This post originally created for my talk in the Sydney Ruby Meetup, I’ve found Rake to be quite a powerful tool and I’m definitely going to use some these features in my projects. https://medium.com/@rudyyazdi/rake-gem-explained-ebee7e6e6f72

1. Exploring
Rake
Aug 2016 #rorosyd

2. @rudyyazdi
GitHub, Twitter, Medium, LinkedIn 👆

3. So what is Rake?
It’s a task runner.
It’s the official Ruby build tool.
As seen in:
rake db:migrate
rake db:schema:load

4. So what is the difference between
a task and a function?
Aren’t they both bunch of commands?

5. A quick detour to FP: side effects
def add(num1, num2)
logger.log("added #{num1} and #{num2}") # logging something
current_user.action_counter.up # say you are counting user’s actions
num1 + num2 # and store them in your database.
end
The first and second line are side effects because they modify something outside the
scope of the function. So this function is impure.

6. Result
focused
Side-
Effect
focused
Pure functions
Functions
Tasks

7. The syntax
Just put this in your Rakefile in the root of your project:
desc 'remove all files from build folder.'
task :clean do
Dir['build/*.*'].each { |file| File.delete(file) }
end
And then just run: $ rake clean
You can also store your .rake files in directory called rakelib or if you’re using
rails you can put them in lib/tasks directory

8. Namespacing
You can namespace your tasks:
namespace :asset do
desc 'remove all files from build folder.'
task :clean do
Dir['build/*.*'].each { |file| File.delete(file) }
end
end
And then just run: $ rake asset:clean

9. Appending a task
task :talk do
puts 'I am talking!'
end
task :talk do
puts 'Still talking!'
end
$ rake talk
I am talking!
Still talking!

10. Dependent tasks.
You can define dependency for each task.
task uglify: [:concat, :clean] do
# do stuff
end

11. :environment
If you’re using rails and want to load your entire app before a task just add
:environment as prerequisite:
task talk: :environment do
User.all.each { |u| u.notify("Happy new year!") }
end

12. Lets compare!!

13. Achieve these objectives:
1. Clear the build folder.
2. Concatenate all the files in .src.js .
3. Uglify the result.
4. Dump everything in a .min.js file.
5. Name the file the result of whoami command in the command line at the time of
build.
6. Put the file in the build folder.

14. There is more:

15. Access to previous tasks
You can invoke tasks from the other parts of your app:
task :talk do
Rake::Task['discussion:small_talk'].invoke
end

16. @already_invoked
task :first do
puts 'first task'
end
task second: :first do
puts 'first second'
end
task third: [:first, :second] do
puts 'first third'
end
$ rake third
first task
second task
third task

17. Enhance your tasks
Let’s say you want to notify a Slack channel if someone drops the database!!
Rake::Task["db:drop"].enhance do
slack_client.message("mayday, mayday, database dropped!")
end
Disclaimer: if someone is really planning to drop your db they’ll find a better way!
😈😈

18. Multitask
If you have a bunch of prerequisites that takes a long time:
multitask main_taks: [:long_task_1, :long_task_2, :long_task_3] do
# do stuff after all the above are finished (they will execute in parallel)
end

19. File tasks
This is for the tasks that generates the files:
file "rudy.min.js" do
# ...
end

20. FileList
files = Rake::FileList["**/*.md", "**/*.markdown"] # take all the matching files
files.exclude("~*") # exclude the ones beginning with ~
files.exclude(/^scratch//) # exclude the ones in the scratch folder
files.exclude do |f|
`git ls-files #{f}`.empty? # exclude the ones that are not tracked by git
end
files.each { |file| file.do_stuff }
* Shamelessly stolen from Avdi Grimm’s blog.

21. Rules
It matches your rake command with the provided regex and if it’s match it runs the
task.
rule '.html' do |t| # t here is the instance of task itself.
sh "touch #{t.name}"
end
$ rake fake.html
# creates an empty file called fake.html

22. Advanced rules
rule '.java' do |t|
puts t
end
rule '.class' => -> (tn) { tn.sub(/.class$/, '.java').sub(/^classes//, 'src/') } do |t|
puts t
end
$ rake classes/my.class
<Rake::FileTask src/my.java => []>
<Rake::FileTask classes/my.class => [src/my.java]>

23. Passing variables
task :sum, [:num1, :num2] do |_, args|
puts "the sum of #{args[:num1]} and #{args[:num2]}
is #{args[:num1].to_i + args[:num2].to_i}"
end
$ rake sum[2,7]
the sum of 2 and 7 is 9
Rake passes the task into the first block argument but since we’re not using it here
we replace it with “_”.
I know it’s kinda ugly so if you are working with too many variables checkout thor.

24. Thanks! 🤖🤖

25. Useful links:
Everything You Always Wanted to Know About Writing Good Rake Tasks * But
Were Afraid to Ask
Automated Tasks with Cron and Rake
Rake tutorial
Rake series by Avdi Grimm