CODEWITHSUNDEEP
javascriptnode.jsfirebasefirebase-realtime-databasegoogle-cloud-functions
E.Bolandian
E.Bolandian

Reputation: 573

Firebase cloud functions - Update nodes

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

enter image description here

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

enter image description here

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.

Upvotes: 2

Views: 1149

Answers (1)

Diego P
Diego P

Reputation: 1758

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]);
  }
});

Upvotes: 2

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