Apply filter to ActiveModel Serializer attributes to change the key

Question

I have a serializer for my rest API. Currently, it looks like:

class TestSerializer < ActiveModel::Serializer
    attributes :id, :name, :field_one__c, :field_two__c
end

I'm wondering if there are any ways to filter all the fields to have the __c removed when serializing, if there is a way to apply logic to ALL fields.

The case is I have a lot of fields with __c on the end, and I'd like to remove them all with a minimal amount of code on the serializer level.

Answer 1

Yes you can customize an attribute name in the serializer using the :key option:

attribute :field_one__c, key: :field_one
attribute :field_two__c, key: :field_two

You can also make any attribute conditional using :if or :unless options.

Doc: https://github.com/rails-api/active_model_serializers/blob/v0.10.6/docs/general/serializers.md#attribute

---

Update:

For your special case, you can hack this by defining the attributes class method before the attributes list:

class TestSerializer < ActiveModel::Serializer
  class << self
    def attributes(*attrs)
      attrs.each do |attr|
        options = {}
        options[:key] = attr.to_s[0..-4].to_sym if attr.to_s.end_with?('__c')

        attribute(attr, options)
      end
    end
  end

  attributes :id, :name, :field_one__c, :field_two__c
end

If you have multiple serializer classes with the same requirement of filtering lots of attributes, you can apply the DRY principle in your solution by creating another serializer class which will inherit from ActiveModel::Serializer. Put the above class method definition inside this new serializer and inherit all the serializers from this new one which have list of attributes with __c.

class KeyFilterSerializer < ActiveModel::Serializer
  class << self
    def attributes(*attrs)
      attrs.each do |attr|
        options = {}
        options[:key] = attr.to_s[0..-4].to_sym if attr.to_s.end_with?('__c')

        attribute(attr, options)
      end
    end
  end
end

class TestSerializer < KeyFilterSerializer
  attributes :id, :name, :field_one__c, :field_two__c
end

class AnotherTestSerializer < KeyFilterSerializer
  attributes :id, :name, :field_one__c, :field_two__c
end