函数指针

    // Call the selector 函数指针
    id result = nil;
    IMP imp = [self methodForSelector:selector];
    if (imp) {
        id(*func)(id, SEL, id, WACallback) = (void *)imp;
        result = func(self, selector, parameter, callback);
    }

-(id)viewImage:(id)parameter callback:(WACallback)callback
{
}