There are two types of iOS developer in the world: those who use Auto Layout, and people who like wasting time. It has bit of a steep learning curve (and we didn't even use the hard way of adding constraints!), but it's an extremely expressive way of creating great layouts that adapt themselves automatically to whatever device they find themselves running on – now and in the future.
Most people recommend you do as much as you can inside Interface Builder, and with good reason – you can drag lines about until you're happy, you get an instant preview of how it all looks, and it will warn you if there's a problem (and help you fix it.) But, as you've seen, creating constraints in code is remarkably easy thanks to the Visual Format language and anchors, so you might find yourself mixing them all to get the best results.
Anyone can sit through a tutorial, but it takes actual work to remember what was taught. It’s my job to make sure you take as much from these tutorials as possible, so I’ve prepared a short review to help you check your learning.
One of the best ways to learn is to write your own code as often as possible, so here are three ways you should try extending this app to make sure you fully understand what’s going on:
widthAnchorof our labels with
trailingAnchorconstraints, which more explicitly pin the label to the edges of its parent.
safeAreaLayoutGuidefor those constraints. You can see if this is working by rotating to landscape, because the labels won’t go under the safe area.
It is vital to your learning that you try the challenges above yourself, and not just for a handful of minutes before you give up.
Every time you try something wrong, you learn that it’s wrong and you’ll remember that it’s wrong. By the time you find the correct solution, you’ll remember it much more thoroughly, while also remembering a lot of the wrong turns you took.
This is what I mean by “there is no learning without struggle”: if something comes easily to you, it can go just as easily. But when you have to really mentally fight for something, it will stick much longer.
But if you’ve already worked hard at the challenges above and are still struggling to implement them, I’m going to write some hints below that should guide you to the correct answer.
If you ignore me and read these hints without having spent at least 30 minutes trying the challenges above, the only person you’re cheating is yourself.
Still here? OK. If you’re stuck on the last challenge, try looking at Xcode’s code completion options for the
constraint() method. We’re using the
equalToConstant option right now, but there are others – the
equalTo option lets you specify another height anchor as its first parameter, along with a multiplier and a constant.
When you use both a multiplier and a constant, the multiplier gets factored in first then the constant. So, if you wanted to make one view half the width of the main view plus 50, you might write something like this:
yourView.widthAnchor.constraint(equalTo: view.safeAreaLayoutGuide.widthAnchor, multiplier: 0.5, constant: 50).isActive = true
SAVE 20% ON iOS CONF SG The largest iOS conference in Southeast Asia is back in Singapore for the 5th time in January 2020, now with two days of workshops plus two days of talks on SwiftUI, Combine, GraphQL, and more! Save a massive 20% on your tickets by clicking on this link.
One of the most effective motivators of success is sharing your progress with other people – when you tell folks what you're doing and what you've learned, it encourages you to come back for more, which in turn will help you reach your app development goals faster.
So, now that you've done all the hard work it's time to share your success: tell folks that you've completed this project, either by clicking the button below to start composing a tweet, or by writing your own message from scratch. This will definitely encourage you to keep learning, but it will also help other folks discover my work – thank you!
Paul Hudson is the creator of Hacking with Swift, the most comprehensive series of Swift books in the world. He's also the editor of Swift Developer News, the maintainer of the Swift Knowledge Base, and a speaker at Swift events around the world. If you're curious you can learn more here.