Swipeable Modifier #swift #swiftui #modifiers

SwipeableModfier.swift

//
//  SwipeableModifier.swift
//  DrinkSum
//
//  Created by Greg Eales on 22/12/20.
//

import SwiftUI

struct Swipeable<V>: ViewModifier where V: View {

    @State private var dragAmount = CGFloat.zero
    @State private var direction: Bool? = nil
    
    let maxDrag: CGFloat
    let underView:  (CGFloat, CGFloat) -> V
    
    func body(content: Content) -> some View {
        ZStack {
            
            HStack {
                Spacer()
                
                underView(self.dragAmount, self.maxDrag)
                    .padding(.leading, 10)
                    .frame(width: self.maxDrag)
            }
            
            content
                .offset(x: self.dragAmount)
                .gesture(
                    DragGesture()
                        .onChanged {
                            if self.direction == nil {
                                if self.dragAmount == -self.maxDrag {
                                    self.direction = true
                                } else if self.dragAmount == 0 {
                                    self.direction = false
                                } else {
                                    self.direction = $0.translation.width > 0
                                }
                            }
                            
                            if self.direction! {
                                self.dragAmount = min(0, max(-maxDrag, -maxDrag + max(0, $0.translation.width)))
                            } else {
                                self.dragAmount = min(0, max(-maxDrag, min(0,$0.translation.width)))
                            }
                        }
                        .onEnded({ _ in
                            withAnimation {
                                self.direction = nil
                                if self.dragAmount < (self.maxDrag * -0.5) {
                                    self.dragAmount = -self.maxDrag
                                } else {
                                    self.dragAmount = 0
                                }
                            }
                        })
                )
                .onTapGesture {
                    withAnimation {
                        self.dragAmount = 0
                    }
                }
        }
    }
}

extension View {
    func swipeable<V>(maxDrag: CGFloat, underView: @escaping (CGFloat, CGFloat) -> V) -> some View where V:View  {
        return self.modifier(Swipeable(maxDrag: maxDrag, underView: underView))
    }
}