实现收发消息

本文将指导你如何利用 RTM Objective-C SDK 构建简单的应用程序，内容涵盖了集成和开发的基础知识：开通声网账号、获取 SDK、发送消息、接收消息等。

准备工作

开始构建项目前，你需要完成开通服务，并检查你的开发环境是否满足平台支持中的最低版本要求。

构建项目

1. 项目配置

根据以下步骤配置你的项目：

1. 在 Xcode 中创建一个 iOS 平台下的 Single View App，项目设置如下：

   • Product Name 设为 RtmQuickstart。
   • Organization Identifier 设为 agora。
   • User Interface 选择 Storyboard。
   • Language 选择 Objective-C。

2. 通过以下任意一种方式获取最新的 RTM Objective-C SDK 并导入你的项目。

   使用 CDN

   1. 点击此处下载最新版本的 Objective-C SDK。
   2. 复制 SDK 包中 /libs 路径下所有的 xcframework 文件至项目路径下。
   3. 打开 Xcode，进入 TARGETS > Project Name > General > Frameworks, Libraries, and Embedded Content 菜单。
   4. 点击 + > Add Other… > Add Files 添加所有的 xcframework 文件，并确保添加的动态库 Embed 属性设置为 Embed & Sign。

   添加完成后，项目会自动链接所需系统库。

   使用 Cocoapods

   1. 开始前请确保你已安装 Cocoapods，如尚未安装 Cocoapods，参考 Getting Started with CocoaPods 安装说明。

   2. 在终端里进入项目根目录，并运行 pod init 命令。项目文件夹下会生成一个 Podfile 文本文件。

   3. 打开 Podfile 文件，修改文件为如下内容。注意将 Your App 替换为你的 Target 名称。

      Ruby

      platform :ios, '11.0'
      target 'Your App' do
         # 将 x.y.z 替换为具体的 SDK 版本号，如 2.2.0
         # 可通过发版说明获取最新版本号
         # 当前示例仅适用于 2.2.0 及之后版本
         # 如需获取 2.2.0 之前的版本，请将包名修改为 AgoraRtm_iOS
         pod 'AgoraRtm', 'x.y.z'
      
         # 如果你使用的是 2.2.2 或之后版本的 RTM SDK，且项目中同时使用了 RTC SDK v4.3.0 或以上版本
         # pod 'AgoraRtm', 'x.y.z', :subspecs => ['RtmKit']
      end

   4. 在终端内运行 pod install 命令安装声网 SDK。成功安装后，Terminal 中会显示 Pod installation complete!。

   5. 成功安装后，项目文件夹下会生成一个后缀为 .xcworkspace 的文件，通过 Xcode 打开该文件进行后续操作。

   信息

   如果你同时集成了 2.2.0 及以上版本的 RTM SDK 和 4.3.0 及以上版本的 RTC SDK，请参考 FAQ 处理集成问题。

2. 初始化 RTM

调用 RTM SDK 的任何 API 之前，需要先初始化一个 AgoraRtmClientKit 对象实例。参考如下步骤创建用户界面、初始化一个 AgoraRtmClientKit 对象实例。

