swizzling)


+ (void)swizzleInstanceSelector:(SEL)originalSelector
                withNewSelector:(SEL)newSelector;


@end

NSObject+Swizzling.mm

#import "NSObject+Swizzling.h"

@implementation NSObject (Swizzling)

+ (void) swizzleInstanceSelector:(SEL)originalSelector
                 withNewSelector:(SEL)newSelector
{
    Method originalMethod = class_getClassMethod(self, originalSelector);
    Method newMethod = class_getClassMethod(self, newSelector);

        method_exchangeImplementations(originalMethod, newMethod);

}


@end

UIImage+Swizzling.h

#import <UIKit/UIKit.h>

@interface UIImage (UIImage_ImageProvider)

+(UIImage *)realImageNamed:(NSString *)name;

@end

UIImage+UIImage+Swizzling..mm

#import "UIImage+UIImage_ImageProvider.h"
#import "NSObject+Swizzling.h"


@implementation UIImage (UIImage_ImageProvider)

+ (void)load {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        [self swizzleInstanceSelector:@selector(imageNamed:)
                      withNewSelector:@selector(realImageNamed:)];
    });
}



+(UIImage *)realImageNamed:(NSString *)name {
    
    NSString *dataPath = [documentsDirectory stringByAppendingPathComponent:someImagePath];
    UIImage *img = [UIImage imageWithContentsOfFile:dataPath];
    
    if (img) {
        return img;
    }
    else {
        
        //Load the default
        return img= [self realImageNamed:name];
    }
}

@end