iOS newbie question: I have a UITableViewController with a navigation controller. I need to add an edit button to that controller. The table view controller is accessed from a tab controller. I have read several posts that suggest overriding the initWithNibName method. While this makes sense, I'm not understanding where/when this overridden method gets called or what I need to do force it to be called.
In other words, when I override this method, I get a successful build but the method never gets called and the code seems unreachable. What have I possibly left out?
Thanks!
if initWithNibName is not called, then your view controller is probably loaded from a storyboard file. In that case, you have to override initWithCoder: instead.
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In UIViewControllers I have several methods such as viewDidLoad, viewWillAppear, viewDidAppear, etc.
The question is: "what is the best place to, for example, set the background color of my view, instantiate, and set the background color of a UILabel, or instantiate an object that I set as #property in my class and things like that? "
Thanks!
So many questions at once!
The first time the view is loaded, in viewDidLoad you will already have access to all the readily initialized UI elements, so it is a great place to configure the view and to set your class properties.
If you come back to the view if it is already loaded (say, by popping a view from a navigation controller, or dismissing a modal view controller), viewDidLoad will not be called. Thus, if you want to change something (background, add a label, change the background of a label, etc.) based on something that might have happened since the view controller was initialized, you have to use viewWillAppear.
You would use viewDidAppear if you want to animate a change so the user can see it after the view has already become visible.
Edit: this is pertinent for if you use IB or storyboard. See CitronEvanescent's answer for the case that you create your view in code.
The feasible method would be viewDidLoad or -(id)init,-(id)initWithNibName constructors of the class.
viewWillAppear and viewDidAppear should be avoided,since you would not like to instantiate your variables again and again since they get called every time the view appears(from pop or tabSwitch).These two methods can be useful in case you want to change some variable values on reappearance
If you are creating your view programaticaly, you can set your properties on - (void) loadView this method will be call once before anything is displayed.
Generally i prefer instantiating the UI elements in the -(id) init and update their UI in loadView.
For further details : View construction reference
In the view controller that has a UITabBarItem, i realized that viewDidLoad() method only gets called the first time when the tab bar item is clicked. So I dont know how to bring up the dynamic graphics when it's clicked the 2nd time. Can some guru help me on this? thanks in advance.
Should I conform to some kind of delegates or should i do it within didSelectViewController method on the root controller of all the tab bars? If i do the later one, it just seems to be weird since i think the controller that has the corresponding tab bar item should render itself instead of doing the rendering on root controller..
You want to put any code that should run every time the view controller appears in viewWillAppear: instead of viewDidLoad. viewDidLoad is designed for code that should run when the view backed by your UIViewController is created (and then possibly re-created after being thrown away during low-memory situations).
Actually i resolved this by using the parameter passed into the callback didSelectViewController(param).
I have created an UIView in my iPhone app. I want to handle something when user closes or opens when UIView is present as current screen. I thought, i can do this under viewWillAppear:. But, viewWillAppear: is not called in UIView. Does it work only on UIViewController? How can i handle viewWillAppear: or viewDidAppear: for an UIView?
Update: UIView what I created everything through program, not in .xib.
Please advise.
Thanks!
From your message I infer that you wrote your viewWillAppear: method on the UIView class. As you suspect, that method is part of [UIViewController]1, not [UIView]2 therefore it only gets called on the UIViewController.
You should connect the property view of the UIViewController to the UIView object in the interface builder and then implement that method in the UIViewController.
If your view is created in response to an user action,
Update for your update:
You should tag the views either in code (view.tag=1) or IB.
Then you can do if (self.window.rootViewController.view.tag == 1) { ... } from your delegate (assuming you are looking for the view of the controller who is the rootController, otherwise post more details).
It's even better if you define constants on one place instead writing 1 as a literal.
These delegate methods are called every time the superview is presented to the screen and should be implemented in the UIViewControllers.
The gotcha is that these methods aren't called when subviews are presented on the screen, so your superview-view-controller will have to respond to these events accordingly.
You can find more information in this post here.
If you study the documentation for UIView and UIViewController what you will find is -(void)viewWillAppear:animated: is a method of UIViewController and not of UIView, so in order to use it, it must be implemented by subclassing UIViewController. Generally for best practice if you want to follow MVC, any functionality that does not pertain to the view itself should be delegated to the view controller and not be in the body of your UIView subclass.
Create a new view controller with xib file, and then link your custom view class to the view in your xib file.
I have a simple custom view that is connected via outlet to a NIB. For this particular view, there are actions that I would like to perform on the view when it is initialized, no matter what NIB it is on.
Trouble is, neither the (id)init or the (id)initWithFrame:(CGRect)frame methods are getting called on the custom view.
Which method gets called on a UIView when it is instantiated from a NIB? I would just use the view controller and viewDidLoad method except that this particular view appears on a lot of different NIBs.
You can use awakeFromNib for this kind of initialization. The regular initialization methods are called when the object is actually created by IB and then archived using NSCoding, so those methods are never called within your application. You could also override initWithCoder: which will be called, but I don't recommend it since other outlets may not be wired at that point.
I'm learning to develop for iPhone without Interface Builder (a personal preference), and I'm not sure which function of a view controller I should be setting up the view in: init, viewDidLoad, or loadView. I read somewhere to only use init for the view controller, if anything, and not setting up the view as it could cause problems. I also read that viewDidLoad is only for loading from nib files, but It worked when I tried using it.. so what stuff should I put in each of these 3 methods?
Thanks!!
Well each method has its own purpose
1) init
This method is intended to just initialize the ViewController , you are not required to override this method, but if you want to do some custom initialization BEFORE any views are loaded then this could be a place to do it. You have different flavors of the init methods, you can look at the in the docs at apple site.
2) loadView
this method here is used to programatically create your view. If this method is not overriden, the default w ill create an empty view for you, but if it is you MUSt initialize viewController.view property, this gets called when a UIViewController view gets pushed into a super view.
3) viewDidLoad
this method is called after you view has loaded on the screen (After loadView has been called and the view is pushed on the super view or window). Here you can do you can add subViews to your controllers views and also do other set up that you want to occur once your view loads. This method works regardless of making a view f rom a nib or programatically.