grape - Call a method from a model on a controller api - Ruby

Question

Working on grape api, with Ruby, I have a Model to define the price of a book that I would like to apply to my api in my controller side, the price is calculated according to several variables like author, ect..

Here is my model in app > model > author:

 def euro_amount
    book.assign_attributes(price: euro_amount)
 end

On the api side, I would like to call this method euro_amount to attribute the price of my book, The price is set as an except attribute because it should be calculate and the user can't set it, Do you know how can I call this method from my api side ?

Answer 1

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