class和superclass源码(runtime源码里有)

Foundation框架里NSObject框架里的有些基础方法是开源的，
objc4源码链接 https://opensource.apple.com/tarballs/objc4/
在源码里搜索NSOject.mm文件，然后搜索class就找到源码了
class的作用是获取对象的类对象，superclass的作用是获取父类。

源码

+ (Class)class {
    return self;
}

- (Class)class {
    return object_getClass(self);
}

+ (Class)superclass {
    return self->superclass;
}

- (Class)superclass {
    return [self class]->superclass;
}

isMemberOfClass

左边对象的类对象是否等于右边的类对象

isKindOfClass

左边的类对象是否是等于右边类对象，或者是右边类对象的子类

源码

重点

看调用方法的是实例对象还是类对象，或者说看是类方法还是对象方法，类方法调用的话，object_getClass((id)self)，这行代码得到的是元类对象，那右边传入的类也应该是元类对象才会相等。右边传入的如果是NSObject，只要左边是NSObject的子类，一般是成立的。

+ (BOOL)isMemberOfClass:(Class)c ls {
    return object_getClass((id)self) == cls;
}

- (BOOL)isMemberOfClass:(Class)cls {
    return  [self class] == cls;
}

+ (BOOL)isKindOfClass:(Class)cls {
    for (Class tcls = object_getClass((id)self); tcls; tcls = tcls->superclass) {
        if (tcls == cls) return YES;
    }
    return NO;
}

- (BOOL)isKindOfClass:(Class)cls {
    for (Class tcls = [self class]; tcls; tcls = tcls->superclass) {
        if (tcls == cls) return YES;
    }
    return NO;
}

+ (BOOL)isSubclassOfClass:(Class)cls {
    for (Class tcls = self; tcls; tcls = tcls->superclass) {
        if (tcls == cls) return YES;
    }
    return NO;
}