A Better MVC. 300 line view controllers or bust. Dave A guy who thinks too deeply about stuff

Transcription

1 A Better MVC 300 line view controllers or bust Dave A guy who thinks too deeply about stuff

2 Heads Up This is all my opinion (! hi legal & pr teams!) Lots of similar terminology View UIView Controller UIViewController This will all be oddly familiar

3 MVC Standard Cocoa architectural pattern

4 Controller Model View

5 MVC Standard Cocoa architectural philsophy Philosophy: separate storage, business logic, and display Easily abused

6 Colin ios architecture, where MVC stands for Massive View Controller 5:27 PM 20 Jan

7 Massive View Controller View Loading IBActions Model observation Networking callbacks Data sources Delegates Trait collections Business Logic

8 Massive View Controller Hard to understand Hard to isolate Hard to change Hard to test 2,000+ lines is common 10,000+ lines isn t rare

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11 Making a Better MVC Don t rewrite; refactor

12 Me FRP MVC

13 Making a Better MVC Don t rewrite; refactor Refactor to a better pattern 8 observations

14 Observation #1 Patterns are like data structures

15 Data Structures Performance characteristics Memory characteristics The right structure makes the right things easy

16 Code Structures Performance characteristics Memory characteristics The right structure makes the right things easy

17 Choosing Structures Hard to go wrong with Array, Set, and Dictionary Hard to go wrong with MVC Other patterns are also valid Learn their respective strengths and weaknesses

18 Observation #2 Naming affects perception

19 The Two Hardest Problems in CS 1. Naming things 2. Cache invalidation 3. Off-by-one errors

20 Naming Affects Perception NS* probably not a UI concept UI* probably a view? *Controller Must be a controller

21 YOU RE A CONTROLLER! YOU RE A CONTROLLER! EVERYTHING IS A CONTROLLER!

22 Naming Affects Perception NS* probably not a UI concept UI* probably a view? *Controller Must be a controller ViewModel ModelController

23 Names reflect intent. Choose good names.

24 Observation #3 UIViewController is not a Controller

25 UIViewController Responsibilities Load views Show views Layout views Rotate views Transition views it s all about views

26 "

27 If UIViewController only does View stuff

28 maybe it s really a View

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30 Implications No networking No data persistence No navigation No business logic No model observation

31 Implications Receive intention from a Controller Put data into UIViews Implement IBActions Translate IBAction in to intention Propagate intention to a Controller Would you do this in a UILabel or UIButton?

32 Observation #4 Views are small

33 Small Views Views are a unit of UI A view a screen

34 Small UIViewControllers A UIViewController a screen You don t have to fill the screen You can show many UIViewControllers on the same screen A single screen can show lots of UIViewControllers

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36 Observation #5 Views are composeable

37 Composing Add together little things to make a big thing Composing is the skill of a programmer

38 Composing UIViewController Child View Controllers Added in ios 5 you have no excuse Guides several key APIs All navigation UISearchController UIRefreshControl

39 Observation #6 Views are reuseable

40 Reusing Views We don t rewrite UIButton or UILabel Why rewrite UIViewControllers? Expect to reuse UIViewControllers

41 Reusable UIViewControllers It s not a It is a TweetListViewController ListViewController that shows tweets UIImageView that hits the network ImageViewController with an image proveder A custom view that gets hidden to show a UIActivityIndicator Container UIViewController that transitions between different child view controllers

42 Observation #7 Views show data or children

43 Constructing Views Views generally do one of two things: Add logic and layout by composing Draw stuff All UIViews follow this pattern UIButton UIProgressView UITextField

44 Constructing UIViewControllers UIViewControllers either: Put data directly into UIViews Compose other UIViewControllers There can be exceptions UITabViewController UINavigationController UISearchController

45 Observation #8 You need actual controllers

46 Controller Model View

47 Where is the logic? This approach dumbs down UIViewControllers UIViewControllers never know their context Delegate intention out to Controllers Pass around protocol-typed Controllers

48 Case Study WWDC App

49 WWDC App Session Details Watch a video Read session information Perform contextual actions Browse related sessions

50 WWDC App Logic Observe model Determine contextual actions Observe action state List related videos Actions Favorite Share Watch Movie Mark as Watched Download Leave Feedback Watch Related Movie

51 HOLY MASSIVE VIEW CONTROLLER, BATMAN! THAT WILL BE A NIGHTMARE TO MAINTAIN!

52 If you wouldn t make it a single UIView subclass

53 don t make it a single UIViewController

54 WWDC App

55 WWDC App Session Video Poster View Controller Session Title View Controller Session Detail View Controller Session Description View Controller Session Actions View Controller Session Related Content View Controller

56 WWDC App Session Video Poster View Controller Session Title View Controller Controller Session Session Detail View Controller Session Description View Controller Session Actions View Controller Session Related Content View Controller

57 WWDC App Approach #1: Delegation / Callbacks Session Video Poster View Controller Session Title View Controller Controller Watch Session Detail View VideoController Session Description View Controller Session Actions View Controller Session Related Content View Controller

58 WWDC App Approach #2: Dependency Injection Session Video Poster View Controller Tapped <MovieWatcher> Tapped Related Poster Video Session Title View Controller Session Detail View Controller Session Description View Controller <SessionActioner> Tapped Action Session Actions View Controller Session Related Content View Controller

59 A Better MVC 1. Patterns are like data structures 5. Views are composeable 2. Naming affects perception 6. Views are reusable 3. UIViewController is not a 7. Views show data or children Controller 4. Views are small 8. You need actual controllers

60 Results Tiny UIViewControllers (usually under 200 lines) Rarely subclass UIView Extremely reusable UIViewControllers Clear separation of concern Happy programmers #

61 Thanks! social media website