There is a ViewController1 which has a stackView.
I created an instance of ViewController2 and added it's view as a subview to the stackView of ViewController1, I wanted to see if only by doing this does viewDidLoad of ViewController2 is invoked and it did so, ViewController2 viewDidLoad was invoked when I added view of ViewController2 to stackView of ViewController1. For ex: In ViewController1self.stackView.addArrangedSubView(viewControler2.view)
Then why do we need to do addChild(viewController2) then add view as subview, those typical lines which adds childController and it's view in parent view controller hierarchy
Certainly viewDidLoad was called. That happened instantly as soon as you referred to ViewController2's view in your code.
But let's say your ViewController2 does other things besides load a view. Suppose its view contains a button that is hooked through an action to a function in ViewController2. If you now tap that button nothing happens.
That's because the ViewController2 itself is dead: it has vanished in a puff of smoke.
You can see that by implementing deinit in ViewController2. You will see that, just as viewDidLoad is called, so is deinit. You are left with a view controller's view that has no view controller. That is bad.
There is a view controller hierarchy that is responsible for maintaining relations between view controllers. When you add ViewController2 as a child view controller of ViewController1, you maintain that hierarchy, and you maintain it correctly according to the rules, which say:
If VC2's view is somewhere inside VC1's view, then VC2 needs to be a child (at some depth) of VC1.
In other words, the view hierarchy and the view controller hierarchy must run together. Otherwise, the responder chain will break and life will become chaos.
(There are other requirements when you make one view controller the child of another, like sending didMoveToParent to the child as part of the opening dance, along with other message forwarding responsibilities later, so as to ensure that the child view controller gets other messages like viewDidAppear at the right time. It's a complex business. However, I've focussed my answer on the very basic part of what you asked.)
I should add: if your goal was merely to fetch a view out of a nib and stuff it into your own view, you can certainly do that, no problem. What you must not do is use a view controller as a kind of magnet or vacuum cleaner to fetch a view for you if your intention is then to let go of the view controller itself.
I have 2 ViewControllers.
VC1 has a 2 views inside it.
I want to get MenuUIVC to appear in one of my views belonging(child) to VC1.
I tried this code inside of VC1 but it didn't work.
MenuUIVC * menuViewVC = [[MenuUIVC alloc] init];
menuUIView = menuViewVC.view;
I expected to be able to see the MenuUIVC inside the view (menuUIView) which is a child of VC1. I have the IBOutlets all hooked up on the storyboard.
You can use Container views to get View Controller inside a View Controller. And, you can get the reference to it through prepareForSegue() method.
Links for description:
iOS Container View
The Easy Way to Switch Container Views in iOS
If you are using UIView, then why don't you use
[menuUIView addSubview:menuViewVC.view];
Another option is to use childviewcontrollers.
See these links for example:-
adding view controller as child view in ios
Add child view controller to current view controller
Using container or child view controller, gives you full fledge option of using View Controller properties, which you will not get in UIView.
Say for example, you can you orientation delegate methods, which you can't using in UIView class directly.
Hope this can help you.
Cheers
Sanjay
you can go for container view if you want to do it using IBOutlets & storyborad.
but if you want to do it using code then follow the below steps :
initialise & create parent view controller.
then add required child view as a subview with negative frame.
now change the frame with UIView animation whenever required. & do add tap gesture recogniser on part of screen other than the child view to remove it back to the initial position.
self.navigationController!.popViewControllerAnimated(true)
So in above line i am having confusion that why I am getting navigation controller instance in the current class. According to the storyboard, navigation controller is present outside this class, but how come are we accessing the navigation controller in the current class?
The current viewController is being managed by the navigationController.
You could think of it in a similar way to a parent / child relationship. The navigationController is somewhat functioning like the parent of the viewController.
That property provides a reference to the navigationController provided it exists. In the same way you can say view.superView to access the parent view that the current view is inside.
I just tried it out and it doesn't seem to work, see picture. However, there is error or warning, and since a reference is a view controller - should it be possible?
Setting up a parent/child relationship with a container view is easy.Just create a container view inside the parent ViewController, create the child view controller scene, and then control-drag from the container view to the child view controller to create the embed segue.
If you want to swap the child view controllers depending on some condition, i.e. multiple child view controllers, just create a custom segue. This custom segue is named Empty and is a subclass of UIStoryboardSegue with empty perform method.
Both the methods add the view as child of parentview and view can receive events. When to use which one?
