Firestore to query by an array's field value

Question

I'm trying to run a simple query, where I search for a document that contains a value inside an object array.

For instance, look at my database structure:

I want to run a query similar to this:

db.collection('identites').where("partyMembers", "array-contains", {name: "John Travolta"})

What is the correct way to achieve this, is it even possible with Firestore?

Thanks.

Answer 1

The array-contains operations checks if an array, contains a specific (complete) value. It can't check if an array of objects, contains an item with a specific value for a property.

The only way to do your query, is to add an additional field to your document with just the value you want to query existence on. So for example: partyMemberNames: ["John Travolta", "Olivia Newton"].

Answer 2

As Frank has explained in his answer it is not possible, with array-contains, to query for a specific property of an object stored in an array.

However, there is a possible workaround: it is actually possible to query for the entire object, as follows, in your case:

db.collection('identites').where("partyMembers", "array-contains", {id: "7LNK....", name: "John Travolta"})

Maybe this approach will suit your needs (or maybe not....).

Answer 3

If you want to extract name: "John Travolta" from "partyMembers" array in a document. you can achieve this by some similar approach in which you can loop through all arrays in a document to find this name.

const [names, setNames] = React.useState([])

const readAllNames = async() => {
const snapshot = await firebase.firestore().collection('identites').doc(documentID).get()
      const filterData = snapshot.data().question.map(val => val.name === "John Travolta" ? val : null)
      setNames( filterData.filter(e=>e) );
}

This technique is used in perticular Document as we are giving .doc(documentID) This way you can get all the arrays having name: "John Travolta" in names constant.