I have a UIViewController that over time has had a lot of delegate events added to it which has made the controller class quite large. The UIViewController class contains quite a few view-management methods that are called from the event-delegate methods to manage the UIView that the controller is managing.
I am now adding further UIActionSheet delegate events to the class. My controller class is getting large and I'm thinking that I should break out the UIActionSheet delegate events and place them in a separate delegate class. This separate delegate class will then have to call back into the view controller class to get the view controller to adjust the view accordingly, using the view-management methods within the view controller. (The view controller accesses a separate model object that the view is representing).
I can see pros and cons to adopting this break-out approach. It feels wrong to be adding more and more delegate events to the controller, but creating separate classes for different categories of events that then need to call back into the controller also seems to introduce an unnecessary layer of complexity and obfuscation. The large controller class is 'simple and straightforward' but feels wrong, whilst using numerous different delegate classes will be somewhat more complex and involved but will result in smaller classes.
Can anyone provide some words of wisdom on this topic, and perhaps point me towards some iOS-specific reading on the matter?
Many thanks.
My approach to this matter is:
Make it work
Make it cleaver
Back to 1.
(Or 1 and 2 both in same turn if you are experienced in a field)
So if code works app looks good but you find that ups some class has 100 methods in it so try different design patters (if you haven`t already) and use those cleaver ideas to make code separation into different classes, delegates, encapsulate them if necessary et.
http://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/CocoaFundamentals/CocoaDesignPatterns/CocoaDesignPatterns.html
Just in case link to Cocoa Design pattern suggestions and i am from time to time looking into Pro objective c design patterns for ios. Might be not the best book out there but it is based on "Gang of four" design patterns book in ios context.
Hope this helps at least somehow,
Cheers
In the end I created quite a few additional classes for dealing with specific UIActionSheet instances. I created a base class and then subclassed this for each UIActionSheet requirement within the main controller.
The end result looks tidy, and doesn't add too much complexity.
Related
I'm trying to understand how to properly implement MVC in swift. Heres my scenario:
I have a signup page with 9 UITextFields, and they're all being made programmatically, and therefore being anchored to the view programmatically. As you can imagine this would be a lot of repetitive code to have in the SignupViewController class file.
Is the convention when following MVC to keep the setup of these text fields in the SignupViewController file, or are you supposed to have a separate file such as SignupView that contains all the text field setup code?
Even though UIViewController has the word "controller" in it, I believe the majority of iOS devs these days assign the UIViewController to the "View" side of MVC. The UIViewController is chiefly specific to a particular view only, plus may manage its subviews as well (until this gets too messy and a container view is added to allow for a nested UIViewController).
In MVC on iOS, the view controller can easily become polluted with business logic, model management, etc... which is why many people jokingly refer to "MVC" in iOS as "Massive View Controller". To combat this, consider using an MVVM architecture instead, which not only keeps the VCs small, but also moves the business logic out to a separate "sidecar" coupled to that ViewController, called a ViewModel. This allows the business logic to be unit tested without any UI involved, making testing much more reliable and easier to read and maintain. With that said, the creation of these 9 controls would still belong in the ViewController.
As for programmatically adding UITextFields to your view vs viewController, if this is to be done just for this single scene, then I'd stick it into the viewController. If you expect to want to reuse the set of them in other scenes, then making a custom view or control containing them would be better, like is typically done for custom cells of a table.
Finally, consider simply using a Nib or Storyboard to layout your scene. Apple has provided so much power to layout and maintain scenes via nibs and storyboards that you're really missing out to go the programmatic route. I find it very rare that I side with programmatic approach. The auto-layout warnings in InterfaceBuilder alone are worth gold to me, and as Apple continues to raise the bar and change layout rules, I can't imagine trying to keep up programmatically when I can't afford to test every device and iOS version combination. And yes, it's possible to do MVVM with dependency injection and storyboards. I do it daily.
Answer to your question is that it has nothing to do with MVC .
AS iOS/Mac developers, we use Interface builder and auto_layout to achieve most UI #IBOUtlet/ #IBAction. This is the V side of MVC.
