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<!DOCTYPE HTML>
<html lang="zh-tw" >
<head>
<meta charset=utf-8"UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=11; IE=10; IE=9; IE=8; IE=7; IE=EDGE" />
<title>动态列表、 ForEach 与 Identifiable 的使用方法 | 精通 SwiftUI - iOS 16 版</title>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
<meta name="description" content="">
<meta name="generator" content="GitBook 2.0.1">
<meta name="author" content="Simon Ng">
<meta name="HandheldFriendly" content="true"/>
<meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no">
<meta name="apple-mobile-web-app-capable" content="yes">
<meta name="apple-mobile-web-app-status-bar-style" content="black">
<link rel="apple-touch-icon-precomposed" sizes="152x152" href="gitbook/images/apple-touch-icon-precomposed-152.png">
<link rel="shortcut icon" href="gitbook/images/favicon.ico" type="image/x-icon">
<link rel="next" href="./swiftui-navigation.html" />
<link rel="prev" href="./swiftui-animation.html" />
</head>
<body>
<link rel="stylesheet" href="gitbook/style.css">
<link rel="stylesheet" href="gitbook/plugins/gitbook-plugin-image-captions/image-captions.css">
<link rel="stylesheet" href="././styles/website.css">
<div class="book" data-level="10" data-basepath="." data-revision="Thu Dec 01 2022 17:36:55 GMT+0800 (HKT)">
<div class="book-summary">
<div class="book-search">
<input type="text" placeholder="输入并搜寻" class="form-control" />
</div>
<ul class="summary">
<li>
<a href="https://www.appcoda.com.tw" target="blank" class="custom-link">Made by AppCoda</a>
</li>
<li>
<a href="https://www.appcoda.com.tw/contact" target="blank" class="custom-link">Contact us / Support</a>
</li>
<li>
<a href="http://twitter.com/share?text=Mastering%20SwiftUI%20via%20@appcodamobile&url=https://www.appcoda.com.tw/swiftui/&hashtags=swiftlang" target="blank" class="custom-link">Tweet this book</a>
</li>
<li class="divider"></li>
<li class="chapter " data-level="0" data-path="index.html">
<a href="./index.html">
<i class="fa fa-check"></i>
序言
</a>
</li>
<li class="chapter " data-level="1" data-path="swiftui-basics.html">
<a href="./swiftui-basics.html">
<i class="fa fa-check"></i>
<b>1.</b>
SwiftUI 介绍
</a>
</li>
<li class="chapter " data-level="2" data-path="swiftui-text.html">
<a href="./swiftui-text.html">
<i class="fa fa-check"></i>
<b>2.</b>
SwiftUI 入门 - 文字的处理
</a>
</li>
<li class="chapter " data-level="3" data-path="swiftui-images.html">
<a href="./swiftui-images.html">
<i class="fa fa-check"></i>
<b>3.</b>
图片的处理
</a>
</li>
<li class="chapter " data-level="4" data-path="swiftui-stacks.html">
<a href="./swiftui-stacks.html">
<i class="fa fa-check"></i>
<b>4.</b>
以堆叠布局使用者介面
</a>
</li>
<li class="chapter " data-level="5" data-path="swiftui-scrollview.html">
<a href="./swiftui-scrollview.html">
<i class="fa fa-check"></i>
<b>5.</b>
ScrollView 与 Carousel UI 的建立
</a>
</li>
<li class="chapter " data-level="6" data-path="swiftui-buttons.html">
