[Dry-Struct] How to create a nested struct in an optional array?

Support
1

I’m trying to create an attrbute that is an optional array with a nested struct.
I’ve tried

attribute :someArray, Types::Array.of(
Dry::Schema.optional do
  attribute :someString, Types::String
attribute :someInteger, Types::Integer
).optional

But that results in an array of empty hashes. What is the correct way to do this?
Thank you for your help!

2

What part of this do you want to be optional? An array type allows itself to be empty unless you constrain it with min_size.

If you want the key itself to be optional, declare it with attribute?

attribute? :someArray, Types::Array.default { [] } do
  attribute :someString, Types::String
  attribute :someInteger, Types::Integer
end
4

I do not want the key to be optional, I want the value of the array to be optional. The value of the array can be nil or it can be an array of structs.

5

Explicitly passing nil is a little trickier, since it doesn’t seem to be compatible with inline nesting. But you can achieve that by decomposing the nested struct.

class Thing < Dry::Struct
  attribute :someString, Types::String
  attribute :someInteger, Types::Integer
end

class Test < Dry::Struct
  attribute :someArray, Types::Array.of(Thing).optional
end

[1] pry(main)> Test.new
Dry::Struct::Error: [Test.new] :someArray is missing in Hash input
[2] pry(main)> Test.new({ someArray: nil })
=> #<Test someArray=nil>
[3] pry(main)> Test.new({ someArray: [] })
=> #<Test someArray=[]>
[4] pry(main)> Test.new({ someArray: [{}] })
Dry::Struct::Error: [Thing.new] :someString is missing in Hash input
[5] pry(main)> Test.new({ someArray: [{ someString: 'foo', someInteger: 123 }] })
=> #<Test someArray=[#<Thing someString="foo" someInteger=123>]>