Dry-struct: "Factory method" / easier type constructor

I’ve been playing around with dry-struct yesterday, and found nothing quite as compact as the following shorthand used with normal Ruby structs:

Person = Struct.new(:age, :name)

Since there are already some capitalized methods that act like “type constructors” in dry-rb, I added a “factory method”, Dry.Struct:

Person = Dry.Struct(name: Types::String, age: Types::Int)
p = Person[name: "Test", age: 42]
#=> #<Person name="Test" age=42>
#=> Person

Like a standard dry-struct this defaults to :permissive, though you can override that easily:

Test = Dry.Struct(:strict, expected: Types::String)
Test[expected: "foo", unexpected: "bar"]
#=> Dry::Struct::Error: [Test.new] unexpected keys [:unexpected] in Hash input

Last but not least there’s the block form, which is nice if you want to be a bit more explicit/have longer attribute definitions with defaults etc. (contrived example):

AllTheThings = Dry.Struct(:strict, name: Types::String) do
  attribute :age, Types::Strict::Int.optional

So before I go ahead and spend time adding YARD docs and adding some tests to open a PR, does anyone else like this form? If you find the class method on the Dry module weird, I also experimented with Dry::Struct.make(...) but preferred the former. I’m open though.


This seems pretty good to me. We might want to get input from @solnic, @flash-gordon, and @backus (if they have any opinions), since they’ve done the most work on dry-struct recently.

Finally got to this :laughing: Was busy removing AR from my project :wink: Anyway, the discussion continues on github

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