<a href="./swiftui-buttons.html">
<i class="fa fa-check"></i>
<b>6.</b>
SwiftUI 按钮与渐层
</a>
</li>
<li class="chapter " data-level="7" data-path="swiftui-state.html">
<a href="./swiftui-state.html">
<i class="fa fa-check"></i>
<b>7.</b>
状态(State)与绑定(Binding)
</a>
</li>
<li class="chapter " data-level="8" data-path="swiftui-path-shape.html">
<a href="./swiftui-path-shape.html">
<i class="fa fa-check"></i>
<b>8.</b>
实现路径(Path)与形状(Shape)来画线与圆饼图
</a>
</li>
<li class="chapter " data-level="9" data-path="swiftui-animation.html">
<a href="./swiftui-animation.html">
<i class="fa fa-check"></i>
<b>9.</b>
基础动画与转场
</a>
</li>
<li class="chapter active" data-level="10" data-path="swiftui-list.html">
<a href="./swiftui-list.html">
<i class="fa fa-check"></i>
<b>10.</b>
动态列表、 ForEach 与 Identifiable 的使用方法
</a>
</li>
<li class="chapter " data-level="11" data-path="swiftui-navigation.html">
<a href="./swiftui-navigation.html">
<i class="fa fa-check"></i>
<b>11.</b>
导航UI与导航列客制化运用
</a>
</li>
<li class="chapter " data-level="12" data-path="swiftui-modal.html">
<a href="./swiftui-modal.html">
<i class="fa fa-check"></i>
<b>12.</b>
强制回应视图、浮动按钮与提示的实现
</a>
</li>
<li class="chapter " data-level="13" data-path="swiftui-form.html">
<a href="./swiftui-form.html">
<i class="fa fa-check"></i>
<b>13.</b>
以选取器(Picker)、开关(Toggle)与步进器(Stepper)来建立一个表单
</a>
</li>
<li class="chapter " data-level="14" data-path="swiftui-form-data.html">
<a href="./swiftui-form-data.html">
<i class="fa fa-check"></i>
<b>14.</b>
使用 Combine 与 Environment 物件进行数据分享
</a>
</li>
<li class="chapter " data-level="15" data-path="swiftui-form-registration.html">
<a href="./swiftui-form-registration.html">
<i class="fa fa-check"></i>
<b>15.</b>
以 Combine 与 视图模型建立一个注册表单
</a>
</li>
<li class="chapter " data-level="16" data-path="swiftui-actionsheet-context.html">
<a href="./swiftui-actionsheet-context.html">
<i class="fa fa-check"></i>
<b>16.</b>
滑动删除、内容菜单与动作列表
</a>
</li>
<li class="chapter " data-level="17" data-path="swiftui-gestures.html">
<a href="./swiftui-gestures.html">
<i class="fa fa-check"></i>
<b>17.</b>
认识手势(Gestures)
</a>
</li>
<li class="chapter " data-level="18" data-path="swiftui-bottom-sheet.html">
<a href="./swiftui-bottom-sheet.html">
<i class="fa fa-check"></i>
<b>18.</b>
以SwiftUI 手势与 GeometryReader 建立一个底部展开式页面
</a>
</li>
<li class="chapter " data-level="19" data-path="swiftui-trip-tinder.html">
<a href="./swiftui-trip-tinder.html">
<i class="fa fa-check"></i>
<b>19.</b>
使用手势与动画建立 Tinder 风格的 UI
</a>
</li>
<li class="chapter " data-level="20" data-path="swiftui-advanced-animations.html">
<a href="./swiftui-advanced-animations.html">
<i class="fa fa-check"></i>
<b>20.</b>
建立像 Apple Wallet App 的动画和转场效果
</a>
</li>
<li class="chapter " data-level="21" data-path="swiftui-json.html">
<a href="./swiftui-json.html">
<i class="fa fa-check"></i>
<b>21.</b>
JSON、滑杆的运用与数据过滤
</a>
</li>
<li class="chapter " data-level="22" data-path="swiftui-core-data.html">
