How to set up a friend system

Hello there, I have a simple live application with auth system, created with phx.gen.auth
And I want to create a friend system.
I have a users (username, email, password and other fields) and friends (has only username field) schemas, which have M:M relation.
In the template I can add friends to the current user, but I want to send a notification to the other user (friend request) and get a confirmation from them, only then they become a friend. I’m not quite sure how this can be implemented. I would be happy to get your advice, thanks in advance

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Hey there,

This is an interesting (and probably fairly common) problem! I’m definitely no expert at crafting database schemas, but I would take one of two approaches to this problem.

First, I would consider having two tables. One for requests that has a schema of (requesting user id, target user id, date time). Then, if a user rejects the friend request it can just delete the specific row. If they accept, the row can basically transfer into your friends table with a schema of (friend 1 id, friend 2 id, date time). Obviously these need the right foreign keys, and associations with them.

The second option I would suggest is to have just one table. Have a query like (friend 1 id, friend 2 id, requested at date time, accepted at date time). Then, when you are displaying lists of friends you will have to filter where accepted at is not null. This way you can also detect and prevent spamming if that is a feature you want, since the friend request isn’t deleted.

I’d definitely be interested to hear what others have to say on the topic - again, take these suggestions with a grain of salt! They might get the job done, but maybe not be very database optimized haha

Hope this helps!


You can check out the ecto guide on self referencing many to many relationships if you’d like.

That came from my experience building Metamorphic and is the foundation for how I model the “friend” system on Metamorphic.

This system design enables all sorts of things that I do in Metamorphic; from asymmetric encryption to one-way agnostic relationship requests for privacy, safety, and kindness. :blush:

Hope it helps you or gives you other ideas. :heart:


2 posts were split to a new topic: Need help with self-referential relationships