一个一对多的表
class Product < ActiveRecord::Base
has_many :tags
数据表是这样的
class AddProductIdToTag < ActiveRecord::Migration
def change
add_column :tags, :product_id, :string
end
end
视图里面是怎样的
<%= text_field :tags %>
在控制台就是这样的
=>ActiveRecord::Associations::CollectionProxy::ActiveRecord_Associations_CollectionProxy_Tag
在 Rails3 还是好好的。怎么到了 Rails4 就这样了，是我那里配置的不对的吗？
We start by creating a migration:
depot> rails generate migration combine_items_in_cart
This time, Rails can’t infer what we are trying to do, so we can’t rely on the generated change() method. What we need to do instead is to replace this method with separate up() and down() methods.
class CombineItemsInCart < ActiveRecord::Migration
def up
Cart.all.each do |cart|
sums=cart.line_items.group(:product_id).sum(:quantity)
sums.each do |product_id,quantity|
if quantity>1
cart.line_items.where(product_id:product_id).delete_all
item=cart.line_items.build(product_id:product_id)
item.quantity=quantity
item.save!
end
end
end
end
def down
LineItem.where("quantity>1").each do |line_item|
line_item.quantity.times do
LineItem.create cart_id: line_item.cart_id,product_id: line_item.product_id,quantity:1
end
line_item.destroy
end
end
end
新版的 agile web development with rails 4 beta 里面的。
今天遇到类似问题，原来 Associations in Rails 4 return a CollectionProxy instead of an Array 建议读一下 http://olivierlacan.com/posts/associations-in-rails-4/