如何在React-native中从Firestore中读取子集合的文档字段 [英] How to read a sub-collection's document fields from Firestore in react-native

问题描述

在本机项目中，尝试从Firebase的Firestore的根级别集合中的文档中读取所有子集合.不太确定要遵循的文档(Web无法执行 getCollections()/node?).Firebase已导入，我已经从firestore中成功检索了其他数据，但是我从未能够读取子集合数据.这没有使用库 react-native-firebase (尽管我已经尝试过react-native-firebase，也没有文档化的解决方案)无论如何，我已经尝试过:

Trying to read all sub collections from a document inside a root-level collection from firebase's Firestore in a react-native project. Not too sure which documentation to follow (web-can't do getCollections() /node?). Firebase is imported and I have successfully retrieved other data from firestore, but never have I been able to read sub collection data. This is not using the library react-native-firebase (Although I’ve tried with react-native-firebase and it has no documented solution to this either) Regardless, I've tried:

componentDidMount() {
    firebase
      .firestore()
      .collection('users')
      .doc(this.props.user.uid)
      .getCollections('conversations')
      .then(collections => {
        collections.forEach(collection => {
          alert(collection.id)
        })
      }) 
}

以上返回'_ firebase.default.firestore().collection("users").doc(this.props.user.uid).getCollections'未定义

也尝试过:

componentDidMount() {
    firebase
      .firestore()
      .collection("users")
      .doc(this.props.user.uid)
      .collection("conversations")
      .get()
      .then(collections => {
        collections.forEach(collection => {
          alert(JSON.stringify(collection)); //collection.id is can be read here
        });
      });

在上面，可以读取集合ID，但是如何读取文档字段?上面给了我循环结构错误.

in the above, the collection id can be read, but how can the document fields be read? the above gives me cyclic structure errors.

alert(collection.data())给了我 [object Object]

alert(JSON.stringify(collection.data())给我循环结构错误

这是消防站:

实际应用中将填充给定用户的所有对话，然后填充给定对话的所有消息.如何在本机项目中从Firestore的所有子集合中读取数据?

The practical application would be populating all conversations for a given user, and then all messages for a given conversation. How Do I read data from all sub collections from Firestore in a react-native project?

推荐答案

要读取子集合文档数据，最终起作用的是:

To read the sub-collection document data what ultimately worked was:

_getConversation() {
    firebase
      .firestore()
      .collection("users")
      .doc(this.props.user.uid)
      .collection("conversations")
      .get()
      .then(querySnapshot => {
        querySnapshot.forEach(queryDocumentSnapshot => {
          alert(queryDocumentSnapshot.get("members"));
        });
      })
      .catch(err => {
        alert(err);
      });
  }

和

_getMessages() {
    firebase
      .firestore()
      .collection("users")
      .doc(this.props.user.uid)
      .collection("conversations")
      .doc("some-document-id-here")
      .collection("messages")
      .get()
      .then(querySnapshot => {
        querySnapshot.forEach(queryDocumentSnapshot => {
          alert(queryDocumentSnapshot.get("content"));
        });
      });
  }

更深入地研究文档确实更有帮助

a deeper dive into documentation was indeed more helpful

这篇关于如何在React-native中从Firestore中读取子集合的文档字段的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！