Setting user_id for post creation in Rails - ruby-on-rails

Question

I am having trouble setting the user_id on the creation of a post
def create
#post = Post.new(post_params)
#post.user_id = session[:id]
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
The error I get is specifically undefined method 'username' for nil:NilClass when redirected to the show action. A look at the database shows that no user_id is set.
I also tried passing the user_id as a hidden field. but this did not work either (a look at the logs showed the hidden field wasn't even being passed for some reason).
Would appreciate a point in the right direction,
Thank you !
EDIT: as requested here is the show controller
def show
#post = Post.find(params[:id])
#original_id = params[:original_id]
#comment = Comment.new
end
<%= form_for [:admin, #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 %>
Below is the form
<div class="field">
<%= f.label :title %><br>
<%= f.text_field :title %>
</div>
<div class="field">
<%= f.label :content %><br>
<%= f.text_area :content %>
</div>
<div class="field">
<%= f.label :category %><br>
<%= f.text_field :category %>
</div>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
Routes:
root 'posts#index'
resources :posts do
resources :comments, shallow: true
end
resources :users, only: [:create]
#Posts
get "/meta", to: "posts#meta"
#User Routes
get "/signup", to: "users#new"
get "/success", to: "users#index"
#login Routes
get "/login", to: "sessions#login"
post "/sessions/login_attempt", to: "sessions#login_attempt"
#session routes
get "/sessions/home", to: "sessions#home"
get "/sessions/logout", to: "sessions#logout"
#admin routes
#resources :posts, module: 'admin', except: [:show, :index]
namespace :admin do
root 'posts#new'
resources :posts, except: [:show, :index]
end

Answer 1

Inside of your create method add
#post = Post.build(params[:post])
#post.user_id = current_user.id
This will grab the current user id for the given post.

Answer 2

If you have a has_many relationship between posts and users, why not do something like this:
#user = User.find(params[:id])
#post = #user.posts.new(params[:post])
The params might be different but this is the 'more ruby' way do do things. It explicitly notes the relationships between the two models. The above code should be in the #new action and then you would save it within the create action.

Answer 3

I feel like an idiot now but the issue was I was using session[:id] as opposed to session[:user_id]
Set in my sessions controller
def login_attempt
authorized_user = RegisteredUser.authenticate(params[:username_or_email],params[:login_password])
if authorized_user
session[:user_id] = authorized_user.id
flash[:notice] = "Wow Welcome again, you logged in as #{authorized_user.username}"
redirect_to(:action => 'index', :controller => "users")
else
flash[:notice] = "Invalid Username or Password"
flash[:color]= "invalid"
render "login"
end
end