最近在项目中遇到过滤某些特殊字符和表情的需求，有正则表达式和NSCharacterSet两种方法可以实现此需求。

1 NSCharacterSet方法，详细的具体API请查阅文档。

- (NSString *)ttLegalNickName
{
    //合法字符集合
    NSCharacterSet *legalPunctuationCharacterSet = [NSCharacterSet characterSetWithCharactersInString:@",.·，。•、"];
    
    //英文和数字字符集合
    NSCharacterSet *alphanumericCharacterSet = [NSCharacterSet alphanumericCharacterSet];
    
    //中文字符集合
    NSCharacterSet *chineseSet = [NSCharacterSet ttChineseSet];
    
    //合法字符  英文和数字字符 中文字符 并集的集合
    NSMutableCharacterSet *characterSet  = [[NSMutableCharacterSet alloc] init];
    [characterSet formUnionWithCharacterSet:legalPunctuationCharacterSet];
    [characterSet formUnionWithCharacterSet:alphanumericCharacterSet];
    [characterSet formUnionWithCharacterSet:chineseSet];
    
    // 除去合法字符  英文和数字字符 中文字符 并集的集合的补集
    NSCharacterSet *illegalCharacterSet = characterSet.invertedSet;
    
    // 将非法字符过滤成 @""
    NSString *legalNickName = [[self componentsSeparatedByCharactersInSet:illegalCharacterSet] componentsJoinedByString:@""];
    
    // 将合法字符过滤成 @"·"
    legalNickName = [[legalNickName componentsSeparatedByCharactersInSet:legalPunctuationCharacterSet] componentsJoinedByString:@"·" ];
    
    return legalNickName;
}

+ (NSCharacterSet *)ttChineseSet
{
    // 中文字符集合
    static NSCharacterSet *chineseSet;
    if (chineseSet == nil)
    {
        NSMutableCharacterSet *aCharacterSet = [[NSMutableCharacterSet alloc] init];
        
        NSRange lcEnglishRange;
        lcEnglishRange.location = (unsigned int)0x4e00;
        lcEnglishRange.length = (unsigned int)0x9fa5 - (unsigned int)0x4e00;
        [aCharacterSet addCharactersInRange:lcEnglishRange];
        chineseSet = aCharacterSet;
    }
    return chineseSet;
}

以上可以根据自己的需求去灵活配置建立分类。

2 正则方法， 后续更新