How to perform a [self.view addSubview: lbl] outside of ViewController Class scope?

Question

How to perform a [self.view addSubview: lbl] outside of ViewController Class scope ?

or:

How do I add a label or another view in the mainview, outside of the ViewController class, in a different class?

thanks

- (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

Well, view is just a property of the UIViewController class. Assuming that you have your UIViewController *controller variable somewhere, you can just use

[controller.view addSubview:subview]

Answer 2

The reason that [v.viewController.view addSubview:lbl]; doesn't work is that v is a new instance of calcRomanAppDelegate. Every application has a shared instance of the app delegate, that can be accessed via [[NSApplication sharedApplication] delegate]. Therefore, your code would become:

calcRomanAppDelegate *v = (calcRomanAppDelegate *)[[NSApplication sharedApplication] delegate]; 
[v.viewController.view addSubview:lbl]; // this compiles but shows a blank form

Also In the code that you wrote, I will point out that the new method returns an initialized object, so you do not need the extra call to init in [[calcRomanAppDelegate new] init]. Instead of using the new method, I suggest using alloc, which doesn't call the initializer. Obviously that is not the issue in this particular case, but it's an important thing to know.