Undefined method `courses' for nil:NilClass - ruby-on-rails

Question

When I visit the courses/new page on my heroku app, it raises an error saying that the method courses is not defined. Also, when I create a course on the console, it has no id or created_at.
Courses Controller:
class CoursesController < ApplicationController
def home
#course = current_user.courses.find(params[:id])
end
def new
#course = current_user.courses.build
end
def create
#course = current_user.courses.build(course_params)
if #course.save
flash[:success] = "Course Created"
redirect_to coursehome_path
else
render 'new'
end
end
private
def course_params
params.require(:course).permit(:name)
end
end
College Model:
class College < ApplicationRecord
has_many :courses, dependent: :destroy
has_secure_password
def College.digest(string)
cost = ActiveModel::SecurePassword.min_cost ?
BCrypt::Engine::MIN_COST : BCrypt::Engine.cost
BCrypt::Password.create(string, cost: cost)
end
end
Course model:
class Course < ApplicationRecord
belongs_to :college
end
Migration:
class CreateCourses < ActiveRecord::Migration[5.1]
def change
create_table :courses do |t|
t.string :name
t.references :college, foreign_key: true
t.timestamps
end
add_index :courses, [:college_id, :created_at]
end
end
Edit:
Actually, I created a controller called collegesessions and added the current_user method in its helper:
module CollegesessionsHelper
def log_in(college)
session[:user_id] = college.id
end
def current_user
if session[:user_id]
#current_user ||= College.find_by(id: session[:user_id])
end
end
def logged_in?
!current_user.nil?
end
def log_out
session.delete(:user_id)
#current_user = nil
end
end

Answer 1

When you are trying to access
current_user.courses, it looks for courses association in usermodel.
Your course model has no user association.
Course Model
class Course < ApplicationRecord
belongs_to :college
belongs_to :user
end
User model
class User < ApplicationRecord
//fields
has_many: courses
end