301 lines
13 KiB
HTML
301 lines
13 KiB
HTML
<!DOCTYPE HTML>
|
||
<html lang="en-US" manifest="../manifest.appcache">
|
||
|
||
<head prefix="og: http://ogp.me/ns# book: http://ogp.me/ns/book#">
|
||
|
||
|
||
<meta charset="UTF-8">
|
||
<title>基础部分 | Swift 编程语言</title>
|
||
|
||
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
|
||
<meta name="robots" content="index, follow">
|
||
<meta name="author" content="">
|
||
<meta name="description" content="Swift 是苹果在 WWDC 2014 上发布的一款全新的编程语言，本书译自苹果官方的 Swift 教程《The Swift Programming Language》。">
|
||
<meta name="keywords" content="gitbook,github" >
|
||
<meta name="generator" content="www.gitbook.io">
|
||
|
||
|
||
|
||
<link rel="prev" href="../chapter2/the_basics.html" />
|
||
|
||
|
||
<meta property="og:title" content="基础部分 | Swift 编程语言">
|
||
<meta property="og:site_name" content="Swift 编程语言">
|
||
<meta property="og:type" content="book">
|
||
<meta property="og:locale" content="en_US">
|
||
|
||
<meta property="book:author" content="https://github.com/">
|
||
<meta property="book:tag" content="GitBook">
|
||
|
||
<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="shortcut icon" href="../gitbook/images/favicon.ico" type="image/x-icon">
|
||
|
||
|
||
</head>
|
||
<body>
|
||
|
||
|
||
|
||
<link rel="stylesheet" href="../gitbook/style.css">
|
||
|
||
|
||
|
||
|
||
<div class="book" data-level="2.1" data-basepath=".." data-revision="1401881908280">
|
||
<div class="book-header">
|
||
<!-- Actions Left -->
|
||
<a href="#" class="btn pull-left toggle-summary" aria-label="Toggle summary"><i class="fa fa-align-justify"></i></a>
|
||
|
||
<a href="https://github.com/null" target="_blank" class="btn pull-left home-bookmark" aria-label="GitHub home"><i class="fa fa-bookmark-o"></i></a>
|
||
|
||
<a href="#" class="btn pull-left toggle-search" aria-label="Toggle search"><i class="fa fa-search"></i></a>
|
||
<span id="font-settings-wrapper">
|
||
<a href="#" class="btn pull-left toggle-font-settings" aria-label="Toggle font settings"><i class="fa fa-font"></i>
|
||
</a>
|
||
<div class="dropdown-menu font-settings">
|
||
<div class="dropdown-caret">
|
||
<span class="caret-outer"></span>
|
||
<span class="caret-inner"></span>
|
||
</div>
|
||
|
||
<div class="btn-group btn-block">
|
||
<button id="reduce-font-size" class="btn btn-default">A</button>
|
||
<button id="enlarge-font-size" class="btn btn-default">A</button>
|
||
</div>
|
||
|
||
<ul class="list-group font-family-list">
|
||
<li class="list-group-item" data-font="0">Serif</li>
|
||
<li class="list-group-item" data-font="1">Sans</li>
|
||
</ul>
|
||
|
||
<div class="btn-group btn-group-xs btn-block color-theme-list">
|
||
<button type="button" class="btn btn-default" id="color-theme-preview-0" data-theme="0">White</button>
|
||
<button type="button" class="btn btn-default" id="color-theme-preview-1" data-theme="1">Sepia</button>
|
||
<button type="button" class="btn btn-default" id="color-theme-preview-2" data-theme="2">Night</button>
|
||
</div>
|
||
</div>
|
||
|
||
</span>
|
||
|
||
<!-- Actions Right -->
|
||
|
||
<a href="#" target="_blank" class="btn pull-right google-plus-sharing-link sharing-link" data-sharing="google-plus" aria-label="Share on Google Plus"><i class="fa fa-google-plus"></i></a>
|
||
|
||
|
||
<a href="#" target="_blank" class="btn pull-right facebook-sharing-link sharing-link" data-sharing="facebook" aria-label="Share on Facebook"><i class="fa fa-facebook"></i></a>
|
||
|
||
|
||
