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SwiftUI by Tutorials

Second Edition · iOS 13 · Swift 5.2 · Xcode 11

Before You Begin

Section 0: 3 chapters
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Section I: Diving Into SwiftUI

Section 1: 5 chapters
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Section II: Building Blocks of SwiftUI

Section 2: 6 chapters
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Section III: Advanced SwiftUI

Section 3: 6 chapters
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6. Intro to Controls: Text & Image
Written by Antonio Bello

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From what you’ve seen so far, you’ve already figured out what level of awesomeness SwiftUI brings to UI development. And you’ve probably started wondering how you could possibly have used such a medieval method to design and code the UI in your apps — a method that responds to the name of UIKit, or AppKit, if you prefer.

In the previous chapters, you’ve only scratched the surface of SwiftUI and learned how to create some basic UI. Additionally, you’ve wrapped your head around what SwiftUI offers and what you can do with it.

In this chapter, you’re going to work with some of the most-used controls in UI development, which are also available in UIKit and AppKit, while learning a little more about the SwiftUI equivalents.

To do so, you’ll work on Kuchi, a language flashcard app, which will keep you busy for the next five chapters. Enjoy!

Getting started

First, open the starter project for this chapter, and you’ll see that it’s almost empty. There’s almost no user interface; only some resources and support files. If you build and run, all you’ll get is a blank view.

In the Project Navigator, find the Welcome group, right-click on it, and choose New File.

In the popup that comes next, choose SwiftUI View, then click Next.

Then type WelcomeView.swift in the Save As field, and click on Create. You now have a blank new view to start with.

Changing the root view

Before doing anything, you need to configure the app to use the new WelcomeView as the starting view. Open SceneDelegate.swift, and locate the line of code where you create EmptyView.

window.rootViewController = UIHostingController(
  rootView: EmptyView()
)

window.rootViewController = UIHostingController(
  rootView: WelcomeView()
)

Welcome, View!

Now, take a look at the newly created view. Open WelcomeView, and you will notice there isn’t much in it:

Text

Input requires context. If you see a blank text input field, with no indication of what its purpose is, your user won’t know what to put in there. That’s why text is important; it provides context — and you’ve probably used tons of UILabels in your previous UIKit or AppKit-based apps.

Text("Welcome to Kuchi")

Modifiers

Now that you’ve displayed some text on your screen, the next natural step is to change its appearance. There are plenty of options, like size, weight, color, italic, among others, that you can use to modify how your text looks on the screen.

Text("Welcome to Kuchi")
  .font(.system(size: 30))

Text("Welcome to Kuchi")
  .font(.system(size: 30))
  .bold()

Text("Welcome to Kuchi")
  .font(.system(size: 30))
  .bold()
  .foregroundColor(.red)

Text("Welcome to Kuchi")
  .font(.system(size: 30))
  .bold()
  .foregroundColor(.red)
  .lineLimit(2)

Text("Welcome to Kuchi")
  .font(.system(size: 30))
  .bold()
  .foregroundColor(.red)
  .lineLimit(2)
  .multilineTextAlignment(.leading)

Are modifiers efficient?

Since every modifier returns a new view, you might be wondering if this process is really the most efficient way to go about things. SwiftUI embeds a view into a new view every time you invoke a modifier. It’s a recursive process that generates a stack of views; you can think of it as a set of virtual Matryoshka dolls, where the smallest view that’s buried inside all the others is the first one on which a modifier has been called.

Order of modifiers

Is the order in which you invoke modifiers important? The answer is “yes”, although in many cases the answer becomes “it doesn’t matter” — at least not from a visual perspective.

Text("Welcome to Kuchi")
  .bold()
  .foregroundColor(.red)

Text("Welcome to Kuchi")
  .foregroundColor(.red)
  .bold()


Text("Welcome to Kuchi")
  .background(Color.red)
  .padding()

Text("Welcome to Kuchi")
  .padding()
  .background(Color.red)


Text("Welcome to Kuchi")
  .background(Color.yellow)
  .padding()
  .background(Color.red)

Image

An image is worth a thousand words. That may be a cliché, but it’s absolutely true when it comes to your UI. This section shows you how to add an image to your UI.

var body: some View {
  Image(systemName: "table")
}

Changing the image size

When you create an image without providing any modifiers, SwiftUI will render the image at its native resolution and maintain the image’s aspect ratio. The image you’re using here is taken from SF Symbols, a new set of icons that Apple introduced in the 2019 iterations of iOS, watchOS and tvOS. For more information, check out the links at the end of this chapter.

var body: some View {
  Image(systemName: "table")
    .frame(width: 30, height: 30)
}


var body: some View {
  Image(systemName: "table")
    .resizable()
    .frame(width: 30, height: 30)
}


// 1
.cornerRadius(30 / 2)
// 2
.overlay(Circle().stroke(Color.gray, lineWidth: 1))
// 3
.background(Color(white: 0.9))
// 4
.clipShape(Circle())
// 5
.foregroundColor(.red)

Brief overview of stack views

Before moving to the next topic, you’ll need to recover the code you removed while working on the Image in the previous section.

