Rails routing when nesting resources - ruby-on-rails

Question

I'm trying to figure out how to specify the route I'm trying to use but I keep getting routing errors. Can someone please point out where I'm going wrong and maybe explain what a better way to do this might be?
I'm working with these (nested) resources:
resources :users do
resources :playlists
end
Models:
class User < ActiveRecord::Base
has_many :playlists
end
class Playlist < ActiveRecord::Base
belongs_to :user
validates :user_id, presence: true
end
Now I'm trying to link to a user's playlists inside the user/show.html.erb file:
<p>
<%= link_to "Playlists", user_playlists_path(#playlist)%></p>
</p>
Which brings me to a Playlists page (/users/1/playlists) successfully but when I try adding a new playlist for this user, I get the following error:
Showing /app/views/playlists/_form.html.erb where line #1 raised:
undefined method `playlists_path' for #<#<Class:0x0000000335c688>:0x00000003d0b238>
This is line #1:
<%= form_for(#playlist) do |f| %>
This is what I get for rake routes if that helps at all:
Prefix Verb URI Pattern Controller#Action
user_playlists GET /users/:user_id/playlists(.:format) playlists#index
POST /users/:user_id/playlists(.:format) playlists#create
new_user_playlist GET /users/:user_id/playlists/new(.:format) playlists#new
edit_user_playlist GET /users/:user_id/playlists/:id/edit(.:format) playlists#edit
user_playlist GET /users/:user_id/playlists/:id(.:format) playlists#show
PATCH /users/:user_id/playlists/:id(.:format) playlists#update
PUT /users/:user_id/playlists/:id(.:format) playlists#update
DELETE /users/:user_id/playlists/:id(.:format) playlists#destroy
users GET /users(.:format) users#index
POST /users(.:format) users#create
new_user GET /users/new(.:format) users#new
edit_user GET /users/:id/edit(.:format) users#edit
user GET /users/:id(.:format) users#show
PATCH /users/:id(.:format) users#update
PUT /users/:id(.:format) users#update
DELETE /users/:id(.:format) users#destroy
root GET / default_pages#home
signup GET /signup(.:format) users#new
signin GET /signin(.:format) users#signin

Answer 1

The errors:
undefined method `playlists_path' for #<#<Class:0x0000000335c688>
and
user_playlist GET /users/:user_id/playlists/:id(.:format)
Gives a clear reason of the error you have.
<%= form_for(#playlist) do|f| %>
should be
<%= form_for([#user, #playlist]) do|f| %>
Or current_user, what is important is you need to pass the user object.
Explanation :
If you have noticed in a update action (taking that you redirect to a show page after you update) instead of redirect_to user_path(#user) we can do just redirect_to #user, from which Rails infers that you are redirecting to the show path of user.
It is a similar situation here, similarly if you are having a form_for for the playlist and you pass only #playlist instead of [#user, #playlist] then it woud try to find new_playlist_path, which isn't in your route and will show an error.
This is a short gist on how you might do it.

Answer 2

This:
<%= form_for(#playlist) do |f| %>
Should be This:
<%= form_for [#user, #playlist] do |f| %>
note the square brackets