iOS isKindOfClass，isMemberOfClass等

在iOS开发中,会遇到需要判断一个对象是否为某类的对象、是否能响应方法等，通过源码我们可以看一下它们区别是什么呢?

实现源码：

Class object_getClass(id obj)
{
    if (obj) return obj->getIsa();
    else return Nil;
}

+ (Class)class {
    return self;
}

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

+ (BOOL)isMemberOfClass:(Class)cls {
    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)instancesRespondToSelector:(SEL)sel {
    if (!sel) return NO;
    return class_respondsToSelector(self, sel);
}

+ (BOOL)respondsToSelector:(SEL)sel {
    if (!sel) return NO;
    return class_respondsToSelector_inst(object_getClass(self), sel, self);
}

- (BOOL)respondsToSelector:(SEL)sel {
    if (!sel) return NO;
    return class_respondsToSelector_inst([self class], sel, self);
}

由源码我们可以分析出：

• + (Class)class 和- (Class)class 均返回类本身
• + (BOOL)isMemberOfClass: 是判断该类的元类是否和class相等
• - (BOOL)isMemberOfClass: 判断该类是和class相等
• + (BOOL)isKindOfClass: 循环遍历该类的元类的父类，判断是否和class相等
• - (BOOL)isKindOfClass: 循环遍历该类的父类，判断是否和class相等
• + (BOOL)instancesRespondToSelector 该类是否能响应实例方法
• + (BOOL)respondsToSelector: 该类是能否响应类方法
• - (BOOL)respondsToSelector: 该对象是否能响应实例方法