Allow parameter only if another parameter is present.

[dblock]

For example:

requires :product_id, type: String # a product id
optional :shelf_id, type: String # only if the product is on this shelf
optional :shelf_reachable, type: Boolean # only if the shelf is reachable

You shouldn't be able to specify shelf_reachable unless :shelf_id is present.

[u2]

That's a good idea.I just have this demand.

        params do
          requires :cid, type: Integer
          requires :car_order, type: Hash do
            optional :cars_params, type: Array do
              requires :id, type: Integer
              requires :quantity, type: Integer #
            end
            optional :car_sets_params, type: Array
          end

We want at least one of cars_params and car_sets_params is present.Maybe can write something like
if: Proc.new { }.

[dblock]

@u2 We already have at_least_one_of.

[u2]

Thank you.:smile:

[rnubel]

After thinking about this for a bit, I think it'd be more useful to be able to say "if shelf_id is given, then require shelf_reachable" rather than the inverse. The two are closely related, at any rate, and I could imagine there being use cases for both. So along those lines, I've quickly prototyped a couple possible ways to implement such logic:

Option 1 (DSL style)

https://github.com/rnubel/grape/compare/dependent_parameters_dsl

params do
  optional :shelf_id, type: Integer
  if_given :shelf_id do
    requires :shelf_reachable, type: Boolean
  end
end

Option 2 (Validation style)

https://github.com/rnubel/grape/compare/dependent_parameters_validation

params do
  optional :shelf_id, type: Integer
  optional :shelf_reachable, type: Boolean
  if_given :shelf_id, require: :shelf_reachable
end

What do you think?

[dblock]

I like the first one, but I don't love the name. Maybe just with?

[rnubel]

Hmm... with is a bit vague. I think that's the tricky part here -- we want a term that's clear about what it means, but still concise. What about just given?

params do
  optional :shelf_id, type: Integer
  given :shelf_id do
    requires :shelf_reachable, type: Boolean
  end
end

[dblock]

I like given, go for it!

[dblock]

This was resolved in #1047.