swift – iOS backside sheet with fraction detents UIKit

I inspected the underlying UISheetPresentationController of a SwiftUI sheet on iOS 17.4, and noticed that the detents have a kind of “customized”.

import SwiftUIIntrospect

struct ContentView: View {

    var physique: some View {
        Textual content("Foo")
            .sheet(isPresented: .fixed(true)) {
                Textual content("Sheet")
                    .presentationDetents([.height(100), .fraction(0.5)])
                    .introspect(.sheet, on: .iOS(.v17)) { x in
                        print((x as! UISheetPresentationController).detents)
                    }
            }
    }
}

/*
Output:
[<UISheetPresentationControllerDetent: 0x600000c62610: _type=custom, _identifier=Fraction:0.5>, <UISheetPresentationControllerDetent: 0x600000c626a0: _type=custom, _identifier=Height:100.0>]
*/

This implies that .fraction(...) and .top(...) in SwiftUI merely creates UIKit detents utilizing the .customized manufacturing facility methodology. Then again, .medium and .giant in SwiftUI does correspond to .medium() and .giant() in UIKit.

Right here is an extension on UISheetPresentationController.Detent that provides a fraction manufacturing facility methodology:

extension UISheetPresentationController.Detent {
    static func fraction(_ worth: CGFloat) -> UISheetPresentationController.Detent {
        .customized(identifier: Identifier("Fraction:(worth)")) { context in
            context.maximumDetentValue * worth
        }
    }
}