<a href="./swiftui-core-data.html">
<i class="fa fa-check"></i>
<b>22.</b>
如何使用 Core Data 建立 ToDo App
</a>
</li>
<li class="chapter " data-level="23" data-path="swiftui-uikit.html">
<a href="./swiftui-uikit.html">
<i class="fa fa-check"></i>
<b>23.</b>
利用 UIViewRepresentable 整合UIKit 组件
</a>
</li>
<li class="chapter " data-level="24" data-path="swiftui-searchbar.html">
<a href="./swiftui-searchbar.html">
<i class="fa fa-check"></i>
<b>24.</b>
建立搜寻栏视图并使用自订绑定(Custom Binding)
</a>
</li>
<li class="chapter " data-level="25" data-path="swiftui-real-world-app.html">
<a href="./swiftui-real-world-app.html">
<i class="fa fa-check"></i>
<b>25.</b>
把所学应用出来!构建个人理财App
</a>
</li>
<li class="chapter " data-level="26" data-path="swiftui-appstoreanimation.html">
<a href="./swiftui-appstoreanimation.html">
<i class="fa fa-check"></i>
<b>26.</b>
创建类似App Store使用的动画视图转换
</a>
</li>
<li class="chapter " data-level="27" data-path="swiftui-carousel.html">
<a href="./swiftui-carousel.html">
<i class="fa fa-check"></i>
<b>27.</b>
如何建立图像轮播(Image Carousel)
</a>
</li>
<li class="chapter " data-level="28" data-path="swiftui-expandable-list.html">
<a href="./swiftui-expandable-list.html">
<i class="fa fa-check"></i>
<b>28.</b>
如何建立展开式列表视图和大纲视图
</a>
</li>
<li class="chapter " data-level="29" data-path="swiftui-gridlayout.html">
<a href="./swiftui-gridlayout.html">
<i class="fa fa-check"></i>
<b>29.</b>
使用 LazyVGrid 和 LazyHGrid 构建集合视图
</a>
</li>
<li class="chapter " data-level="30" data-path="swiftui-progress-ring.html">
<a href="./swiftui-progress-ring.html">
<i class="fa fa-check"></i>
<b>30.</b>
使用 Shape 和 Animatable 开发带动画的环形进度条
</a>
</li>
<li class="chapter " data-level="31" data-path="swiftui-library.html">
<a href="./swiftui-library.html">
<i class="fa fa-check"></i>
<b>31.</b>
如何使用 AnimatableModifier 和 LibraryContentProvider
</a>
</li>
<li class="chapter " data-level="32" data-path="swiftui-texteditor.html">
<a href="./swiftui-texteditor.html">
<i class="fa fa-check"></i>
<b>32.</b>
使用 TextEditor 支持多行文字输入
</a>
</li>
<li class="chapter " data-level="33" data-path="swiftui-matchedgeometry.html">
<a href="./swiftui-matchedgeometry.html">
<i class="fa fa-check"></i>
<b>33.</b>
使用 matchedGeometryEffect为 App 建立绚丽的视图动画
</a>
</li>
<li class="chapter " data-level="34" data-path="swiftui-grid-animation.html">
<a href="./swiftui-grid-animation.html">
<i class="fa fa-check"></i>
<b>34.</b>
ScrollViewReader 和网格动画
</a>
</li>
<li class="chapter " data-level="35" data-path="swiftui-tabview.html">
<a href="./swiftui-tabview.html">
<i class="fa fa-check"></i>
<b>35.</b>
标签视图的运用与自订标签列
</a>
</li>
<li class="chapter " data-level="36" data-path="swiftui-asyncimage.html">
<a href="./swiftui-asyncimage.html">
<i class="fa fa-check"></i>
<b>36.</b>
利用 AsyncImage 非同步加载和显示图像
</a>
</li>
<li class="chapter " data-level="37" data-path="swiftui-searchable.html">
<a href="./swiftui-searchable.html">
<i class="fa fa-check"></i>
<b>37.</b>
