276 lines
11 KiB
HTML
276 lines
11 KiB
HTML
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<title>基础部分 | Swift编程语言</title>
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<meta name="description" content="Swift是苹果在WWDC2014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》。">
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<a href="../" >Swift编程语言</a>
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<a href="../"><i class="fa fa-check"></i> Introduction</a>
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<a href="../swift/README.html">
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<i class="fa fa-check"></i> <b>1.</b> 欢迎使用Swift
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</a>
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<i class="fa fa-check"></i> <b>1.1.</b> 关于Swift
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</a>
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</li>
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<li class="chapter " data-level="1.2" data-path="a_swift_tour.html">
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<a href="../a_swift_tour.html">
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<i class="fa fa-check"></i> <b>1.2.</b> Swift初见
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</a>
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</li>
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<a href="../chapter2/the_basics.html">
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<i class="fa fa-check"></i> <b>2.</b> Swift教程
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</a>
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<ul class="articles">
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<li class="chapter " data-level="2.1" data-path="chapter2/article_1.html">
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<a href="../chapter2/article_1.html">
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<i class="fa fa-check"></i> <b>2.1.</b> 基础部分
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</a>
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</li>
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<a href="http://www.gitbook.io/" target="blank" class="gitbook-link">Generated using GitBook</a>
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<a href="../index.html" title="Introduction" class="chapter done new-chapter" data-progress="0" style="left: 0%;"></a>
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<a href="../a_swift_tour.html" title="Swift初见" class="chapter done " data-progress="1.2" style="left: 60%;"></a>
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<div class="page-inner">
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<section class="normal" id="section-gitbook_1204">
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<h1 id="-">基础部分</h1>
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<p>Swift是iOS和OS X应用开发的一门新雨燕。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>
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<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>，具体内容在<code>集合类型(待添加连接)</code>一章中。</p>
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<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>
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<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>
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<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>
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<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>
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<h2 id="-">常量和变量</h2>
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<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>
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<p>（未完）</p>
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</section>
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</div>
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