Rails：基于另一个模型的控制器中的参数创建新模型

Question

I'm trying to create a model where every blog post has a number of tags (a separate model) associated to it. In my form, I pass back a separated string of tags along with the post, like "apples,oranges,bananas". I'm eventually going to try and split this string and then create a tag for each string. However, for now I'm just trying to see if I can make one tag with the whole string.

The request is handled by the create method of the posts controller. However, I can't figure out how to create and commit the tag in the posts controller, or at least call the tags controller to delegate the creation. I get the error:

undefined method `new=' for Tag(id: integer, tag_name: string, post_id: integer):Class

This points to the line Tag.new = @post.tags.create(post_params[:tag_name]) of the posts_controller.

Relevant code:

posts_controller

def new
        @post = Post.new
    end

    def create
        @post = current_user.posts.create(post_params)
        Tag.new = @post.tags.create(post_params[:tag_name])
        if @post.save
            redirect_to post_path(@post), :notice => "Post was created successfully."
        else
            render :new
        end
    end

private
    def post_params
        params.require(:post).permit(:title, :content_md, :image, :user_id, :year_created, :medium, :dimension_height, :dimension_width, :measurement, :weight_in_pounds, :price, :quantity)
    end

tags_controller

class TagsController < ApplicationController

  def new
    @tag = Tag.new
  end

  def create
    @tag = tag.create(tag_params)
  end

  private
  def tag_params
    params.require().permit(:tag_name, :user_id)
  end

end

post.rb

class Post < ActiveRecord::Base

  # Relations
  belongs_to :user
  has_many :comments
  has_many :post_votes
  has_many :tags
  accepts_nested_attributes_for :tags
end

tag.rb

class Tag < ActiveRecord::Base
  validates :tag_name, presence: true
  validates :post_id, presence: true
  belongs_to :post
end

Edit:

Also tried:

def create
        @tag = Tag.new(post_params[:tag_name])
        @tag.save
        @post = current_user.posts.create(post_params)
                # @post.tags.create(post_params[:tag_name])
        if @post.save
            redirect_to post_path(@post), :notice => "Post was created successfully."
        else
            render :new
        end
    end

for the posts controller. It creates the post, but doesn't seem to actually save the @tag

Answer 1

Without going into much deep, I see you you've the following line in your code (in posts_controller)

Tag.new = @post.tags.create(post_params[:tag_name])

which is not correct. If you want to just create (but not persist) you should call,

@post.tags.new(post_params[:tag_name])

For persist

@post.tags.create(post_params[:tag_name])

This will get rid of the error that you've posted. However, you shouldn't require these as your Post model can accept nested attributes for tags. Just make sure you've generated form correctly (hint: fields_for )

Answer 2

This line

Tag.new = @post.tags.create(post_params[:tag_name])

has no sense. Without further discussion:

@post.tags.create(post_params[:tag_name])

will work and actually create the tag.