It all depends on how you want to manage the new subview. If you want the new subview to be managed by the current view's view controller (e.g. you're adding something simple like a few UILabel objects), you simply call addSubview. If, on the other hand, the new subview has its own view controller (i.e. it's sufficiently complicated collection of views, with rich functionality, that you want to encapsulate all of this complexity with its own controller to manage everything this new subview does) then you call addChildViewController to add the new view controller, but then call addSubview, too.
So, note that addChildViewController, itself, does nothing with the views. You generally immediately follow it with calls that add its view, too, e.g. here is a slightly clarified example from the Implementing a Custom Container View Controller section of the View Controller Programming Guide for iOS:
[self addChildViewController:childViewController]; // add subview's view controller
childViewController.view.frame = ... // specify where you want the new subview
[self.view addSubview:childViewController.view]; // now you can add the child view controller's view
[childViewController didMoveToParentViewController:self]; // now tell the child view controller that the adding of it and its views is all done
So, it's not a question of addSubview vs addChildViewController, but rather addSubview vs addChildViewController+addSubview. If you call addChildViewController, you're doing so with the intent of calling addSubview for its view at some point.
Frankly, this question of addSubview vs. addChildViewController+addSubview is rarely how we think about this. A more logical way of thinking of this is determine whether this new view has its own view controller. If it does, you perform the addChildViewController sequence of calls. If not, you just call addSubview.
For a good introduction to view controller containment (e.g. the rationale for that API, the importance of keeping the view hierarchy synchronized with the view controller hierarchy, etc.), see WWDC 2011 video Implementing UIViewController Containment.
They are very different. addChildViewController associates a view controller with a parent container view controller, while addSubview adds a view to the view hierarchy of the view it is being added to. In the former case, the new child view controller will be responsible for handling events when it is the selected view controller of its parent. Think of a tab bar controller--each tab has its own associated "child" view controller that displays its view within the parent tab bar controller's content area and handles any user interaction within that view when its corresponding tab is selected in the tab bar. You should only use addChildViewController when you have a custom container view and want to add a new view controller to its childViewControllers property. If you just want to add a new view to the view hierarchy that can receive events, which is what it kind of sounds like, addSubview is the way to go. "Implementing a Container View Controller" section explains what addChildViewController is for.
addChildViewController is method in UIViewController class and
addSubview is in UIView class
Both have entirely different behavior.
addChildViewController just puts a view controller in front of the current one. You have to manage the flow of controllers. This method is only intended to be called by an implementation of a custom container view controller.
addSubview adds another view as sub view to the view of that object.
Knowing that MVC means Model-View-Controller:
If you only intend to add the view, then use addSubview. e.g. adding a label, button.
However if you intend to a d view + controller then you must use addChildViewController to add its controller and ALSO addSubView to add its view. e.g. adding another viewController, tableViewController.
In addition:
There are two categories of events that are forwarded to child view controllers:
1- Appearance Methods:
- viewWillAppear:
- viewDidAppear:
- viewWillDisappear:
- viewDidDisappear:
2- Rotation Methods:
- willRotateToInterfaceOrientation:duration:
- willAnimateRotationToInterfaceOrientation:duration:
- didRotateFromInterfaceOrientation:
An example of where you would run into an issue if you don't do such is here
For more information I strongly recommend to see answers on this question.
Available from iOS 5, the addChildViewController:
- (void)addChildViewController:(UIViewController *)childController NS_AVAILABLE_IOS(5_0);
method let you add any view controller as a child to some other view controller, but first it removes any parent from the childController and than add it as a child view controller to the specified controller.
The child controller is nothing but an instance of UIViewController and thus it will provide the functionality of view controller (i.e it will receive the events like -(void)viewWillAppear, -(void)viewWillDisappear, etc as a normal UIViewController does).
On the other hand
- (void)addSubview:(UIView *)view;
addSubview: will add any view as subview on any other view.
It's not the choice which to use when rather it's the type which asks to use specific method.
For Instance -
If you have an instance of UIViewController than you will definitely use addChildViewController: (also you can use presentModalViewController, pushViewController) and if you have an instance of UIView than definitely you have to use addSubview.
Note : You can also add view controller's view as a subview to any other view as well.
Based on some test, I found that: If child view controller is not added to parent view controller (supposing the parent view controller is under the root view controller), only child view controller's view is added to parent view controller's view, then:
the sub view controller can still receive messages directly related to view, such as - viewWillAppear:, - viewWillLayoutSubviews, etc.
But
the sub view can not receive some system messages, such as - willRotateToInterfaceOrientation:duration:
I can't give the messages list now, however.
addChildViewController is used to prevent the added sub view controller from releasing, in other word, the parent view controller will hold a strong reference to the sub view controller.