ActiveRecord的聲譽系統不工作

Question

我做了一個小項目引用Quick Start，但是當我訪問的評價值出現了錯誤

answer.reputation_for :avg_rating

NoMethodError: undefined method `to_sym' for nil:NilClass 
from /Users/Juo/.rvm/gems/ruby-2.0.0-p195/bundler/gems/activerecord-reputation-system-01197ad78cac/lib/reputation_system/models/reputation.rb:189:in `get_target_type_for_sti' 
from /Users/Juo/.rvm/gems/ruby-2.0.0-p195/bundler/gems/activerecord-reputation-system-01197ad78cac/lib/reputation_system/models/reputation.rb:198:in `set_target_type_for_sti' 
from /Users/Juo/.rvm/gems/ruby-2.0.0-p195/gems/activesupport-4.0.0/lib/active_support/callbacks.rb:377:in `_run__3152603553061474011__validation__callbacks'` 

有人幫幫我嗎？

假設我們想跟蹤Q &中的用戶業力用戶業力是提問技能和應答技能總和的網站。提問技巧是用戶問題的投票總數，而回答技巧是用戶答案的​​平均評分的總和。這可以被定義如下：

class User < ActiveRecord::Base 
    has_many :answers 
    has_many :questions 

    has_reputation :karma, 
     :source => [ 
      { :reputation => :questioning_skill, :weight => 0.8 }, 
      { :reputation => :answering_skill }] 

    has_reputation :questioning_skill, 
     :source => { :reputation => :votes, :of => :questions } 

    has_reputation :answering_skill, 
     :source => { :reputation => :avg_rating, :of => :answers } 
end 

class Answer < ActiveRecord::Base 
    belongs_to :user, :as => :author 

    has_reputation :avg_rating, 
     :source => :user, 
     :aggregated_by => :average, 
     :source_of => [{ :reputation => :answering_skill, :of => :author }] 
end 


class Question < ActiveRecord::Base 
    belongs_to :user 

    has_reputation :votes, 
     :source => :user 
end 

Answer 1

嘗試刪除：爲=>：筆者從回答模型，並設置：用戶在has_reputation的初始化：AVG_RATING =>的。