【iOS_Development】isKindOfClass && isMemberOfClass

API文档

• isKindOfClass

Returns a Boolean value that indicates whether the receiver is an instance of given class or an instance of any class that inherits from that class. (required)

• isMemberOfClass

Returns a Boolean value that indicates whether the receiver is an instance of a given class. (required)

异同点

相同点

都是NSObject的比较Class的方法

不同点

1. isKindOfClass来确定一个对象是否是一个类的成员，或者是派生自该类的成员
2. isMemberOfClass只能确定一个对象是否是当前类的成员
即isMemberOfClass不能检测任何的类都是基于NSObject类这一事实，而isKindOfClass可以

[[NSMutableData data] isKindOfClass:[NSData class]]; // YES 
[[NSMutableData data] isMemberOfClass:[NSData class]]; // NO 
例: 
- (void)testIsKindOfClass {     
    Class1 *c1=[[Class1 alloc] init];     
    if ([c1 isKindOfClass: [NSObject class]]) {         
        NSLog(@"c1 is a kind of NSObject.");     
    } 
    if ([c1 isMemberOfClass:[Class1 class]]) {         
        NSLog(@"c1 is Member of Class1 !");     
    } 
    if (![c1 isMemberOfClass:[NSObject class]]) {         
        NSLog(@"c1 is't Member of NSObject !");     
    } 
} 
输出结果： 
c1 is a kind of NSObject . 
c1 is Member of Class1 ! 
c1 is't Member of NSObject !

特殊情况

苹果官方文档有这样一段描述

Be careful when using this method on objects represented by a class cluster. Because of the nature of class clusters, the object you get back may not always be the type you expected. If you call a method that returns a class cluster, the exact type returned by the method is the best indicator of what you can do with that object. For example, if a method returns a pointer to an NSArray object, you should not use this method to see if the array is mutable, as shown in the following code:
// DO NOT DO THIS!

if ([myArray isKindOfClass:[NSMutableArray class]]) {
// Modify the object
}
If you use such constructs in your code, you might think it is alright to modify an object that in reality should not be modified. Doing so might then create problems for other code that expected the object to remain unchanged.

If the receiver is a class object, this method returns YES if aClass is a Class object of the same type, NO otherwise.

测试如下
NSArray *myArr = [[NSArray alloc] init];
NSMutableArray *myArr2 = [[NSMutableArray alloc] init];
if ([myArr isKindOfClass:[NSArray class]]) {
    NSlog(@"myArr isKindOfClass of NSArray");
}
if ([myArr isMemberOfClass:[NSArray class]]) {
    NSlog(@"myArr isMemberOfClass of NSArray");
}
if ([myArr2 isKindOfClass:[NSMutableArray class]]) {
    NSlog(@"myArr2 isKindOfClass of NSMutableArray");
}
if ([myArr2 isMemberOfClass:[NSMutableArray class]]) {
    NSlog(@"myArr2 isMemberOfClass of NSMutableArray");
}

输出结果：
myArr isKindOfClass of NSArray
myArr2 isKindOfClass of NSMutableArray

• 总结如下

1. NSArray、NSMutableArray属于类簇，使用isMemberOfClass不能得到正确的结果
   原因：由于类簇的性质，这类对象实际返回的实例有不确定性
2. NSArray对象可能会在运行时发现其实运作的是NSCFArray(来自Core Foundation框架(C语言的实现版本)，很多Cocoa对象都是如此做桥接的)
3. 对于类簇的判断要谨慎

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