Question

我试图找到一些旧模型，创建一些新模型，如果保存成功则删除旧模型。

这是我的代码（如果不是Rails-y，我道歉）：

# find the old pages that are in my book... if my new pages save, delete these
old_pages = Page.where(:book_id => params['pages']['page0']['book_id'])


error_with_page_save = false

params['pages'].each do |t|
  t.each do |k|
    book_id = k['book_id']
    if k['page_type']
      tt = get_page_type_id(k['page_type'])
      page = Page.new do |t|
        t.book_id = k['book_id']
        t.sample_text = URI.decode(k['sample_text'])
        t.page_position = k['page_position']
        t.page_type_id = tt
        t.regex = URI.decode(k['regex'])
      end
      unless page.save!
        # HAD AN ISSUE SAVING ONE OF THE NEW PAGES
        error_with_page_save = true
      end
    end
  end
end

unless error_with_page_save
  puts "if there were no issues, delete all the old ones"
  old_pages.delete_all
end

问题是，这会删除新的，因为直到删除才会实际调用find方法。

如何让“.where”方法实际执行？

Answer 1

最后致电.all - 这被视为＆＃34; final＆＃34;并将立即执行查询

Answer 2

你可以省去ids。如果数据集很大，这可以消耗更少的资源。

old_page_ids = Page.where(:book_id => params['pages']['page0']['book_id']).pluck(:id)
# ...
Page.where(id: old_page_ids).delete_all

如何立即执行rails db查询？

2 个答案: