Undefined method `update' for nil:NilClass rails 4.0.0

Question

I'm a beginner in Ruby on Rails and stack overflow. So sorry if there are mistakes in asking this question or...

I'm trying to write edit/update for my blogger project. This is my controller:

  def edit
    @post = Post.find params[:id] 
  end   

  def update
    @post.update(params[:post].permit(:title, :summary, :content))
    redirect_to posts_path
  end 

This is my view:

<h1>Edit Page</h1>
        <%= form_for @post do |f| %>
        Title: <%= f.text_field :title %>
        Summary: <%= f.text_area :summary %>
        Content: <%= f.text_area :content %>
        <%= f.submit "Update" %>
<% end %>

and when I want to update any post I keep getting this error:

NoMethodError in PostsController#update

undefined method `update' for nil:NilClass

Any help will be appreciated! :)

Answer 1

You must set @post instance variable to point appropriate Post object in order to perform update on it:

@post = Post.find params[:id]

Answer 2

You can also set @post using a before_action

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

  # GET /posts/1/edit
  def edit
  end

  # PATCH/PUT /posts/1
  # PATCH/PUT /posts/1.json
  def update
  end

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

Now, whenever rails hits your edit or update actions it will set @post to the "current" post.