Method Swizzle on iPhone device

Question

I tried both JRSwizzle, and MethodSwizzle. They compile fine on the simulator but throw a bunch of errors when I try to compile for Device (3.x)

How do we do swizzling on the iPhone? What's the trick?

Answer 1

The CocoaDev wiki has an extensive discussion on method swizzling here. Mike Ash has a relatively simple implementation at the bottom of that page:

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

void Swizzle(Class c, SEL origSelector, SEL newSelector)
{
    Method origMethod = class_getInstanceMethod(c, origSelector);
    Method newMethod = class_getInstanceMethod(c, newSelector);
    if(class_addMethod(c, origSelector, method_getImplementation(newMethod), method_getTypeEncoding(newMethod)))
        class_replaceMethod(c, newSelector, method_getImplementation(origMethod), method_getTypeEncoding(origMethod));
    else
        method_exchangeImplementations(origMethod, newMethod);
}

I have not tested this, simply because I regard method swizzling as an extremely dangerous process and haven't had the need to use it yet.