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Craft GraphQL APIs in Elixir with Absinthe

Resolver Function

Learn how to create a resolver function and how to return data from mutations.

We'll cover the following...

Building the resolver

Let’s build the resolver function. It will grab the :input argument for us, and then call a general-purpose PlateSlate.Menu.create_item/1 unction that will handle persisting the record:

def create_item(_, %{input: params}, _) do 
  case Menu.create_item(params) do
    {:error, _} ->
      {:error, "Could not create menu item"}
    {:ok, _} = success ->
      success
   end
end

Here’s how we’ve implemented PlateSlate.Menu.create_item/1:

def create_item(attrs \\ %{}) do 
  %Item{}
  |> Item.changeset(attrs)
  |> Repo.insert()
end

The actual persistence of the menu items is straightforward, but requires us to know a little about how Ecto works. The important thing to know here is that an Ecto changeset ...