在 ruby​​ on rails 中显示存储在我的发票表中的联系人 ID 列中的联系人姓名

Question

我显然是使用 Ruby on Rails 4 开发的新手。我有一个 Company 模型、一个 Contact 模型和一个 Invoice 模型。联系人嵌套在公司中，发票嵌套在公司中。我的 Invoice 表有一个 contact_id 列，该列基于从 @company.contacts 填充的下拉菜单存储在我的 invoice 表中。我不想显示@invoice.contact_id（即10），而是从联系人表中显示contact_id 10 的名字。 我很确定我需要在发票控制器中定义@contacts，但似乎无法找到正确的语法来表示获取contact_id 的名称，其中contact.id = @invoice.contact_id。

Routes.rb：

resources :companies do
  resources :contacts 
  resources :invoices 
end

Company.rb：

class Company < ActiveRecord::Base
  has_many :invoices
  has_many :contacts
end

Contact.rb：

class Contact < ActiveRecord::Base
  belongs_to :company
end

Invoice.rb：

class Invoice < ActiveRecord::Base 
  belongs_to :company 
  has_many :contacts, through: :company 
end

Schema.rb

create_table "companies", force: true do |t|
t.string   "name"
t.string   "street"
t.string   "city"
t.string   "province"
t.string   "postal_code"
t.string   "tel"
t.datetime "created_at"
t.datetime "updated_at"
end
create_table "contacts", force: true do |t|
t.integer  "company_id"
t.string   "first_name"
t.string   "last_name"
t.string   "title"
t.string   "tel"
t.string   "email"
t.datetime "created_at"
t.datetime "updated_at"
end

add_index "contacts", ["company_id"], name: "index_contacts_on_company_id", using: :btree

create_table "invoices", force: true do |t|
t.integer  "company_id"
t.integer  "contact_id"
t.integer  "item_id"
t.decimal  "total",      precision: 7, scale: 2
t.datetime "created_at"
t.datetime "updated_at"
end
  add_index "invoices", ["company_id"], name: "index_invoices_on_company_id", using: :btree
add_index "invoices", ["contact_id"], name: "index_invoices_on_contact_id", using: :btre
add_index "invoices", ["item_id"], name: "index_invoices_on_item_id", using: :btree

Answer 1

使用 Rails 很容易实现：

# controller
def index
  @invoices = Invoice.all.includes(:contacts) # .inclutes(:contacts) is Eager Loading (n+1 Queries)
end

# view
@invoices.each do |invoice|
  invoice.contacts.each do |contact|
    contact.name
  end
end