Adding new function to model module: Undefined function: Expected MyModule to define such a function or for it to be imported, but none are available

chrisdel101

I’ve use the generators to create a project. Inside the project schema when I add a new function to the others that exist I get an error.

In registration_changeset I call validate_email (given by the generartor) and confirm_emails_match written by me. Only confirm_emails_match gives an error. Why? It’s clearly right there.

note: def of defp has no effect. Nor does moving it up in the file.

Error:
lib/myModule/administration/admin.ex:56: undefined function confirm_emails_match/2 (expected MyModule.Administration.Admin to define such a function or for it to be imported, but none are available)

def registration_changeset(admin, attrs, opts \\ []) do
    admin
    |> cast(attrs, [:email])
    |> validate_email()
    |> confirm_emails_match(attrs)
  end

defp validate_email(changeset) do
    changeset
    |> validate_required([:email])
    |> validate_format(:email, ~r/^[^\s]+@[^\s]+$/, message: "must have the @ sign and no spaces")
    |> validate_length(:email, max: 160)
    |> unsafe_validate_unique(:email, TurnStile.Repo)
    |> unique_constraint(:email)
  end

def confirm_emails_match(_attrs) do
    IO.puts("TEST")
    # if attrs.email1 !== email2 do
    #   "todo"
    # end
  end

4 comments

/phoenix #function #basics

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2023-03-03 17:06:27 UTC

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chrisdel101

I noticed that validate_email takes changeset as a param, and yet this is never passed in. I guess this must be some auto-pass-in feature?

I tried the same thing with confirm_emails_match, and it now compiles, but MANY new warnings have cropped up caused by this. Baby steps.

defp confirm_emails_match(changeset, _attrs) do
    changeset
    IO.puts("TEST")
    # if attrs.email1 !== email2 do
    #   "todo"
    # end
  end

EDIT: I also see there is a validation_cofirmation which does this same thing. Still don’t understand why where the undefined error was coming from though.

Additional Info: I have another question similar to this. This was caused by passing in the incorrect params while inside of the pipes. I guess that’s similar to what is happening here?

Post #1

al2o3cr

The |> (read as “pipe”) operator can be confusing at first: it passes the left-hand side as the first argument to the right-hand side. The docs go into a lot of detail, but the TL;DR is that this code:

    admin
    |> cast(attrs, [:email])
    |> validate_email()
    |> confirm_emails_match(attrs)

means the same thing as:

  temp1 = cast(admin, attrs, [:email])

  temp2 = validate_email(temp1)

  confirm_emails_match(temp2, attrs)

That’s why the compiler is looking for a confirm_emails_match head that takes two arguments.

Post #2

BradS2S

When i run across these errors, one thing I check is the arity. You’ve written a function with an arity of 1 but you’re using a function with an arity of two so even though it has the same name they are treated as different functions which is why it says it can’t find it even though you have one with that name in the module.

Post #3

chrisdel101

Thanks for links to that docs. I’ve looked it up so many time [here](https://elixir-lang.org/getting-started/enumerables-and-streams.html#the-pipe-operator) which never really gave me enough to know what was happening.

Using the pipe, I’m still not sure what the first param on the right side is most of the time. Looks like it’s usually empty? Lots of trial and error.