Rails: Undefined method create for nil class - activerecord

Question

I am creating a sample project but when I am trying to create a new post getting an error "undefined method create for nil class"
My code is as follows.
user.rb
class User < ActiveRecord::Base
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
has_one :post, dependent: :destroy
end
post.rb
class Post < ActiveRecord::Base
belongs_to :user
end
posts_controller.rb
class PostsController < ApplicationController
def create
#user = current_user
if #user.post.blank?
#post = #user.post.create(params[:post].permit(:title, :text))
end
redirect_to user_root_path
end
end
new.html.erb
<%= form_for([current_user, current_user.build_post]) do |f| %>
<p>
<%= f.label :title %><br>
<%= f.text_field :title %>
</p>
<p>
<%= f.label :text %><br>
<%= f.text_area :text %>
</p>
<p>
<%= f.submit %>
</p>
<% end %>
But after trying so many times i have made some changes and it started working but i dont know what is the difference between both the codes.
user.rb
class User < ActiveRecord::Base
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
has_many :posts, dependent: :destroy
end
post.rb
class Post < ActiveRecord::Base
belongs_to :user
end
posts_controller.rb
class PostsController < ApplicationController
def create
#user = current_user
if #user.posts.blank?
#post = #user.posts.create(params[:post].permit(:title, :text))
end
redirect_to user_root_path
end
end
new.html.erb
<%= form_for([current_user, current_user.posts.build]) do |f| %>
<p>
<%= f.label :title %><br>
<%= f.text_field :title %>
</p>
<p>
<%= f.label :text %><br>
<%= f.text_area :text %>
</p>
<p>
<%= f.submit %>
</p>
<% end %>
my routes.rb is
UserBlog::Application.routes.draw do
devise_for :users, controllers: { registrations: "registrations" }
resources :users do
resources :posts
end
# You can have the root of your site routed with "root"
root 'home#index'
end
Please help me and tell me what is the difference between both the codes ?

Answer 1

The difference is in the helper methods that are added allowing you to build or create a new association object. The approach is slightly different for a has_one compared to a has_many association.
For a has_one association the method to create a new associated object would be user.create_post.
For a has_many association the method to create a new associated object would be user.posts.create.