Unknown action:The action 'rsvp' could not be found for PostsController - ruby-on-rails

Question

So I'm getting the error stated in the title. What code would I have to write in my Postscontroller to fix this? I'm not sure what I would have to do here, would I have to define rsvp in my post controller? If thats the case how would I go about doing that?
class RsvpController < ApplicationController
def create
rsvp = current_user.rsvps.build({post_id: params[:id]})
if rsvp.save
end
end
end
Show.html.erb
<p>
<strong>Date:</strong>
<%= #post.date %>
</p>
<p>where:<%=#post.longitude %>, <%=#post.latitude%></p>
<p>
<strong>Name:</strong>
<%= #post.name %>
</p>
<p>
<strong>User_id:</strong>
<%= #post.user_id %>
</p>
<p>
<strong>Description:</strong>
<%= #post.description %>
</p>
<% if current_user == #post.user %>
<%= link_to 'Edit', edit_post_path(#post) %> |
<%end%>
<%= link_to 'Back', posts_path %>
<%= button_to "Rsvp now", rsvp_post_path(#post), class: "btn btn-primary" %>
routes.rb
Rails.application.routes.draw do
mount RailsAdmin::Engine => '/admin', as: 'rails_admin'
resources :posts
devise_for :users
root 'home#index'
get 'home/ruby_meetup'
resources :posts do
post 'rsvp', on: :member
end
Also I want it so it shows the list of people who already rsvped for the event. How would I go about doing that? I would appreciate some help as I'm still learning rails and this is my first project.

Answer 1

By the following line, you define the route:
resources :posts do
post 'rsvp', on: :member
end
By this line you're requesting this route:
To process the request, you need a controller action rsvp, which actually the error states.
Thus, just define the action (method) and process the request:
class RsvpController < ApplicationController
def create
rsvp = current_user.rsvps.build({post_id: params[:id]})
if rsvp.save
end
end
def rsvp
# process the request here...
end
end