若您需要实现简单的 @ 功能，可以参考网易云信在 IM UIKit 上使用的艾特（@）逻辑，以实现简单的类微信的 @ 功能。

效果展示

@消息是一种即时通讯功能，用户可以在群聊或频道中通过“@”符号提及特定用户或角色，被提及的用户会收到提醒通知，从而快速注意到相关消息。效果如下图所示：

方案介绍

@ 消息通过扩展参数，保留 @ 消息的相关内容。在消息体 NIMMessage 中可以通过 remoteExt 来获取和设置消息体中的远程传输的扩展参数，@ 消息的内容就以 Object 形式保存在该消息体中，数据格式如下：

JSON//@消息的 key 值
"yxAitMsg": {
    //被@的账号，如果是 @All 则为 ait_all
    "332917623668992": {
        "text": "@昵称 01 ",//在消息中@的展示内容
        "segments": [{//在消息中@的展示位置
            "start": 0,//在消息中@的展示起始位置
            "end": 5,//在消息中@的展示终止位置
        }]
    }
}

在发送一条 @ 消息时，会将上述 @ 消息的内容，设置到该消息的 remoteExt 中。

实现流程

1. 创建一条文本消息。

   Swift

   Swift// text 代表要发送的内容
   let message = MessageUtils.textMessage(text: text)
   

   Objective-C

   Objective-C// text 代表要发送的内容
   V2NIMMessage *message = [MessageUtils textMessageWithText:text];    
   

2. 设置 @ 信息和推送配置。

   Swift

   Swiftopen func getAtRemoteExtension(_ attri: NSAttributedString?) -> [String: Any]? {
       guard let attribute = attri else {
       return nil
       }
       var atDic = [String: [String: Any]]()
       let string = attribute.string
       attribute.enumerateAttribute(
       NSAttributedString.Key.foregroundColor,
       in: NSMakeRange(0, attribute.length)
       ) { value, findRange, stop in
       guard let findColor = value as? UIColor else {
           return
       }
       if isEqualToColor(findColor, UIColor.ne_normalTheme) == false {
           return
       }
       if let range = Range(findRange, in: string) {
           let text = string[range]
           let model = MessageAtInfoModel()
           print("range text : ", String(text))
           // 计算 at 前有表情导致索引新增的数量
           let expandIndex = getConvertedExtraIndex(attribute.attributedSubstring(from: NSRange(location: 0, length: findRange.location)))
           print("expand index value ", expandIndex)
           model.start = findRange.location + expandIndex
           let nameExpandCount = getConvertedExtraIndex(attribute.attributedSubstring(from: findRange))
           print("name expand index value ", nameExpandCount)
           model.end = model.start + findRange.length + nameExpandCount
           print("model start : ", model.start, " model end : ", model.end)
           var dic: [String: Any]?
           var array: [Any]?
           if let accid = nickAccidDic[String(text)] {
           if let atCacheDic = atDic[accid] {
               dic = atCacheDic
           } else {
               dic = [String: Any]()
           }
   
           if let atCacheArray = dic?[atSegmentsKey] as? [Any] {
               array = atCacheArray
           } else {
               array = [Any]()
           }
   
           if let object = model.yx_modelToJSONObject() {
               array?.append(object)
           }
           dic?[atSegmentsKey] = array
           dic?[atTextKey] = String(text) + " "
           dic?[#keyPath(MessageAtCacheModel.accid)] = accid
           atDic[accid] = dic
           }
       }
       }
       if atDic.count > 0 {
       return [yxAtMsg: atDic]
       }
       return nil
   }
   

