Question

我正在尝试创建一个聊天屏幕，以显示用户正在/的所有聊天（（类似Facebook Messenger的东西，其中包含时间戳，lastMessage，conversationTitle和profilePicture）最后发送消息的人的图片）

这是我的JSON（我想将聊天频道信息与用户元信息结合起来）

"Chats" : {
    "MAIN" : {
      "isPrivateChannel" : false,
      "lastMessageSent" : "Ye",
      "messageUID" : "pdXI7oALkBRPK7Gyk4cjaiGspfU2",
      "timestamp" : 1551844495595,
      "title" : "Ye",
      "users" : {
        "ZAX7EnwfLRZU8IYRMLiVMRJm3mH2" : true,
        "pdXI7oALkBRPK7Gyk4cjaiGspfU2" : true
      }
    },
    "ZAX7EnwfLRZU8IYRMLiVMRJm3mH2_pdXI7oALkBRPK7Gyk4cjaiGspfU2" : {
      "isPrivateChannel" : true,
      "lastMessageSent" : "Yo",
      "messageUID" : "ZAX7EnwfLRZU8IYRMLiVMRJm3mH2",
      "timestamp" : 1551844710716,
      "title" : "Yo",
      "users" : {
        "ZAX7EnwfLRZU8IYRMLiVMRJm3mH2" : true,
        "pdXI7oALkBRPK7Gyk4cjaiGspfU2" : true
      }
    },
    "desWJdrhJffGzp9Ou4tPFGyuGfO2_pdXI7oALkBRPK7Gyk4cjaiGspfU2" : {
      "isPrivateChannel" : true,
      "lastMessageSent" : "Ya",
      "messageUID" : "desWJdrhJffGzp9Ou4tPFGyuGfO2",
      "timestamp" : 1551844671583,
      "title" : "Ya",
      "users" : {
        "desWJdrhJffGzp9Ou4tPFGyuGfO2" : true,
        "pdXI7oALkBRPK7Gyk4cjaiGspfU2" : true
      }
    }
  },
   "users" : {
    "ZAX7EnwfLRZU8IYRMLiVMRJm3mH2" : {
      "chats" : {
        "MAIN" : true,
        "ZAX7EnwfLRZU8IYRMLiVMRJm3mH2_pdXI7oALkBRPK7Gyk4cjaiGspfU2" : true
      },
      "meta" : {
        "about" : "Nice",
        "email" : "teest3@test.com",
        "profilePicture" : "https://platform-lookaside.fbsbx.com/platform/profilepic/?...PROFILE_PIC_WOULD_BE_HERE",
        "username" : "test3"
      }
    },
    "desWJdrhJffGzp9Ou4tPFGyuGfO2" : {
      "chats" : {
        "desWJdrhJffGzp9Ou4tPFGyuGfO2_pdXI7oALkBRPK7Gyk4cjaiGspfU2" : true
      },
      "meta" : {
        "about" : "Tall",
        "email" : "test2@test.com",
        "profilePicture" : "none",
        "username" : "test2"
      }
    },
    "pdXI7oALkBRPK7Gyk4cjaiGspfU2" : {
      "chats" : {
        "MAIN" : true,
        "ZAX7EnwfLRZU8IYRMLiVMRJm3mH2_pdXI7oALkBRPK7Gyk4cjaiGspfU2" : true,
        "desWJdrhJffGzp9Ou4tPFGyuGfO2_pdXI7oALkBRPK7Gyk4cjaiGspfU2" : true
      },
      "meta" : {
        "about" : "Smart",
        "email" : "test@test.com",
        "profilePicture" : "none",
        "username" : "test"
      }
    }
  }

我目前正在尝试使用快照内部的快照来执行此操作。我当时想，我只是下拉了相关的用户信息，而不必下载所有用户并在前端使用某种过滤器或地图。

这是我的代码：

  export const getUserChannels = () => {
  return dispatch => {
  dispatch(loadChannels());
  let currentUserID = firebaseService.auth().currentUser.uid;

    firebaseService.database().ref("Chats").orderByChild('timestamp').once('value').then(snapshot => {
      let data = []

      snapshot.forEach((child) =>{
      const childVal = child.val();
      const promise = firebaseService
       .database()
        .ref("users/" + childVal.messageUID + '/meta').once("value").then(userSnapshot => {
          return userSnapshot.val();
        }).catch(error=> console.log(error))
        data.push({...child.val(), ...promise})
        })
      return Promise.all(data)
  }).catch(error => {
    dispatch(loadChannelsError(error.message));
  }).then( data => {
    console.log("DATAAAA", JSON.stringify(data));
    const filteredData = data.filter(chat => chat.users[`${currentUserID}`] === true);
    dispatch(loadChannelsSuccess(filteredData));
  })
}
}

这是我遇到的问题：

我无法弄清楚如何在forEach语句中获得承诺来解决。我还尝试了多种方法来解决promise和async await语法，但是在推送到数据之前无法获得解决的诺言。

在另一个快照解决承诺中响应本机Firebase快照

0 个答案: