make views draggable

draggable.swift

//
//  ContentView.swift
//
//  Created by Ray Fix on 5/9/20.
//  Copyright © 2020 Ray Fix. All rights reserved.
//

import SwiftUI

struct ContentView: View {
  
  func card(_ color: Color) -> some View {
    Rectangle()
      .foregroundColor(color)
      .frame(width: 100, height: 130)
      .cornerRadius(5)
  }
  
  var body: some View {
    HStack {
      card(.green)
      card(.red)
    }
  }
}

extension View {
  func draggable() -> some View  {
    modifier(DraggingModifier())
  }
}

struct DraggingModifier: ViewModifier {
  
  @GestureState private var isDragging = false
  @GestureState private var dragOffset: CGSize = .zero
  
  var dragGesture: some Gesture {
    DragGesture()
      .updating($isDragging) { (value, state, transaction) in
        state = true
      }
    .updating($dragOffset) { (value, state, transaction) in
      state = value.translation
    }
  }
  
  func body(content: Content) -> some View {
    content
      .rotationEffect(Angle(degrees: isDragging ? 5:0))
      .animation(.default)
      .offset(dragOffset)
      .zIndex(isDragging ? 1 : 0)
      .gesture(dragGesture)
  }
}

struct ContentView_Previews: PreviewProvider {
  static var previews: some View {
    ContentView()
  }
}