iOS开发- 日志打印(常见)

布满荆棘的人生 2022-08-06 08:16 286阅读 0赞

Q：如何打印当前的函数和行号？

A：我们可以在打印时使用一些预编译宏作为打印参数，来打印当前的函数和行号。如：

NSLog(@"%s:%d obj=%@", __func__, __LINE__, obj);

NSLog(@"%s:%d obj=%@", __func__, __LINE__, self);
        //输出样式:
        //2015-01-06 17:13:17.852 justTest[15079:613]
        // -[ViewController viewDidLoad]:38 obj=<ViewController: 0x109949aa0>

其中func和LINE都是预编译的宏，编译时会分别替换为当前函数和当前行号。 下面是一些常用于打印日志的宏。

<table style="color: rgb(46, 48, 54); font-family: inherit; font-size: 16px; line-height: inherit; margin: 0px 0px 1.5em; padding: 0px; border-width: 0px 1px 1px 0px; border-style: solid; border-color: rgb(204, 204, 204); font-style: inherit; font-variant: inherit; vertical-align: baseline; border-collapse: collapse; border-spacing: 0px; width: 853px;"> 
 <thead style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"> 
  <tr style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"> 
   <th style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(244, 244, 244);">宏&nbsp;</th> 
   <th style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(244, 244, 244);">说明</th> 
  </tr> 
 </thead> 
 <tbody style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"> 
  <tr style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">__func__&nbsp;</td> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">打印当前函数或方法，c字符串</td> 
  </tr> 
  <tr style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">__LINE__&nbsp;</td> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">打印当前行号，整数</td> 
  </tr> 
  <tr style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">__FILE__&nbsp;</td> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">打印当前文件路径，c字符串</td> 
  </tr> 
  <tr style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">__PRETTY_FUNCTION__&nbsp;</td> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">打印当前函数或方法（在C++中会包含参数类型），c字符串</td> 
  </tr> 
 </tbody> 
</table>

Q：如何打印一个类名，消息名，当前堆栈信息？

A：你可以使用以下方法在运行时动态获取这些信息。

<table style="color: rgb(46, 48, 54); font-family: inherit; font-size: 16px; line-height: inherit; margin: 0px 0px 1.5em; padding: 0px; border-width: 0px 1px 1px 0px; border-style: solid; border-color: rgb(204, 204, 204); font-style: inherit; font-variant: inherit; vertical-align: baseline; border-collapse: collapse; border-spacing: 0px; width: 853px;"> 
 <thead style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"> 
  <tr style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"> 
   <th style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(244, 244, 244);">代码&nbsp;</th> 
   <th style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(244, 244, 244);">说明</th> 
  </tr> 
 </thead> 
 <tbody style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"> 
  <tr style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">NSStringFromSelector(SEL)&nbsp;</td> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">获取selector的名字</td> 
  </tr> 
  <tr style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">NSStringFromSelector(_cmd)&nbsp;</td> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">获取当前方法名</td> 
  </tr> 
  <tr style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">NSStringFromClass([object class])&nbsp;</td> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">获取object的类名</td> 
  </tr> 
  <tr style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; vertical-align: baseline;"> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">[NSThread callStackSymbols]&nbsp;</td> 
   <td style="margin: 0px; padding: 5px 10px; border-width: 1px 0px 0px 1px; border-style: solid; border-color: rgb(204, 204, 204); font-family: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; font-size: 16px; vertical-align: middle; background-color: rgb(253, 253, 253);">获取当前线程的栈，是一个NSArry，包含堆栈中所有函数名。</td> 
  </tr> 
 </tbody> 
</table>

Q：如何将日志打印到一个文件

A：可以使用freopen函数重定向标准输出和标准出错文件。因为printf函数会向标准输出（stdout）打印，而NSLog函数会向标准出错（stderr）打印。重新定向标准输出（stdout）和标准出错（stderr）到一个文件将会使他们打印日志到一个文件中。

freopen("/tmp/log.txt", "a+", stdout);
    freopen("/tmp/log.txt", "a+", stderr);