Rails form params not being saved

Question

I'm very new to Ruby on Rails and I'm struggling with my scaffolded controller. I made a nested resource where my comments are placed in posts.

class Post < ActiveRecord::Base
  validates :name,  :presence => true
  validates :title, :presence => true, :length => { :minimum => 5 }
  has_many :comments
end

class Comment < ActiveRecord::Base
  validates :commenter, :presence => true
  validates :body, :presence => true     
  belongs_to :post
end

A simplified version of the controller is

class CommentsController < ApplicationController
  before_action :set_comment, only: [:show, :edit, :update, :destroy]

  # omited new, index, show... 

  # POST /comments
  # POST /comments.json
  def create
    post = Post.find(params[:post_id])
    @comment = post.comments.create(params[:comment].permit(:name, :title, :context))

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

  # PATCH/PUT /comments/1
  # PATCH/PUT /comments/1.json
  def update
    post = Post.find(params[:post_id])
    @comment = post.comments.find(params[:comment])
    respond_to do |format|
      if @comment.update(comment_params)
        format.html { redirect_to @comment, notice: 'Comment was successfully updated.' }
        format.json { head :no_content }
      else
        format.html { render action: 'edit' }
        format.json { render json: @comment.errors, status: :unprocessable_entity }
      end
    end
  end

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

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

When i filled in the form, i get this exception:

2 errors prohibited this comment from being saved: Commenter can't be blank Body can't be blank

I tried this guide but i think it isn't 100% compatible with Rails 4.

Answer 1

You are reading from params attributes for a Post (:name, :title, :context), but you need to read Comments attributes (:commenter, :body)

replace this:

@comment = post.comments.create(params[:comment].permit(:name, :title, :context))

with

@comment = post.comments.create(params[:comment].permit(:commenter, :body))

or, much better, with:

@comment = post.comments.create(comment_params)

Answer 2

It appears that you are explicitly permitting different set of attributes in your create action.

You should update your create action to use comment_params like you've done in update action. The reason being your Comment is definitely expecting Commenter and Body and not :name, :title, :context which you've permitted in your create action.

Update controller's create action as:

  # POST /comments
  # POST /comments.json
  def create
    ...
    @comment = post.comments.create(comment_params)
    ...
  end