Firebase cloud functions - Update nodes

Question

I'm using Firebase cloud functions in my app to count likes of users. I have node of likes that when user like a video it saves his ID and a boolean parameter (true).

Here example

On the Firebase cloud functions i listen to that node, when new like added it count the likes. as you can see "likes:3".

Cloud function code - update the counter

   exports.countlikechange = functions.database.ref('/likes/{postid}/{userUID}').onWrite(event => {
const collectionRef = event.data.ref.parent;    
console.log(collectionRef);

const countRef = collectionRef.child('likes');


// Return the promise from countRef.transaction() so our function 
// waits for this async event to complete before it exits.
return countRef.transaction(current => {
  if (event.data.exists() && !event.data.previous.exists()) {
    return (current || 0) + 1;
  }
  else if (!event.data.exists() && event.data.previous.exists()) {
    return (current || 0) - 1;
  }
}).then(() => {
  console.log('Counter updated.');
   });
 });

That method listens to the "likes" node and when a child added it trigger that method and update the "likes:.." on each videoID.

What im trying to do is first i want to update the counter in other node

On that node i also want to update the counter.

My problem is that i dont know how to get the reference to that node. On the "HipHop" node, videos are saved, each video saved under his ID.

How can i reference from the cloud functions to that node and update the "likes"??

EDIT Also how can i retrive the data from the node that i'm listening.

for example im listening to the "likes" node, i want to retrive the data that just update in that node.

Mixing objects with static and dynamic properties is a bad idea. — Jonas Wilms
Since the key for the video is the same that the key for the likes, just get the key for the video and then use it to get the likes, is other the problem? — cutiko
Have any idea how do i get the key of the video? I mean what should i write in JavaScript to get the key? — E.Bolandian

Diego P Diego P · Accepted Answer · 2018-01-17T14:12:03

You could write something like this:

exports.countlikechange = functions.database.ref('/likes/{postid}/{userUID}').onWrite(event => {
const collectionRef = event.data.ref.parent;
const countRef = collectionRef.child('likes');
  const promises = [];
  if (event.data.exists() && !event.data.previous.exists()) {
    const promisseadd1 = countRef.transaction(current => {
      return (current || 0) + 1;
    });
    const promisseadd2 = admin.database().ref(`/enter/here/new/path/likes`).transaction(current => {
      return (current || 0) + 1;
    });
    return Promise.all([promisseadd1, promisseadd2]);
  } else if (!event.data.exists() && event.data.previous.exists()) {
    const promissesubs1 = countRef.transaction(current => {
      return (current || 0) - 1;
    });
    const promissesubs2 = admin.database().ref(`/enter/here/new/path/likes`).transaction(current => {
      return (current || 0) - 1;
    });
    return Promise.all([promissesubs1, promissesubs2]);
  }
});

Firebase cloud functions - Update nodes

1 Answers