1. 创建用户界面。实时消息 App 一般会有如下输入框和按钮：

   • 用户名、频道名、消息输入框
   • 登录、登出按钮
   • 订阅、取消订阅频道按钮
   • 发送消息按钮

   本节提供简易的 UI 界面设计以便于验证功能特性，你可以根据实际项目需求进行修改。

   1. 使用 Code View 打开 Main.storyboard 并将文件内容替换为以下代码：

      XML

      <?xml version="1.0" encoding="UTF-8"?>
      <document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="21701" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" useSafeAreas="YES" colorMatched="YES" initialViewController="BYZ-38-t0r">
          <device id="retina6_1" orientation="portrait" appearance="light"/>
          <dependencies>
              <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="21679"/>
              <capability name="Safe area layout guides" minToolsVersion="9.0"/>
              <capability name="System colors in document resources" minToolsVersion="11.0"/>
              <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
          </dependencies>
          <scenes>
              <!--View Controller-->
              <scene sceneID="tne-QT-ifu">
                  <objects>
                      <viewController id="BYZ-38-t0r" customClass="ViewController" sceneMemberID="viewController">
                          <view key="view" contentMode="scaleToFill" id="8bC-Xf-vdC">
                              <rect key="frame" x="0.0" y="0.0" width="414" height="896"/>
                              <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                              <subviews>
                                  <button opaque="NO" contentMode="scaleToFill" fixedFrame="YES" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="system" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="M2K-rz-dlO">
                                      <rect key="frame" x="254" y="103" width="38" height="30"/>
                                      <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                      <state key="normal" title="Login"/>
                                      <connections>
                                          <action selector="Login:" destination="BYZ-38-t0r" eventType="touchUpInside" id="UEU-up-ksL"/>
                                      </connections>
                                  </button>
                                  <button opaque="NO" contentMode="scaleToFill" fixedFrame="YES" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="system" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="CZ1-G5-AkG">
                                      <rect key="frame" x="326" y="103" width="48" height="30"/>
                                      <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                      <state key="normal" title="Logout"/>
                                      <connections>
                                          <action selector="Logout:" destination="BYZ-38-t0r" eventType="touchUpInside" id="a0d-8h-eyX"/>
                                      </connections>
                                  </button>
                                  <button opaque="NO" contentMode="scaleToFill" fixedFrame="YES" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="system" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="0px-1e-aMC">
                                      <rect key="frame" x="242" y="172" width="62" height="30"/>
                                      <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                      <state key="normal" title="Subcribe"/>
                                      <connections>
                                          <action selector="SubscribeChannel:" destination="BYZ-38-t0r" eventType="touchUpInside" id="12c-US-VQk"/>
                                      </connections>
                                  </button>
                                  <button opaque="NO" contentMode="scaleToFill" fixedFrame="YES" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="system" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="SDQ-Zt-rBD">
                                      <rect key="frame" x="307" y="172" width="87" height="30"/>
                                      <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                      <state key="normal" title="Unsubscribe"/>
                                      <connections>
                                          <action selector="UnsubscribeChannel:" destination="BYZ-38-t0r" eventType="touchUpInside" id="u4T-ze-wtj"/>
                                      </connections>
                                  </button>
                                  <textField opaque="NO" contentMode="scaleToFill" fixedFrame="YES" contentHorizontalAlignment="left" contentVerticalAlignment="center" text="User ID" borderStyle="roundedRect" textAlignment="natural" minimumFontSize="17" translatesAutoresizingMaskIntoConstraints="NO" id="69v-UU-ObH">
                                      <rect key="frame" x="40" y="99" width="187" height="34"/>
                                      <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                      <fontDescription key="fontDescription" type="system" pointSize="14"/>
                                      <textInputTraits key="textInputTraits"/>
                                  </textField>
                                  <textField opaque="NO" contentMode="scaleToFill" fixedFrame="YES" contentHorizontalAlignment="left" contentVerticalAlignment="center" text="Channel name" borderStyle="roundedRect" textAlignment="natural" minimumFontSize="17" translatesAutoresizingMaskIntoConstraints="NO" id="dGk-g2-qHK">
                                      <rect key="frame" x="40" y="168" width="187" height="34"/>
                                      <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                      <fontDescription key="fontDescription" type="system" pointSize="14"/>
                                      <textInputTraits key="textInputTraits"/>
                                  </textField>
                                  <button opaque="NO" contentMode="scaleToFill" fixedFrame="YES" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="system" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="Qqk-6X-Tcb">
                                      <rect key="frame" x="304" y="247" width="88" height="30"/>
                                      <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                      <state key="normal" title="Publish MSG"/>
                                      <connections>
                                          <action selector="SendMessageToMessageChannel:" destination="BYZ-38-t0r" eventType="touchUpInside" id="XcX-nz-fPl"/>
                                      </connections>
                                  </button>
                                  <textField opaque="NO" contentMode="scaleToFill" fixedFrame="YES" contentHorizontalAlignment="left" contentVerticalAlignment="center" text="Message content" borderStyle="roundedRect" textAlignment="natural" minimumFontSize="17" translatesAutoresizingMaskIntoConstraints="NO" id="lKg-ap-M6p">
                                      <rect key="frame" x="40" y="245" width="252" height="34"/>
                                      <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                      <fontDescription key="fontDescription" type="system" pointSize="14"/>
                                      <textInputTraits key="textInputTraits"/>
                                  </textField>
                                  <textView clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="scaleToFill" fixedFrame="YES" textAlignment="natural" translatesAutoresizingMaskIntoConstraints="NO" id="e1v-i8-spC">
                                      <rect key="frame" x="40" y="416" width="330" height="428"/>
                                      <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
                                      <color key="backgroundColor" systemColor="systemBackgroundColor"/>
                                      <color key="textColor" systemColor="labelColor"/>
                                      <fontDescription key="fontDescription" type="system" pointSize="14"/>
                                      <textInputTraits key="textInputTraits" autocapitalizationType="sentences"/>
                                  </textView>
                              </subviews>
                              <viewLayoutGuide key="safeArea" id="6Tk-OE-BBY"/>
                              <color key="backgroundColor" systemColor="systemBackgroundColor"/>
                          </view>
                          <connections>
                              <outlet property="ChannelIDTextField" destination="dGk-g2-qHK" id="Iuh-ow-1MH"/>
                              <outlet property="GroupMsgButton" destination="Qqk-6X-Tcb" id="TV4-sg-bY7"/>
                              <outlet property="GroupMsgTextField" destination="lKg-ap-M6p" id="2Me-Z0-QIH"/>
                              <outlet property="LoginButton" destination="M2K-rz-dlO" id="ZxJ-oV-UKy"/>
                              <outlet property="LogoutButton" destination="CZ1-G5-AkG" id="ZQE-B7-yya"/>
                              <outlet property="MsgTextView" destination="e1v-i8-spC" id="76J-8Q-kKp"/>
                              <outlet property="SubsctibeButton" destination="0px-1e-aMC" id="9TL-8M-l6w"/>
                              <outlet property="UnSubscribeButton" destination="SDQ-Zt-rBD" id="tgd-fK-EfO"/>
                              <outlet property="UserIDTextField" destination="69v-UU-ObH" id="3BH-ci-t7A"/>
                          </connections>
                      </viewController>
                      <placeholder placeholderIdentifier="IBFirstResponder" id="dkx-z0-nzr" sceneMemberID="firstResponder"/>
                  </objects>
                  <point key="canvasLocation" x="131.8840579710145" y="97.767857142857139"/>
              </scene>
          </scenes>
          <resources>
              <systemColor name="labelColor">
                  <color red="0.0" green="0.0" blue="0.0" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
              </systemColor>
              <systemColor name="systemBackgroundColor">
                  <color white="1" alpha="1" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/>
              </systemColor>
          </resources>
      </document>

