categories struggle

categorization.rb

class Categorization < ActiveRecord::Base
	belongs_to :post 
	belongs_to :category
end

category.rb

class Category < ActiveRecord::Base
	has_many :categorizations 
	has_many :posts, through: :categorizations

end

post.rb

class Post < ActiveRecord::Base
	belongs_to :user
	belongs_to :category

	has_many :categorizations
end 

post_form.html.erb

<% if signed_in? && current_user?(@user) %>
<%= form_for(@post) do |f| %> 
<%= f.hidden_field :user_id, value: current_user.id %>
	<%= render 'shared/error_messages', object: f.object %>
	<div class="title-area"> 
		<%= f.text_field :title, placeholder: "Enter title..." %>
	</div>
	<div class="text-area">
		<%= f.text_area :content, placeholder: "Compose new post..." %>
	</div>
		<%= f.submit "Story", class: "post-button", id: "left" %>
		<%= f.submit "Question", class: "post-button", id: "right" %>
		<% end %>
<% end %>

posts_controller.rb

def create 
    @post = current_user.posts.build(post_params)
    @story = Category.find(1)
    @question = Category.find(2)
    if params[:commit] == 'Story'
      @post.category = @story
      @story.posts << @post
    elsif params[:commit] == 'Question'
      @post.category = @question
      @question.posts << @post
    end 
    if @post.save
      flash[:success] = "Post created!"
      redirect_to @post
    else 
      flash.now[:error] = "Couldn't post!"
      redirect_to :back
    end
  end

  def destroy
    Post.find(params[:id]).destroy
    flash[:success] = "Successfully deleted!"
    redirect_to current_user
  end

schema.rb

 create_table "categories", force: true do |t|
    t.string   "name"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

 create_table "posts", force: true do |t|
    t.string   "content"
    t.integer  "user_id"
    t.datetime "created_at"
    t.datetime "updated_at"
    t.string   "title"
    t.integer  "category_id"
  end

user.rb

class User < ActiveRecord::Base
  def show
  	@user = User.find(params[:id])
    @post = current_user.posts.build if signed_in?
    @posts = @user.posts.paginate(page: params[:post_page], per_page: 5)
    @feed_items = @user.followed_posts.paginate(page: params[:feed_item_page], per_page: 2)
  end