   Objective-C

   Objective-C- (nullable NSDictionary *)getAtRemoteExtension:(nullable NSAttributedString *)attri {
       if (!attri) return nil;
       NSMutableDictionary *atDic = [NSMutableDictionary dictionary];
       NSString *string = attri.string;
       [attri enumerateAttribute:NSForegroundColorAttributeName
                       inRange:NSMakeRange(0, attri.length)
                       options:0
                   usingBlock:^(id value, NSRange findRange, BOOL *stop) {
           if (![value isKindOfClass:[UIColor class]]) return;
           if (![self isEqualToColor:(UIColor *)value color2:UIColor.ne_normalTheme]) return;
           if (findRange.location + findRange.length > string.length) return;
           NSString *text = [string substringWithRange:findRange];
           NSString *accid = self.nickAccidDic[text];
           if (accid) {
               id oldDic = atDic[accid];
               NSMutableDictionary *dic = [oldDic isKindOfClass:[NSDictionary class]] ? [oldDic mutableCopy] : [NSMutableDictionary dictionary];
               id oldArray = dic[atSegmentsKey];
               NSMutableArray *array = [oldArray isKindOfClass:[NSArray class]] ? [oldArray mutableCopy] : [NSMutableArray array];
               MessageAtInfoModel *model = [[MessageAtInfoModel alloc] init];
               // 计算at前有表情导致索引新增的数量
               NSRange frontRange = NSMakeRange(0, MIN(findRange.location, attri.length));
               NSInteger expandIndex = [self getConvertedExtraIndex:[attri attributedSubstringFromRange:frontRange]];
               model.start = findRange.location + expandIndex;
               NSInteger nameExpandCount = [self getConvertedExtraIndex:[attri attributedSubstringFromRange:findRange]];
               model.end = model.start + findRange.length + nameExpandCount;
               id object = [model yx_modelToJSONObject];
               if (object) [array addObject:object];
               dic[atSegmentsKey] = array;
               dic[atTextKey] = [text stringByAppendingString:@" "];
               dic[@"accid"] = accid;
               atDic[accid] = dic;
           }
       }];
       return atDic.count > 0 ? @{yxAtMsg: atDic} : nil;
   }
   

   @ 信息需要按照上述的 JSON 格式配置，如果使用 UIKit，则可以通过 NEBaseChatInputView 提供的方法。示例代码可参考 ChatViewController 中的 sendContentText 方法。

3. 发送消息。

   Swift

   Swiftlet params = ChatRepo.shared.getSendMessageParams()
   ChatRepo.shared.sendMessage(message: message,
                        conversationId: conversationId,
                                params: params,
                               completion)
   

   Objective-C

   Objective-CV2NIMSendMessageParams *params = [[ChatRepo shared] getSendMessageParams];
   [[ChatRepo shared] sendMessage:message
                   conversationId:conversationId
                           params:params
                       completion:completion];
   

4. 接受方对接收到的消息进行解析。

   Swift

   Swift/// 解析消息中的 @
   /// - Parameters:
   ///   - message: 消息
   ///   - attributeStr: 消息富文本
   /// - Returns: 高亮 @ 后的消息富文本
   public static func loadAtInMessage(_ message: V2NIMMessage?, _ attributeStr: NSMutableAttributedString?) -> NSMutableAttributedString? {
       // 数字人回复的消息不展示高亮（serverExtension 会被带回）
       if message?.aiConfig != nil, message?.aiConfig?.aiStatus == .MESSAGE_AI_STATUS_RESPONSE {
       return nil
       }
   
       let text = message?.text ?? ""
       let messageTextFont = UIFont.systemFont(ofSize: ChatUIConfig.shared.messageProperties.messageTextSize)
   
       // 兼容老的表情消息，如果前面有表情而位置计算异常则回退回老的解析
       var notFound = false
   
       // 计算表情(根据转码后的 index)
       if let remoteExt = getDictionaryFromJSONString(message?.serverExtension ?? ""), let dic = remoteExt[yxAtMsg] as? [String: AnyObject] {
       for (_, value) in dic {
           if let contentDic = value as? [String: AnyObject] {
           if let array = contentDic[atSegmentsKey] as? [AnyObject] {
               if let models = NSArray.yx_modelArray(with: MessageAtInfoModel.self, json: array) as? [MessageAtInfoModel] {
               for model in models {
                   // 前面因为表情增加的索引数量
                   var count = 0
                   if text.count > model.start {
                   let frontAttributeStr = NEEmotionTool.getAttWithStr(
                       str: String(text.prefix(model.start)),
                       font: messageTextFont
                   )
                   count = getReduceIndexCount(frontAttributeStr)
                   }
                   let start = model.start - count
                   if start < 0 {
                   notFound = true
                   break
                   }
                   var end = model.end - count
   
