Rails “undefined method for ActiveRecord_Associations_CollectionProxy”

Question

I have this models:

class Student < ActiveRecord::Base

    has_many :tickets
    has_many :movies, through: :tickets

end


class Movie < ActiveRecord         


        

Answer 1

As described by Nermin you're trying to request a collection of children, from a collection of children.

You could use collect to gather the students from the companies along the lines of:

@movie.cinema.companies.collect(&:students).flatten.uniq

But I think you would do better to add a scope to your Student model along the lines of:

scope :for_companies, ->(_companies) {joins(:companies).where(company: _companies)}

Called with Student.for_companies(@movie.cinema.companies)

Disclaimer: untested, but should be a starting point!

Answer 2

@students = @movie.cinema.companies.students.all to explain why this throws error

@movie.cinema will give you cinema of the movie

@movie.cinema.companies will give you a list of companies for that cinema as an ActiveRecord_Association_CollectionProxy

Then when you call students on the CollectionProxy of companies via @movie.cinema.companies.students it throws an error because CollectionProxy has no such method.

@students = @movie.cinema.companies.find(6).students.all will work because you get a list of companies, then from that list you find a single company with id 6 and list all students for that single company.