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，我对此表示歉意）：
# 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，这将删除新的，因为直到删除才实际调用find方法。
我如何获得真正执行的“ .where”方法？
您可以保存ID。如果数据集很大，这样做的好处是消耗更少的资源。
old_page_ids = Page.where(:book_id => params['pages']['page0']['book_id']).pluck(:id)
# ...
Page.where(id: old_page_ids).delete_all
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我来说两句