How to get data from wildcard in firebase cloud functions

Question

Assuming that I trigger events on the following ref(\'/users/{userId}/items/{newItem}\') I want to get a value from inside the wildcard userId

Answer 1

In firestore you can use this.

exports.getUser = functions.firestore
    .document('users/{userId}').onWrite((change, context) => {
        let userId = context.params.userId;
        //...
    });

Answer 2

Token is not a parameter returned automatically from trigger events. In trigger wild cards only parameters corresponding directly to the wildcard are returned. So You need to do the following if you want to use the

var userId = event.params.userId

And then inside the function you can make another Promise

return admin.database().ref(/users/userId/token).once('value').then(data => { 
//do something here
 })

This will help you get the token. Or if you want to do it in one step, you can try the following with userID as wild card.

return admin.database().ref(/users/{userId}/token).once('value').then(data => { 
    //do something here
     })

But here you will receive multiple tokens and then you will have to iterate through the children to decide which userId is of relevance to you

Answer 3

You can find wildcard values like this

wildCardValue = context.params.wildCardName