Provide custom size for UIViews wrapped in UIViewRepresentable


Starting from iOS 16 the UIViewRepresentable protocol has a new API sizeThatFits(_:uiView:context:) that lets us provide custom sizing logic for wrapped UIViews in SwiftUI apps.

The method gets passed the size proposal and the UIView itself, so we can calculate the desired dimensions or simply return a fixed predefined size.

struct MyUIViewWrapper: UIViewRepresentable 
    func sizeThatFits(
        _ proposal: ProposedViewSize,
        uiView: UITextField, context: Context
    ) -> CGSize? 

If we return nil or don’t define this method at all, the system will fallback to the default sizing algorithm.

I found this method useful when wrapping UITextField in SwiftUI, if I want it to respect the frame coming from the SwiftUI code and not overflow the provided width.

struct ContentView: View 
    @State private var text = "Hello, world!"
    var body: some View 
        WrappedTextField(text: $text)
            .frame(width: 200, height: 50)

struct WrappedTextField: UIViewRepresentable 
    @Binding var text: String
    func makeUIView(context: Context) -> UITextField 
        let textField = UITextField()
        return textField
    func sizeThatFits(
        _ proposal: ProposedViewSize,
        uiView: UITextField, context: Context
    ) -> CGSize? 
            let width = proposal.width,
            let height = proposal.height
        else  return nil 
        return CGSize(width: width, height: height)

If you are working with both UIKit and SwiftUI in one project, you might like my recent book Integrating SwiftUI into UIKit Apps. It focuses on gradually adopting SwiftUI in UIKit projects and also covers how to start migrating to the SwiftUI app lifecycle while reusing existing UIKit views and components along the way.

Integrating SwiftUI into UIKit Apps by Natalia Panferova book cover
Black Friday offer

Our book “Integrating SwiftUI into UIKit apps” is now 30% off!

Discover various ways to adopt SwiftUI in existing UIKit projects and take full advantage of the new iOS 16 frameworks and APIs such as Swift Charts.

The offer is active until the 1st of December.



Please enter your comment!
Please enter your name here