Apple's 字符串格式说明符文件索赔,
NSString 格式化方法和 CFString 格式化函数支持的格式说明符遵循IEEE printf 规范; ...您还可以将这些格式说明符与 NSLog 函数一起使用。
但是,虽然printf
规范定义%C
作为等价于%lc
and %S
作为等价于%ls
, only %C
and %S
似乎可以正确使用NSLog
and +[NSString stringWithFormat:]
.
例如,考虑以下代码:
#import <Foundation/Foundation.h>
int main (int argc, const char * argv[]) {
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
unichar str[3];
str[0] = 63743;
str[1] = 33;
str[2] = (unichar)NULL;
NSLog(@"NSLog");
NSLog(@"%%S: %S", str);
NSLog(@"%%ls: %ls", str);
NSLog(@"%%C: %C", str[0]);
NSLog(@"%%lc: %lc", str[0]);
NSLog(@"\n");
NSLog(@"+[NSString stringWithFormat:]");
NSLog(@"%%S: %@", [NSString stringWithFormat:@"%S", str]);
NSLog(@"%%ls: %@", [NSString stringWithFormat:@"%ls", str]);
NSLog(@"%%C: %@", [NSString stringWithFormat:@"%C", str[0]]);
NSLog(@"%%lc: %@", [NSString stringWithFormat:@"%lc", str[0]]);
[pool drain];
return 0;
}
鉴于printf
规范,我希望上面的每一对打印相同的东西。但是,当我运行代码时,我得到以下输出:
2009-03-20 17:00:13.363 UnicharFormatSpecifierTest[48127:10b] NSLog
2009-03-20 17:00:13.365 UnicharFormatSpecifierTest[48127:10b] %S: !
2009-03-20 17:00:13.366 UnicharFormatSpecifierTest[48127:10b] %ls: ˇ¯!
2009-03-20 17:00:13.366 UnicharFormatSpecifierTest[48127:10b] %C:
2009-03-20 17:00:13.367 UnicharFormatSpecifierTest[48127:10b] %lc:
2009-03-20 17:00:13.367 UnicharFormatSpecifierTest[48127:10b]
2009-03-20 17:00:13.368 UnicharFormatSpecifierTest[48127:10b] +[NSString stringWithFormat:]
2009-03-20 17:00:13.368 UnicharFormatSpecifierTest[48127:10b] %S: !
2009-03-20 17:00:13.369 UnicharFormatSpecifierTest[48127:10b] %ls: ˇ¯!
2009-03-20 17:00:13.369 UnicharFormatSpecifierTest[48127:10b] %C:
2009-03-20 17:00:13.370 UnicharFormatSpecifierTest[48127:10b] %lc:
是我做错了什么,还是苹果代码中的一个错误?