instancesRespondToSelector与respondsToSelector的区别

Test1.h

@interface Test1 : NSObject

- (void)objectFun;

+ (void)classFun;

@end

Test1.m

@implementation Test1

- (void)objectFun
{
    NSLog(@"object function");
}

+ (void)classFun
{
    NSLog(@"class function");
}

@end

测试类：

BOOL flag;

flag = [Test1 instancesRespondToSelector:@selector(objectFun)]; //YES

flag = [Test1 instancesRespondToSelector:@selector(classFun)]; //NO

flag = [Test1 respondsToSelector:@selector(objectFun)]; //NO

flag = [Test1 respondsToSelector:@selector(classFun)]; //YES

Test1 *obj = [[Test1 alloc] init];

flag = [obj respondsToSelector:@selector(objectFun)]; //YES

flag = [obj respondsToSelector:@selector(classFun)]; //NO

总结：

1. instancesRespondToSelector只能写在类名后面，respondsToSelector可以写在类名和实例名后面。

2. [类 instancesRespondToSelector]判断的是该类的实例是否包含某方法，等效于：[该类的实例 respondsToSelector]。

3. [类 respondsToSelector]用于判断是否包含某个类方法。