BottomSheetView in SwiftUI https://swiftwithmajid.com/2019/12/11/building-bottom-sheet-in-swiftui/

BottomSheetView.swift

//
//  BottomSheetView.swift
//
//  Created by Majid Jabrayilov
//  Copyright © 2019 Majid Jabrayilov. All rights reserved.
//
import SwiftUI

fileprivate enum Constants {
    static let radius: CGFloat = 16
    static let indicatorHeight: CGFloat = 6
    static let indicatorWidth: CGFloat = 60
    static let snapRatio: CGFloat = 0.25
    // static let minHeightRatio: CGFloat = 0.3
}

struct BottomSheetView<Content: View>: View {
    @State private var isOpen: Bool = false

    let maxHeight: CGFloat
    let minHeight: CGFloat
    let keyboardOffset: CGFloat
    
    let content: Content
    
    @GestureState private var translation: CGFloat = 0

    private var offset: CGFloat {
        return max (
            (offsetForState + self.translation > self.maxHeight - self.minHeight)
                ? self.maxHeight - self.minHeight
                : offsetForState + self.translation
            , 0
        )
    }
    
    private var offsetForState: CGFloat {
        isOpen ? 0 : self.maxHeight - self.minHeight
    }

    private var grabControlIndicator: some View {
        if self.keyboardOffset < 0 {
            return AnyView(EmptyView())
        } else {
            return AnyView (
                VStack {
                    RoundedRectangle(cornerRadius: Constants.radius)
                        .fill(Theme.secondaryBackgroundColor)
                        .frame(
                            width: Constants.indicatorWidth,
                            height: Constants.indicatorHeight
                    )
                    .onTapGesture {
                        self.isOpen.toggle()
                    }
                }
            )
        }
    }

    init (
        // isOpen: Binding<Bool>,
        minHeight: CGFloat,
        maxHeight: CGFloat,
        keyboardOffset: CGFloat,
        @ViewBuilder content: () -> Content
    ) {
        // self.minHeight = maxHeight * Constants.minHeightRatio
        self.minHeight = minHeight
        self.maxHeight = maxHeight
        self.keyboardOffset = keyboardOffset
        
        self.content = content()
        // self._isOpen = isOpen
    }

    var body: some View {
        GeometryReader { geometry in
            VStack(spacing: 0) {
                self.grabControlIndicator.padding()
                
                Rectangle()
                    .fill(Theme.secondaryBackgroundColor)
                    .frame(height: 1)
                    .edgesIgnoringSafeArea(.horizontal)
                
                self.content
            }
            .frame(width: geometry.size.width, height: self.maxHeight, alignment: .top)
            .background ( RoundedCorner (
                tl: self.isOpen ? 0 : Constants.radius,
                tr: self.isOpen ? 0 : Constants.radius,
                bl: 0,
                br: 0
            )
            .fill(Theme.backgroundColor))
            .frame(height: geometry.size.height, alignment: .bottom)
            .offset(y: self.offset)
            .animation(.interactiveSpring())
            .gesture (
                DragGesture().updating(self.$translation) { value, state, _ in
                    state = value.translation.height
                }
                .onEnded { value in
                    let snapDistance = self.maxHeight * Constants.snapRatio
                    
                    guard abs(value.translation.height) > snapDistance else {
                        return
                    }
                    
                    self.isOpen = value.translation.height < 0
                }
            )
        }
    }
}

#if DEBUG
struct BottomSheetView_Previews: PreviewProvider {
    static var previews: some View {
        BottomSheetView (
            // isOpen: .constant(false),
            minHeight: 250,
            maxHeight: 600,
            keyboardOffset: 0
        ) {
            Rectangle().fill(Color.blue)
        }
    }
}
#endif