No struct defined in changeset


I am trying to build a many to many relationship between users and comments using this blog post

I am uisng the second method after the title The right way — Use Ecto powers.

This can be found in the middle of the blog post.

I have the following problem

My code

def changeset(user, attrs) do
    |> cast(attrs, [:username, :email, :password, :role, :confirmed, :attempts, :locked])
    |> validate_required([:username, :email, :password, :role, :confirmed, :attempts, :locked])

  def changeset_update_comments(%User{} = user, comment) do
    |> cast(%{}, @required_fields)
    # associate projects to the user
    |> put_assoc(:comment, comment)

Also getting this error:

** (CompileError) lib/medium_graphql_api/accounts/user.ex:25: User.__struct__/0 is undefined, cannot expand struct User
    lib/medium_graphql_api/accounts/user.ex:25: (module)

What is the correct way to define my user struct?

Why is it undefined?

Why can’t I expand struct User?

The git with the full aplication is available here

Thanks in advance

You can’t reference the current module like that you’ll need to reference User by it’s full namespace or by using __MODULE__.

def changeset_update_comments(%__MODULE__{} = user, comment) do

You could also alias the local module which will allow you to reference as you are now.

  alias __MODULE__

Thanks didn’t know that you can’t do it like this alias MediumGraphqlApi.Blog.Comment

I will try your suggestion and select the solution button of it works is that okay?

1 Like

I wouldn’t match on the struct for changeset functions because sometimes you already have a changeset and you want to cast additional parameters into it. Ecto.Changeset.cast does accept both as first argument.

How would be the best way to do it?

I just do changeset(struct_or_changeset, params) and be fine. Ecto.Changeset.cast will already yell if I try to use the function with non supported input.

1 Like

So in this case I would create a single changset not a pattern match between changesets as i have now?

Something like this?:
Move everything into a single changeset?

def changeset(%User{} = user, comment) do
    |> cast(%{}, [:username, :email, :password, :role, :confirmed, :attempts, :locked])
    |> validate_required([:username, :email, :password, :role, :confirmed, :attempts, :locked])
    |> put_assoc(:comment, comment)

Well it doesn’t yeld any errors, so probably this is what you ,meant by

Thank you everyone for helping me identify the problems and also propose new ways to write the same code better.

So thanks to @sjoconnor and @LostKobrakai