   2. 打开 ViewController.h 文件，将文件内容替换为如下代码：

      Objective-C

      #import <UIKit/UIKit.h>
      
      #import <AgoraRtmKit/AgoraRtmKit.h>
      
      @interface ViewController : UIViewController
      
      // Buttons
      @property (weak, nonatomic) IBOutlet UIButton *LoginButton;
      @property (weak, nonatomic) IBOutlet UIButton *LogoutButton;
      @property (weak, nonatomic) IBOutlet UIButton *SubsctibeButton;
      @property (weak, nonatomic) IBOutlet UIButton *UnSubscribeButton;
      @property (weak, nonatomic) IBOutlet UIButton *GroupMsgButton;
      
      // Textfields
      @property (weak, nonatomic) IBOutlet UITextField *UserIDTextField;
      @property (weak, nonatomic) IBOutlet UITextField *ChannelIDTextField;
      @property (weak, nonatomic) IBOutlet UITextField *GroupMsgTextField;
      
      @property (weak, nonatomic) IBOutlet UITextView *MsgTextView;
      
      @end

2. 打开 ViewController.m 文件，将文件内容替换为如下代码。你会发现此程序并不完整，不用紧张，我们在后续步骤中将一步步指导你补充完善代码。

   信息

   你需要将示例中的 your_appid 和 your_token 字段替换成你项目的 App ID 和 Token。在测试阶段，为快速验证功能，我们建议你在创建声网项目时将鉴权模式设置为调试模式，然后将示例中的 your_appid 和 your_token 字段都替换成你项目的 App ID。

   Objective-C

   #import "ViewController.h"
   
   @interface ViewController ()<AgoraRtmClientDelegate>
   
   @property(nonatomic, strong)AgoraRtmClientKit* kit;
   
   @property NSString* appID;
   @property NSString* token;
   
   @property NSString* uid;
   @property NSString* peerID;
   @property NSString* channelID;
   @property NSString* peerMsg;
   @property NSString* channelMsg;
   
   @property NSString* text;
   @property NSMutableArray* textArray;
   
   - (void)AddMsgToRecord:(NSString*)text;
   