<a href="#" target="_blank" class="btn pull-right twitter-sharing-link sharing-link" data-sharing="twitter" aria-label="Share on Twitter"><i class="fa fa-twitter"></i></a>
|
||
|
||
|
||
|
||
|
||
<!-- Title -->
|
||
<h1>
|
||
<i class="fa fa-spinner fa-spin"></i>
|
||
<a href="../" >Swift 编程语言</a>
|
||
</h1>
|
||
</div>
|
||
|
||
|
||
|
||
<div class="book-summary">
|
||
<div class="book-search">
|
||
<input type="text" placeholder="Search" class="form-control" />
|
||
</div>
|
||
<ul class="summary">
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
<li data-level="0" data-path="index.html">
|
||
<a href="../"><i class="fa fa-check"></i> Introduction</a>
|
||
</li>
|
||
|
||
|
||
<li class="chapter " data-level="1" data-path="chapter1/README.html">
|
||
|
||
<a href="../chapter1/README.html">
|
||
<i class="fa fa-check"></i> <b>1.</b> 欢迎使用 Swift
|
||
</a>
|
||
|
||
|
||
<ul class="articles">
|
||
|
||
|
||
<li class="chapter " data-level="1.1" data-path="chapter1/swift.html">
|
||
|
||
<a href="../chapter1/swift.html">
|
||
<i class="fa fa-check"></i> <b>1.1.</b> 关于 Swift
|
||
</a>
|
||
|
||
|
||
</li>
|
||
|
||
<li class="chapter " data-level="1.2" data-path="chapter1/a_swift_tour.html">
|
||
|
||
<a href="../chapter1/a_swift_tour.html">
|
||
<i class="fa fa-check"></i> <b>1.2.</b> Swift 初见
|
||
</a>
|
||
|
||
|
||
</li>
|
||
|
||
|
||
</ul>
|
||
|
||
</li>
|
||
|
||
<li class="chapter " data-level="2" data-path="chapter2/the_basics.html">
|
||
|
||
<a href="../chapter2/the_basics.html">
|
||
<i class="fa fa-check"></i> <b>2.</b> Swift 教程
|
||
</a>
|
||
|
||
|
||
<ul class="articles">
|
||
|
||
|
||
<li class="chapter " data-level="2.1" data-path="chapter2/article_1.html">
|
||
|
||
<a href="../chapter2/article_1.html">
|
||
<i class="fa fa-check"></i> <b>2.1.</b> 基础部分
|
||
</a>
|
||
|
||
|
||
</li>
|
||
|
||
|
||
</ul>
|
||
|
||
</li>
|
||
|
||
|
||
|
||
|
||
<li class="divider"></li>
|
||
<li>
|
||
<a href="http://www.gitbook.io/" target="blank" class="gitbook-link">Generated using GitBook</a>
|
||
</li>
|
||
|
||
</ul>
|
||
</div>
|
||
|
||
<div class="book-body">
|
||
<div class="body-inner">
|
||
<div class="page-wrapper" tabindex="-1">
|
||
<div class="book-progress">
|
||
<div class="bar">
|
||
<div class="inner" style="width: 100%;min-width: 80%;"></div>
|
||
</div>
|
||
<div class="chapters">
|
||
|
||
<a href="../index.html" title="Introduction" class="chapter done new-chapter" data-progress="0" style="left: 0%;"></a>
|
||
|
||
<a href="../chapter1/README.html" title="欢迎使用 Swift" class="chapter done new-chapter" data-progress="1" style="left: 20%;"></a>
|
||
|
||
<a href="../chapter1/swift.html" title="关于 Swift" class="chapter done " data-progress="1.1" style="left: 40%;"></a>
|
||
|
||
<a href="../chapter1/a_swift_tour.html" title="Swift 初见" class="chapter done " data-progress="1.2" style="left: 60%;"></a>
|
||
|
||
<a href="../chapter2/the_basics.html" title="Swift 教程" class="chapter done new-chapter" data-progress="2" style="left: 80%;"></a>
|
||
|
||
<a href="../chapter2/article_1.html" title="基础部分" class="chapter done " data-progress="2.1" style="left: 100%;"></a>
|
||
|
||
</div>
|
||
</div>
|
||
|
||
<div class="page-inner">
|
||
|
||
<section class="normal" id="section-gitbook_144">
|
||
|
||
<h1 id="-">基础部分</h1>
|
||
<p>Swift 是 iOS 和 OS X 应用开发的一门新语言。然而，如果你有 C 或者 Objective-C 开发经验的话，你会发现 Swift 的很多内容都是你熟悉的。</p>
|
||
<p>Swift 的类型是在 C 和 Objective-C 的基础上提出的，<code>Int</code>是整型；<code>Double</code>和<code>Float</code>是浮点型；<code>Bool</code>是布尔型；<code>String</code>是字符串。Swift 还有两个有用的集合类型，<code>Array</code>和<code>Dictionary</code>，详情参见<code>集合类型(待添加链接)</code>。</p>
