gistfile1.m

+ (NSInvocation *)invocationWithTarget:(id)target action:(SEL)selector arguments:(NSArray *)arguments retainArguments:(BOOL)retainArguments {
    NSMethodSignature *signature = nil;

    if (isClass(target)) {
        signature = [target methodSignatureForSelector:selector];
    } else {
        signature = [[target class] instanceMethodSignatureForSelector:selector];
    }

    NSInvocation *invocation = [self invocationWithMethodSignature:signature];
    [invocation setTarget:target];
    if (retainArguments) {
        [invocation retainArguments];
    }
    
    NSInteger index = 2;
    for (id argument in arguments) {
        [invocation setArgument:&argument atIndex:index++];
    }
    
    return invocation;
}