Possible error in Changeset Docs

Questions / Help
1

Hi All.

I’ve recently needed to use Ecto.Changeset.validate_change and I “think” I may have found a problem in the documentation. The docs state that you should return a list of errors and shows an example [title: “cannot be foo”] but I believe this should be [{title: “cannot be foo”}].

I’ve no experience in raising issues and just wanted to check with you good people that simply raising something on the appropriate Github page is the thing to do.

cheers

Dave

2

What makes you think so?

The example you copied from the docs looks like idiomatic elixir code while yours is a list with a one-tuple containing another keyword list.

Also as far as I remember, the copied example matches the format of errors in the changeset as far as I remember.

3

Hi @NobbZ - when I tried the example I received an error

##### FunctionClauseError <small>at POST</small> <small>/cost_centres</small>

# no function clause matching in anonymous fn/1 in Ecto.Changeset.validate_change/3

My code:

  def validate_uppercase(changeset, field) do
    IO.puts "about to validate uppercase"
    validate_change changeset, field, fn field, value ->
        if (String.upcase(value) != value) do
            [field, "value must be uppercase"]
        else
            []
        end
    end 
end

If I change the return error to

[{field, "value must be uppercase"}]

then all is good.

cheers

Dave

4

[foo: "bar"] is syntactical sugar for [{:foo, "bar}].

And since you can not use that syntactical sugar when the key is a variable, you have to write out the tuple on your own as [{key, message}].

Still the documentation is correct.

iex(1)> key = :foo
:foo
iex(2)> [{key, "value"}]
[foo: "value"]
3 Likes
5

Ah that makes perfect sense. I knew it was a good idea to check here first.

Many thanks for your help @NobbZ.

cheers

Dave

1 Like