cclark
How to use Enum and Custom Scalars together in Absinthe?
I’m new to Elixir, Phoenix and Absinthe but trying to write an API onto an existing dataset. The dataset includes information about trails and they have a status attribute with values of 1, 2, 3 or 4. In the domain these map to Green (1), Yellow(2), Amber(3) and Red(4) so I’d like to use the actual enum values as it would be much more expressive.
For the GraphQL API onto this it would be much nicer if I could write a query like:
query {
trails(havingStatus: RED) {
id
name
status
}
}
In my schema I’ve defined an enum as
@desc "Current status of the trail"
enum :trail_status do
value :green, as: 1, description: "Green: Clear"
value :yellow, as: 2, description: "Yellow: Minor Issue"
value :amber, as: 3, description: "Amber: Significant Issue"
value :red, as: 4, description: "Red: Major Issue"
end
This allows me to query and enforce that the user chooses valid values for havingStatus. However, in my results I see the raw value of
{
"status": 4,
"name": "Lost Loop",
"id": "16601"
}
where I’d really like to have the 3 be returned as RED.
First does this make sense to do? If the client already knows about GREEN, YELLOW, AMBER and RED when making the query then it seems like a failure to make the client know how to receive 1-4 and map it to those values.
It seems like a custom scalar might be one way to get at this. All of the examples I can find are for dates and make sense. But when I have a very specific enumeration of four values I wonder if that is overkill and it seems like I’d lose the nice ability to introspect and see the only valid values. So I think I want a combination of an enum and a custom scalar type?
Any thoughts or pointers to Absinthe/GraphQL articles on the subject would be greatly appreciated.
Most Liked
kokolegorille
Hello, welcome to the forum.
I use simple atoms, without as when I don’t need to use db, like so
enum :sort_order do
value :asc
value :asc_nulls_last
value :asc_nulls_first
value :desc
value :desc_nulls_last
value :desc_nulls_first
end
But if You want to persists Int in the DB and keep nice looking status, I would use a scalar. Nothing really complicate, You just need a parse and a serialize functions.
I use this for json.
scalar :json do
parse fn input ->
case Jason.decode(input.value) do
{:ok, result} -> result
_ -> :error
end
end
serialize &Jason.encode!/1
end
And with your Enum requirement, it would be simple to write those 2 functions. For example…
scalar :status do
parse fn 1 -> :green; 2 -> :yellow; 3 -> :amber; 4 -> :red; _ -> :error end
serialize fn :green -> 1; :yellow -> 2; :amber -> 3; :red -> 4; _ -> :error end
end
StefanL
You might want to have a look at EctoEnum, it will probably provide the casting from/to integers in ecto that you are searching for.
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