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NSArray技巧两则

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發布： 2016-06-07 15:36:11

原創

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原文出自：http://nijino.cn/blog/2014/01/05/nsarray-skills/ 之前我在网易的技术博客中讲到去除NSArray中重复元素的方法。最近在看WWDC2013视频，发现苹果工程师对数组去重有更为简便的方法，还有一个对数组逆序的简便方法，赶紧记录下来备用。 NSArray逆

原文出自：http://nijino.cn/blog/2014/01/05/nsarray-skills/

之前我在网易的技术博客中讲到去除NSArray中重复元素的方法。最近在看WWDC2013视频，发现苹果工程师对数组去重有更为简便的方法，还有一个对数组逆序的简便方法，赶紧记录下来备用。

NSArray逆序

Reverse sequence of NSArray

<span>1</span>
<span>2</span>
<span>3</span>

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<code><span><span>NSArray</span> <span>*</span><span>arr</span> <span>=</span> <span>@</span><span>[</span><span>@"first"</span><span>,</span><span>@"second"</span><span>];</span>
</span><span><span>arr</span> <span>=</span> <span>arr</span><span>.</span><span>reverseObjectEnumerator</span><span>.</span><span>allObjects</span><span>;</span>
</span><span><span>NSLog</span><span>(</span><span>@"%@"</span><span>,</span><span>arr</span><span>);</span>
</span></code>

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输出结果为：

Reverse Result

<span>1</span>
<span>2</span>
<span>3</span>
4

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<code><span>2014-01-05 13:52:09.303 CircleAudio[39584:70b] (
</span><span>second,
</span><span>first
</span><span>)</span></code>

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NSArray快速去重

Make NSArray distinct

<span>1</span>
<span>2</span>
<span>3</span>

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<code><span><span>NSArray</span> <span>*</span><span>arr</span> <span>=</span> <span>@</span><span>[</span><span>@"first"</span><span>,</span><span>@"second"</span><span>,</span><span>@"first"</span><span>];</span>
</span><span><span>arr</span> <span>=</span> <span>[</span><span>arr</span> <span>valueForKeyPath:</span><span>@"@distinctUnionOfObjects.self"</span><span>];</span>
</span><span><span>NSLog</span><span>(</span><span>@"%@"</span><span>,</span><span>arr</span><span>);</span>
</span></code>

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输出结果：

Result

<span>1</span>
<span>2</span>
<span>3</span>
4

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<code><span>2014-01-05 13:54:53.457 CircleAudio[39976:70b] (
</span><span>first,
</span><span>second
</span><span>)</span></code>

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以上的技巧都是从WWDC2013 session 228中学到的，其中还有一些技巧比如：联合两个数组并去重，感兴趣的同学可以自行下载视频研究。