Hello,
I am trying to build a many to many relationship between users and comments using this blog post https://medium.com/coletiv-stories/ecto-elixir-many-to-many-relationships-66403933f8c1.
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
user
|> cast(attrs, [:username, :email, :password, :role, :confirmed, :attempts, :locked])
|> validate_required([:username, :email, :password, :role, :confirmed, :attempts, :locked])
end
def changeset_update_comments(%User{} = user, comment) do
user
|> cast(%{}, @required_fields)
# associate projects to the user
|> put_assoc(:comment, comment)
end
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)
Elixir
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 https://github.com/wolfiton/medium_graphql_api/tree/dao
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__
2 Likes
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
user
|> cast(%{}, [:username, :email, :password, :role, :confirmed, :attempts, :locked])
|> validate_required([:username, :email, :password, :role, :confirmed, :attempts, :locked])
|> put_assoc(:comment, comment)
end
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