NoMethodError - undefined method `get' for nil:NilClass - ruby-on-rails

Question

Here is the tutorial which I follow for implement: Finally Trying ActionCable
This code is too long, so I don't put this code into this question I just put some of the codes as like into the user model
def online_now?
$redis.get("users:online:#{id}").present?
end
and the view is:
<% User.all.each do |user| %>
<%= user.name %>
<div class="online-indicator">
<% if !user.online_now? && 'xs-none' %>
Online
<% else %>
Offline
<% end %>
</div>
<% end %>
but always throwing an error as like
NoMethodError - undefined method get' for nil:NilClass
Did you mean? gem:
app/models/user.rb:34:inonline_now?'
which indicating this line
$redis.get("users:online:#{id}").present?
I don't why throwing this error.
But it's working on rails console as like
irb(main):005:0> redis.set("mykey", "hello world")
=> "OK"
irb(main):006:0> redis.get("mykey")
=> "hello world"
Thanks

Answer 1

From comment #Ilya Konyukhov how do you define $redis variable in your model method. It's clear it should be a Redis API, but where do you connect to the Redis and store its connection?
Yes, that is a very nice comment & helpful for clearing the concept from a commentator.
If your Redis server is running in the system then need to configure this in Rails own way, I would writing some configuration files & if you already created that you can compare these & if you not created till now I think that is the issue & need to create ASAP if you need this feature.
First, install the gem redis-rails
gem 'redis-rails'
after that add this into environment file
config.cache_store = :redis_store, {
host: "localhost",
port: 6379,
db: 0,
password: "mysecret",
namespace: "cache"
}, {
expires_in: 90.minutes
}
create a file into app/config/initializer/ which redis.rb then put into this
$redis = Redis.new(:host => 'localhost', :port => 6379)
after all restart the server and check it out.
make sure redis-server is running.
Hope it will work.