在哪裏放置has_many關係的方法？

Question

class Project 
    has_many :pages 
end 

class Page 
    belongs_to :project 
end 


@project = Project.first 
@project.pages.list_out 

我應該在哪裏爲頁面提供一個list_out方法？

Answer 1

class Project 
    has_many :pages 

    scope :list_out, joins(:pages).where('pages.project_id = ?', self.id) 
end 

class Page 
    belongs_to :project 
end 

@project = Project.first 
@project.list_out 

Answer 2

class Project 
    has_many :pages 

    def list_out 
    pages.map(&:id) 
    end 
end 

class Page 
    belongs_to :project 
end 

@project = Project.first 
@project.list_out