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September 15, 2019 07:49
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// | |
// ContentView.swift | |
// SwiftyPageControl | |
// | |
// Created by crea on 2019/09/15. | |
// Copyright © 2019 crea. All rights reserved. | |
// | |
import SwiftUI | |
enum PageControlError: Swift.Error { | |
case failedInitialization | |
} | |
struct ContentView: View { | |
@State var currentIndex = 0 | |
@State var hidesForSinglePage = false | |
var body: some View { | |
try! PageControl( | |
numOfContents: 3, | |
currentPageColor: .blue, | |
tintColor: .green, | |
currentIndex: $currentIndex, | |
hidesForSinglePage: $hidesForSinglePage | |
) | |
} | |
} | |
struct PageControl: View { | |
let numOfContents: Int | |
let currentPageColor: Color | |
let tintColor: Color | |
@Binding var currentIndex: Int | |
@Binding var hidesForSinglePage: Bool | |
var shouldHide: Bool { numOfContents == 1 && hidesForSinglePage } | |
// @Stateは、プロパティ宣言で初期値を代入しておかないと、 | |
// init内で参照できない = 代入できない。ふーん...?🤔 | |
// と思いきや、もっと事態は悪い! | |
// @Stateの値に bodyの外からアクセスするとクラッシュするのだから。、 | |
// initの目的・仕組み上、initで@Stateを初期化するのは無理! | |
// あくまで@Stateはローカル目的だ! | |
init( | |
numOfContents: Int, | |
currentPageColor: Color = .blue, | |
tintColor: Color = .red, | |
currentIndex: Binding<Int>, | |
hidesForSinglePage: Binding<Bool> | |
) throws { | |
guard currentIndex.wrappedValue + 1 <= numOfContents else { | |
throw PageControlError.failedInitialization | |
} | |
self.numOfContents = numOfContents | |
self.currentPageColor = currentPageColor | |
self.tintColor = tintColor | |
self._currentIndex = currentIndex | |
self._hidesForSinglePage = hidesForSinglePage | |
} | |
var body: some View { | |
HStack { | |
ForEach(0..<numOfContents, id: \.self) { index in | |
Circle() | |
.fill(index == self.currentIndex ? self.currentPageColor : self.tintColor) | |
.frame(width: 7, height: 7) | |
.onTapGesture { | |
self.currentIndex = index | |
} | |
} | |
} | |
.opacity(shouldHide ? 0 : 1) | |
} | |
} | |
struct PageControl_Previews: PreviewProvider { | |
// @Stateをstaticにしたら、.constantではないbindingを渡せるのでは?と思ったが、 | |
// ビルドは通ったがプレビューがクラッシュする | |
static var previews: some View { | |
try! PageControl(numOfContents: 3, | |
currentPageColor: .yellow, | |
tintColor: .purple, | |
currentIndex: .constant(0), | |
hidesForSinglePage: .constant(false) | |
) | |
} | |
} |
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