Image(systemName: "table")
  .resizable()
  .frame(width: 30, height: 30)
  .overlay(Circle().stroke(Color.gray, lineWidth: 1))
  .background(Color(white: 0.9))
  .clipShape(Circle())
  .foregroundColor(.red)

Text("Welcome to Kuchi")
  .font(.system(size: 30))
  .bold()
  .foregroundColor(.red)
  .lineLimit(2)
  .multilineTextAlignment(.leading)

HStack {
  Image(systemName: "table")
    ...

  Text("Welcome to Kuchi")
    ...
}

More on Image

Two sections ago, you played with the Image view, creating an icon at the end of the process. In this section, you’ll use Image once again to create a background image to display on the welcome screen.

ZStack {
  HStack {
    ...
  }
}

Image("welcome-background", bundle: nil)


// 1
Image("welcome-background", bundle: nil)
  // 2
  .resizable()
  // 3
  .scaledToFit()
  // 4
  .aspectRatio(1 / 1, contentMode: .fill)
  // 5
  .edgesIgnoringSafeArea(.all)
  // 6
  .saturation(0.5)
  // 7
  .blur(radius: 5)
  // 8
  .opacity(0.08)

.aspectRatio(2 / 1, contentMode: .fill)


Image("welcome-background", bundle: nil)
  .resizable()
  .aspectRatio(1 / 1, contentMode: .fill)
  .edgesIgnoringSafeArea(.all)
  .saturation(0.5)
  .blur(radius: 5)
  .opacity(0.08)

Splitting Text

Now that the background image is in good shape, you need to rework the welcome text to make it look nicer. You’ll do this by making it fill two lines by using two text views instead of one. Since the text should be split vertically, all you have to do is add a VStack around the welcome text, like so:

VStack {
  Text("Welcome to Kuchi")
    .font(.system(size: 30))
    .bold()
    .foregroundColor(.red)
    .lineLimit(2)
    .multilineTextAlignment(.leading)
}


VStack {
  Text("Welcome to")
    .font(.system(size: 30))
    .bold()
    .foregroundColor(.red)
    .lineLimit(2)
    .multilineTextAlignment(.leading)
  Text("Kuchi")
    .font(.system(size: 30))
    .bold()
    .foregroundColor(.red)
    .lineLimit(2)
    .multilineTextAlignment(.leading)
}

VStack {
  Text("Welcome to")
    .font(.system(size: 30))
    .bold()
  Text("Kuchi")
    .font(.system(size: 30))
    .bold()
}
.foregroundColor(.red)
.lineLimit(2)
.multilineTextAlignment(.leading)

.font(.headline)

.font(.largeTitle)

VStack(alignment: .leading) {
  Text("Welcome to")
    .font(.headline)
    .bold()
  Text("Kuchi")
    .font(.largeTitle)
    .bold()
}
.foregroundColor(.red)
.lineLimit(2)
.multilineTextAlignment(.leading)
.padding(.horizontal)

Accessibility with fonts

Initially, all of your views that display text used a font(.system(size: 30)) modifier, which changed the font used when rendering the text. Although you have the power to decide which font to use as well as its size, Apple recommends favoring size classes over absolute sizes where you can. This is why, in the previous section, you used styles such as .headline and .largeTitle in place of .system(size: 30)

Key points

  • You use the Text and Image views to display and configure text and images respectively.
  • You use modifiers to change the appearance of your views. Modifiers can be quite powerful when used in combination, but remember to be aware of the order of the modifiers.
  • Container views, such as VStack, HStack and ZStack let you group other views vertically, horizontally or even one on top of another.

Where to go from here?

SwiftUI is brand-new and is still evolving as a technology, even now that it’s out of beta. During this period of adjustment, features can change, APIs can be renamed, or even removed altogether. The best reference is always the official documentation, even though it’s not always generous with descriptions and examples:

5. The Apple Ecosystem
7. Controls & User Input
Have a technical question? Want to report a bug? You can ask questions and report bugs to the book authors in our official book forum here.
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