runtime-object_setClass

object_setClass 可以将一个对象的类进转换

例如类Person

@implementation Person

@interface Person : NSObject
- (void)name;
@end

@implementation Person
- (void)name {
    NSLog(@"name");
}
@end

@interface Test : NSObject
- (void)eat;
@end

@implementation Test

- (void)eat {
    NSLog(@"eat");
}

@end

将Person对象的类转到Test上面

    Person *p = [Person new];
    object_setClass(p, [Test class]);
    [p performSelector:@selector(eat)];
    [p name];

打印如下

TESTRuntime[2053:65068] eat
TESTRuntime[2053:65068] -[Test name]: unrecognized selector sent to instance 0x600001dd4460

p进行类装换后, 不能在执行原来Person类的对象方法了, 只能执行Test类的对象方法