利用 Searchable 建立搜寻栏
</a>
</li>
<li class="chapter " data-level="38" data-path="swiftui-charts.html">
<a href="./swiftui-charts.html">
<i class="fa fa-check"></i>
<b>38.</b>
利用 Charts 框架建立图表
</a>
</li>
<li class="chapter " data-level="39" data-path="swiftui-live-text.html">
<a href="./swiftui-live-text.html">
<i class="fa fa-check"></i>
<b>39.</b>
利用 Live Text API 从图片中撷取文本
</a>
</li>
<li class="chapter " data-level="40" data-path="swiftui-sharelink.html">
<a href="./swiftui-sharelink.html">
<i class="fa fa-check"></i>
<b>40.</b>
通过 ShareLink 来分享文本和图像等数据
</a>
</li>
<li class="chapter " data-level="41" data-path="swiftui-imagerenderer.html">
<a href="./swiftui-imagerenderer.html">
<i class="fa fa-check"></i>
<b>41.</b>
利用 ImageRenderer API 轻松把 SwiftUI 视图转换为图像
</a>
</li>
<li class="chapter " data-level="42" data-path="swiftui-pdf-doc.html">
<a href="./swiftui-pdf-doc.html">
<i class="fa fa-check"></i>
<b>42.</b>
如何把 SwiftUI 视图转换为 PDF 文件
</a>
</li>
<li class="chapter " data-level="43" data-path="swiftui-gauge.html">
<a href="./swiftui-gauge.html">
<i class="fa fa-check"></i>
<b>43.</b>
使用 Gauge 视图显示进度并创建速度计
</a>
</li>
<li class="chapter " data-level="44" data-path="swiftui-grid.html">
<a href="./swiftui-grid.html">
<i class="fa fa-check"></i>
<b>44.</b>
使用Grid API 创建网格布局
</a>
</li>
<li class="chapter " data-level="45" data-path="swiftui-anylayout.html">
<a href="./swiftui-anylayout.html">
<i class="fa fa-check"></i>
<b>45.</b>
利用 AnyLayout 切换 UI 布局
</a>
</li>
<li class="chapter " data-level="46" data-path="swiftui-navigationstack.html">
<a href="./swiftui-navigationstack.html">
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<h1 id="%E7%AC%AC-10-%E7%AB%A0-br-%E5%8B%95%E6%85%8B%E6%B8%85%E5%96%AE%E3%80%81foreach-%E8%88%87%E8%AD%98%E5%88%A5">第 10 章<br>动态清单、ForEach 与识别</h1>
<p>在 UIKit 中,表格视图是 iOS 中最常见的 UI 控制组件之一。如果你之前使用过 UIKit 开发 App,则你应该知道可使用表格视图显示数据清单。这个 UI 控制组件在以内容为主的App 很常见,例如:报纸 App。图 10.1 展示了一些清单 / 表格视图,你可在诸如 Instagram、Twitter、Airbnb 与 Apple News 等流行应用程序中找到这些视图。</p>
<figure id="fig10.1"><img src="images/list/swiftui-list-1.jpg" alt="图 10.1. 清单视图示例"><figcaption>图 10.1. 清单视图示例</figcaption></figure>
<p>在 SwiftUI 中,我们使用 <code>List</code> 代替表格视图来显示数据列。如果你之前使用过 <code>UIKit</code> 建立表格视图,你应该知道实现一个简单的表格视图,就需要花一点工夫。而若是要建立自订 Cell 布局的表格视图,则要做的工作更多。SwiftUI 简化了整个过程,只需几行代码,你就能以表格形式来陈列数据。即使你需要自订列的布局,也只需要极少的工夫即可办到。</p>
<p>仍是觉得困惑吗?待会你就能明白我的意思。</p>
<p>在本章中,我们将从一个简单的清单来开始。当你了解这些基础知识,我将教你如何以更复杂的布局来陈列数据清单,如图 10.2 所示。</p>
<figure id="fig10.2"><img src="images/list/swiftui-list-2.jpg" alt="图 10.2. 建立一个简单且多样化的清单"><figcaption>图 10.2. 建立一个简单且多样化的清单</figcaption></figure>
<h3 id="%E5%BB%BA%E7%AB%8B%E4%B8%80%E5%80%8B%E7%B0%A1%E5%96%AE%E7%9A%84%E6%B8%85%E5%96%AE">建立一个简单的清单</h3>
<p>我们从简单的清单来开始。首先,开启 Xcode,并使用“App”模板建立一个新项目。在下一个画面中,设定项目名称为“SwiftUIList”(或你喜欢的任何名称),并填入所有必填的值,只需确保在“Interface”选项中选取“SwiftUI”。</p>
<p>Xcode 应会在 <code>ContentView.swift</code> 档中产生一些代码。现在修改代码如下: </p>
