ruby-on-rails - 尝试仅使用 delete_if 从 Active Record 集合中删除

Question

我想从 Active Record 集合中删除元素，为此我尝试使用 delete_if。以下是我的收藏:

categories = Category.all
groups = Group.all

  result = []
  groups.each do |g|
    result.push({ :name => g[:name], :amount => g[amount_column], :drilldown => [] })
    categories.where( { :group_id => g.id } ).each do |c, index|
      result.last[:drilldown].push({ :name => c[:name], :amount => c[amount_column], :drilldown => nil })
    end
    # lastly, remove these categories from this collection (not working)
    categories.delete_if {|c| c.group_id == g.id }
    # tried this too - categories.select! { |c| c.group_id != g.id }
  end

  abort(categories.size.inspect)

..我想对每个组的类别做一些事情，然后从数组中删除它们。在循环 block 之后，我想留下不属于某个组的类别——这就是为什么我删除那里每个组的类别。这是首次获取组和类别的数据(抱歉，数量很多，但请注意某些 category.group_id 和 group.id 匹配:

#categories
#<ActiveRecord::Associations::CollectionProxy [#<Category id: 13, name: "Internet", user_id: 1, created_at: "2014-03-09 13:15:19", updated_at: "2014-03-15 05:13:47", amount: #<BigDecimal:7f0c283806e0,'0.0',9(18)>, group_id: nil, amount_in: #<BigDecimal:7f0c28380578,'0.0',9(18)>, amount_out: #<BigDecimal:7f0c283804b0,'0.0',9(18)>>, #<Category id: 15, name: "Electricity", user_id: 1, created_at: "2014-03-09 13:15:39", updated_at: "2014-03-15 05:14:03", amount: #<BigDecimal:7f0c2838f5a0,'0.0',9(18)>, group_id: nil, amount_in: #<BigDecimal:7f0c2838f460,'0.0',9(18)>, amount_out: #<BigDecimal:7f0c2838f2f8,'0.0',9(18)>>, #<Category id: 6, name: "Phone", user_id: 1, created_at: "2014-02-18 10:07:47", updated_at: "2014-03-15 05:16:21", amount: #<BigDecimal:7f0c2838e470,'0.0',9(18)>, group_id: nil, amount_in: #<BigDecimal:7f0c2838e308,'0.0',9(18)>, amount_out: #<BigDecimal:7f0c2838e240,'0.0',9(18)>>, #<Category id: 9, name: "Trains", user_id: 1, created_at: "2014-02-22 03:08:08", updated_at: "2014-03-15 05:16:21", amount: #<BigDecimal:7f0c2838d340,'-0.5E3',9(18)>, group_id: nil, amount_in: #<BigDecimal:7f0c2838d138,'0.0',9(18)>, amount_out: #<BigDecimal:7f0c2838cf08,'-0.5E3',9(18)>>, #<Category id: 5, name: "Resaurants", user_id: 1, created_at: "2014-02-17 12:12:44", updated_at: "2014-03-15 05:16:21", amount: #<BigDecimal:7f0c2839be18,'-0.235E3',9(18)>, group_id: 16, amount_in: #<BigDecimal:7f0c2839bc38,'0.0',9(18)>, amount_out: #<BigDecimal:7f0c2839baa8,'-0.235E3',9(18)>>, #<Category id: 14, name: "Gas", user_id: 1, created_at: "2014-03-09 13:15:27", updated_at: "2014-03-15 05:16:21", amount: #<BigDecimal:7f0c2839a680,'0.0',9(18)>, group_id: 16, amount_in: #<BigDecimal:7f0c2839a3d8,'0.0',9(18)>, amount_out: #<BigDecimal:7f0c2839a1d0,'0.0',9(18)>>, #<Category id: 3, name: "Snowboarding", user_id: 1, created_at: "2014-02-11 09:43:52", updated_at: "2014-03-15 05:16:21", amount: #<BigDecimal:7f0c28398d30,'-0.1111E4',9(18)>, group_id: 16, amount_in: #<BigDecimal:7f0c28398b28,'0.0',9(18)>, amount_out: #<BigDecimal:7f0c28398a38,'-0.1111E4',9(18)>>]>

# groups
#<ActiveRecord::Associations::CollectionProxy [#<Group id: 16, name: "Testing", user_id: 1, amount: #<BigDecimal:31c0ce8,'-0.1346E4',9(18)>, created_at: "2014-03-09 13:48:50", updated_at: "2014-03-15 05:35:57", amount_in: #<BigDecimal:31d3118,'0.0',9(18)>, amount_out: #<BigDecimal:26b9728,'-0.1346E4',9(18)>>, #<Group id: 17, name: "test", user_id: 1, amount: #<BigDecimal:31d2a88,'0.0',9(18)>, created_at: "2014-03-15 05:38:36", updated_at: "2014-03-15 05:39:00", amount_in: #<BigDecimal:31d14f8,'0.0',9(18)>, amount_out: #<BigDecimal:2e4e650,'0.0',9(18)>>]>

.. 但我的 delete_if 什么也不做(无论是否有 delete_if，abort 都显示相同的大小)。请注意有 group.id = 16 和 category.group_id = 16 所以 delete_if 应该删除那些 - 但它没有。我做错了什么吗？

Answer 1

试试这个，我认为它会有所帮助

categories.delete_if {|x| x.group_id==16}