   @end
   
   @implementation ViewController
   
   - (void)viewDidLoad {
   [super viewDidLoad];
   // Enter your App ID
   self.appID = @"your_appid";
   self.MsgTextView.textColor = UIColor.blueColor;
   self.textArray = [[NSMutableArray alloc]init];
   }
   
   // Add the event listener
   
   // Add message to the UI TextView
   - (void)AddMsgToRecord:(NSString*)text {
   
   
   [self.textArray addObject:(self.text)];
   self.MsgTextView.text = [self.textArray componentsJoinedByString:(@"\n")];
   
   }
   
   - (IBAction)Login:(id)sender {
       self.uid = self.UserIDTextField.text;
       // Enter your token
       self.token = @"your_token";
   
       AgoraRtmClientConfig*  rtm_config = [[AgoraRtmClientConfig alloc] initWithAppId:_appID userId:_uid];
   
       NSError* initError = nil;
       _kit = [[AgoraRtmClientKit alloc] initWithConfig:rtm_config delegate:self error:&initError];
       if (initError != nil) {
           self.text = [NSString stringWithFormat:@"init error %@",initError];
           NSLog(@"%@", self.text);
           [self AddMsgToRecord:(self.text)];
       }
       // Log in the RTM server
   }
   
   - (IBAction)Logout:(id)sender {
   if (_kit != nil) {
       // Log out from the RTM server
       }
   }
   
   - (IBAction)SubscribeChannel:(id)sender {
   self.channelID = self.ChannelIDTextField.text;
   if (_kit != nil) {
       // Subscribe to a channel
       }
   }
   
   - (IBAction)UnsubscribeChannel:(id)sender {
       if (_kit == nil)
           return;
       // Unsubscribe from a channel
   }
   
   - (IBAction)SendMessageToMessageChannel:(id)sender {
   self.channelID = self.ChannelIDTextField.text;
   self.channelMsg = self.GroupMsgTextField.text;
       // Publish a message
   }
   @end

如需了解更多初始化的信息，查看初始配置。

3. 添加事件监听

事件监听程序帮助你实现频道中消息、事件到达后的处理逻辑，添加以下代码到你的程序中以显示收到的消息或事件通知：

Objective-C

// Paste the following code snippet below "Add the event listener" comment
- (void)rtmKit:(AgoraRtmClientKit *)rtmKit didReceiveMessageEvent:(AgoraRtmMessageEvent *)event {
    NSLog(@"%@", self.text);
    self.text = [NSString stringWithFormat:@"receive message\nFrom channel: %@\npublisher:%@\nmessage:%@\n",event.channelName,event.publisher, event.message.stringData];
    [self AddMsgToRecord:(self.text)];
}

4. 登录服务

你需要执行登录操作才能建立与 RTM 服务器的连接，然后才能调用 SDK 的其他 API。将以下代码添加到程序中：

Objective-C

// Paste the following code snippet below "Log in the RTM server" comment
[_kit loginByToken:self.token completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo.errorCode != AgoraRtmErrorOk){
        self.text = [NSString stringWithFormat:@"Login failed for user %@. Code: %ld",self.uid, (long)errorInfo.errorCode];
        NSLog(@"%@", self.text);
    } else {
        NSLog(@"%@", self.text);
        self.text = [NSString stringWithFormat:@"Login successful for user %@. Code: %ld",self.uid, (long)errorInfo.errorCode];
    }
    [self AddMsgToRecord:(self.text)];
}];

5. 收发消息

调用 publish 方法向 Message Channel 发送消息后，RTM 会把该消息分发给该频道的所有订阅者，以下代码演示如何发送字符串类型的消息，将此代码片段添加到程序中：

信息

你需要先对消息负载进行字符串序列化，才能调用 publish 方法发送消息。

Objective-C

// Paste the following code snippet below "Publish a message" comment
[_kit publish:self.channelID message:self.channelMsg option:nil completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil) {
        self.text = [NSString stringWithFormat:@"Message sent to channel %@ : %@", self.channelID, self.channelMsg];
    } else {
        self.text = [NSString stringWithFormat:@"Message failed to send to channel %@ : %@ ErrorCode: %ld", self.channelID, self.channelMsg, (long)errorInfo.errorCode];
    }

    [self AddMsgToRecord:(self.text)];
}];