Typically, If you have data, database, json or whatever formats, you need to model them and handle logics. That'M of MVC.
The C(Controller) side of MVC is a kind of glue between M and V. In most cases of mobile , you can think Controllers are all C you need.
So controller class is the only portion you need to put code to simplify everything.
In your case, 9 UITextfields should be ideally put into V side job. Please don't write code for them unless there is no better way to do.
I don't agree with above statement about using Interface Builder... I prefer to write most of my views in code and also set the anchors that way as well.
to minimize the file you can create an extension of the ViewController in a separate file to contain all of this code.
so for SignupViewController you would create a new file called SignupViewController+SetupUI.swift.
import UIKit
extension SignupViewController {
// add your setup methods here
// as just an FYI you can call the methods you create from your
// SignupViewController file just like you would any other method.
}
you can read more about extensions here.
After reading about good practices to write maintainable and readable code you should do the whole design in interface builder. If you get good understanding of constraints you don't need to write any code to setup design in your view controller. The ViewController.swift file should not be used to fetch-handle data or to setup the UI. It should just be responsible to display and update values which are fetched and get handled in a separate ViewControllerDatasource.swift file. So to sum up, view controller does not have any logic implemented it just handles the show data and the design updates(not setup). I hope i helped you with your question.
I'm having a problem with the app I am developing right now : one of my UIViewControllers is huge ( around 3000 lines ).
For now, I created extensions of this view controller to handle delegate methods in order to "split" this controller. For instance, I have my main view controller called XYZMainViewController and as this controller is the delegate of a UITextField, I created an extension XYZMainViewControllerTextFieldDelegateExtension.swift in which I manage UITextFieldDelegate methods.
It's still pretty dirty to do that this way. I'm wondering what would be a good practice to handle huge controllers like this one.
did you consider to design your app using MVVM (model view view model) the idea of MVVM is to avoid huge controllers. There are a lot of user guides out there which explain how to use MVVM in your IOS app. I was facing the same situation half a year ago and then i adopt MVVM in my app and i am very happy with it since my controllers are not huge, i can reuse code easily in my app and also it's much more easy to create unit tests.
Please follow this guide which explain what is MVVM and how to use
ithttps://www.raywenderlich.com/74106/mvvm-tutorial-with-reactivecocoa-part-1
https://www.raywenderlich.com/74131/mvvm-tutorial-with-reactivecocoa-part-2
3000 lines is hmmmm hugeeeeee.
You have performed huge numbers of tasks in your controller. Controllers are supposed to control views.In my opinion(the way i create my iOS app structure) controller is suppose to perform view control,passing data from models to view(more specifically from classes which manipulates data).
"Separate of concerns" is important here. Don't implement your business logic inside controllers. There should be a separate module which do all of your business logic. How to manipulate models and complete a functionality. Then this class is used by controller to perform view updates.
No matter what type os view you have designed ,its controller can't be of 3000 lines. Delegation is not a problem. Controller is a good place to do delegation. Inside those delegate methods ,to perform some business is not the work of controller. There are some design patterns for IOS apps like MVC, MVVM.
But still you have to use "these design patterns efficiently. move the common functionality in one place etc. Implementation of business logic. Manipulation of models. Communication with DataBase.
Thanks.
This is probably largely preferential but I'd like to know if there are any reasons to decide one way or another on this.
When designing with storyboards you invariably end up with a number of view controllers. I'm looking at the overhead of a strict MVC approach where each controller is implemented in its own UIViewController subclass with corresponding UIView subclass (and even view model class for MVVM), and that seems to get out of hand quickly – it takes no time to add dozens of files to the project (many with little function). An alternative approach would be to link all the views to a common controller representative of all of the storyboard functionality.
My inclination is that if you don't have substantial controller code for any individual view controller, then the combination of all of them into one shouldn't be of harm to the readability of the code (and may enhance it over adding a large number of source files). On the other hand, if you have significant functionality to implement for any particular view controller, then it should be encapsulated within it's own controller.
In most situations I'd build all controllers to be as reusable as possible (encapsulated in their own custom UIViewController subclasses). Storyboards put this in an interesting light though since they seem to be geared towards sequences of views that typically have few entry points.
