## router.rb
Merb::Router.prepare do
  resources :comments
  resources :posts do
    member :add_comment, :method => :post
  end

  ...
end

## show.html.haml
= form_for @comment, :action => resource(@post, :add_comment), :method => :post do
  .input
    = text_field :name => "posted_by", :label => "Posted By"
  .input
    = text_field :name => "url", :label => "Website"
  .input
    = text_field :name => "email", :label => "Email"
  .input
    = text_area :name => "body", :label => "Comment"
  .input
    = submit "Post Comment"

## posts.rb (controller)
class Posts < Application
  # provides :xml, :yaml, :js
  before :ensure_authenticated  #, :only => [:index :edit :create :update :destroy]

  def index
    @posts = Post.all
    display @posts
  end

  def show(id)
    @post = Post.get(id)
    raise NotFound unless @post
    @comment = Comment.new
    display @post
  end

  def new
    only_provides :html
    @post = Post.new
    display @post
  end

  def edit(id)
    only_provides :html
    @post = Post.get(id)
    raise NotFound unless @post
    display @post
  end

  def create(post)
    @post = Post.new(post)
    if @post.save
      redirect resource(@post), :message => {:notice => "Post was successfully created"}
    else
      message[:error] = "Post failed to be created"
      render :new
    end
  end

  def update(id, post)
    @post = Post.get(id)
    raise NotFound unless @post
    if @post.update_attributes(post)
       redirect resource(@post)
    else
      display @post, :edit
    end
  end

  def destroy(id)
    @post = Post.get(id)
    raise NotFound unless @post
    if @post.destroy
      redirect resource(:posts)
    else
      raise InternalServerError
    end
  end

  def add_comment(id)
    @post = Post.get(id)
    raise NotFound unless @post

=begin ## Something I was playing with
    #props = Comment.properties.map {|p| p.name}
    #c_params = params.select {|k,v| props.include?(k)}
    #raise c_params.to_yaml
    #@comment = @post.comments.build(c_params)
=end

    #@comment = @post.comments.build(params) #=> Does not work
    @comment = @post.comments.build( # ugly but it works
                  :posted_by => params[:posted_by],
                  :email => params[:email],
                  :body => params[:body]
                  ## Other params here
               )
    if @comment.save
      message[:message] = "Comment Created"
    else
      message[:error] = "Comment failed to be created"
    end
    redirect resource(@post)
  end
end # Posts