What is does this error method mean: undefined method `method name' for nil:NilClass (NoMethodError) - ruby

Question

I am fairly new to automation testing and I am writing BDD automation test scenarios in Ruby using selenium-webdriver, when running my tests, they fail at the first step. (tumblr just as an example)
What does this error message mean and how do I fix it? Any help would be much appreciated!
In my feature file:
Feature: tumblr
#s1
Scenario: Logging in to Tumblr
Given I am on the Tumblr login page
When I enter my login details
Then I should be sent to the dashboard
In my login_page.rb:
def visit
#browser.goto "#{EnvConfig.base_url}/login"
await_on_page
end
In my login_step_defs.rb:
Given /^I am on the Odicci login page$/ do
#app.tumblr_login.visit
end
When /^I enter my login details$/ do
#app.tumblr_login.login
end
Then /^I should be sent to the dashboard$/ do
#app.tumblr_dashboard.go_to_dashboard
end
Initially when I was running 'cucumber features.feature' but the step definitions could not be located so the scenarios were finishing off as 'undefined' so running 'cucumber features.feature -r step_definitions works to run the tests but they fail because of this error message:
Scenario: Logging in to Tumblr # features.feature:4
Given I am on the Tumblr login page # step_definitions/login_step_defs.rb:2
undefined method `tumblr_login' for nil:NilClass (NoMethodError)
./step_definitions/login_step_defs.rb:3:in `/^I am on the Tumblr login page$/'
features.feature:5:in `Given I am on the Tumblr login page'

Answer 1

#maxpleaner
if ENV['HEADLESS']
require 'headless'
require 'selenium-webdriver'
headless = Headless.new display: '100'
headless.start
end
# Set up browser
# browser = Watir::Browser.new (ENV['BROWSER'] || 'chrome').to_sym
driver = Selenium::WebDriver.for :chrome
browser_type = ENV['BROWSER'] || 'chrome'
$setup_done = false
Before do |scenario|
#browser = browser
#app = App.new #browser
unless $setup_done
$setup_done = true
# This stuff will only run before the first scenario executed. Use it to set up data etc.
end
end
After do |scenario|
end
at_exit do
browser.quit
end