Athunnea
How do you provide custom error message for Ecto's cast errors?
If you provide a string to an :integer field you get
errors: [count: {"is invalid", [type: :integer, validation: :cast]}]
in a changeset, which is not helpful for a user. Unfortunately Ecto.Schema.field/3 doesn’t accept custom error messages (as of v3.9 at least).
I want to return something like “should be a number” to a user instead of “is invalid”.
One solution could be a create a custom integer type, which can return a custom error message. Another way could be processing this in web layer in some kind of humanize_error function, replacing default “is invalid” with “should be a number”.
For now I’ve settled with custom ecto types, but as their number started to grow, I want to re-evaluate my approach. So I wonder how do others solve similar issues? I would appreciate your thoughts.
PS. What I like about custom types, is that I can also use them to clean up values before casting them. I can trim strings, remove double spaces, drop “.0” and “,0” from integers.
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D4no0
Have you tried using gettext for this? You should have some examples in a generated phoenix project.
LostKobrakai
The metadata in the error would allow you to do the transformation you mention to the error in Ecto.Changeset.traverse_errors (which is likely already called somewhere in your codebase). You can ignore the existing error string and match on metadata[:validation] + metadata[:type].
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endymion
I made a post discussing how we solved this issue.
It boils down to creating a function
@doc """
Overwrites the error message for `Ecto.Changeset.cast/4` from `"is invalid"` to the
custom supplied error message.
"""
def custom_cast_error_message(changeset, field, message) do
errors = Enum.map(changeset.errors, fn {error_field, {_msg, opts}} = error ->
if field == error_field && opts[:validation] == :cast do
{field, {message, opts}}
else
error
end
end)
%{changeset | errors: errors}
end
and calling it like
message = "This is our custom error message for cast/4"
Ecto.Changeset.cast(answer, params, [:value])
|> Aw.Changeset.custom_cast_error_message(:value, message)
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