NEW: Subscribe to Hacking with Swift+ and accelerate your learning! >>

How to automatically switch between HStack and VStack based on size class

Paul Hudson    @twostraws   

Updated for Xcode 12.0

SwiftUI lets us monitor the current size class to decide how things should be laid out, for example switching from a HStack when space is plentiful to a VStack when space is restricted.

With a little thinking, we can write a new AdaptiveStack view that automatically switches between horizontal and vertical layouts for us. This makes creating great layouts on iPad simpler, because our layouts will automatically adjust to split view and slipover scenarios.

Here’s how it looks:

struct AdaptiveStack<Content: View>: View {
    @Environment(\.horizontalSizeClass) var sizeClass
    let horizontalAlignment: HorizontalAlignment
    let verticalAlignment: VerticalAlignment
    let spacing: CGFloat?
    let content: () -> Content

    init(horizontalAlignment: HorizontalAlignment = .center, verticalAlignment: VerticalAlignment = .center, spacing: CGFloat? = nil, @ViewBuilder content: @escaping () -> Content) {
        self.horizontalAlignment = horizontalAlignment
        self.verticalAlignment = verticalAlignment
        self.spacing = spacing
        self.content = content
    }

    var body: some View {
        Group {
            if sizeClass == .compact {
                VStack(alignment: horizontalAlignment, spacing: spacing, content: content)
            } else {
                HStack(alignment: verticalAlignment, spacing: spacing, content: content)
            }
        }
    }
}

With that in place we can now write layouts such as this one:

struct ContentView: View {
    var body: some View {
        AdaptiveStack {
            Text("Horizontal when there's lots of space")
            Text("but")
            Text("Vertical when space is restricted")
        }
    }
}

To try it out, simply run the app in an iPad simulator, then try different sizes of split view – you’ll see ContentView automatically switch to a VStack when space runs low.

Now to explain how the custom view works:

  • It monitors the horizontalSizeClass environment key, so that it will be updated every time that size class changes.
  • We’ve given it parameters to store horizontal and vertical alignment individually, so you can control exactly how your layout should adapt.
  • There’s an optional CGFloat for spacing, because that’s what VStack and HStack work with. If you wanted even more control you could add horizontalSpacing and verticalSpacing properties.
  • The content property is a function that accepts no parameters and returns some sort of content, which is the view builder end users will rely on to create their layouts.
  • Our initializer stashes them all away for later.
  • Inside the body property we can read the horizontal size class, then wrap a call to content() in either a VStack or HStack.

And that’s it! The actual code is pretty simple, but it gives us some really helpful flexibility.

Hacking with Swift is sponsored by Paw

SPONSORED Use Paw to build, test and describe web APIs. Paw has a lightning fast native macOS interface to compose requests, collaborate in real-time on API specs, and generate client code for your applications. You can import and export API definitions.

Discover Paw for Mac

Sponsor Hacking with Swift and reach the world's largest Swift community!

Similar solutions…

BUY OUR BOOKS
Buy Pro Swift Buy Swift Design Patterns Buy Testing Swift Buy Hacking with iOS Buy Swift Coding Challenges Buy Swift on Sundays Volume One Buy Server-Side Swift (Vapor Edition) Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Advanced iOS Volume Three Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with macOS Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Server-Side Swift (Kitura Edition) Buy Beyond Code

Was this page useful? Let us know!

Average rating: 4.5/5

Link copied to your pasteboard.