                   if model.end + atRangeOffset > text.count {
                   notFound = true
                   break
                   }
                   // 获取起始索引
                   let startIndex = text.index(text.startIndex, offsetBy: model.start)
                   // 获取结束索引
                   let endIndex = text.index(text.startIndex, offsetBy: model.end + atRangeOffset)
                   let frontAttributeStr = NEEmotionTool.getAttWithStr(
                   str: String(text[startIndex ..< endIndex]),
                   font: messageTextFont
                   )
                   let innerCount = getReduceIndexCount(frontAttributeStr)
                   end = end - innerCount
                   if end <= start {
                   notFound = true
                   break
                   }
   
                   if attributeStr?.length ?? 0 > end {
                   attributeStr?.addAttribute(NSAttributedString.Key.foregroundColor, value: UIColor.ne_normalTheme, range: NSMakeRange(start, end - start + atRangeOffset))
                   }
               }
               }
           }
           }
       }
       }
   
       if notFound == true, let remoteExt = getDictionaryFromJSONString(message?.serverExtension ?? ""), let dic = remoteExt[yxAtMsg] as? [String: AnyObject] {
       for (_, value) in dic {
           if let contentDic = value as? [String: AnyObject] {
           if let array = contentDic[atSegmentsKey] as? [AnyObject] {
               if let models = NSArray.yx_modelArray(with: MessageAtInfoModel.self, json: array) as? [MessageAtInfoModel] {
               for model in models {
                   if attributeStr?.length ?? 0 > model.end {
                   attributeStr?.addAttribute(NSAttributedString.Key.foregroundColor, value: UIColor.ne_normalTheme, range: NSMakeRange(model.start, model.end - model.start + atRangeOffset))
                   }
               }
               }
           }
           }
       }
       }
   
       return attributeStr
   }
   

   Objective-C

   Objective-C/// 解析消息中的 @
   /// - Parameters:
   ///   - message: 消息
   ///   - attributeStr: 消息富文本
   /// - Returns: 高亮 @ 后的消息富文本
   + (nullable NSMutableAttributedString *)loadAtInMessage:(nullable V2NIMMessage *)message
                                          attributeStr:(nullable NSMutableAttributedString *)attributeStr {
   // 数字人回复的消息不展示高亮
   if (message.aiConfig != nil &&
       message.aiConfig.aiStatus == V2NIM_MESSAGE_AI_STATUS_RESPONSE) {
       return nil;
   }
   
   NSString *text = message.text ?: @"";
   BOOL isSelf = (message.isSelf == YES);
   CGFloat messageTextSize = isSelf
                               ? [ChatUIConfig shared].messageProperties.selfMessageTextSize
                               : [ChatUIConfig shared].messageProperties.receiveMessageTextSize;
   UIFont *messageTextFont = [UIFont systemFontOfSize:messageTextSize];
   UIColor *messageTextColor = isSelf
                               ? [ChatUIConfig shared].messageProperties.selfMessageTextColor
                               : [ChatUIConfig shared].messageProperties.receiveMessageTextColor;
   
   // 兼容老的表情消息，如果前面有表情而位置计算异常则回退回老的解析
   BOOL notFound = NO;
   
   NSDictionary *remoteExtDict = getDictionaryFromJSONString(message.serverExtension ?: @"");
   if (![remoteExtDict isKindOfClass:[NSDictionary class]]) {
       return attributeStr;
   }
   NSDictionary *atDic = remoteExtDict[kYxAtMsg];
   if (![atDic isKindOfClass:[NSDictionary class]]) {
       return attributeStr;
   }
   
