I know it's possible to attach a custom view controller class to several different view controllers on a storyboard, but can it be done in the other direction; that is, depending on the situation, I want to bind different custom classes to a single view controller on the storyboard that will be instantiated using:
[self.storyboard instantiateViewControllerWithIdentifier:]
background: I used to have several view controllers on my storyboard that are almost identical. In fact, the custom classes that they each bind to are very similar as well. In an effort to clean this up, I refactored my custom classes into one base class and several subclasses. I then removed all the similar view controllers from the storyboard leaving only one which I've bounded to my base class. I then call:
MySubclass* mySubclass = [self.storyboard instantiateViewControllerWithIdentifier:#"StoryboardControllerBoundToBaseClass"];
Unfortunately, my subclass code is being ignored and only the base class code is ever run. Does anyone know how I can make it work without duplicating view controllers on the storyboard and binding each one to a different subclass?
It's not possible. Just because you say MySubclass *object = something doesn't magically convert object into a MySubclass object. It's stored in the storyboard with whatever class was assigned at storyboard compile time.
Rather than using subclassing, I figure I can reuse a view controller on the storyboard by using a delegate/proxy model. More specifically, I can bind the storyboard's view controller to a custom class that delegates all of its methods/events to others classes to handle. This isn't as elegant as subclassing but at least I can keep my storyboard leaner, not having to keep several copies of pretty much the same view controller. Plus, I won't need to duplicate future changes to every copy of these controllers to boot.
As guylegend writes. Apple doesn't support the way to do that. There are many workarounds e.g. with delegates but I finally found the answer and answered in another topic. Hope it helps!
https://stackoverflow.com/a/32103618/1943053
Related
I have a view table view controllers that contain a fairly large set of functionality and many lines of code - Is there an accepted way to split the single controller into multiple controllers or objects to help make it more readable and easier to navigate/maintain?
Yes there are ways to make your code more modular. First off using a UITableView there is a Delegate and a DataSource. You can create separate NSObject classes for each of these.
The DataSource class would contain things like tableView:cellForRowAtIndexPath: and tableView:numberOfRowsInSection:. With the full list here: UITableViewDataSource.
The Delegate class would contain things like: tableView:didSelectRowAtIndexPath: and tableView:willDisplayCell:forRowAtIndexPath:. WIth the full list of here: UITableViewDelegate
It really matter on where most of your code is. If its all in creating a custom cell create a class for that and just send it the info it needs to build its self.
You could just use two subclasses of UIView (or tableView depending on what your are doing) to make the View code a bit more modular. Without more details on what you are attempting it is hard to be more specific.
I am getting incredibly frustrated with interface builder at the moment, and would appreciate some help before I ragequit it and code everything by hand (which seems to be much, much, much easier).
The basic situation is this: I need to make a model variable accessible to each view controller in my application.
The simplest way I can see to do this is to just create a property on the view controllers that retains the model, and to set that after the controller is initialised.
However, I can't find any of the actual initialisation code for the views shown on the storyboard in my project. There's no reference to any of them at all. Does the interface builder really generate not generate any code reference to its controllers in the app delegate?
For that matter, why is there no reference to any of the top level controller objects (tabview, tableview etc) in code at all?
All I want to know is how to force xcode to actually generate the controller creation code in AppDelegate.m - so that I have access to the created instance of the controller - or, failing that, a way to share the model between these amorphous objects.
Maybe it would be easier to create a singleton class where you can store all your global variables and methods. Example here.
You will need to manually create a subclass of your view controller and then override the methods you want to inject code into. In Interface Builder you can then choose to make your View controllers of this custom type.
I am learning iOS programming through the Big Nerd Ranch guide by Hillegass and Conway. I’m writing an app of my own as I go through the book, and one of the questions that has been bugging me is exactly when I need to subclass UIViewController (and its ilk) and when I can just instantiate it.
For example, my app consists of generic building blocks: the interface is tabbed, and the tabs lead to a UITableView, a UINavigationController that creates UITableViews, and so on. Following the book’s instructions, I have subclassed UITableViewController to create the table views. However, in creating the UITabBarController that contains all of my app’s content, it seems sufficient to instantiate a UITabBarController and then add a bunch of views to it. (All of this is done in the application:didFinishLaunchingWithOptions: method of my app delegate. Since most of my app consists of simple combinations of basic UI parts, I’m trying to do build the UI programmatically whenever possible.)
I get the impression that what I should be doing is creating a subclass of UIViewController (or UITableViewController or whatever) for every interface in my project. This seems weird to me, since most of these classes would only ever be instantiated once. Am I just misunderstanding how OO should be used in this case? (I have a good amount of programming experience but relatively little has been with OOP.) Should I be creating a subclass for each and every screen that the user will see?
Should I be creating a subclass for each and every screen that the user will see?
If each view requires different logic, yes.
Don't shy away from creating new classes for conceptually separate things. Programmers coming from non-OOP to OOP might feel that a file with only a small amount of code is a waste. Suppress this feeling. Classes are cheap, and help enormously to organise your thinking.
So you have two types of UIViewControllers in iOS. "Container" viewControllers and "Content" viewcontrollers. Both are subclasses of UIViewController but have very different purposes.
The Container type is what the UINavigationController and UITabController are. They are rarely subclassed and typically used as is (in fact, I believe Apple doesn't allow the subclassing of UINavigationController at all). These "Containers" take care of moving "Content" view controller around for you. They do not have much content of their own, beyond adding things like a tab bar or a navigation bar.
The "Content" view controller are the ones you create most of the time. You will rarely be able to use a UIViewController as is, because it will not have any functionality. That is why you subclass them. These are meant to represent a single "screenful" of content. So in effect, every "screen" the user sees should be controlled by a UIViewController subclass.
