ruby-on-rails - 无法获取对象属性

Question

模型:

class Car < ActiveRecord::Base
  ...
  belongs_to :manufacturer
  ...
end


class Manufacturer < ActiveRecord::Base
  ...
  has_many :cars
  ...
end

汽车 Controller :

  def index
     @title = "All cars"
     @cars = Car.paginate(:page => params[:page], :per_page => 20)
  end

查看:

<%= car.manufacturer.name %>

显示:nil:NilClass 的未定义方法“名称”

好的。查看:

<%= car.manufacturer[name] %>

显示:#<#:0x460c488> 的未定义局部变量或方法“名称”

但是!查看:

<%= car.manufacturer.to_yaml %>

显示:

--- !ruby/object:Manufacturer
attributes:
  id: 1
  name: Acura
  created_at: 2011-11-30 09:59:19.750976000 Z
  updated_at: 2011-12-06 10:38:46.569531000 Z

那么我如何读取 Car.manufacturer 的名称？

Answer 1

<%= car.manufacturer.name if car.manufacturer %>由于某些结果不会设置属性，这可确保您仅在设置属性时才调用属性 getter 方法。