Is there a proper way to use dry-transformer with dry-struct?

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1

I’m trying to use dry-transformer with dry-struct to take a JSON api response and transform it into a struct. Is there any “official” way to do this? The best way I could figure out was to override the self.new method which I don’t love doing:

class MyStruct < Dry::Struct
  class Transformer < Dry::Transformer::Pipe
    import Dry::Transformer::HashTransformations

    define! do
      # ...
    end
  end

  def self.new(attributes)
    data = Transformer.new.call(attributes)
    super(data)
  end
end
2

You could write an instance method to do this but building structs is so common I like to have a helper for this.

module MyTransformations
  extend Dry::Transformer::Registry
  def self.struct(attributes, klass) = klass.new(**attributes)
end

class Transformer < Dry::Transformer::Pipe
  import MyTransformations

  define! do
    struct MyStruct
  end
end

Transformer.new(attributes)

The alternate way to do a one-off would be

class Transformer < Dry::Transformer::Pipe
  define! do
    build_struct
  end

  def build_struct(attributes)
    MyStruct.new(**attributes)
  end
end
1 Like
3

Interesting! So instead of having the Struct do the transformation, have the Transformer return a struct. I’ll try that out, thank you!