重建一个集市仓库，同时只保留一些分支机构(Recreating a bazaar repository while only retaining a few of the branches)

 从您的日志中，您可以看到您在某些内容上调用方法状态为零。 
 
 7月28日19:14:21域app / web.1：NoMethodError（未定义方法state' for nil:NilClass): Jul 28 19:14:21 domain app/web.1: app/models/user.rb:75:in类似的'7月28日19:14:21域应用程序/ web.1：app / models / user.rb：75：在'类似' 
 
 在您编辑的答案中，您可以看到罪魁祸首。 你在这个else语句中返回nil。 
 
  def location
      if Location.by_zip_code(self.zip_code.to_s).any?
          # you can return all here if you want more than one
          # for testing just returning the first one
          return Location.by_zip_code(self.zip_code.to_s).first
      else
          return nil
      end
  end
 
 但你不要在这里检查nil（c.location.state） 
 
def similar
    arr = User.where(:gender => self.gender).where.not(:id => self.id)
    arr.select{|c| c.location.state == self.location.state }
end
 
 像我下面的东西可能会有所作为 
 
def similar
    arr = User.where(:gender => self.gender).where.not(:id => self.id)
    arr.select{ |c|
        if !c.location.nil? 
            return c.location.state == self.location.state
        else
            return false
        end
    }
end
 
 对于问题的其他部分，您可能会在Location模型中出现错误。 没有看到代码我无法帮助你，但上述内容将帮助您的代码优雅地失败。 

From your logs you can see that you're calling the method state on something thats nil.
 
Jul 28 19:14:21 domain app/web.1: NoMethodError (undefined method state' for nil:NilClass): Jul 28 19:14:21 domain app/web.1: app/models/user.rb:75:inblock in similar' Jul 28 19:14:21 domain app/web.1: app/models/user.rb:75:in `similar' 
 
In your edited answer you can see the culprit. You return nil in this else statement.
 
  def location
      if Location.by_zip_code(self.zip_code.to_s).any?
          # you can return all here if you want more than one
          # for testing just returning the first one
          return Location.by_zip_code(self.zip_code.to_s).first
      else
          return nil
      end
  end
 
But you don't check for nil here (c.location.state)
 
def similar
    arr = User.where(:gender => self.gender).where.not(:id => self.id)
    arr.select{|c| c.location.state == self.location.state }
end
 
Something like what I have below might do the trick
 
def similar
    arr = User.where(:gender => self.gender).where.not(:id => self.id)
    arr.select{ |c|
        if !c.location.nil? 
            return c.location.state == self.location.state
        else
            return false
        end
    }
end
 
For the other part of the problem, you could potentially have errors in your Location model. Without seeing that code I can't help you but the above will help your code to fail gracefully.