Rails HABTMfields_for –检查是否存在同名记录 [英] Rails HABTM fields_for – check if record with same name already exists

问题描述

我在模型片段"和标签"之间存在HABTM关系.当前，当我保存带有一些标签的代码片段时，每个标签都另存为新记录.

I have a HABTM-relation between the models "Snippets" and "Tags". Currently, when i save a snippet with a few tags, every tag is saved as a new record.

现在，我要检查是否已存在具有相同名称的标签，如果是这种情况，我不希望有新记录，只需在snippets_tags中添加一个到现有记录的条目即可.

Now i want to check if a tag with the same name already exists and if that´s the case, i don´t want a new record, only an entry in snippets_tags to the existing record.

我该怎么做?

snippet.rb:

snippet.rb:

class Snippet < ActiveRecord::Base
  accepts_nested_attributes_for :tags, :allow_destroy => true, :reject_if => lambda { |a| a.values.all?(&:blank?) }
  ...
end

_snippet.html.erb:

_snippet.html.erb:

<% f.fields_for :tags do |tag_form| %>
  <span class="fields">
    <%= tag_form.text_field :name, :class => 'tag' %>
    <%= tag_form.hidden_field :_destroy %>
  </span>
<% end %>

推荐答案

好吧，我很不耐烦……过了一会儿，我找到了适合我的解决方案.我不知道这是否是最好的方法，但是我想展示一下.

Ok, i´m impatient… after a while i found a solution that works for me. I don´t know if this is the best way, but i want to show it though.

我必须修改Ryan Bates Railscast的解决方案自动完成协会" ，它处理一个Emirates_to-association以使其与HABTM一起使用.

I had to modify the solution of Ryan Bates Railscast "Auto-Complete Association", which handles a belongs_to-association to get it working with HABTM.

在我的代码段形式中，是一个名为tag_names的新文本字段，该字段需要逗号分隔的标签列表.

In my snippet-form is a new text field named tag_names, which expects a comma-separated list of tags.

像Ryan一样，我使用虚拟属性来获取和设置标签.我认为其余的内容不言而喻，所以这里是代码.

Like Ryan, i use a virtual attribute to get and set the tags. I think the rest is self-explanatory, so here´s the code.

查看"_snippet.html.erb"

View "_snippet.html.erb"

<div class="float tags">
  <%= f.label :tag_names, "Tags" %>
  <%= f.text_field :tag_names %>
</div>

模型"snippet.rb":

Model "snippet.rb":

def tag_names
  # Get all related Tags as comma-separated list
  tag_list = []
  tags.each do |tag|
    tag_list << tag.name
  end
  tag_list.join(', ')
end

def tag_names=(names)
  # Delete tag-relations
  self.tags.delete_all

  # Split comma-separated list
  names = names.split(', ')

  # Run through each tag
  names.each do |name|
    tag = Tag.find_by_name(name)

    if tag
      # If the tag already exists, create only join-model
      self.tags << tag
    else
      # New tag, save it and create join-model
      tag = self.tags.new(:name => name)
      if tag.save
        self.tags << tag
      end
    end
  end
end

这只是基本代码，没有经过很好的测试，还需要改进，但是它似乎可行，我很高兴有一个解决方案！

This is just the basic code, not very well tested and in need of improvement, but it seemingly works and i´m happy to have a solution!

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