ruby-on-rails - 其他模型方法中的 current_model

Question

在 book/show 中，我想在不滥用 View 的情况下查看它在每个现有图书馆中的销量。逻辑能否以某种方式传输到模型中？当前 book/show.haml:

= @book.name    
- @libraries.each do |library|
      = library.sales.where(book_id: @book.id).map(&:quantity).sum

我的想法是在 library.rb 中添加一个方法，例如:

  def current_book_sold_by_library
    @book = Book.find(:id)
    #sales.where(book_id: @book.id).map(&:quantity).sum
    sales.map(&:quantity).sum
  end

但是玩这个并没有帮助。我的设置:

书.rb:

class Book < ActiveRecord::Base
end

图书馆.rb

class Library < ActiveRecord::Base
  has_many :books, through: :sales
end

销售.rb

class Sale < ActiveRecord::Base
  belongs_to :book
  belongs_to :library
end

books_controller.rb

class BooksController < ApplicationController
  def show
    @libraries = Library.all
    @sales = @book.sales
  end
end

Answer 1

你可以添加一个以书作为参数的方法到Library模型:

# view
- @libraries.each do |library|
      = library.book_sold_by_library(@book)

# Library model
def book_sold_by_library(book)
  sales.where(book_id: book.id).map(&:quantity).sum
end