调用 subscribeWithChannel 方法订阅此频道以接收此频道中的消息。将以下代码添加到程序中：

Objective-C

// Paste the following code snippet below "Subscribe to a channel" comment
[_kit subscribeWithChannel:self.channelID option:nil completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if(errorInfo == nil) {
        self.text = [NSString stringWithFormat:@"Successfully subscribe channel %@",self.channelID];
        NSLog(@"%@", self.text);
    } else {
        self.text = [NSString stringWithFormat:@"Failed to subscribe channel %@ Code: %ld",self.channelID, (long)errorInfo.errorCode];
        NSLog(@"%@", self.text);
    }

    [self AddMsgToRecord:(self.text)];
}];

如果你不再需要在此频道收发消息，你可以调用 unsubscribeWithChannel 方法取消订阅此频道。将以下代码添加到程序中：

Objective-C

// Paste the following code snippet below "Unsubscribe from a channel" comment
[_kit unsubscribeWithChannel:self.channelID completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil){
        self.text = [NSString stringWithFormat:@"Leave channel successful"];
    } else {
        self.text = [NSString stringWithFormat:@"Failed to leave channel Code: %ld", (long)errorInfo.errorCode];
    }

    [self AddMsgToRecord:(self.text)];
}];

如需了解更多收发消息的信息，查看消息。

6. 登出服务

当不再需要使用 RTM 服务时，你可以调用 logout 方法登出 RTM 系统。将以下代码添加到程序中：

Objective-C

// Paste the following code snippet below "Log out from the RTM server" comment
[_kit logout:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
    if (errorInfo == nil){
        self.text = [NSString stringWithFormat:@"Logout successful"];
        NSLog(@"%@", self.text);
        [_kit destroy];
        _kit = nil;
    } else {
        self.text = [NSString stringWithFormat:@"Logout failed. Code: %ld",(long)errorInfo.errorCode];
        NSLog(@"%@", self.text);
    }

    [self AddMsgToRecord:(self.text)];
}];

信息

本操作会影响你账单中的 PCU 计费项。

7. 组合到一起

经过上述步骤，你程序中的代码应该如下所示：

Objective-C

#import "ViewController.h"

@interface ViewController ()<AgoraRtmClientDelegate>

@property(nonatomic, strong)AgoraRtmClientKit* kit;

@property NSString* appID;
@property NSString* token;

@property NSString* uid;
@property NSString* peerID;
@property NSString* channelID;
@property NSString* peerMsg;
@property NSString* channelMsg;

@property NSString* text;
@property NSMutableArray* textArray;

- (void)AddMsgToRecord:(NSString*)text;

@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];
// Enter your App ID
self.appID = @"your_appid";
self.MsgTextView.textColor = UIColor.blueColor;
self.textArray = [[NSMutableArray alloc]init];
}

- (void)rtmKit:(AgoraRtmClientKit *)rtmKit didReceiveMessageEvent:(AgoraRtmMessageEvent *)event {
    NSLog(@"%@", self.text);
    self.text = [NSString stringWithFormat:@"receive message\nFrom channel: %@\npublisher:%@\nmessage:%@\n",event.channelName,event.publisher, event.message.stringData];
    [self AddMsgToRecord:(self.text)];
}

// Add message to the UI TextView
- (void)AddMsgToRecord:(NSString*)text {


[self.textArray addObject:(self.text)];
self.MsgTextView.text = [self.textArray componentsJoinedByString:(@"\n")];

}

- (IBAction)Login:(id)sender {
    self.uid = self.UserIDTextField.text;
    // Enter your token
    self.token = @"your_token";

    AgoraRtmClientConfig*  rtm_config = [[AgoraRtmClientConfig alloc] initWithAppId:_appID userId:_uid];

    NSError* initError = nil;
    _kit = [[AgoraRtmClientKit alloc] initWithConfig:rtm_config delegate:self error:&initError];
    if (initError != nil) {
        self.text = [NSString stringWithFormat:@"init error %@",initError];
        NSLog(@"%@", self.text);
        [self AddMsgToRecord:(self.text)];
    }
    // Log in the RTM server
    [_kit loginByToken:self.token completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
        if (errorInfo.errorCode != AgoraRtmErrorOk){
            self.text = [NSString stringWithFormat:@"Login failed for user %@. Code: %ld",self.uid, (long)errorInfo.errorCode];
            NSLog(@"%@", self.text);
        } else {
            NSLog(@"%@", self.text);
            self.text = [NSString stringWithFormat:@"Login successful for user %@. Code: %ld",self.uid, (long)errorInfo.errorCode];
        }
        [self AddMsgToRecord:(self.text)];
    }];

