你如何从firestore读取数据？

Question

I'm trying to learn how to use firestore.

The google documentation says to try this format:

db.collection("users").get().then((querySnapshot) => {
    querySnapshot.forEach((doc) => {
        console.log(`${doc.id} => ${doc.data()}`);
    });
});

So, I used that to do this (changing the db to fsDB and "users" to "newsletters"

fsDB.collection("newsletters").get().then((querySnapshot) => {
    querySnapshot.forEach((doc) => {
        console.log(`${doc.id} => ${doc.data()}`);
    });
});

When I try this, I get an error that says querySnapshot is not defined. Screen shot of error message is attached.

I've seen this post and tried its suggestion as follows:

fsDB.collection("newsletters").query.get().then(function(querySnapshot) { 

                            if (querySnapshot.empty) { 
                                console.log('no documents found');
                            } else {
                                    querySnapshot.docs.map(function (documentSnapshot) {
                                        console.log(documentSnapshot.data().name); 
                                    });
                            }

                        });

This attempt generates a parsing error with the if statement, but I can't find a way to solve that either.

This must have a simple solution, but I can't figure out how to get a record from the database.

NEXT ATTEMPT

I tried moving the code above the return statement and putting in inside a variable as follows shown in the attached screen shot, but it still produces errors as shown. These errors are the same regardless of whether i keep or lose the brackets around querySnapshot.

ADD STATE

class Fndate extends React.Component {
    state = {
        options: [],
        anzic: [],
        country: [],
        region: [],

    }

    selectCountry (val) {
        this.setState({ country: val });
      }

      selectRegion (val) {
        this.setState({ region: val });
      }

    async componentDidMount() {
        // const fsDB = firebase.firestore(); // Don't worry about this line if it comes from your config.
        let options = [];
        await fsDB.collection("abs_for_codes").get().then(function (querySnapshot) {
        querySnapshot.forEach(function(doc) {
            console.log(doc.id, ' => ', doc.data());
            options.push({
                value: doc.data().title.replace(/( )/g, ''),
                label: doc.data().title + ' - ABS ' + doc.id
            });
            });
        });


        let anzic = [];
        await fsDB.collection("anzic_codes").get().then(function (querySnapshot) {
        querySnapshot.forEach(function(doc) {
            console.log(doc.id, ' => ', doc.data());
            anzic.push({
                value: doc.data().Title.replace(/( )/g, ''),
                label: doc.data().Title + ' - ANZIC ' + doc.id
            });
            });
        });


            await fsDB
            .collection("newsletter")
            .get().then((querySnapshot) => {
                querySnapshot.forEach((doc) => {
                console.log(`${doc.id} => ${doc.data().email}`);
                }
            );
            });

        this.setState({
            options,
            anzic
        });
    }

5 ] 5

Answer 1

I believe you're using React, and I just realized that you're calling the method in question in the render method.

try doing it in componentDidMount . A reference can be found here

so your code would be like this:

class YourClass extends React.Component {
   componentDidMount(){
      fsDB.collection("newsletters").get().then((querySnapshot) => {
         querySnapshot.forEach((doc) => {
            console.log(`${doc.id} => ${doc.data()}`);
         });
      });
   }
   render(){
      return (....your existing jsx....)
   }
}

Note that I don't know your class name or how you define your component. But I'm just saying that you need to move your code in the componentDidMount .

We couldn't see your entire file. But I'm sure that it's a syntax error (especially with JSX)

Answer 2

I think you should get rid of '.query'. and the .empty returns false if you have data in the collection. but i wonder, why is querySnapshot undefined in your case.

db.collection("lessons").get()
  .then(function(querySnapshot) { 
    if (!querySnapshot.empty) {
        querySnapshot.docs.map(function(documentSnapshot) {
        console.log(documentSnapshot.data().name); 
     })
    } else {
    console.log('no documents found');
    }   
});

console

Answer 3

You can use an automated script for this. All you need is python and firebase_admin.

1. pip install firebase_admin
2. download https://github.com/harshit0209/firestore_backup
3. now run getData.py script.
4. give it the path of your firebase project private key.
5. now give the document name.