警告：格式字符串不是字符串文字 [英] Warning: Format string is not a string literal

问题描述

我收到格式字符串不是字符串字面值警告从以下行

I am getting "Format string is not string literal" warning from following line

NSString *formattedString = [[NSString alloc] initWithFormat:format arguments:valist];

我在以下函数中使用这个函数

I using this in following function

- (void)logMessage:(NSString *)format
         level:(LoggingLevel)level
withParameters:(va_list)valist {
         if (level >= self.loggingLevel) {
              NSString *formattedString = [[NSString alloc] initWithFormat:format arguments:valist];        
         } 

任何想法如何解决这个问题？我使用Xcode 4.6.3

Any idea how to fix this ? I am using Xcode 4.6.3

推荐答案

如果你告诉编译器你的方法有一个格式化的参数， b $ b NS_FORMAT_FUNCTION 宏：

If you tell the compiler that your method has a format-like argument, using the NS_FORMAT_FUNCTION macro:

- (void)logMessage:(NSString *)format
         level:(LoggingLevel)level
withParameters:(va_list)valist NS_FORMAT_FUNCTION(1,0) {
         if (level >= self.loggingLevel) {
              NSString *formattedString = [[NSString alloc] initWithFormat:format arguments:valist];        
         } 
}

然后

• 您的方法中的编译器警告消失，

示例：

NSString *abc = @"foo %@ bar";
[self logMessage:abc level:7 withParameters:NULL];

warning: format string is not a string literal [-Wformat-nonliteral]
[self logMessage:abc level:7 withParameters:NULL];
                 ^~~

ADDED：函数。
它们也应该被标记为 NS_FORMAT_FUNCTION ：

+ (void)logVeryFineWithFormat:(NSString *)format, ... NS_FORMAT_FUNCTION(1,2)
{
    va_list ap;
    va_start(ap, format);
    [[self sharedInstance] logMessage:format level:VERY_FINE withParameters:ap];
    va_end(ap);
}

+ (void)say:(NSString *)formatstring, ... NS_FORMAT_FUNCTION(1,2)
{
    va_list arglist;
    va_start(arglist, formatstring);
    // This is not needed: 
    // NSString *litralString = [NSString stringWithFormat:@"%@",formatstring];
    NSString *statement = [[NSString alloc] initWithFormat:formatstring arguments:arglist];
    va_end(arglist);
    [ModalAlert ask:statement withCancel:@"Okay" withButtons:nil];
}

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