字符串 转utf8和unicode再转回来

//utf8转中文

NSString* strA = [@"%E4%B8%AD%E5%9B%BD"stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

//中文转unicode

NSString *strB = [@"中国"stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

ios9之后

NSString *urlStr = @"url地址";

//中文转utf8

urlStr = [urlStr stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];

//utf8转中文

urlStr = [urlStr stringByRemovingPercentEncoding];

//中文转成unicode

- (NSString *) utf8ToUnicode:(NSString *)string{

    NSUInteger length = [string length];
    NSMutableString *str = [NSMutableString stringWithCapacity:0];
    for (int i = 0;i < length; i++){
        NSMutableString *s = [NSMutableString stringWithCapacity:0];
        unichar _char = [string characterAtIndex:i];
        // 判断是否为英文和数字
        if (_char <= '9' && _char >='0'){
            [s appendFormat:@"%@",[string substringWithRange:NSMakeRange(i,1)]];
        }else if(_char >='a' && _char <= 'z'){
            [s appendFormat:@"%@",[string substringWithRange:NSMakeRange(i,1)]];
        }else if(_char >='A' && _char <= 'Z')
        {
            [s appendFormat:@"%@",[string substringWithRange:NSMakeRange(i,1)]];
        }else{
            // 中文和字符
            [s appendFormat:@"\\u%x",[string characterAtIndex:i]];
            // 不足位数补0 否则解码不成功
            if(s.length == 4) {
                [s insertString:@"00" atIndex:2];
            } else if (s.length == 5) {
                [s insertString:@"0" atIndex:2];
            }
        }
        [str appendFormat:@"%@", s];
    }
    return str;
}