Objective c 使用NSCharacterSet删除所有不需要的字符

我想从我的NSString中删除所有不是（数字、字母、come、space或句点）的字符

我正在使用NSCharacterSet，但它没有添加到其中的方法。我尝试了可变版本来添加空格、逗号和句点，但没有成功

 // str is my string
 NSCharacterSet *charactersToRemove =
 [[ NSCharacterSet letterCharacterSet ] invertedSet ];

 NSString *trimmedReplacement =
 [[ str componentsSeparatedByCharactersInSet:charactersToRemove ]
 componentsJoinedByString:@"" ];
 // this removes spaces, periods, and commas too. How do I add in to the character set to keep them

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创建可变字符集并添加要保留的其他字符。此外，如果您还想在字符串中保留数字，您可能打算使用AlphaNumericCharacterSet而不是letterCharacterSet

NSMutableCharacterSet *charactersToKeep = [NSMutableCharacterSet alphanumericCharacterSet];
[charactersToKeep addCharactersInString:@" ,."];

NSCharacterSet *charactersToRemove = [charactersToKeep invertedSet];

NSString *trimmedReplacement = [[ str componentsSeparatedByCharactersInSet:charactersToRemove] componentsJoinedByString:@"" ];

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使用不可变字符集的反转比反转可变字符集更有效。