<pre><code class="lang-swift"><span class="hljs-class"><span class="hljs-keyword">struct</span> <span class="hljs-title">ContentView</span>: <span class="hljs-title">View</span> </span>{
<span class="hljs-keyword">var</span> body: some <span class="hljs-type">View</span> {
<span class="hljs-type">List</span> {
<span class="hljs-type">Text</span>(<span class="hljs-string">"Item 1"</span>)
<span class="hljs-type">Text</span>(<span class="hljs-string">"Item 2"</span>)
<span class="hljs-type">Text</span>(<span class="hljs-string">"Item 3"</span>)
<span class="hljs-type">Text</span>(<span class="hljs-string">"Item 4"</span>)
}
}
}
</code></pre>
<p>以上是建立一个简单的清单或表格所需要的代码。当你将文字视图嵌入 <code>List</code> 中时,清单视图会以列显示数据。这里,每一列显示具不同叙述的文字视图。</p>
<figure id="fig10.3"><img src="images/list/swiftui-list-3.png" alt="图 10.3. 建立一个简单的清单"><figcaption>图 10.3. 建立一个简单的清单</figcaption></figure>
<p>相同的代码片段可以使用 <code>ForEach</code> 来编写,如下所示: </p>
<pre><code class="lang-swift"><span class="hljs-class"><span class="hljs-keyword">struct</span> <span class="hljs-title">ContentView</span>: <span class="hljs-title">View</span> </span>{
<span class="hljs-keyword">var</span> body: some <span class="hljs-type">View</span> {
<span class="hljs-type">List</span> {
<span class="hljs-type">ForEach</span>(<span class="hljs-number">1</span>...<span class="hljs-number">4</span>, id: \.<span class="hljs-keyword">self</span>) { index <span class="hljs-keyword">in</span>
<span class="hljs-type">Text</span>(<span class="hljs-string">"Item <span class="hljs-subst">\(index)</span>"</span>)
}
}
}
}
</code></pre>
<p>由于这些文字视图非常相似,因此你可在 SwiftUI 中使用 <code>ForEach</code> 回圈来建立视图。</p>
<blockquote>
<p>从已识别的底层集合中,依照需求计算视图的一种结构。</p>
<p>- Apple 官方文件 (<a href="https://developer.apple.com/documentation/swiftui/foreach" target="_blank">https://developer.apple.com/documentation/swiftui/foreach</a>)</p>
</blockquote>
<p>你可以提供 <code>ForEach</code> 一组数据集合或一个范围。不过,你必须要注意的是,你需要告诉 <code>ForEach</code> 如何识别集合中的每个项目,参数 <code>id</code> 的目的在于此,为什么 <code>ForEach</code> 需要识别项目的唯一性呢? SwiftUI 功能强大,可在部分或全部集合内的项目修改时自动修改 UI, 因此当修改或删除项目时,需要一个识别码来识别该项目。</p>
<p>在上面的代码中,我们传送给 <code>ForEach</code> 一个范围的值来逐一运行。该识别码设定为其值(即 1、2、3、4),<code>index</code> 参数储存回圈的目前值,例如:它从“1”这个值开始, <code>index</code> 参数的值则为“1”。</p>
<p>在闭包中,即是渲染视图所需的代码,这里也是我们需要建立的文字视图,其叙述将依据回圈中的 <code>index</code> 值而变化。如此,你就可以在清单中建立四个不同标题的项目。</p>
<p>我再教你一种技巧,相同的代码片段也可以进一步重写如下: </p>
<pre><code class="lang-swift"><span class="hljs-class"><span class="hljs-keyword">struct</span> <span class="hljs-title">ContentView</span>: <span class="hljs-title">View</span> </span>{
<span class="hljs-keyword">var</span> body: some <span class="hljs-type">View</span> {
<span class="hljs-type">List</span> {
<span class="hljs-type">ForEach</span>(<span class="hljs-number">1</span>...<span class="hljs-number">4</span>, id: \.<span class="hljs-keyword">self</span>) {
<span class="hljs-type">Text</span>(<span class="hljs-string">"Item <span class="hljs-subst">\($<span class="hljs-number">0</span>)</span>"</span>)
