Auto Layout Workshop
A couple of weeks ago at work I ran a workshop with our iOS team on auto layout skills and best practices. It was great to spend some time as a team discussing different approaches to solving challenging layouts and sharing Interface Builder tips and tricks.
I created a sample project for the workshop and published it on GitHub. It consists of three screens in a storyboard with no constraints and instructions in the README on how the screens should adapt to different screen sizes. Everyone on the team was asked to spend roughly one hour laying out the screens to meet the given criteria, and then later in the week we would get together and discuss how it went and share our solutions.
Each screen in the project was designed to teach specific auto layout skills. The Profile screen is the most complex of the three screens, but also the most important. A developer with a good grasp of auto layout basics would be able to make a decent attempt at this screen, but it requires an understanding of some of the more advanced auto layout techniques to fully meet the criteria provided. These techniques include aspect ratio and equal width constraints, understanding how the multiplier affects constraints, using spacer and container views to improve the layout, inequality constraints, constraint priorities, and compression resistance and content hugging priorities.
The Choose Recent Photo screen is an easy one to lay out manually by dragging constraints between each of the photos, but that's time consuming and unnecessary. The hint I gave for this screen was that it should take under 30 seconds to complete. The point of this exercise was not to get the layout correct (that's easy), but to become more familiar with the tools Interface Builder has for adding multiple constraints at once. This screen can be fully laid out from one menu by adding 53 constraints and updating the frames in one go. The idea for this screen came from a demo in lecture 2 of the Stanford iTunes U course Developing iOS 8 Apps with Swift where Paul Hegarty lays out a screen of calculator buttons in the same way. Watching someone else use Interface Builder is a great way to learn auto layout. My advice for anyone who's new to auto layout is to watch lots of demos (like the Stanford course and the WWDC videos in the resources below) and pair with as many different developers as you can.
The Take Photo screen is an adaptation of a camera screen in an app our team was working on at the time. If you were able to complete the Profile screen, this screen should be straightforward. However, for those who struggled with the Profile screen this is another chance to practice constraint priorities in a simpler layout. The main purpose of this screen is to demonstrate how high priority inequality constraints can be paired with lower priority equality constraints to achieve the desired layout.
A few days after giving the team this auto layout challenge, we met to discuss our solutions to the layout problems and talk more generally about auto layout best practices. Auto layout is a hard topic to talk about in any detail without having Interface Builder open in front of you. I definitely recommend running the workshop in a meeting room where the presenter can have the project up on a screen and walk through some of the more complex layouts step by step.
After the workshop I emailed out my solutions to the team (which is now in the GitHub repo here). I suggested they checkout the master branch and look over my storyboard, then go back to their project to refine their layout further or fix anything they couldn't get working (or give me feedback if their solution was better than mine!).
Auto layout resources
There are a lot of great WWDC sessions on auto layout, including:
- Mysteries of Auto Layout, Part 1 (WWDC 2015, Session 218)
- Mysteries of Auto Layout, Part 2 (WWDC 2015, Session 219)
- Taking Control of Auto Layout in Xcode 5 (WWDC 2013, Session 406)
- Introduction to Auto Layout for iOS and OS X (WWDC 2012, Session 202)
- Best Practices for Mastering Auto Layout (WWDC 2012, Session 228)
- Auto Layout by Example (WWDC 2012, Session 232)
I also recommend the objc.io article Advanced Auto Layout Toolbox, which covers topics such as intrinsic content size, the alignment rect, animation and debugging.
Adaptive Auto Layout by Tyler Fox is one of the best videos I've seen on adaptive layout and size classes.
I picked up a lot of useful Interface Builder tips and tricks from the demos in the Stanford iTunesU course Developing iOS 8 Apps with Swift. (The Choose Recent Photo screen in this workshop was inspired by the calculator demo in lecture 2.)