#import <objc/runtime.h>

UIButton *btn = // create the button

objc_setAssociatedObject(btn, "firstObject", obj, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

[btn addTarget:self action:@selector(onClick:) forControlEvents:UIControlEventTouchUpInside];  

- (void)click:(UIButton *)sender

{

    id first = objc_getAssociatedObject(btn, "firstObject"); //取参

}