Validate before Posting a text or an image - ruby-on-rails

Question

I am working on a self-learning Rails application (the source code can be found here. I want to validate the presence of the content before posting a text or an image:
.
Those are my models or look below:
class Post < ActiveRecord::Base
belongs_to :user
default_scope { order ("created_at DESC")}
belongs_to :content, polymorphic: true
has_reputation :votes, source: :user, aggregated_by: :sum
end
class PhotoPost < ActiveRecord::Base
has_attached_file :image, styles: {
post: "200x200>"
}
end
class TextPost < ActiveRecord::Base
attr_accessible :body
end
Here are my controllers in case they have a relation with this. Any other files can be found in my Github account. I am sure it will be messy to copy the whole project (that is why I am giving links for the controllers and for my project).
So what I have tried so far. (I tried those on the Posts Model)
=> Using validates_associated
validates_associated :content, :text_post
and getting an error "undefined method `text_post' for #Post:0x517c848>"
=> Used validates
validates :content, :presence => true
and getting no error however a post is created with no text.
validates :body, :presence => true
and getting an error "undefined method `body' for #Post:0x513e4a8>"
If you need any other information please let me know and I will provide it asap.
Thank you.

Answer 1

It would seem you have quite a confusing model setup with some key missing relation rules. E.g. Polymorphic rule which is not being utilised and a has_many relation between User and Post with no sign a of a user_id value in the Post model. Here is how I would set it up:
User.rb
def User << ActiveRecord::Base
has_many :text_posts
has_many :photo_posts
end
TextPost.rb
def TextPost << ActiveRecord::Base
attr_accessible :body, :user_id
belongs_to :user
validates :body, :presence => true
end
PhotoPost.rb
def PhotoPost << ActiveRecord::Base
attr_accessible :image, :user_id
belongs_to :user
validates :file, :presence => true, :format => {
:with => %r{\.(gif|png|jpg)$}i,
:message => "must be a URL for GIF, JPG or PNG image."
}
end
Then in your view you would need to do:
<%= form_for #text_post do |f| %>
# ...
<% end %>
And in your controller you can modify the create method to include the current_user from devise and assign it to the new text post record (user_id attribute):
text_posts_controller.rb
def create
#text_post = current_user.text_posts.new(params[:text_post])
end
This adheres more to the DRY principle which Ruby on Rails excels at - you shouldn't be writing alot of code to just create a new record.
I would advise on reading up on some Ruby on Rails standard and best practises. You shouldn't need to create a method in the Dashboard Model in order to create a new TextPost or PhotoPost record. This is a very confusing way of going about it; instead you should be utilising the power of ActiveRecord relation.
I would advise checking out Railscasts. They have alot of fulfilling content.