}
}
}
}
</code></pre>
<p>你可以省略 <code>index</code> 参数,并使用参数名称缩写 <code>$0</code>,它表示闭包的第一个参数。</p>
<p>我们进一步将代码重写得更简单些,你可将数据集合直接传送到 <code>List</code> 视图,代码如下: </p>
<pre><code class="lang-swift"><span class="hljs-class"><span class="hljs-keyword">struct</span> <span class="hljs-title">ContentView</span>: <span class="hljs-title">View</span> </span>{
<span class="hljs-keyword">var</span> body: some <span class="hljs-type">View</span> {
<span class="hljs-type">List</span>(<span class="hljs-number">1</span>...<span class="hljs-number">4</span>, id: \.<span class="hljs-keyword">self</span>) {
<span class="hljs-type">Text</span>(<span class="hljs-string">"Item <span class="hljs-subst">\($<span class="hljs-number">0</span>)</span>"</span>)
}
}
}
</code></pre>
<p>如你所见,只需两行代码,即可建立一个简单的清单 / 表格。</p>
<h3 id="%E5%BB%BA%E7%AB%8B%E5%85%B7%E6%96%87%E5%AD%97%E5%8F%8A%E5%9C%96%E7%89%87%E7%9A%84%E6%B8%85%E5%96%AE%E8%A6%96%E5%9C%96">建立具文字及图片的清单视图</h3>
<p>现在你已经知道如何建立一个简单的清单,接着我们来看如何使用更多样化的布局。在大多数的情况下,清单视图的项目皆会包含文字与图片,而你该如何实现呢?如果你知道 <code>Image</code>、<code>Text</code>、<code>VStack</code> 与 <code>HStack</code> 的用法的话,你应该对如何建立它有概念了。</p>
<p>如果你阅读过《<a href="https://www.appcoda.com.tw/swift" target="_blank">iOS App 程序开发实务心法</a>》一书,你应该非常熟悉这个示例。我们以此为例来看使用 SwiftUI 建立相同的表格有多么容易,如图 10.4 所示。</p>
<figure id="fig10.4"><img src="images/list/swiftui-list-4.png" alt="图 10.4 显示餐厅列的简单表格视图"><figcaption>图 10.4 显示餐厅列的简单表格视图</figcaption></figure>
<p>要使用 UIKit 建立表格,你需要建立一个表格视图或表格视图控制器,然后自订 Prototype Cell。另外,你还必须编写表格视图数据来源的代码,以提供数据。建立一个表格UI 需要很多的步骤,现在我们来看如何在 SwiftUI 中实现相同的表格视图。</p>
<p>首先,我们至下列网址来下载图片素材:<a href="https://www.appcoda.com/resources/swiftui/SwiftUISimpleTableImages.zip" target="_blank">https://www.appcoda.com/resources/swiftui/SwiftUISimpleTableImages.zip</a> 然后将 zip 档解压缩,并把所有图片汇入素材目录,如图 10.5 所示。</p>
<figure id="fig10.5"><img src="images/list/swiftui-list-5.png" alt="图 10.5. 汇入图片至素材目录"><figcaption>图 10.5. 汇入图片至素材目录</figcaption></figure>
<p>现在,切换到 <code>ContentView.swift</code> 来编写 UI 的代码。首先,我们在 <code>ContentView</code> 中声明两个数组,这些数组是用来储存餐厅名称与图片。下列是完整的代码: </p>
<pre><code class="lang-swift"><span class="hljs-class"><span class="hljs-keyword">struct</span> <span class="hljs-title">ContentView</span>: <span class="hljs-title">View</span> </span>{
<span class="hljs-keyword">var</span> restaurantNames = [<span class="hljs-string">"Cafe Deadend"</span>, <span class="hljs-string">"Homei"</span>, <span class="hljs-string">"Teakha"</span>, <span class="hljs-string">"Cafe Loisl"</span>, <span class="hljs-string">"Petite Oyster"</span>, <span class="hljs-string">"For Kee Restaurant"</span>, <span class="hljs-string">"Po's Atelier"</span>, <span class="hljs-string">"Bourke Street Bakery"</span>, <span class="hljs-string">"Haigh's Chocolate"</span>, <span class="hljs-string">"Palomino Espresso"</span>, <span class="hljs-string">"Upstate"</span>, <span class="hljs-string">"Traif"</span>, <span class="hljs-string">"Graham Avenue Meats And Deli"</span>, <span class="hljs-string">"Waffle & Wolf"</span>, <span class="hljs-string">"Five Leaves"</span>, <span class="hljs-string">"Cafe Lore"</span>, <span class="hljs-string">"Confessional"</span>, <span class="hljs-string">"Barrafina"</span>, <span class="hljs-string">"Donostia"</span>, <span class="hljs-string">"Royal Oak"</span>, <span class="hljs-string">"CASK Pub and Kitchen"</span>]
