Post and Location Association with ancestry gem

问题:

My Rails application have two model. Location and Post, Location have many post.I am Using ancestry gem.

class Post < ActiveRecord::Base
 belongs_to :location, :counter_cache => true
end

class Location < ActiveRecord::Base
 include Tree
 has_ancestry :cache_depth => true
 has_many :posts
end

My Post Controller

class PostsController < ApplicationController
before_action :set_post, only: [:show, :edit, :update, :destroy]

def index
@posts = Post.all
end

def show
end

def new
 @post = Post.new
end


 def edit
 end

def create
 @post = Post.new(post_params)

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

def update
respond_to do |format|
  if @post.update(post_params)
    format.html { redirect_to @post, notice: 'Post was successfully updated.' }
    format.json { head :no_content }
  else
    format.html { render action: 'edit' }
    format.json { render json: @post.errors, status: :unprocessable_entity }
  end
end
end

def destroy
@post.destroy
respond_to do |format|
  format.html { redirect_to posts_url }
  format.json { head :no_content }
end
end

private
 # Use callbacks to share common setup or constraints between actions.
 def set_post
   @post = Post.find(params[:id])
 end

 # Never trust parameters from the scary internet, only allow the white list through.
 def post_params
  params.require(:post).permit(:name)
 end
end

If i am create new Post with which Location belongs in _form.html.erb

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

  <ul>
  <% @post.errors.full_messages.each do |msg| %>
    <li><%= msg %></li>
  <% end %>
  </ul>
</div>
<% end %>

<div class="field">
 <%= f.label :name %><br />
 <%= f.text_field :name %>
</div>

<%= select :location_id, Location.all.at_depth(4) { |l| [ l.name, l.id ] } %> 

<div class="actions">
 <%= f.submit %>
</div>

Browser show error message which is display bellow

ArgumentError in Posts#new

回答1:

Not sure if this fixes your error, but:

To make the dropdown working, change the select line to:

<%= f.select :location_id, Location.all.at_depth(4) { |l| [ l.name, l.id ] } %>

This is because you want the formbuilder f to handle the creation of the form element.

You also have to whitelist the :location_id parameter in the controller:

def post_params
  params.require(:post).permit(:name, :location_id)
end