Swizzle methods in Objective-C

swizzle.m

#import <objc/runtime.h>


static void SwizzleClassMethod(Class klass, SEL original, SEL new)
{
    Method origMethod = class_getClassMethod(klass, original);
    Method newMethod = class_getClassMethod(klass, new);

    if (class_addMethod(klass, original, method_getImplementation(newMethod), method_getTypeEncoding(newMethod))) {
        class_replaceMethod(klass, new, method_getImplementation(origMethod), method_getTypeEncoding(origMethod));
    } else {
        method_exchangeImplementations(origMethod, newMethod);
    }
}

static void SwizzleInstanceMethods(Class klass, SEL original, SEL new)
{
    Method origMethod = class_getInstanceMethod(klass, original);
    Method newMethod = class_getInstanceMethod(klass, new);

    if (class_addMethod(klass, original, method_getImplementation(newMethod), method_getTypeEncoding(newMethod))) {
        class_replaceMethod(klass, new, method_getImplementation(origMethod), method_getTypeEncoding(origMethod));
    } else {
        method_exchangeImplementations(origMethod, newMethod);
    }
}