添加事件监听

如需收到消息和事件通知，你需要先实现事件监听程序，然后订阅或者加入你想要接收消息或事件通知的频道。

添加事件监听

RTM 采用统一入口的方式处理消息和事件通知，每一种消息和事件通知都有对应的事件处理程序入口，你可以在其中实现自己的业务处理逻辑：

Objective-C

// define RTM Event Listener
@interface RtmListener : NSObject <AgoraRtmClientDelegate>

@end

@implementation RtmListener

// triggered when received message from remote
- (void)rtmKit:(AgoraRtmClientKit *)rtmKit didReceiveMessageEvent:(AgoraRtmMessageEvent *)event {
    NSString* channel = event.channelName;
    AgoraRtmChannelType channel_type = event.channelType;
    if (channel_type == AgoraRtmChannelTypeStream) {
        NSString* topic = event.channelTopic; // if message from stream channel, user can get topic name
    }

    if (event.message.rawData != nil) {
        NSData* message =event.message.rawData; // get binary message
    } else {
        NSString* message = event.message.stringData; // get string message
    }
    NSString* publisher = event.publisher;

}

// triggered when channel lock info changed
- (void)rtmKit:(AgoraRtmClientKit *)rtmKit didReceiveLockEvent:(AgoraRtmLockEvent *)event {
    NSString* channel = event.channelName;
    AgoraRtmChannelType channel_type = event.channelType;
    AgoraRtmLockEventType event_type = event.eventType;
    if (event.lockDetailList != nil) {
        NSArray<AgoraRtmLockDetail *> *lock_details = event.lockDetailList; //get detail lock info

    }
}

// triggered when prensence info changed
- (void)rtmKit:(AgoraRtmClientKit *)rtmKit didReceivePresenceEvent:(AgoraRtmPresenceEvent *)event {
    NSString* channel = event.channelName;
    AgoraRtmChannelType channel_type = event.channelType;
    AgoraRtmPresenceEventType event_type = event.type;
    NSString* publisher = event.publisher;
    if (event_type  == AgoraRtmPresenceEventTypeInterval) {
        AgoraRtmPresenceIntervalInfo* interval = event.interval;
    }else if (event_type == AgoraRtmPresenceEventTypeSnapshot) {
        NSArray<AgoraRtmUserState *> * snapshot = event.snapshot;
    } else {
        NSArray<AgoraRtmStateItem *> *states = event.states;
    }
}

// triggered when subscribed strorage changed
-(void)rtmKit:(AgoraRtmClientKit *)rtmKit didReceiveStorageEvent:(AgoraRtmStorageEvent *)event {
    AgoraRtmStorageType storage_type = event.storageType;
    if (storage_type == AgoraRtmStorageTypeChannel) {
        NSString* channel = event.target;
        AgoraRtmChannelType channel_type = event.channelType;
    } else {
        NSString* user = event.target;
    }
    AgoraRtmMetadata* data = event.data;
}

// triggered when token will expire
- (void)rtmKit:(AgoraRtmClientKit *)rtmKit tokenPrivilegeWillExpire:(NSString *)channel {
    if (channel != nil) {
        //renew specific stream channel's token
    } else {
        // renew rtm client's token
    }
}

// triggered when connection state changed
- (void)rtmKit:(AgoraRtmClientKit *)kit channel:(NSString *)channelName connectionChangedToState:(AgoraRtmClientConnectionState)state reason:(AgoraRtmClientConnectionChangeReason)reason {
    if (channelName != nil) {
        NSLog(@"stream channel connection changed now state is %d change reason is %d",state, reason);
    } else {
        NSLog(@"rtm client connection changed now state is %d change reason is %d",state, reason);
    }
}

// triggered when link state changed
- (void)rtmKit:(AgoraRtmClientKit *)rtmKit didReceiveLinkStateEvent:(AgoraRtmLinkStateEvent *)event {
    if (event.serviceType == AgoraRtmServiceTypeStream) {
        // receive stream channel link event
    } else {
        // receive message link event
    }
}
@end

AgoraRtmClientConfig* rtm_cfg = [[AgoraRtmClientConfig alloc] initWithAppId:@"your_appid" userId:@"your_userid"];

// add event listener
RtmListener* handler =  [[RtmListener alloc] init];
NSError* initError = nil;
AgoraRtmClientKit* rtm = [[AgoraRtmClientKit alloc] initWithConfig:rtm_cfg delegate:handler error:&initError];

删除事件监听

为避免内存泄漏、错误和异常（即空指针异常）引起的性能下降，声网建议你在不需要使用某个事件处理程序时对其进行注销。例如，如果不想关注 Lock 事件通知，删除对 didReceiveLockEvent 函数的定义即可。

事件通知类型

RTM 一共有 7 种类型事件，对应的有 7 种事件监听程序。你可以查看 API 参考的事件监听章节，了解每个事件监听程序传入参数的详细信息。

事件监听程序	描述
didReceiveMessageEvent	接收所有订阅的 Message Channel 中的消息通知或你加入的所有 Stream Channel 中订阅的 Topic 消息通知。事件负载数据中包含频道名称、频道类型、Topic 名称、事件发送者、消息负载数据类型等信息。
didReceivePresenceEvent	接收所有订阅的 Message Channel 或者你加入的所有 Stream Channel 中远端用户的在线状态事件通知。事件负载数据中包含频道名称、频道类型、事件类型、事件发送者、用户临时状态数据等信息。
didReceiveTopicEvent	接收加入的所有 Stream Channel 中 Topic 变更事件通知。事件负载数据中包含频道名称、事件类型、Topic 名称、事件发送者（即 Topic 详情）等信息。
didReceiveStorageEvent	接收订阅的 Message Channel 及加入的 Stream Channel 中所有的 Channel Metadata 事件通知，以及所有订阅用户的 User Metadata 事件通知。事件负载数据中包含频道名称、频道类型、事件类型（即具体 Metadata 数据）等信息。
didReceiveLockEvent	接收订阅的 Message Channel 及加入的 Stream Channel 中所有的 Lock 事件通知。事件负载数据中包含有频道名称、频道类型、事件类型、锁详情等信息。
didReceiveLinkStateEvent	接收客户端网络连接状态变更的事件通知，包含变更前后的连接状态、服务类型、导致变更的操作类型、变更原因、频道列表等信息。
tokenPrivilegeWillExpire	接收客户端 Token 将要过期的事件通知。

完成事件监听处理程序后，你可以通过订阅频道或 Topic 来接收指定的 Message Channel 或 Stream Channel 中的消息和事件通知了。详见订阅 Message Channel 和订阅 Topic。