Your thinking is correct
If you don't have much functionality in each VC (ViewController) them combine all your code into one VC. The only drawback to this approach is that you won't be able to implement view specific code and every view where you will use this common VC will execute the same code whether its needed there or not. e.g. code in viewWillAppear etc.
Similarly if you have a lot of functionality for a particular view then its better to put it under its own VC
This is just a suggestion, if you need to use some common code logic between multiple VCs then instead of doing copy and paste in each VC of the same code, make it into a method of type Category and then call it where ever its needed. So change the code only at 1 place.
More VCs doesn't necessarily mean bad design. In my opinion its easier to maintain that way. My two cents. :-)
Each scene in your storyboard should have its own UIViewController subclass. Even doing it like this it's way too easy to get huge unmaintainable view controllers (MVC = Massive View Controller). Putting all the code for multiple scenes in the same view controller would create even bigger ones and also violate the Single Responsibility Principle. Each class should do only a single thing.
That also means you shouldn't duplicate the common functionality into all your UIViewController subclasses. Then they again would do multiple things - the common stuff and their actual purpose. Instead you can put your common code in other controller objects (which are not descendants of UIViewController) and use them in your view controllers.
Depending on the usecase a common base class would work as well, but it's always preferable to use composition instead of inheritance.
Another nice thing about other controller objects is that you also can add them directly in Interface Builder and connect actions and outlets to them. Your main view controller class often doesn't even have to know they exist.
In my project, I have two UIViewControllers in a tab bar application, each one contains a UITableView which displays information from RSS feeds. The two view controllers are supposed to be perfectly identical, except for a single NSString parameter (the feed URL).
I know that I can simply copy and paste the code from one UIViewController to another, but I was wondering if there is a better way to do this. I'm not sure if I'm phrasing this correctly, but I think I want to create a separate file which contains a UIViewController "instance" and apply that instance to each view controller in my app.
I'm wondering if something like I'm asking for is possible, and how it would be done.
I'm assuming these 2 view controllers are both installed as tabs of your tab bar controller.
If that's the case, then you want the two view controllers to be different instances of the same view controller class. Identical twins, if you will. Let's call it MyRSSTableViewController. You'd just give the MyRSSTableViewController class a feedURL property, and set that property as part of creating each instance of your MyRSSTableViewController class.
This is a fundamental concept of object-oriented programming, and if you don't get it then you need to stop and do some reading. You might want to check out the "Objective-C programming: The Big Nerd Ranch Guide". That book will teach you programming in C and Objective C from the beginning.
If you already have programming experience in other procedural languages then that book might not be the best choice for you. Tell us about your current skills and we can make better recommendations.
Personally I would just have the title switch and have the data source of the array change based on a bool value. and then call reload when you want to switch.
But the best method is definitely Duncan C's
what you can do is overload the constructor of your UIViewController (just like you would do with any class) and add the url as parameter.
Using this approach, you would create 2 instances of the UIViewController with the only difference in the parameter used when creating them.
If I want to build a generic UI Component (one that will handle its own view and logic, data source,
etc), is it a good practice to subclass UIViewController?
I would say no. But it depends. If your component manages other view controllers or has/will have any kind of logic that's not specific to a view (e.g. navigation logic, business logic etc) , then you should subclass a view controller. Then again that makes it more than an UI component.
Otherwise, you should subclass an UIView, like Apple does with many components, including UITableView (speaking of datasource), GLKView, UICollectionView.
My overly simplistic answer is "no, when building a generic component do not automatically start with a UIViewController subclass". However that alone is not a useful answer and in some cases a UIViewController subclass is exactly the right solution.
Instead let's consider how to decide what your component should be. I think the best way to figure that out is to answer three questions:
What is this component responsible for?
How do you want to interact with it?
What are its dependencies?
In all cases we can try to start as simple as possible and add complexity only when the answers to those questions require it.
Could this component just be a function? No objects, no classes, if all you want to add is some behavior then maybe all we need is a function. If this behavior only applies to specific existing types then maybe we need a category on an existing class.