The UITableViewController is simply a specialized sublass of UIViewController that already contains some methods for managing tables.
The way the UIKit framework was designed was for you to use subclasses of UIViewController to display content and to use out-of-the-box "Container" controllers to facilitate the management of your UIViewController subclasses.
You need a subclass of UIViewController if you want to do any of the following (not an exhaustive list, but some examples)
customize the view hierarchy when the view hierarchy is loaded (in
viewDidLoad)
provide some behaviour as the view controller's views become visible
(or not) (in viewWillAppear:, viewDidAppear:, viewWillDisappear:,
etc.)
clean up after yourself as needed in viewDidUnload
create outlets to views in the hierarchy so you can adjust them as
needed in the above lifecycle methods
My reasoning behind subclassing UIViewController, and other classes is that:
Almost always you must initialize variables and assign values to the instances of classes. You add subviews and set their frames, define actions for the UIViewController instance, etc. If this UIViewController instance is directly from the base class, its initialization should be done outside of it. If this initialization is required at different places for multiple times, you may have to deal with repeated initialization process.
So, you've compiled these processes into a method, making it reusable from wherever this UIViewController instance is used. But where do you want to put it? Don't you think it's much better to put it inside the subclass of UIViewController? Also, you don't even have to come up with specific name for this initialization method. Just override the default -(id)init from the super class.
Though you may think it's suffice to use UIViewController without subclassing it for now, as your project grows, it will be challenged to deal with reusability issues. Take some time to look at your codes. Check if there is too much repetition for such as initializing an object, or assigning values to it. If you are doing same things with an instance of a class in multiple places, compile them into a method to be reused. And as number of such methods grow, you will find the need to use subclass which will contain these relevant methods for the instance.
No matter the size of your project, using classes to distinguish different objects is important. Almost always, the basic essential classification is done by the framework, making it unnecessary to introduce new concept for a class. However, this doesn't mean the framework also knows how your project and its objects can be classified into. By using subclass, you can utilize every benefit the development framework can provide and still keeping the objects in your project to be as unique as possible, based on the purpose you've designed for them.
Well about the UITabBarController you are right. There is no reason for you to subclass anything if the default behavior is sufficient. However once you need to do some custom things you will need to subclass it..
Also, why are you trying to build the GUI programmatically? For the learning curve? There is no real reason not to use InterfaceBuilder, it saves you a lot of time.
You should subclass the UITableViewController in order to get your data in the view, that is how the MVC model works. The default implementation does not offer anything in order to get your data in the view, I don't think they will ever do that in order to make sure that nothing is wasted, their 'connection' to the model object might be different from the one you want and you would end up writing an adapter if your model object is not compatible.
I hope this will help you out a bit.
And merry x-mas.
I have a custom ViewController that is meant to be reusable, and an arbitrary number of instances will be chained together in a NavigationController in Storyboard, all sharing the same model as a delegate.
The ViewControllers need to tell the model which instance they are. Currently, they have an int property that they get from the segue, but it doesn't seem very idiomatic and doesn't lend itself to having multiple instances onscreen (for iPad). I figure there's got to be a cleaner way to do this, so does anyone know what it is? Thanks.
RESULT: self.view.tag
A UIViewController's UIView has a tag property which you can set from anywhere you want. You could also simply identify the type of the controller by using [self class]. Or simply use the memory location by referencing the controller directly.
Update You could simply implement a unique identifier for a UIViewController using a category.
I guess the "cleanest" way in terms of design architecture would perhaps be an array of ViewControllers. (It could be managed in the app delegate.) However, there are memory considerations - on the iPhone you would likely want to create and the destroy the view controllers as needed. The array could contain the identifier and perhaps some other model-related information in order to recreated the controllers as needed.
Too bad there is no property storyboardIdentifier of UIViewController. They can be instantiated with this id but it would be helpful if the viewcontroller can query its id.
I recently ran into this. I figured out you can add a "Restoration ID" in the storyboard. Then you can access it perhaps like this (depending on your use case)
navigationController?.viewControllers.first?.restorationIdentifier
So, I've been making iOS apps since the first iPod touch came out, but something has always flabbergasted me; why is the list of new Cocoa Touch classes restricted to subclasses of NSObject, UIView, and UITableView? I routinely make subclasses of UIImageView and UIViewController.
Am I "Doing It Wrong™?" Have I totally misunderstood MVC to the point where I make Controller classes where I shouldn't? What is the philosophical reasoning for requiring classes to never descend from a basic controller class?
What gives you the idea that you aren't supposed to subclass UIViewController? This is directly from the documentation for UIViewController:
In a typical iPhone application, there is usually at least one custom subclass of UIViewController and more often there are several.
The C of MVC is supposed to be the least re-usable part it's whole job is to mediate between M & V. If you find something that is in the C section of your code that you have to copy and paste into several subclasses of a given object or into several projects that code should be moved elsewhere.
If you are just basing this off the fact that there is not a nice popup menu item that says UIViewController, don't worry about it Apple has just not bothered to write a template file for that class yet.
Uhm... maybe it's just me, but I see a UIViewController subclass template when I choose new File.
UIViewController template http://files.me.com/aclark78/obnp83
Like #theMikeSwan says, there simply aren't GUI templates for this when you create a new class in Xcode GUI. But you can always create a new subclass whose parent is initially NSObject. After that, you just go to your code and change the parent class to whatever you like.
So... no, you are not doing it wrong in the sense that you rightly understand that often you want to subclass UIViewController; but yes, you are doing it wrong since you assume you shouldn't do this only because Xcode GUI does not support it :)