   // 第一轮：根据转码后的 index 处理 @
   for (id key in atDic) {
       id value = atDic[key];
       if (![value isKindOfClass:[NSDictionary class]]) continue;
       NSDictionary *contentDic = (NSDictionary *)value;
       NSArray *array = contentDic[kAtSegmentsKey];
       if (![array isKindOfClass:[NSArray class]]) continue;
   
       NSArray<MessageAtInfoModel *> *models = [NSArray yx_modelArrayWithClass:[MessageAtInfoModel class]
                                                                       json:array];
       if (![models isKindOfClass:[NSArray class]]) continue;
   
       for (MessageAtInfoModel *model in models) {
       if (model.start < 0 || model.end < model.start ||
           model.start >= (NSInteger)text.length ||
           model.end + kAtRangeOffset > (NSInteger)text.length) {
           notFound = YES;
           break;
       }
   
       // 前面因为表情增加的索引数量
       NSInteger countOffset = 0;
       if (model.start > 0 && (NSInteger)text.length > model.start) {
           NSString *frontStr = [text substringToIndex:model.start];
           NSMutableAttributedString *frontAttrStr =
               [NEEmotionTool getAttWithStr:frontStr
                                       font:messageTextFont
                                   color:messageTextColor
                                   offset:CGPointZero];
           countOffset = [ChatMessageHelper getReduceIndexCount:frontAttrStr];
       }
   
       NSInteger start = model.start - countOffset;
       if (start < 0) {
           notFound = YES;
           break;
       }
   
       NSInteger rawLength = model.end - model.start + kAtRangeOffset;
       if (rawLength <= 0 || model.start + rawLength > (NSInteger)text.length) {
           notFound = YES;
           break;
       }
       NSString *rangeStr = [text substringWithRange:NSMakeRange(model.start, rawLength)];
       NSMutableAttributedString *rangeAttrStr =
           [NEEmotionTool getAttWithStr:rangeStr
                                   font:messageTextFont
                                   color:messageTextColor
                                   offset:CGPointZero];
       NSInteger innerCount = [ChatMessageHelper getReduceIndexCount:rangeAttrStr];
       NSInteger end = model.end - countOffset - innerCount;
       if (end <= start) {
           notFound = YES;
           break;
       }
   
       NSInteger attrLength = end - start + kAtRangeOffset;
       if (attrLength > 0 && start >= 0 &&
           start + attrLength <= (NSInteger)attributeStr.length) {
           [attributeStr addAttribute:NSForegroundColorAttributeName
                               value:[UIColor ne_normalTheme]
                               range:NSMakeRange(start, attrLength)];
       }
       }
   
       if (notFound) break;
   }
   
   // 第二轮回退：直接用原始 index 处理
   if (notFound) {
       for (id key in atDic) {
       id value = atDic[key];
       if (![value isKindOfClass:[NSDictionary class]]) continue;
       NSDictionary *contentDic = (NSDictionary *)value;
       NSArray *array = contentDic[kAtSegmentsKey];
       if (![array isKindOfClass:[NSArray class]]) continue;
   
       NSArray<MessageAtInfoModel *> *models = [NSArray yx_modelArrayWithClass:[MessageAtInfoModel class]
                                                                           json:array];
       if (![models isKindOfClass:[NSArray class]]) continue;
   
       for (MessageAtInfoModel *model in models) {
           NSInteger attrLength = model.end - model.start + kAtRangeOffset;
           if (model.start >= 0 && attrLength > 0 &&
               model.start + attrLength <= (NSInteger)attributeStr.length) {
           [attributeStr addAttribute:NSForegroundColorAttributeName
                               value:[UIColor ne_normalTheme]
                               range:NSMakeRange(model.start, attrLength)];
           }
       }
       }
   }
   
   return attributeStr;
   }
   

参考信息

消息构建和发送消息的示例代码可以参考：

• ChatViewController 中的 sendContentText 方法。
• @相关的数据组装和解析参考 NEBaseChatInputView。
• @消息接受和解析参考 NEBaseChatInputView 和 NEAtMessageManager。