undefined method `comments' for nil:NilClass - ruby-on-rails

Question

I'm trying to create a way to have users comment on my posts. Currently I have All user posts showing up on my home page and then in the user profile only the current users posts. I would like to have it so that the comments appear only on the posts in the users profile. I tried to add a comment form in the user profile but I got an undefined method `comments' for nil:NilClass error.
My comments_controller looks like
class CommentsController < ApplicationController
def create
#post = Post.find(params[:post])
#comment = #post.comments.create(params[:comment])
redirect_to post_path(#post)
end
I have a partial (_comment_form.html.erb) that I am rendering in the user profile which looks like
<h2>Add a comment:</h2>
<%= form_for ([#post, #post.comments.build]) do |f| %>
<div class="field">
<%= f.label :commenter %><br />
<%= f.text_field :commenter %>
</div>
<div class="field">
<%= f.label :body %><br />
<%= f.text_area :body %>
</div>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
My Comment model looks like
class Comment < ActiveRecord::Base
belongs_to :post
end
My Post model looks like
class Post < ActiveRecord::Base
attr_accessible :content
belongs_to :user
validates :content, :presence => true
validates :user_id, :presence => true
validates :user, :presence => true
validates :title, :presence => true
has_many :comments
default_scope :order => 'posts.created_at DESC'
end
My User Profile Looks like show.html.erb
<table class="profile" summary="Profile information">
<tr>
<td class="main">
<h1>
<%= gravatar_for #user %>
<%= #user.name %>
</h1>
<% unless #user.posts.empty? %>
<table class="posts" summary="User posts">
<%= render #posts %>
<%= render 'comments/comment_form' %>
</table>
<% end %>
</td>
<td class="sidebar round">
<strong>Name</strong> <%= #user.name %><br />
<strong>URL</strong> <%= link_to user_path(#user), #user %><br />
<strong>Tasks</strong> <%= #user.posts.count %>
</td>
</tr>
</table>

Answer 1

It might be that you haven't initialized #post in the new method of your controller and it's being used as nil. Always construct an empty model for your new form if it's practical:
def new
#post = Post.new(params[:post])
end

Answer 2

#post = Post.find_by_id(params[:post_id])

Answer 3

Are you initializing the #post in the show action of your PostsController? That would be required because you are redirecting from the create action of your CommentsController.

Answer 4

<%= render #posts %>
This line should reference #post instead. Note the trailing s, compared to all the other references to it in your code.

Answer 5

Can you see log/development.log to see where the error occurred? It wasn't clear from the question. But judging from your code, there are two possible locations:
#comment = #post.comments.create(params[:comment])
here is unlikely because the last line of code is Post.find which will raise a RecordNotFound if the id is not found
<%= form_for ([#post, #post.comments.build]) do |f| %>
This is very likely, can you do a puts #post.inspect and check your development.log to see if that is null. Assuming that it is null, you need to instantiate a Post object wherever you rendered _comment_form.html.erb