ruby-on-rails - 未定义的方法提取数组？

Question

所以我有这个数据结构:

+[#<Folder id: 1, name: "mollitia", parent_id: nil, user_id: 1, created_at: "2014-06-27 16:00:59", updated_at: "2014-06-27 16:00:59">,
+ #<Folder id: 2, name: "porro", parent_id: 1, user_id: 1, created_at: "2014-06-27 16:00:59", updated_at: "2014-06-27 16:00:59">, 
+ #<Folder id: 3, name: "omnis", parent_id: 2, user_id: 1, created_at: "2014-06-27 16:00:59", updated_at: "2014-06-27 16:00:59">]

由 self.ancestors 返回
我可以取它的名字吗？

def pwd
    self.ancestors.pluck(:name)
end

以上结果在

undefined method `pluck' for #<Array:0x007ff4da780290>

更新

结构的真棒打印:

[
    [0] #<Folder:0x007fd2946a5f18> {
                :id => 3,
              :name => "blanditiis",
         :parent_id => 2,
           :user_id => 1,
        :created_at => Fri, 27 Jun 2014 18:04:02 UTC +00:00,
        :updated_at => Fri, 27 Jun 2014 18:04:02 UTC +00:00
    },
    [1] #<Folder:0x007fd2946ad1c8> {
                :id => 2,
              :name => "neque",
         :parent_id => 1,
           :user_id => 1,
        :created_at => Fri, 27 Jun 2014 18:04:02 UTC +00:00,
        :updated_at => Fri, 27 Jun 2014 18:04:02 UTC +00:00
    },
    [2] #<Folder:0x007fd2946b80c8> {
                :id => 1,
              :name => "ut",
         :parent_id => nil,
           :user_id => 1,
        :created_at => Fri, 27 Jun 2014 18:04:02 UTC +00:00,
        :updated_at => Fri, 27 Jun 2014 18:04:02 UTC +00:00
    }
]

Answer 1

pluck与 rails 一起使用以更改针对数据库的关联查询。它将从 SELECT * 改变它至 SELECT [attr]哪里[attr]是 pluck 的论据。因为它是一个数组，所以你不能使用它。你应该改用普通的旧 map从 ruby 。在你的情况下，它看起来像:

def pwd
  self.ancestors.map(&:name)
end