accepted_nested_attributes_for undefined方法錯誤

Question

我正在嘗試使用accepts_nested_attributes來創建一個複雜的表單。基於該Nested Attributes文檔，examples，等等，我已經建立了模型，像這樣：

用戶模式：

require 'digest' 
class User < ActiveRecord::Base 
    attr_accessor :password 
    attr_accessible :first_name, :last_name, :email, :password, 
        :password_confirmation, :ducks_attributes 

    has_many :ducks, :class_name => 'Duck' 
    accepts_nested_attributes_for :ducks 
    . 
    . 
    . 
end 

鴨型號：

class Duck < ActiveRecord::Base 
    belongs_to :user 
    accepts_nested_attributes_for :user 
end 

但是，當我嘗試訪問控制檯中的嵌套屬性，我得到

ruby-1.9.2-p290 :003 > User.first.ducks_attributes 
NoMethodError: undefined method `ducks_attributes' for #<User:0x007ffc63e996e0> 
    from ~/.rvm/gems/ruby-1.9.2-p290@rails3tutorial/gems/activemodel-3.0.9/lib/active_model/attribute_methods.rb:392:in `method_missing' 
    from ~/.rvm/gems/ruby-1.9.2-p290@rails3tutorial/gems/activerecord-3.0.9/lib/active_record/attribute_methods.rb:46:in `method_missing' 
    from (irb):3 
    from ~/.rvm/gems/ruby-1.9.2-p290@rails3tutorial/gems/railties-3.0.9/lib/rails/commands/console.rb:44:in `start' 
    from ~/.rvm/gems/ruby-1.9.2-p290@rails3tutorial/gems/railties-3.0.9/lib/rails/commands/console.rb:8:in `start' 
    from ~/.rvm/gems/ruby-1.9.2-p290@rails3tutorial/gems/railties-3.0.9/lib/rails/commands.rb:23:in `<top (required)>' 
    from script/rails:6:in `require' 
    from script/rails:6:in `<main>' 

什麼我做錯了嗎？提前謝謝了。

Answer 1

僅定義了屬性書寫器。

class User < ActiveRecord::Base 
    has_many :ducks 
    accepts_nested_attributes_for :ducks 
end 

class Duck < ActiveRecord::Base 
    belongs_to :user 
end 

# This works: 
User.first.ducks_attributes = [ { :name => "Donald" } ] 

# This is more common (attributes posted from a form): 
User.create :ducks_attributes => [ { :name => "Donald" }, { :name => "Dewey" } ]