Designated initializer : 特定構(gòu)造方法(方法聲明后面帶有NS_DESIGNATED_INITIALIZER)

 注意:子類如果重寫了父類的特定構(gòu)造方法, 那么必須使用super調(diào)用父類的特定構(gòu)造方法,
比如下面的系統(tǒng)構(gòu)造方法重寫時(shí),如果沒(méi)有調(diào)用super則會(huì)報(bào)錯(cuò)提示:
 Designated initializer missing a 'super' call to a designated initializer of the super class

- (instancetype)initWithFrame:(CGRect)frame
{
   if (self = [super initWithFrame:frame])
{
        self.titleLabel.font= [UIFontsystemFontOfSize:16];
      // 文字顏色
        [selfsetTitleColor:[UIColordarkGrayColor] forState:UIControlStateNormal];
        [selfsetTitleColor:[UIColorredColor] forState:UIControlStateSelected];
    }
    returnself;
}

如果不是構(gòu)造方法,也想讓子類重寫時(shí)不要忘記調(diào)用super,則可以使用NS_REQUIRES_SUPER

@interface XMGTest : NSObject
//模仿系統(tǒng)方法
- (instancetype)initWithName:(NSString *)name NS_DESIGNATED_INITIALIZER;
- (instancetype)initWithAge:(NSInteger)age NS_DESIGNATED_INITIALIZER;
//自己的方法,提示需要調(diào)用super
- (void)run NS_REQUIRES_SUPER;
@end