如何判断一个类是系统的类，还是自定义的类

customClass *_customClass = [[customClass alloc] init];
    
    NSBundle *mainB = [NSBundle bundleForClass:[_customClass class]];
    if (mainB == [NSBundle mainBundle]) {
        NSLog(@"自定义的类");
    }else
    {
        NSLog(@"系统的类");
    }