NSStrings“包含下划线字符”在 NSMutableDictionary 中设置时用引号括起来？

Question

我将 NSString 添加到 NSMutableDictionary 中。有些字符串包含下划线，有些则不包含：

NSMutableDictionary *testDict = [[NSMutableDictionary alloc] init];
[testDict setObject:@"_startWithUnderscore" forKey:@"firstKey"];
[testDict setObject:@"NoUnderscore" forKey:@"secondKey"];
[testDict setObject:@"underscores_in_middle" forKey:@"thirdKey"];
NSLog(@"%@", testDict);`

OUTPUT:

firstKey = "_startWithUnderscore"; //注意添加的引号！

secondKey = NoUnderscore; //没有引号。

thirdKey = "underscores_in_middle"; //也获取引号。

呃，这是怎么回事？引号从哪里来？

Answer 1

这只是NSLog的一个特性。

Answer 2

if ([[testDict objectForKey:@"firstKey"] substringWithRange:NSMakeRange(0, 1)] isEqualToString:@"_"])
{
    NSLog(@"I guess the quotes are just things that NSLog prints, definitely not actually in the NSString.");
}