EASwizzler is an Objective-C class used for easy Method Swizzling, and it even supports swizzling methods on classes that are apart of a Class Cluster like NSArray and NSString.
Method Swizzling is a well worn technique for swapping method implementations, allowing you to modify methods in code you don't have access to, like Foundation or Cocoa.
For example, let's say you want to modify NSArray's lastObject method to log a message every time it was called. The first step is to create your own method implementation that has as different selector but conforms to the same return type and arguments. Create the custom method on a Category of NSArray, like this:
@interface NSArray (CustomLastObject)
- (id)custom_lastObject;
@end
@implementation NSArray (CustomLastObject)
- (id)custom_lastObject {
NSLog(@"lastObject was sent to %@", self);
return [self custom_lastObject];
}
@endNotice how inside of the custom_lastObject implementation, we are returning the result of [self custom_lastObject]. That's because after the swizzling occurs, the original implementation of lastObject will still be accessible by sending custom_lastObject.
Now we use EASwizzler to swizzle the class of an instance of NSArray:
[EASwizzler swizzleClassOfInstance:[[NSArray alloc] init]
replaceMethod:@selector(lastObject)
withMethod:@selector(custom_lastObject)];The reason we use swizzleClassOfInstance:replaceMethod:withMethod: instead of swizzleClass:replaceMethod:withMethod is because NSArray is apart of a class cluster and [[[NSArray alloc] init] class] isn't an NSArray, but __NSArrayI, so just trying to swizzle the NSArray class won't work.
Always use swizzleClassOfInstance with objects like NSString and NSArray. For almost everything else you can just use swizzleClass.
Pull requests are always welcome. There are no tests so don't worry about that ;)
MIT
Eric Allam