Get Key For Object Created After Push (angular And Firebase)

I'm having problems understanding how to use Firebase. I wrote a function to push some data in my firebase database. I need to get the Key generated after I push the data into my d

Solution 1:

I would make a small change to the post line and add / to the transactions

postData(order: orderInfo) {
    let uid = firebase.auth().currentUser.uid;

// Change this next line to save the transaction

    var newRef = this.db.list('/transactions').push({
      currency: order.currency,
      total: order.total,
      rate: order.rate,
      uid: uid
    });

// get just the key reference
var newKey= newRef.key;

//then change this refer

    console.log(newKey);

//To update you would change the next line

    this.db.list('transactionsPerUser').update(newKey, order.newInfo);
}