Rails为具有多对多关系的模型创建表单 [英] Rails create form for model with many to many relation

问题描述

我有两个具有has_and_belongs_to_many关系的模型，Recipe和Tag.对于这种关系，我有一个简单的联接表RecipesTags.

I have two models, Recipe and Tag, with a has_and_belongs_to_many relation. For this relation I have a simple join table, RecipesTags.

食谱:

has_and_belongs_to_many :tags

标签:

has_and_belongs_to_many :recipes

现在，在创建新食谱时，用户可以以复选框的形式填写食谱所属的类别，例如肉"，鱼"等.这些类别实际上只是数据库中的标记.

Now upon creating a new recipe, the user gets to fill in which category the recipe belongs to in forms of checkboxes, like "Meat", "Fish", and so on. These categories are in fact just tags in the database.

问题:食谱没有保存任何标签.

配方new和create控制器方法:

    def new
    @recipe = Recipe.new
    @ingredients = Ingredient.all
    @tags = Tag.all

    respond_to do |format|
      format.html # new.html.erb
      format.json { render json: @recipe }
    end
  end



  # POST /recipes
  # POST /recipes.json
  def create
    @recipe = Recipe.new(params[:recipe])
    if (params[:tags])
      @recipe.tags << params[:tags]
    end

    respond_to do |format|
      if @recipe.save
        format.html { redirect_to @recipe, notice: 'Recipe was successfully created.' }
        format.json { render json: @recipe, status: :created, location: @recipe }
      else
        format.html { render action: "new" }
        format.json { render json: @recipe.errors, status: :unprocessable_entity }
      end
    end
  end

视图:

<%= form_for(@recipe, :html => {:multipart => true}) do |f| %>
  <% if @recipe.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@recipe.errors.count, "error") %> prohibited this recipe from being saved:</h2>

# [ fields that get's saved for the recipe and works fine ]

<% @tags.each do |t| %>
      <%= f.label t.name  %>
      <%= f.check_box :tags, t.name  %>
      <br />
    <% end %>

<%= f.submit 'Submit recipe', :class => 'btn btn-primary' %>

<% end %>

此刻，我收到一条错误消息: 未定义的方法合并"为肉":字符串

At the moment, I get an error message saying: undefined method `merge' for "Meat":String

肉"是标签名称.

那么，我在这里做什么错了?

So, what am I doing wrong here?

推荐答案

我认为问题出在这行@recipe.tags << params[:tags]. 您使用<<调用的关联方法需要一个对象(在这种情况下，需要一个标签对象)，但是在这种情况下，似乎您可能要向它传递一个字符串.

I think the issue is this line @recipe.tags << params[:tags]. The association method you're calling with << takes an object (in this case expecting a tag object), but in this case it seems you might be passing it a string.

有关更多信息，此链接可能有帮助. org/association_basics.html#has_and_belongs_to_many-association-reference ，尤其是在引用collection<<(object, …)的地方.

For more info this link may be helpful http://guides.rubyonrails.org/association_basics.html#has_and_belongs_to_many-association-reference, in particular where it refers to collection<<(object, …).

在控制器中，您需要执行类似@recipe.tags << tag的操作，其中tag是特定的标记对象.

In your controller you'll want to do something like @recipe.tags << tag where tag is a specific tag object.

因此，请尝试以下操作:

So, try this:

在您的控制器中

params[:tags].each do |k,v|
   @recipe.tags << Tag.find(k)
end

您认为

<% @tags.each do |t| %>
  <%= f.label t.name  %>
  <%= f.check_box "tags[#{t.id}]"  %>
  <br />
<% end %>

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