首先#pragma在本質上是聲明，常用的功能就是注釋，尤其是給Code分段注釋；而且它還有另一個強大的功能是處理編譯器警告，但卻沒有上一個功能用的那么多。

clang diagnostic 是#pragma 第一個常用命令：

#pragmaclang diagnostic push#pragmaclang diagnostic ignored"-相關命令"http:// 你自己的代碼#pragmaclang diagnostic pop

常見的用法

1. 方法棄用告警

#pragmaclang diagnostic push#pragmaclang diagnostic ignored"-Wdeprecated-declarations"[TestFlight setDeviceIdentifier:[[UIDevice currentDevice] uniqueIdentifier]];#pragmaclang diagnostic pop

2. 不兼容指針類型

#pragmaclang diagnostic push#pragmaclang diagnostic ignored"-Wincompatible-pointer-types"http://? #pragmaclang diagnostic pop

3. 循環引用

// completionBlock is manually nilled out in AFURLConnectionOperation to break the retain cycle.? #pragmaclang diagnostic push#pragmaclang diagnostic ignored"-Warc-retain-cycles"self.completionBlock = ^ {? ? ? ? ? ...? ? ? };#pragmaclang diagnostic pop

4. 未使用變量

#pragmaclang diagnostic push#pragmaclang diagnostic ignored"-Wunused-variable"inta;#pragmaclang diagnostic pop

#pargma 用法詳情：Which Clang Warning Is Generating This Message?