Looking for advice on how to insert entity that reference other entity with Ecto ? This may help you.
A very consice description of how to insert an new entity with reference to an already inserted entity.
When I was trying to do this with ecto, I did’t find reference on this. I’ve found solution to much more advanced questions, but simple one also need guidance for beginners.
So here is my problem.
I have an entity User, I’ve created it with phoenix tool chain, like this:
$ mix
mix phoenix.gen.model User users email:string password:string
Quite easy, I’ve made a couple of changes to this model as described (here)[http://meatherly.github.io/2015/05/11/phoenixauthentication/], in order to add an encrypted password.
Then I’ve added another entity Couple. The couple is an entity that group two user together, like a couple.
mix phoenix.gen.model Couple couples partner_1:references:users partner_2:references:users
Here is how you could create the couple in db from your app
def couple(conn, %{:other_user_id => other_user_id ) do
current_user_id = get_session(conn, :current_user)
changeset = %Couple{}
|> Couple.changeset(%{})
|> Changeset.put_change(:partner1_id, current_user_id)
|> Changeset.put_change(:partner2_id, other_user_id)
#Then do stuff like
changeset.valid?
#or
Repo.insert changeset
end
At first this seams strange, when you never worked with Ecto. Once you’ve got the idea, you’ll understand that hibernate session is really a terrible idea.
In Ecto you create a changeset for an entity. You will accumulate manipulation on your changeset, like with your git/mercurial. Once your happy with the changeset you’ll insert it into the db, like a commit.
I didn’t explain why nor how to validate and insert. For thoses information the official Ecto documentation is well done.
I hope this very tiny guide will help some of use to progress a little bit further will Elixir and Phoenix.