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编写高质量OC代码52建议总结:10.关联对象

2019-11-09 15:27:57
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  OBJC_EXPORT void objc_setAssociatedObject(id object, const void *key, id value, objc_AssociationPolicy policy)  OBJC_EXPORT id objc_getAssociatedObject(id object, const void *key)  OBJC_EXPORT void objc_removeAssociatedObjects(id object)    注意:

  1.可以通过关联对象机制把两个对象连起来。

  2.定义关联对象时可指定内存管理语义,定义属性时采用的“拥有关系”与“非拥有关系”。

  3.只有在其他办法都没用的时候再引入关联对象,这种做法通常会产生难以查找的BUG。

关联策略

/**         *  OBJC_ASSOCIATION_ASSIGN              等价于@PRoperty (assign) ,                 @property (unsafe_unretained)            弱引用关联对象                  *  OBJC_ASSOCIATION_RETAIN_NONATOMIC            等价于@property (strong, nonatomic)            强引用关联对象,且为非原子操作                  *  OBJC_ASSOCIATION_COPY_NONATOMIC            等价于@property (copy, nonatomic)            复制关联对象,且为非原子操作                           *  OBJC_ASSOCIATION_RETAIN            等价于@property (strong, atomic)            强引用关联对象,且为原子操作                  *  OBJC_ASSOCIATION_COPY            等价于@property (copy, atomic)            复制关联对象,且为原子操作                  其中,第 2 种与第 4 种、第 3 种与第 5 种关联策略的唯一差别就在于操作是否具有原子性。         */        objc_setAssociatedObject(button, buttonKey, _imgView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

例:

1、倒入头文件,声明key:

#import <objc/runtime.h>char* const buttonKey = "buttonKey";2、设置关联:

if (groupModel.isOpened) {        UIImageView * _imgView = [[UIImageView alloc]initWithFrame:CGRectMake(10, (44-16)/2, 14, 16)];        [_imgView setImage:[UIImage imageNamed:@"ico_list"]];        [sectionView addSubview:_imgView];        CGAffineTransform currentTransform = _imgView.transform;        CGAffineTransform newTransform = CGAffineTransformRotate(currentTransform, M_PI/2); // 在现在的基础上旋转指定角度        _imgView.transform = newTransform;        objc_setAssociatedObject(button, buttonKey, _imgView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);    }else{        UIImageView * _imgView = [[UIImageView alloc]initWithFrame:CGRectMake(10, (44-16)/2, 14, 16)];        [_imgView setImage:[UIImage imageNamed:@"ico_list"]];        [sectionView addSubview:_imgView];        objc_setAssociatedObject(button, buttonKey, _imgView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);    }3、获取关联:

- (void)buttonPress:(UIButton *)sender//headButton点击{    GroupModel *groupModel = dataSource[sender.tag];    UIImageView *imageView =  objc_getAssociatedObject(sender,buttonKey);    if (groupModel.isOpened) {            [UIView animateWithDuration:0.3 delay:0.0 options:UIViewAnimationOptionTransitionNone animations:^{                CGAffineTransform currentTransform = imageView.transform;                CGAffineTransform newTransform = CGAffineTransformRotate(currentTransform, -M_PI/2); // 在现在的基础上旋转指定角度                imageView.transform = newTransform;            } completion:^(BOOL finished) {                            }];                            }else{                    [UIView animateWithDuration:0.3 delay:0.0 options: UIViewAnimationOptionAllowUserInteraction |UIViewAnimationOptionCurveLinear animations:^{                CGAffineTransform currentTransform = imageView.transform;                CGAffineTransform newTransform = CGAffineTransformRotate(currentTransform, M_PI/2); // 在现在的基础上旋转指定角度                imageView.transform = newTransform;                        } completion:^(BOOL finished) {                            }];        }    groupModel.isOpened = !groupModel.isOpened;    [expandTable reloadSections:[NSIndexSet indexSetWithIndex:sender.tag] withRowAnimation:UITableViewRowAnimationAutomatic];}


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