Add subview programmatically using instance method - ios

Question

I am trying to add a subview programmatically to my ViewController : UIViewController by using a method declared in my ThirdClass : NSObject class. Here is my code:
In the ViewController.m file I do:
- (void)viewDidLoad {
[super viewDidLoad];
ThirdClass *instanceOfThirdClass = [[ThirdClass alloc] init];
[instanceOfThirdClass createView];
}
And in my ThirdClass.m I declare the instance method:
-(void)createView{
NSLog(#"enter create app");
UIView *myView = [[UIView alloc]initWithFrame:CGRectMake(50, 0, 320, 100)];
[myView setBackgroundColor:[UIColor redColor]];
ViewController *instanceOfViewController = [[ViewController alloc]init];
[instanceOfViewController.view addSubview:myView];
}
so the problem apparently is that I was trying to add the created view to the class instance, the correct way to do it is the one posted by #gary-riches below,

Answer 1

You are attaching the view you create to a new instantiated view controller, but the view you are displaying is that of the one belonging ViewController.m. You need to add the view to the ViewController.m's view.
Update your createView method to handle a view:
-(void)createViewInView:(UIView *)aView{
NSLog(#"enter create app");
UIView *myView = [[UIView alloc]initWithFrame:CGRectMake(50, 0, 320, 100)];
[myView setBackgroundColor:[UIColor redColor]];
[aView addSubview:myView];
}
Then change your call to be:
[instanceOfThirdClass createViewInView:self.view];
Also, make sure you have the method signature in the header of ThirdClass.h. It should be:
-(void)createViewInView:(UIView *)aView;