|
||
<p>就像 C 语言一样，Swift 使用变量来进行存储并通过变量名来关联值。在 Swift 中，值不可变的变量有着广泛的应用，它们就是常量，而且比 C 语言的常量更强大。在 Swift 中，如果你要处理的值不需要改变，那使用常量可以让你的代码更加安全并且更好地表达你的意图。</p>
|
||
<p>除了我们熟悉的类型，Swift 还增加了 Objective-C 中没有的类型比如元组（Tuple）。元组可以让你创建或者传递一组数据，比如作为函数的返回值时，你可以用一个元组可以返回多个值。</p>
|
||
<p>Swift 还增加了可选（Optional）类型，用于处理值缺失的情况。可选表示“那儿有一个值，并且它等于 x ”或者“那儿没有值”。可选有点像在 Objective-C 中使用<code>nil</code>，但是它可以用在任何类型上，不仅仅是类。可选类型比 Objective-C 中的<code>nil</code>指针更加安全也更具表现力，它是 Swift 许多强大特性的重要组成部分。</p>
|
||
<p>Swift 是一个类型安全的语言，可选就是一个很好的例子。Swift 可以让你清楚地知道值的类型。如果你的代码期望得到一个<code>String</code>，类型安全会阻止你不小心传入一个<code>Int</code>。你可以在开发阶段尽早发现并修正错误。</p>
|
||
<h2 id="-">常量和变量</h2>
|
||
<p>常量和变量把一个名字（比如<code>maximumNumberOfLoginAttempts</code>或者<code>welcomeMessage</code>）和一个指定类型的值（比如数字<code>10</code>或者字符串<code>Hello</code>）联系起来。常量的值一旦设定就不能改变，而变量的值可以随意更改。</p>
|
||
<h3 id="-">声明常量和变量</h3>
|
||
<p>常量和变量必须在使用前声明，用<code>let</code>来声明常量，用<code>var</code>来声明变量。下面的例子展示了如何用常量和变量来记录用户尝试登录的次数：</p>
|
||
<pre><code>let maximumNumberOfLoginAttempts = 10
|
||
var currentLoginAttempt = 0
|
||
</code></pre><p>这两行代码可以被理解为：</p>
|
||
<p>“声明一个名字是<code>maximumNumberOfLoginAttempts</code>的新常量，并给它一个值<code>10</code>。然后，声明一个名字是<code>currentLoginAttempt</code>的变量并将它的值初始化为0.”</p>
|
||
<p>在这个例子中，允许的最大尝试登录次数被声明为一个常量，因为这个值不会改变。当前尝试登录次数被声明为一个变量，因为每次尝试登录失败的时候都需要增加这个值。</p>
|
||
<p>你可以在一行中声明多个常量或者多个变量，用逗号隔开：</p>
|
||
<pre><code>var x = 0.0, y = 0.0, z = 0.0
|
||
</code></pre><blockquote>
|
||
<p>注意：如果你的代码中有不需要改变的值，最好将它声明为常量。只将需要改变的值声明为变量。</p>
|
||
</blockquote>
|
||
<h3 id="-">类型标注</h3>
|
||
<p>当你声明常量或者变量的时候可以加上类型标注，说明常量或者变量中要存储的值的类型。如果要添加类型标注，在常量或者变量名后面加上一个冒号和空格，然后加上类型名称。</p>
|
||
<p>这个例子给<code>welcomeMessage</code>变量添加了类型标注，表示这个变量可以存储<code>String</code>类型的值：</p>
|
||
<pre><code>var welcomeMessage: String
|
||
</code></pre><p>声明中的冒号代表着“是...类型”，所以这行代码可以被理解为：：</p>
|
||
<p>“声明一个类型为<code>String</code>，名字为<code>welcomeMessage</code>的变量。”</p>
|
||
<p>“类型为<code>String</code>”的意思是“可以存储任意<code>String</code>类型的值。”</p>
|
||
<p><code>welcomeMessage</code>变量现在可以被设置成任意字符串：</p>
|
||
<pre><code>welcomeMessage = "Hello"
|
||
</code></pre><blockquote>
|
||
<p>注意：一般来说你很少需要写类型标注。如果你在声明常量或者变量的时候赋了一个初始值，Swift可以推断出这个常量或者变量的类型，详情参见<code>类型安全和类型推断(待添加链接)</code>。在上面的例子中，没有给<code>welcomeMessage</code>赋初始值，所以添加了一个类型标注。</p>
|
||
</blockquote>
|
||
<h3 id="-">常量和变量的命名</h3>
|
||
<p>（未完）</p>
|
||
|
||
|
||
</section>
|
||
|
||
</div>
|
||
</div>
|
||
</div>
|
||
|
||
|
||
<a href="../chapter2/the_basics.html" class="navigation navigation-prev navigation-unique" aria-label="Previous page: Swift 教程"><i class="fa fa-angle-left"></i></a>
|
||
|
||
|
||
</div>
|
||
</div>
|
||
|
||
|
||
|
||
<script src="http://cdn.bootcss.com/ace/1.1.3/ace.js"></script>
|
||
<script src="http://cdn.bootcss.com/ace/1.1.3/mode-javascript.js"></script>
|
||
<script src="../gitbook/jsrepl/jsrepl.js" id="jsrepl-script"></script>
|
||
<script src="../gitbook/app.js"></script>
|
||
|
||
|
||
|
||
<script src="../gitbook/plugins/gitbook-plugin-mixpanel/plugin.js"></script>
|
||
|
||
|
||
|
||
<script src="http://cdn.mathjax.org/mathjax/2.0-latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script>
|
||
|
||
|
||
|
||
<script src="../gitbook/plugins/gitbook-plugin-mathjax/plugin.js"></script>
|
||
|
||
|
||
<script>
|
||
require(["gitbook"], function(gitbook) {
|
||
var config = {};
|
||
gitbook.start(config);
|
||
});
|
||
</script>
|
||
|
||
|
||
</body>
|
||
|
||
</html>
|