NoMethodError (undefined method `posts' for nil:NilClass) - ruby-on-rails

Question

I'm very new to rails and was using the gem griddler to hopefully parse some incoming emails. I used all the code from the github site, and it provides an example emailprocessor.rb here:
class EmailProcessor
def initialize(email)
#email = email
end
def process
//re-done with help from #Kris
user = User.find_or_create_by(email: #email.from[:email]) do |u|
u.email = #email.from[:email]
u.name = #email.from[:name]
end
user.posts.create!(
subject: #email.subject,
body: #email.body,
attachment: #email.attachments,
from: #email.from[:email]
)
end
end
I know i need to declare posts somehow and somewhere, but I have looked around on here and on the rails site and havent found anything to help me create it. I get the error in the title when running heroku logs -t when the email server tries to post to the page.
here are the rest of my files that may be needed and what I've tried:
User.rb:
class User < ActiveRecord::Base
has_many :posts
end
Post.rb:
class Post < ActiveRecord::Base
belongs_to :user
end
create_posts.rb
class CreatePosts < ActiveRecord::Migration
def change
create_table :posts do |t|
t.string :subject
t.string :body
t.string :from
t.string :attachment
t.timestamps
end
end
end
users_controller.rb
class UserController < ApplicationController
def list
#users = User.find(:all)
end
def index
#users = User.all
end
def show
#user = User.find(params[:id])
end
def new
#user = User.new
end
def edit
end
def create
#user = User.new(params[:user])
if #user.save
redirect_to :action => 'list'
else
render :action => 'new'
end
end
end
post_controller.rb
class PostController < ApplicationController
def list
#posts = Post.find(:all)
end
def index
#posts = Post.all
end
def show
#post = Post.find(params[:id])
end
def new
#post = Post.new
end
def edit
end
def create
#post = Post.new(params[:post])
if #post.save
redirect_to :action => 'list'
else
#post = Subject.find(:all)
render :action => 'new'
end
end
end
Any help is really appreciated, I'd like to know what I'm doing wrong so I can avoid it in the future

Answer 1

The e-mail address is not found in the database and therefor user is nil. You can create a user on the fly with the following code:
def process
user = User.find_or_create_by(email: #email.from[:email]) do |u|
# todo: set some other properties on the new user u, e.g. the name
end
user.posts.create!(
subject: #email.subject,
body: #email.body,
attachment: #email.attachments,
from: #email.from[:email]
)
end
See also ActiveRecord::Relation::find_or_create_by.