Not enough to cover what we want to do? Ok, I guess we might be talking about a new type so let's create a class. Can it just be a subclass of NSObject?
Want to display something in a view? Ok, then we at least have a UIView subclass, maybe a UIControl subclass if it is more interactive.
The view needs some data to back it? No problem sounds like we now need two pieces; a view to display data and a data source to provide it. Here the view shouldn't need to know who creates and owns this data source. As long as one was provided to the view we can use it, anything else is outside of the view's area of responsibility. Similarly we might add a delegate to notify some other object of interactions with the view.
If we still haven't covered all of this component's responsibilities then maybe we need yet another piece, something in the controller layer to manage our view. We're still not (yet) talking about a UIViewController though! It's fine to have a "controller" or "service" that is a NSObject subclass. If all this piece needs to do is manage network connections, or map NSFetchedResultController results to our view's data source protocol and update the view, or just provide a convenient implementation of the most common mapping of model objects to the view's data source then a simple "controller" object is still all we need.
Still not enough? Finally we get to the point where we consider providing a UIViewController subclass. Maybe we want to allow users of the component to just present a modal view controller to hand off responsibility for an interaction (send an email, compose a tweet). Maybe there's a common set of default behaviors we want to provide that are tied to view controller life cycle events (UITableViewController flashing scroll bars in -viewDidAppear:).
Build your component from the pieces you need to support the behaviors you want to provide but keep it as small and simple as possible.
Yes, it's good practice in many cases. The iOS SDK contain many examples of UIViewController subclasses. A few of them contain only a small amount of generic behavior and are essentially useless without customization:
GLKViewController
UICollectionViewController
UITableViewController
And some of them provide significant generic behavior but are still mainly containers for your own view controllers:
UINavigationController
UIPageViewController
UISplitViewController
UITabBarController
But most of them are essentially complete packages with little or no need (or ability) to customize their behavior:
ABNewPersonViewController
ABPersonViewController
ABUnknownPersonViewController
EKCalendarChooser
EKEventEditViewController
EKEventViewController
GKAchievementViewController
GKFriendRequestComposeViewController
GKGameCenterViewController
GKLeaderboardViewController
GKMatchmakerViewController
GKTurnBasedMatchmakerViewController
MFMailComposeViewController
MFMessageComposeViewController
MPMediaPickerController
MPMoviePlayerViewController
PKAddPassesViewController
QLPreviewController
SKStoreProductViewController
SLComposeViewController
TWTweetComposeViewController
UIActivityViewController
UIImagePickerController
UIReferenceLibraryViewController
UIVideoEditorController
If you think about what all of these have in common, you may conclude that they all have two things in common:
Each has a specific model (in the MVC sense) that it interacts with, and that model is not specific to your app. The models vary widely (UIVideoEditorController's model is a single video; UIImagePickerController's model is the entire photo library; GKAchievementViewController's model is a database possibly on an Apple server in “the cloud”), in some cases you provide the model (or some properties of the model) up front, and in some cases you receive the model (or a fragment of it) at the end. But in every case, the view controller handles all the interaction between the user and the model with little or no ongoing help from your app.
Each provides its own view hierarchy, with little or no customization required (or even permitted).
In other words, each of these view controllers isn't just the “C” of an MVC pattern. It's the tip of an entire MVC iceberg.
If your component is also an MVC iceberg, then exposing the tip of your iceberg as a UIViewController subclass is quite appropriate.
It depends on the iOS version you used.
A. prior to iOS 5.0, It's not a good practice, and not recommend.
B. start with iOS 5.0, It's just ok.
subclass a view controller for a UI component (UIView), , that means you wanna use the view controller life cycle method, to manage the user interaction and view display procedure, data model etc. So, if the life cycle method can not easily automatic called, the view controller is not that meaningful.
start with iOS 5.0, it's possible to create custom view controller container, so, it's ok to build custom generic ui component with view controller to add as a child view controller.
prior to iOS 5.0. Subclass a UIView with custom delegate protocol is the right way. one other thing is about the code organize. put the all custom delegate method to another custom class, not in the view controller, in the view controller just init a delegate class instance, and set this to the view delegate property.