oc的关联的作用在我看来就是将两个对象关联起来,用的时候通过key和对象把和这个对象关联的对象再取出来(我做的项目就是和UITableView里面的一个属性关联起来了)
举个栗子:
- (void)viewDidLoad {
[super viewDidLoad];
UIButton * button = [UIButton buttonWithType:UIButtonTypeCustom];
button.frame = CGRectMake(100, 100, 100, 100);
[button setTitle:@"关联测试" forState:UIControlStateNormal];
[button setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
[button addTarget:self action:@selector(buttonTap) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:button];
}
- (void)buttonTap{
UIAlertView * alert = [[UIAlertView alloc] initWithTitle:@""
message:@"How (are) you doing" delegate:self cancelButtonTitle:@"Not bad" otherButtonTitles:@"Fine", nil];
void (^block)(NSInteger) = ^(NSInteger buttonIndex){
if (buttonIndex == 0) {
NSLog(@"buttonIndex:0");
}else{
NSLog(@"buttonIndex:1");
}
};
objc_setAssociatedObject(alert, key, block, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
[alert show];
}
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{
void (^block)(NSInteger) = objc_getAssociatedObject(alertView, key);
block(buttonIndex);
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
}
@end
OBJC_ASSOCIATION_ASSIGN | @property (assign) or @property (unsafe_unretained) | Specifies a weak reference to the associated object. |
OBJC_ASSOCIATION_RETAIN_NONATOMIC | @property (nonatomic, strong) | Specifies a strong reference to the associated object, and that the association is not made atomically. |
OBJC_ASSOCIATION_COPY_NONATOMIC | @property (nonatomic, copy) | Specifies that the associated object is copied, and that the association is not made atomically. |
OBJC_ASSOCIATION_RETAIN | @property (atomic, strong) | Specifies a strong reference to the associated object, and that the association is made atomically. |
OBJC_ASSOCIATION_COPY | @property (atomic, copy) | Specifies that the associated object is copied, and that the association is made atomically. |
参考链接:http://nshipster.com/associated-objects/
http://kingscocoa.com/tutorials/associated-objects/