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

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.

Answer 3

Not sure what you tried to accomplish.
But let's say you are in the view1 and want to create another view (view2) with your UILabel lbl added to this view2. Here are what you would do:
UIView *view2 = [[UIView alloc] initWithFrame:CGRectMake(x, y, w, h)]; //x,y, w h are for your view2
[view addSubview:lbl];
[self.view addSubview:view2]; //self is your current viewcontroller - you add view2 on top of view1
On the other hand if you already have a ViewController class ViewController2.h, ViewController2.m and a ViewController2.xib defined. Here are what you would do:
ViewController2 *viewController2 = [[ViewController2 alloc] initWithNibName:#"ViewController2" bundle:nil];
[viewController2.view addSubview:lbl];
[self.view addSubview:viewController2.view]; //same as before, you need to add viewController2's view to the current view
Hope this help.