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返回我能说出它的名字吗？

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

以上结果

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

更新

令人敬畏的结构打印：

[
    [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一起用于更改与数据库的关联查询。它会将其从SELECT *更改为SELECT [attr]，其中[attr]是要采摘的参数。因为它是一个数组，所以你不能使用它。您应该使用ruby中的常规旧map。在您的情况下，它看起来像：

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

Answer 2

pluck已添加到Rails 5的Enumerable中，因此确实过时了https://github.com/rails/rails/issues/20339

但是，我认为最好的做法是将返回的Array更改为ActiveRecord关系

数组的未定义方法？

2 个答案: