Syntax abuse in ObjC

syntax-abuse.m

#import <objc/runtime.h>

#import <Foundation/Foundation.h>

@interface NSObject ()

- (id)objectForKeyedSubscript:(id)key;

@end

@interface MyMagicObject : NSObject

- (id)initWithInteger:(NSInteger)value;
- (void(^)(NSInteger))magicMethod;

@end

@implementation MyMagicObject
{
    NSInteger _value;
    void(^_magicBlock)(NSInteger);
}

- (id)initWithInteger:(NSInteger)value
{
    if((self = [super init]))
    {
        _value = value;
        __weak MyMagicObject *weakSelf = self;
        _magicBlock = [^(NSInteger value){
            MyMagicObject *self = weakSelf;
            if(self == nil) return;
            NSLog(@"%ld and %ld", _value, value);
        } copy];

        Class cls = objc_allocateClassPair(object_getClass(_magicBlock), "MagicBlockClass", 0);

        IMP imp = imp_implementationWithBlock(^ id (id self, id key) {
            return [NSString stringWithFormat:@"Magic string: %@", key];
        });

        class_addMethod(cls, @selector(objectForKeyedSubscript:), imp, "@@:@");

        objc_registerClassPair(cls);

        object_setClass(_magicBlock, cls);
    }
    return self;
}

- (void(^)(NSInteger))magicMethod;
{
    return _magicBlock;
}

@end

int main(int argc, const char * argv[])
{
    @autoreleasepool
    {
        MyMagicObject *obj = [[MyMagicObject alloc] initWithInteger:42];

        obj.magicMethod(13);
        NSLog(@"Result: %@", ((id)obj.magicMethod)[@"Hello"]);
    }
    return 0;
}