在Objective-C的Category中使用属性的懒加载在Objective-C的Category中使用属性

@interface VC (Pay) @property (nonatomic, strong) PayView *choiceView; @end

两种写法：
1，使用指针

#import static void *choiceViewKey = &choiceViewKey; @implementation VC (Pay) - (PayTypeView *)choiceView { PayTypeView *choiceView = objc_getAssociatedObject(self, choiceViewKey); if (!choiceView) { choiceView = [[NSBundle mainBundle] loadNibNamed:@"PayTypeView" owner:nil options:nil].firstObject; choiceView.frame = self.view.window.frame; [choiceView.alipayTap addTarget:self action:@selector(alipayAction)]; [choiceView.wechatPayTap addTarget:self action:@selector(wechatAction)]; objc_setAssociatedObject(self, choiceViewKey, choiceView, OBJC_ASSOCIATION_RETAIN_NONATOMIC); }return choiceView; } - (void)setChoiceView:(PayTypeView *)choiceView { objc_setAssociatedObject(self, choiceViewKey, choiceView, OBJC_ASSOCIATION_RETAIN_NONATOMIC); }@end

2，使用@selector()

#import @implementation VC (Pay) - (PayView *)choiceView { PayView *choiceView = (PayView *)objc_getAssociatedObject(self, @selector(choiceView)); if (!choiceView) { choiceView = [[NSBundle mainBundle] loadNibNamed:@"PayView" owner:nil options:nil].firstObject; choiceView.frame = self.view.window.frame; [choiceView.alipayTap addTarget:self action:@selector(pay)]; objc_setAssociatedObject(self, @selector(choiceView), choiceView, OBJC_ASSOCIATION_RETAIN_NONATOMIC); } return choiceView; } @end - (void)setChoiceView:(PayView *)choiceView { objc_setAssociatedObject(self, @selector(choiceView), choiceView, OBJC_ASSOCIATION_RETAIN_NONATOMIC); }

【在Objective-C的Category中使用属性的懒加载】注意：

对于普通的OC对象, 通常采用OBJC_ASSOCIATION_RETAIN_NONATOMIC.

对于NSString等通常采用copy关键字的属性, 通常采用OBJC_ASSOCIATION_COPY_NONATOMIC.

对于枚举等通常采用assign关键字的属性, 通常采用OBJC_ASSOCIATION_ASSIGN.

参考:

在Objective-C的Category中使用属性的懒加载

另外：

在Category的.m中，写一个类的声明，重写一个同名属性，可以使用VC中的属性，这样也不需要再另外写getter/setter方法。

vc的.m中

@interface VC () @property (copy, nonatomic) NSString * price; @end

vc的Category的.m中

@interface VC () @property (copy, nonatomic) NSString * price; @end @implementation VC (Pay) - (void)payWithPrice:(NSString *)price completion:(PayBlock)completion { self.price = price; } @end