iOS的super

isKindOfClass

isMemberClass

@implementation Teacher

-(id)init
{
      self = [super init];
      if (self) {
        [self class];//  Teacher
        [self superclass]; // NSObject
// 这两块，打印输出是一样的？
        [super class];  // Teacher
        [super superclass];//  NSobject
        // objc_msgSuper( { self, 父类 } ,  selector()) ;
      }
}

@end

• 这时候要看一下 objc_super的源代码了
  • [super class] [self class] 里 class 的方法实现都在NSObject里
  • -(Class)class 的实现，objc_getClass(self)，返回值取决于 self是谁，取决于消息机制
  • 消息接收者仍然子类对象，只不过是从父类里开始查找方法，objc_msgSuper( { self, 父类 } , selector()) ;

struct objc_super {
    /// Specifies an instance of a class.
    __unsafe_unretained _Nonnull id receiver;

    /// Specifies the particular superclass of the instance to message. 
#if !defined(__cplusplus)  &&  !__OBJC2__
    /* For compatibility with old objc-runtime.h header */
    __unsafe_unretained _Nonnull Class class;
#else
    __unsafe_unretained _Nonnull Class super_class;
#endif
    /* super_class is the first class to search */
};