}

- (IBAction)Logout:(id)sender {
if (_kit != nil) {
    // Log out from the RTM server
    [_kit logout:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
        if (errorInfo == nil){
            self.text = [NSString stringWithFormat:@"Logout successful"];
            NSLog(@"%@", self.text);
            [_kit destroy];
            _kit = nil;
        } else {
            self.text = [NSString stringWithFormat:@"Logout failed. Code: %ld",(long)errorInfo.errorCode];
            NSLog(@"%@", self.text);
        }

        [self AddMsgToRecord:(self.text)];
    }];
}

- (IBAction)SubscribeChannel:(id)sender {
self.channelID = self.ChannelIDTextField.text;
if (_kit != nil) {
    // Subscribe to a channel
    [_kit subscribeWithChannel:self.channelID option:nil completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
        if(errorInfo == nil) {
            self.text = [NSString stringWithFormat:@"Successfully subscribe channel %@",self.channelID];
            NSLog(@"%@", self.text);
        } else {
            self.text = [NSString stringWithFormat:@"Failed to subscribe channel %@ Code: %ld",self.channelID, (long)errorInfo.errorCode];
            NSLog(@"%@", self.text);
        }

        [self AddMsgToRecord:(self.text)];
    }];
    }
}

- (IBAction)UnsubscribeChannel:(id)sender {
    if (_kit == nil)
        return;
    // Unsubscribe from a channel
    [_kit unsubscribeWithChannel:self.channelID completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
        if (errorInfo == nil){
            self.text = [NSString stringWithFormat:@"Leave channel successful"];
        } else {
            self.text = [NSString stringWithFormat:@"Failed to leave channel Code: %ld", (long)errorInfo.errorCode]; }

        [self AddMsgToRecord:(self.text)];
    }];
}

- (IBAction)SendMessageToMessageChannel:(id)sender {
self.channelID = self.ChannelIDTextField.text;
self.channelMsg = self.GroupMsgTextField.text;
    // Publish a message
    [_kit publish:self.channelID message:self.channelMsg option:nil completion:^(AgoraRtmCommonResponse * _Nullable response, AgoraRtmErrorInfo * _Nullable errorInfo) {
        if (errorInfo == nil)
        {
            self.text = [NSString stringWithFormat:@"Message sent to channel %@ : %@", self.channelID, self.channelMsg];        }
        else
        {
            self.text = [NSString stringWithFormat:@"Message failed to send to channel %@ : %@ ErrorCode: %ld", self.channelID, self.channelMsg, (long)errorInfo.errorCode];        }

        [self AddMsgToRecord:(self.text)];
    }];
}
@end

现在，你可以开始运行你的程序：

1. 保存项目。
2. 复制当前项目，使用相同的 appId 和不同的 userId。
3. 运行上面的两个项目。成功运行后，你可以在两个设备中看到 App 界面。
4. 将一个设备作为接收端，进行如下操作：
   1. 输入用户名，点击 Login。
   2. 输入频道名，点击 Subscribe。
5. 将另一个设备作为发送端，进行如下操作：
   1. 输入不同的用户名，点击 Subscribe。
   2. 输入相同的频道名。
   3. 输入消息，点击 Publish MSG。
6. 将上面的发送端和设备端互换，重复步骤 4 和 5。

如果两个设备均可收发消息，那么你已经成功集成并正确使用了 RTM 服务。

贯穿始终

相比于介绍如何写出代码，声网更愿意帮助你掌握上述程序编写的过程和逻辑。上述程序依次完成了以下操作，让你可以正确地收发消息：

1. 设置并初始化 RTM 对象。
2. 添加 didReceiveMessageEvent 事件监听函数。
3. 调用 loginByToken 登录了 RTM 服务。
4. 调用 subscribeWithChannel 订阅了一个 Message Channel。
5. 调用 publish 发送消息。
6. 调用 unsubscribeWithChannel 取消订阅一个 Message Channel。
7. 调用 logout 登出 RTM 系统。

下一步

现在，你已经学会了如何使用 RTM Objective-C SDK 来实现 Message Channel 的收发消息功能。下一步，你可以通过 SDK 的 API 参考了解更多功能的使用方法。