How to implement the Like button with Fire Store?

Question

I want to implement the Like button and Dislike button using Firestore. I've already implemented login, and I think I'll have to create a user ID Set of people who pressed the like button or dislike and mark the number of likes or dislikes as the number of Set's elements, but I don't know how to use Set in the Fire Store.

Answer 1

Sounds like this is an array within the "post" document. You can update an array like this:

https://cloud.google.com/firestore/docs/manage-data/add-data#update_elements_in_an_array

There's no way to query only the count of items in an array. Your options are:

• get the whole likes array and count them (lot of data transfer, don't suggest)

• keep an extra likes counter field and update it each time someone likes. This is what I would do, maybe use an onUpdate function trigger: https://firebase.google.com/docs/firestore/extend-with-functions