runtime动态创建类和对象

如图

- (void)viewDidLoad {
    [super viewDidLoad];
    //定义一个 Person 类, 继承自 NSObject
    Class Person = objc_allocateClassPair([NSObject class], "Person", 0);
    //添加属性
    objc_property_attribute_t type = { "T", "@\"NSString\"" };
    objc_property_attribute_t ownership = { "C", "" }; // C = copy
    objc_property_attribute_t backingivar  = { "V", "_privateName" };
    objc_property_attribute_t attrs[] = { type, ownership, backingivar };
    class_addProperty(Person, "name", attrs, 3);
    //添加方法
    class_addMethod(Person, @selector(name), (IMP)nameGetter, "@@:");
    class_addMethod(Person, @selector(setName:), (IMP)nameSetter, "v@:@");
    //注册该类
    objc_registerClassPair(Person);
    
    //获取实例
    id instance = [[Person alloc] init];
    NSLog(@"%@", instance);
    [instance setName:@"hxn"];
    
    NSLog(@"%@", [instance name]);
    
    
}
//get方法
NSString *nameGetter(id self, SEL _cmd) {
    Ivar ivar = class_getInstanceVariable([self class], "_privateName");
    return object_getIvar(self, ivar);
}
//set方法
void nameSetter(id self, SEL _cmd, NSString *newName) {
    Ivar ivar = class_getInstanceVariable([self class], "_privateName");
    id oldName = object_getIvar(self, ivar);
    if (oldName != newName) object_setIvar(self, ivar, [newName copy]);
}