object_isClass 判断是否是一个不为空的类对象 ~~~ /** * Returns whether an object is a class object. * * @param obj An Objective-C object. * * @return true if the object is a class or metaclass, false otherwise. */ OBJC_EXPORT BOOL object_isClass(id obj) __OSX_AVAILABLE_STARTING(__MAC_10_10, __IPHONE_8_0); ~~~ ~~~ #import "ViewController.h" #import <objc/runtime.h> #import "Person.h" #import "Dog.h" @interface ViewController () @end @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. Person * p1 = [[Person alloc] init]; BOOL isp1 = object_isClass([p1 class]); Person * p2; BOOL isp2 = object_isClass([p2 class]); NSString * p3 = @"test"; BOOL isp3 = object_isClass([p3 class]); NSLog(@"%i", isp1); NSLog(@"%i", isp2); NSLog(@"%i", isp3); } ~~~ 输出：