iOS性能调优之Analyze静态分析

素颜马尾好姑娘i 2022-08-18 12:08 215阅读 0赞

### iOS性能调优之Analyze静态分析 ###

目前关于IOS性能优化的教程较少，决定写一个《IOS性能调优系列》，主要关注与内存泄漏、性能优化、流量和电量分析几个方面。

XCode已经提供了非常强大的性能调优工具，结合几个第三方工具和一些技巧，进行性能优化非常简单。

第一篇先写写最简单的，Analyze静态分析。

相信IOS开发者在App进行Build或Archive时，会产生很多编译警告，这些警告是编译时产生的，静态分析的过程也类似，在XCode Product菜单下，点击Analyze对App进行静态分析。

![iOS性能调优之Analyze静态分析][iOS_Analyze]

Analyze主要分析以下四种问题：

1、逻辑错误：访问空指针或未初始化的变量等；

2、内存管理错误：如内存泄漏等；

3、声明错误：从未使用过的变量；

4、Api调用错误：未包含使用的库和框架。

Analyze内存泄漏分析：

声明错误、逻辑错误、Api调用错误基本在编译时都会有警告，Analyze的主要优势在于静态分析内存泄漏及代码逻辑错误。

比如在开启arc的环境下，输入以下一段代码：

[?][Link 1]

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       &nbsp; 
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     <div style="line-height:15.4px; padding:0px 1em!important; margin:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; white-space:pre!important"> 
      <code style="white-space:nowrap; padding:0px!important; margin:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="white-space:nowrap; padding:0px!important; margin:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; color:rgb(185,189,182)!important; background:none!important">UIImage* smallImage = [UIImage imageWithCGImage:imageRef];</code> 
     </div> 
     <div style="line-height:15.4px; padding:0px 1em!important; margin:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; white-space:pre!important"> 
      <code style="white-space:nowrap; padding:0px!important; margin:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="white-space:nowrap; padding:0px!important; margin:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; color:rgb(135,138,133)!important; background:none!important">//CGImageRelease(imageRef);</code> 
     </div> 
     <div style="line-height:15.4px; padding:0px 1em!important; margin:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; white-space:pre!important">
       &nbsp; 
     </div> 
     <div style="line-height:15.4px; padding:0px 1em!important; margin:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; white-space:pre!important"> 
      <code style="white-space:nowrap; padding:0px!important; margin:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; background:none!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="white-space:nowrap; padding:0px!important; margin:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-weight:bold!important; font-size:1em!important; min-height:auto!important; color:rgb(91,161,207)!important; background:none!important">return</code> 
      <code style="white-space:nowrap; padding:0px!important; margin:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; color:rgb(185,189,182)!important; background:none!important"> smallImage;</code> 
     </div> 
     <div style="line-height:15.4px; padding:0px 1em!important; margin:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-size:1em!important; min-height:auto!important; white-space:pre!important"> 
      <code style="white-space:nowrap; padding:0px!important; margin:0px!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,'Bitstream Vera Sans Mono','Courier New',Courier,monospace!important; font-size:1em!important; min-height:auto!important; color:rgb(185,189,182)!important; background:none!important">}</code> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

用注释注释掉CGImageRelease(imageRef)这行，虽然开起了arc，不过仍然会导致imageRef对象泄漏。

使用Analyze进行分析，在导航栏Analyze选择Analyzer查看分析结果：

![iOS性能调优之Analyze静态分析][iOS_Analyze 1]

Analyze已经分析出imageRef对象有内存泄漏，这种情况在编译时是无法发现的。

如果你没有使用ARC，那么Analyze更有用。

Analyze的其他三种分析也可以使用，相比编译器给出的信息更明确。

Analyze逻辑错误监测：

![iOS性能调优之Analyze静态分析][iOS_Analyze 2]

这种情况在codereview时也较难发现，可以借助Analyze。

如上代码，当Tag不等于1、2和3的时候，就会出现很问题了。

Analyze还给出了箭头提示：len is a garbage value。建议在声明变量时，同时进行初始化。

[iOS_Analyze]: /images/20220731/633e51b290bb4f31ae893876a6c1af32.png
[Link 1]: http://www.open-open.com/lib/view/open1425305071212.html#
[iOS_Analyze 1]: /images/20220731/1889b2505c7142399b246955430d84ff.png
[iOS_Analyze 2]: /images/20220731/cdfa41f71f6d4d5fbf6840f655ed4146.png