在线教育平台开发中，教学白板是如何实现的

{
    [WhiteUtils getRoomTokenWithUuid:self.roomUuid completionHandler:^(NSString * _Nullable roomToken, NSError * _Nullable error) {
        if (roomToken) {
            self.roomToken = roomToken;
//获取到token之后加入房间
             [self joinRoomWithToken:roomToken];
         } else {
            UIAlertController *alertVC = [UIAlertController alertControllerWithTitle:NSLocalizedString(@"获取 RoomToken 失败", nil) message:[NSString stringWithFormat:@"错误信息:%@", [error description]] preferredStyle:UIAlertControllerStyleAlert];
            UIAlertAction *action = [UIAlertAction actionWithTitle:NSLocalizedString(@"确定", nil) style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
                [self.navigationController popViewControllerAnimated:YES];
            }];
            [alertVC addAction:action];
            [self presentViewController:alertVC animated:YES completion:nil];
        }
    }];
}

{
    //配置头像，可以在操作的白板的时候展示头像
    NSDictionary *payload = @{@"avatar": [Config getavatarThumb]};
    WhiteRoomConfig *roomConfig = [[WhiteRoomConfig alloc] initWithUuid:self.roomUuid roomToken:roomToken userPayload:payload];
    // * isWritable 默认为 yes，此处为了单元测试用
    roomConfig.isWritable = YES;
    // 配置，橡皮擦是否能删除图片。默认为 false，能够删除图片。
    // roomConfig.disableEraseImage = YES;

    [self.sdk joinRoomWithConfig:roomConfig callbacks:nil completionHandler:^(BOOL success, WhiteRoom * _Nonnull room, NSError * _Nonnull error) {
        if (success) {

            self.roomToken = roomToken;
            self.room = room;
            isDisableTeachingAids = YES;
//禁止用户的教具操作 ture为禁止
            [_room disableDeviceInputs:YES];

        } else {
            self.title = NSLocalizedString(@"加入失败", nil);
            UIAlertController *alertVC = [UIAlertController alertControllerWithTitle:NSLocalizedString(@"加入房间失败", nil) message:[NSString stringWithFormat:@"错误信息:%@", [error localizedDescription]] preferredStyle:UIAlertControllerStyleAlert];
            UIAlertAction *action = [UIAlertAction actionWithTitle:NSLocalizedString(@"确定", nil) style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
                [self.navigationController popViewControllerAnimated:YES];
            }];
            [alertVC addAction:action];
            [self presentViewController:alertVC animated:YES completion:nil];
        }
    }];
}

/*
WhiteApplianceNameKey const AppliancePencil = @"pencil";
WhiteApplianceNameKey const ApplianceSelector = @"selector";
WhiteApplianceNameKey const ApplianceText = @"text";
WhiteApplianceNameKey const ApplianceEllipse = @"ellipse";
WhiteApplianceNameKey const ApplianceRectangle = @"rectangle";
WhiteApplianceNameKey const ApplianceEraser = @"eraser";
*/
        currentmState.currentApplianceName = AppliancePencil;
//颜色可以自定义
        currentmState.strokeColor = [UIColor redColor];
//画线宽度可以自定义
        currentmState.strokeWidth = 10;
        [self.room setMemberState:currentmState];

[self.room disconnect:nil];