downcase删除重复的轨道保存数据库(downcase remove duplicates rails save database)

downcase删除重复的轨道保存数据库(downcase remove duplicates rails save database)

我试图做一个简单的downcase并删除rails中的重复项。 还保存到数据库。

Tag.all.each do |tag| tag_name = tag.name.downcase! tag_name.uniq! tag.save! end

错误

NoMethodError: undefined method `uniq!' for nil:NilClass

也试着采摘

tag_name = Tag.pluck(:name) tag_name.each do |tag| name = tag.downcase! name.uniq! end

错误

NoMethodError: undefined method `uniq!' for nil:NilClass

I'm trying to do a simple downcase and remove duplicates in rails. Also save to the database.

Tag.all.each do |tag| tag_name = tag.name.downcase! tag_name.uniq! tag.save! end

Error

NoMethodError: undefined method `uniq!' for nil:NilClass

Also tried with pluck

tag_name = Tag.pluck(:name) tag_name.each do |tag| name = tag.downcase! name.uniq! end

Error

NoMethodError: undefined method `uniq!' for nil:NilClass

最满意答案

使用group_by查找过滤器查询。

found_tags = Tag.all.group_by { |tag| tag.name.downcase } found_tags.each do |key, val| if found_tags[key].count > 1 tag_to_keep = val.shift val.each do |t| t.taggings.update_all(tag_id: tag_to_keep.id) t.destroy! end tag_to_keep.update(name: tag_to_keep.name.downcase) end end

Used group_by to find filter query.

found_tags = Tag.all.group_by { |tag| tag.name.downcase } found_tags.each do |key, val| if found_tags[key].count > 1 tag_to_keep = val.shift val.each do |t| t.taggings.update_all(tag_id: tag_to_keep.id) t.destroy! end tag_to_keep.update(name: tag_to_keep.name.downcase) end end