objective-c - 如何执行 [self.view addSubview : lbl] outside of ViewController Class scope?

Question

如何在 ViewController 类范围之外执行 [self.view addSubview: lbl]？

或:

如何在 ViewController 类之外的主视图中的不同类中添加标签或其他 View ？

谢谢

- (void)viewDidLoad { 
    [super viewDidLoad]; 

    UILabel *lbl = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 100, 100)]; 
    [lbl setText:@"hi there"];

    [self.view addSubview:lbl];// <-- this works, but ...
        // what is "self" referring to? 
        // and how can I declare and call from another class? 

    ...


    UILabel *lbl = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 100, 100)]; 
    [lbl setText:@"hi there"];

    calcRomanAppDelegate *v = [[calcRomanAppDelegate new] init]; 
    [v.viewController.view addSubview:lbl]; // this compiles, but...
         // fails to shows a label on the form

     ...


    UILabel *lbl = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 100, 100)]; 
    [lbl setText:@"hi there"];

    calcRomanViewController *v = [[calcRomanViewController new] init];
    [v.view addSubview:lbl]; // this just makes a call back to viewDidLoad... endless loop

}

Answer 1

好吧，view 只是 UIViewController 类的一个属性。假设你的 UIViewController *controller 变量在某处，你可以使用

[controller.view addSubview:subview]