<span class="hljs-keyword">var</span> restaurantImages = [<span class="hljs-string">"cafedeadend"</span>, <span class="hljs-string">"homei"</span>, <span class="hljs-string">"teakha"</span>, <span class="hljs-string">"cafeloisl"</span>, <span class="hljs-string">"petiteoyster"</span>, <span class="hljs-string">"forkeerestaurant"</span>, <span class="hljs-string">"posatelier"</span>, <span class="hljs-string">"bourkestreetbakery"</span>, <span class="hljs-string">"haighschocolate"</span>, <span class="hljs-string">"palominoespresso"</span>, <span class="hljs-string">"upstate"</span>, <span class="hljs-string">"traif"</span>, <span class="hljs-string">"grahamavenuemeats"</span>, <span class="hljs-string">"wafflewolf"</span>, <span class="hljs-string">"fiveleaves"</span>, <span class="hljs-string">"cafelore"</span>, <span class="hljs-string">"confessional"</span>, <span class="hljs-string">"barrafina"</span>, <span class="hljs-string">"donostia"</span>, <span class="hljs-string">"royaloak"</span>, <span class="hljs-string">"caskpubkitchen"</span>]
<span class="hljs-keyword">var</span> body: some <span class="hljs-type">View</span> {
<span class="hljs-type">List</span>(<span class="hljs-number">1</span>...<span class="hljs-number">4</span>, id: \.<span class="hljs-keyword">self</span>) {
<span class="hljs-type">Text</span>(<span class="hljs-string">"Item <span class="hljs-subst">\($<span class="hljs-number">0</span>)</span>"</span>)
}
}
}
</code></pre>
<p>两个数组具有相同项目数,<code>restaurantNames</code> 数组储存餐厅名称,<code>restaurantImages</code> 变量储存你刚汇入的图片名称。要建立如图 10.4 所示的清单视图,你只需要修改 <code>body</code> 变量如下: :</p>
<pre><code class="lang-swift"><span class="hljs-keyword">var</span> body: some <span class="hljs-type">View</span> {
<span class="hljs-type">List</span>(restaurantNames.<span class="hljs-built_in">indices</span>, id: \.<span class="hljs-keyword">self</span>) { index <span class="hljs-keyword">in</span>
<span class="hljs-type">HStack</span> {
<span class="hljs-type">Image</span>(<span class="hljs-keyword">self</span>.restaurantImages[index])
.resizable()
.frame(width: <span class="hljs-number">40</span>, height: <span class="hljs-number">40</span>)
.cornerRadius(<span class="hljs-number">5</span>)
<span class="hljs-type">Text</span>(<span class="hljs-keyword">self</span>.restaurantNames[index])
}
}
}
</code></pre>
<p>我们做了一些修改,首先是 <code>List</code> 视图,我们传送餐厅名称的范围(即 <code>restaurantNames. indices</code> ),而不是一个固定的范围。例如:<code>restaurantNames</code> 数组有 21 个项目,范围是从 0 至 20。</p>
