downcase删除duplicates rails保存数据库

Question

我正在尝试做一个简单的小写并删除rails中的重复项。也保存到数据库。

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

还尝试了采摘

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

Answer 1

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