Answer by NobodysNightmare for How to dynamically add properties to a ROAR representer?

I ended up dynamically creating classes from my basic representer:

class TicketRepresenter  property :subject  property :description  def self.create(ticket, context = {})    klass = Class.new(TicketRepresenter) # create a subclass of my representer    ticket.custom_attributes.each do |attribute|      # for each custom attribute in the actual instance insert a property into the created class      property "customField#{attribute.id}".to_sym               getter: -> (*) { attribute.value }    end    # return an instance of the class created above    klass.new(ticket, context)  endend

Basically that means the actual representer class used to create the JSON is a different one for each Ticket.

If you wanted to read a Ticket back from JSON, it is neccessary to correctly initialize the representer so that the created representer class knows about your custom fields and also define setters.

You will now need to conventionally call the new create method instead of new.If you need your representer to be created by ROAR (e.g. for a collection), you can use the Polymorphic Object Creation mechanism of ROAR.

Note: The code above does not exactly fit the example of custom attributes posted in my question, but you should get the idea (in the example an attribute did not have members like id and value, but was list consisting of key and value).