<p>在闭包中,代码会修改,以建立列的布局,我将不会深入探讨细节,因为如果你对堆叠视图已经完全了解,那么代码一看便明白了。为了修改<code>List</code> 视图的样式,我们附加了<code>listStyle</code> 修饰器并将样式设置为<code>plain</code>。</p>
<p>就是这样,使用不到 10 行的代码,我们已经建立了一个自订布局的清单(或表格)。</p>
<figure id="fig10.6"><img src="images/list/swiftui-list-6.png" alt="图 10.6. 自订列布局的清单视图"><figcaption>图 10.6. 自订列布局的清单视图</figcaption></figure>
<h4 id="%E4%BD%BF%E7%94%A8%E8%B3%87%E6%96%99%E9%9B%86%E5%90%88">使用数据集合</h4>
<p>如前所述,<code>List</code> 可以带入一个范围或一个数据集合。你已经学过如何处理范围,我们来看如何将 <code>List</code> 与餐厅数据的数组一起使用。</p>
<p>我们将建立一个 <code>Restaurant</code> 结构来加以组织数据,而不是将餐厅数据储存在两个单独的数组中。这个结构有两个属性:“name”与“image”。在 <code>ContentView.swift</code> 档的最后面, 插入下列代码: </p>
<pre><code class="lang-swift"><span class="hljs-class"><span class="hljs-keyword">struct</span> <span class="hljs-title">Restaurant</span> </span>{
<span class="hljs-keyword">var</span> name: <span class="hljs-type">String</span>
<span class="hljs-keyword">var</span> image: <span class="hljs-type">String</span>
}
</code></pre>
<p>使用这个结构,我们可以将 <code>restaurantNames</code> 与 <code>restaurantImages</code> 数组合并为一个数组。现在删除<code>restaurantNames</code> 与 <code>restaurantImages</code> 变量,并以 <code>ContentView</code>中的这个变量来代替: </p>
<pre><code class="lang-swift"><span class="hljs-keyword">var</span> restaurants = [ <span class="hljs-type">Restaurant</span>(name: <span class="hljs-string">"Cafe Deadend"</span>, image: <span class="hljs-string">"cafedeadend"</span>),
<span class="hljs-type">Restaurant</span>(name: <span class="hljs-string">"Homei"</span>, image: <span class="hljs-string">"homei"</span>),
<span class="hljs-type">Restaurant</span>(name: <span class="hljs-string">"Teakha"</span>, image: <span class="hljs-string">"teakha"</span>),
<span class="hljs-type">Restaurant</span>(name: <span class="hljs-string">"Cafe Loisl"</span>, image: <span class="hljs-string">"cafeloisl"</span>),
<span class="hljs-type">Restaurant</span>(name: <span class="hljs-string">"Petite Oyster"</span>, image: <span class="hljs-string">"petiteoyster"</span>),
<span class="hljs-type">Restaurant</span>(name: <span class="hljs-string">"For Kee Restaurant"</span>, image: <span class="hljs-string">"forkeerestaurant"</span>),
<span class="hljs-type">Restaurant</span>(name: <span class="hljs-string">"Po's Atelier"</span>, image: <span class="hljs-string">"posatelier"</span>),
<span class="hljs-type">Restaurant</span>(name: <span class="hljs-string">"Bourke Street Bakery"</span>, image: <span class="hljs-string">"bourkestreetbakery"</span>),
<span class="hljs-type">Restaurant</span>(name: <span class="hljs-string">"Haigh's Chocolate"</span>, image: <span class="hljs-string">"haighschocolate"</span>),
<span class="hljs-type">Restaurant</span>(name: <span class="hljs-string">"Palomino Espresso"</span>, image: <span class="hljs-string">"palominoespresso"</span>),
<span class="hljs-type">Restaurant</span>(name: <span class="hljs-string">"Upstate"</span>, image: <span class="hljs-string">"upstate"</span>),