Simple learning app with Rails 4 - Course / Enrolment / User Not working - ruby-on-rails

Question

I am trying to build a simple learning app with rails 4.
here are my models:
class User < ActiveRecord::Base
has_many :enrollments
has_many :lectures, through: :enrollments
accepts_nested_attributes_for :enrollments
end
class Enrollment < ActiveRecord::Base
belongs_to :user
belongs_to :lecture
end
class Lecture < ActiveRecord::Base
has_many :enrollments
has_many :users, through: :enrollments
end
And here are my controllers
class EnrollmentsController < ApplicationController
before_action :authenticate_user!
def create
#enrollments = current_user.enrollments.build(enrollment_params)
if #enrollments.save
flash[:success] = "You have successfully enrolled."
redirect_to profile_path(current_user)
else
flash[:danger] = "Please try again."
redirect_to root_path
end
end
private
def enrollment_params
params.require(:enrollment).permit(:user_id, :lecture_id)
end
end
Here are my views:
lectures/index.html.erb
<% #lectures.each do |lecture| %>
<%= image_tag lecture.picture.url(:medium) %>
<p><%= truncate(lecture.description, length: 80) %> </p>
<%= link_to "Enroll Now", {:action=>"create", :controller=>"enrollments"}, :method => :post %>
<% end %>
The problem is that when you click on Enroll Now I have the following error:
ActionController::ParameterMissing in EnrollmentsController#create
param is missing or the value is empty: enrollment
def enrollment_params
params.require(:enrollment).permit(:user_id, :lecture_id)
end
How can i make it work? Need help please

Answer 1

In your lectures/index.html.erb file, you are not passing any data to the controller's action method.
<%= link_to "Enroll Now", {:action=>"create", :controller=>"enrollments"}, :method => :post %>
Might be better served with something a la
<%= link_to "Enroll Now", {:action=>"create", :controller=>"enrollments", :user_id => current_user.id**, :lecture_id => lecture.id}, :method => :post %>
# ** not sure how you snag the current user's id in your app but you'd need it.
Also, take a look at Routing in Rails. There are some super handy helper methods you can use that will allow you to do something like this (this was done quickly and may not be totally accurate but is offered to show you how you can use a route's path helper to clean up the code and make it even more readable):
<%= link_to 'Enroll Now', enrollments_path({enrollment: { user_id: current_user.id, lecture_id: lecture.id }}), :method => :post %>