clang diagnostic用例

clang命令格式大致如下：

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-相关命令"
    //需要操作的代码
#pragma clang diagnostic pop

栗子1：怱略警告

UIAlertView *alertView = [[UIAlertView alloc]initWithTitle:@"" message:@"" delegate:nil cancelButtonTitle:@"" otherButtonTitles:@"", nil];
[alertView show];


//方法弃用告警    
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
    UIAlertView *alertViewTmp = [[UIAlertView alloc]initWithTitle:@"" message:@"" delegate:nil cancelButtonTitle:@"" otherButtonTitles:@"", nil];
    [alertViewTmp show];
#pragma clang diagnostic pop

栗子2：忽略不兼容指针类型

//   不兼容指针类型 
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wincompatible-pointer-types"
    //
#pragma clang diagnostic pop

栗子3：循环引用

break the retain cycle.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-retain-cycles"
//    self.completionBlock = ^ {
//        ...
//    };
#pragma clang diagnostic pop

栗子4：未使用变量

// 未使用变量   
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-variable"
    int a;
#pragma clang diagnostic pop

栗子5：未使用default

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wcovered-switch-default"
//    switch (style) {
//        case UITableViewCellStyleDefault:
//        case UITableViewCellStyleValue1:
//        case UITableViewCellStyleValue2:
//        case UITableViewCellStyleSubtitle:
//            // ...
//        default:
//            return;
//    }
#pragma clang diagnostic pop