Add UIView to a view controller from another class

Question

I am trying to add a UIView to a view controller, but through an object of another class whose objects are currently present on the view controller in question.

myViewController is on screen -> It has objects of myNodeView added to it. I click on myNodeView and call a method in myViewController class to add a view to it.

I instantiate using myVc = [[myViewController alloc]init]; and then call the method. Is this the problem, that this is a new instance and that's why it does not add to the view currently visible. Please help me out.

Code - 
    // in nodeView
    -(void)loadMap{


    if(myVc==nil){
        myVc=[[MyViewController alloc]init];
    }
    [myVc loadMapView];


}


// in MyViewController
-(void)loadMapView
{
    if(mapView==nil)
        {
            self.mapView = [[MapView alloc]initWithFrame:CGRectMake(0, 0, 400, 400)];
            self.mapView.backgroundColor=[UIColor whiteColor];

        }
        [self.view addSubview:self.mapView];
}

Answer 1

You are creating a new instance of MyViewController each time you call loadMap method. You can do something like this:

// Getting current viewcontroller
UIViewController *topController = [UIApplication sharedApplication].keyWindow.rootViewController;

while (topController.presentedViewController)
    topController = topController.presentedViewController;

// Call the method
MyViewController *myVc = (MyViewController *)topController;
[myVc loadMapView];

Answer 2

In MyViewcontroller, when you create the nodeView, you should be assigning the nodeView's myVc property, like this nodeView.myVc = self.

You should also make sure that nodeView's myVc property is assign.

You also don't need to check if myVc == nil in the nodeView.

Answer 3

我认为使MyViewController是childViewController（实现一个容器视图控制器）在传递视图和事件的行为方面更具可预测性。