Rails Custom foreign_key 给出 NoMethodError

Question

我有以下型号：

用户

class User < ActiveRecord::Base
  ...
  attr_accessible :email

  has_many :ingredients, class_name: "Ingredient", foreign_key: "created_by"
end

成分

class Ingredient < ActiveRecord::Base
 ...
 attr_accessible :created_by
  belongs_to :user
end

我创建了一种成分，并填充了 created_by 字段。如果我这样做：

> u = User.find(1)
> u.ingredients.size
=> 1

所以这种关系是有效的！但如果我这样做：

Ingrendient.last.created_by.email

我收到以下错误：

1.9.3-p362 :012 > Ingredient.last.created_by.email
Ingredient Load (0.3ms)  SELECT "ingredients".* FROM "ingredients" ORDER BY "ingredients"."id" DESC    LIMIT 1
NoMethodError: undefined method `email' for 1:Fixnum
from (irb):12
from /Users/andreucasadella/.rvm/gems/ruby-1.9.3-p362/gems/railties-3.2.11/lib/rails/commands/console.rb:47:in `start'
from /Users/andreucasadella/.rvm/gems/ruby-1.9.3-p362/gems/railties-3.2.11/lib/rails/commands/console.rb:8:in `start'
from /Users/andreucasadella/.rvm/gems/ruby-1.9.3-p362/gems/railties-3.2.11/lib/rails/commands.rb:41:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'

为什么？

Answer 1

应该是：

class Ingredient < ActiveRecord::Base
 # ...
 belongs_to :user, foreign_key: :created_by
end

class User < ActiveRecord::Base

  has_many :ingredients, foreign_key: :created_by
end

另外，从users 表中删除created_by 并添加到ingredients。我假设您想将Ingredient 与User 关联，这是合理的，因此Ingredient 需要created_by 外键。

请注意，我已删除 attr_accessible。对于 Rails 4.0+，使用 strong parameters（除非您使用的是 Rails