Best Practices / Understanding %Scope{}

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1

Thinking out loud so that you can give me feedback if I got this correct.

I can use Scope both to make sure that the calls I’m making are properly scope and I can use it to have a few handy things at hand on each different LiveView.

So, if I take the example from the docs.

defmodule MyApp.Scope do
  defstruct [:current_user, :current_tenant, :locale]

  defimpl Ash.Scope.ToOpts do
    def get_actor(%{current_user: current_user}), do: {:ok, current_user}
    def get_tenant(%{current_tenant: current_tenant}), do: {:ok, current_tenant}
    def get_context(%{locale: locale}), do: {:ok, %{shared: %{locale: locale}}}
    # You typically configure tracers in config files
    # so this will typically return :error
    def get_tracer(_), do: :error

    # This should likely always return :error
    # unless you want a way to bypass authorization configured in your scope
    def get_authorize?(_), do: :error
  end
end

current_user and current_tenant should be the :id , correct? Everything else I want to “carry with me” I should put in the :context.

I’m asking this because I initially started putting together a project and I thought it would be best to put the whole %User{} and the %Tenant{} so that I can access it all easily, but I’m not sure that’s what the rest of the community is doing.

So, if I want to have the tenant_slug with me at all times, I should modify the above example like:


defmodule MyApp.Scope do
  defstruct [:current_user, :current_tenant, :locale, :slug]

  defimpl Ash.Scope.ToOpts do
    def get_actor(%{current_user: current_user}), do: {:ok, current_user}
    def get_tenant(%{current_tenant: current_tenant}), do: {:ok, current_tenant}

    def get_context(%{locale: locale, slug: slug}) do
      {:ok, %{shared: %{locale: locale, slug: slug}}}
    end

    def get_tracer(_), do: :error
    def get_authorize?(_), do: :error
  end
end
2

current_user and current_tenant are the stucts representing the actor and the tenant which should be applied.
for the tenant, you can implement the protocol Ash.ToTenant that would transform the tenant to what is needed (id in case of attribute multitenancy, or schema name in case of schema multintenancy)

defimpl Ash.ToTenant, for: MyApp.Tenant do
  def to_tenant(%{id: id}, _resource), do: id
end
1 Like
3

I think for the tenant_slug you aredoing fine, as with the locale.
What is the use of the slug in your context? I would have taken it in tenant struct (tenant.slug) everywhere I need to use it.
But if you’re using a schema based multitenancy, just implemented the Ash.ToTenant protocol and return the slug in to_tenant/2

4

Thanks! I’m going to give this a try.

I’ll set the scope with the %User{} and %Org{} instead of just the id to reference them. That way I can get rid of the slug – the %Org{} already has the slug inside of it. (I use the slug for navigation /orgs/{slug}/stuff)