我正在使用Rails 3.2.0.
我有一个简单的模型,如下所示
class Favorite < ActiveRecord::Base
validates :lst,:presence => true
validates :uuid,:presence => true,:uniqueness => {:scope => :lst}
end
如果我试试这个
f = Favorite.new f.valid?
我收到以下错误消息：
NoMethodError: undefined method `zero?' for nil:NilClass
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.2.0/lib/active_record/associations/alias_tracker.rb:28:in `aliased_name_for'
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.2.0/lib/active_record/associations/join_dependency.rb:17:in `initialize'
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.2.0/lib/active_record/relation/finder_methods.rb:219:in `new'
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.2.0/lib/active_record/relation/finder_methods.rb:219:in `construct_join_dependency_for_association_find'
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.2.0/lib/active_record/relation/finder_methods.rb:192:in `exists?'
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activerecord-3.2.0/lib/active_record/validations/uniqueness.rb:32:in `validate_each'
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activemodel-3.2.0/lib/active_model/validator.rb:153:in `block in validate'
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activemodel-3.2.0/lib/active_model/validator.rb:150:in `each'
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activemodel-3.2.0/lib/active_model/validator.rb:150:in `validate'
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.2.0/lib/active_support/callbacks.rb:310:in `_callback_before_15'
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.2.0/lib/active_support/callbacks.rb:429:in `_run__1275595979440079611__validate__42615372200132002__callbacks'
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.2.0/lib/active_support/callbacks.rb:405:in `__run_callback'
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.2.0/lib/active_support/callbacks.rb:385:in `_run_validate_callbacks'
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activesupport-3.2.0/lib/active_support/callbacks.rb:81:in `run_callbacks'
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activemodel-3.2.0/lib/active_model/validations.rb:212:in `run_validations!'
from /Users/ragrawal/.rvm/gems/ruby-1.9.2-p290/gems/activemodel-3.2.0/lib/active_model/validations/callbacks.rb:53:in `block in run_validations!'
....
....
解决方法
ActiveRecord AREL表别名正在破坏
该错误可能是由于ActiveRecord AREL失去了如何对空数组求和的记录.
count.sum
如果count是一个空数组,那么该行的计算结果如下：
[].sum
在Ruby中失败：
$irb > [].sum NoMethodError: undefined method `sum' for []:Array
Rails ActiveSupport Enumerable#sum
在Rails中成功,因为ActiveSupport正在创建Enumerable#sum
$irb > require 'active_support/core_ext/enumerable' > [].sum => 0
您的问题可能是您的应用程序的某些不相关区域也在创建Enumerable#sum或Array#sum.不相关的代码覆盖了Rails方法.
可能发生在您的代码或不相关的gem中. Rails gem早期加载,通常首先在你的Gemfile中加载,任何后来的gem都会干扰Rails.
怎么解决？
你有没有写过一个名为sum的方法,可能在一个名为Enumerable或Array的模块中？如果是这样,那是一个很好的起点.您可以重命名您的方法,或者您可以尝试使用以下代码替换#sum代码来更改您的方法以匹配Rails方法：
module Enumerable
def sum(identity = 0,&block)
if block_given?
map(&block).sum(identity)
else
inject(:+) || identity
end
end
end
如果你还没有在你的代码中编写一个名为sum的方法,那么冲突就可能出现在你正在使用的gem中.尝试评论您正在使用的宝石,然后重新加载您的应用.
$cd /usr/lib/ruby/gems $find | xargs grep "def sum\b"
你在使用名为sixarm的任何宝石吗？如果是这样,请与我联系,我会为您解决.这些是由我来完成的,其中一些确实定义了#sum用于统计工具和实用程序.
希望这可以帮助.如果能解决你的问题,你能在这里发帖吗？