[NOTES] Pluck It: Extracting Micro-libraries into RubyGems

## SPEAKER NOTES INCLUDED ##
How many times have you written the same bits of code, over and over, and thought, “You know, if only this was big enough to be a gem, I would pluck it out." Often, we think of a RubyGem as a larger library of code that we “bolt on” to an app. And, these smaller code blobs become a hassle to distribute to the multiple apps that use them.

A small micro-library, done the right way, at the right time, can greatly improve an app.

But, when can you benefit from extracting a micro-library? And, how do you build and publish that code into a RubyGem? I'll go through the process, from A to Z.

Transcript

1. Pluck It Extracting micro-libraries and building rubygems @AdamCuppy Covering: 1. Identifying opportunities for extraction (using Rails, but don’t need to) 2. Building a gem and publishing it to RubyGems. 3. Pros/Cons
2. Welcome to our sample Rails 4.2 application
3. Like many apps, we have a collection of models
4. User Object * Attribute to access the user’s gravatar_url
5. User Object * We have some gravatar functionality
6. User Object * We have some gravatar functionality
7. User Object * We have some gravatar functionality Related to the User object? No.
8. Let’s fix this…
9. Add /lib/gravatar.rb Move it to lib (app agnostic)
10. Moved from app/models/user.rb Move it to lib (app agnostic)
12. Require our new dependency
13. Move it to lib (app agnostic)
14. Build the url with the new code
15. Question: * How many times have you written the same bits of code, over and over, and thought, “You know, if only this was big enough to be a gem, I would pluck it out.” * Most engineers don’t know how to craft a gem… Who does?
16. Problem * Copy lib files around? * What about updates? * What if you lose direct access to the application?
17. https://rubygems.org/ What’s a RubyGem? * Packaged code libraries * RubyGems.org is a database of RubyGems
18. “Pay no attention to the man behind the curtain!”
19. It’s a simple package: a self-contained collection of one or more files. rubygem: * RubyGems then modifies the $LOAD_PATH to include the `lib` directory (and files) of the package. * When you require a file from the package, your app knows where to look.
20. http://bundler.io/ What is Bundler? * DEPENDENCY manager * Bundler is a rubygem, itself
21. /path/to/myapp/Gemfile The Gemfile is an application’s rubygem dependency manifest
22. $ bundle install RubyGems Who knows what RubyGem is? * No: Packaged code libraries * RubyGems.org is a database of RubyGems
23. App Bundle Bundler + RubyGems + MyApp RubyGems.org rails-4.2 rspec-core-3.2 Private Gem Server priv_gem-1.0 priv_gem-1.0 RubyGems have version dependencies, as well. So, bundler makes sure the proper gem versions are included. NEXT: Let’s extract a simple gem.
24. App Bundle $ bundle install Bundler + RubyGems + MyApp RubyGems have version dependencies, as well. So, bundler makes sure the proper gem versions are included. NEXT: Let’s extract a simple gem.
25. Here’s another example…
26. The function of this code is to find differences between two hashes. Looking the model there is a lot of extra code - let’s fix that. Well this is useful!
27. $ bundle gem hash_diff ——test
28. $ bundle gem hash_diff ——test Created a lib directory with the first files Remember: it’s a package of one or more files
29. $ bundle gem hash_diff ——test Templates files (options flags on build can change this behavior) * Readme, Code of Conduct, License
30. $ bundle gem hash_diff ——test “— test” flag added resources to support automated testing (default RSpec, but can use MiniTest) Included .travis.yml defaults
31. $ bundle gem hash_diff ——test Remember: Just a collection of files.
32. $ bundle help gem
33. Open ‘hash_diff.rb’ manifest * Creates a namespace for the gem (“hash_diff”)
34. Open ‘hash_diff/version’ => Sets a default version This is used to track releases of the gem. Default is semantic versioning
35. Migrate our code in from the implementation Don’t forget your tests!
36. $ cd /path/to/my_gem $ bundle install $ rake Default rake task runs the test suite
37. Once the code is migrate and tests are passing Update the “gemspec”
38. Dependencies are not in the Gemfile
39. Dependencies are not in the Gemfile
40. But you will still run… $ bundle install
41. Build: $ cd /path/to/my_gem $ gem build hash_diff.gemspec THE PACKAGE!!
42. Publish: $ gem push hash_diff-0.1.0.gem PUBLISH THE PACKAGE!!
43. https://rubygems.org/gems/hash_diff
44. /path/to/myapp/Gemfile PUBLISH THE PACKAGE!!
45. $ cd /path/to/myapp $ bundle install
46. I’m Famous like @the_zenspider!
48. HashDiff.diff is a module method that calls to HashDiff::Comparison https://github.com/CodingZeal/hash_diff/blob/master/lib/hash_diff.rb
49. 1. Modify code 2. Increment VERSION constant 3. Rebuild gem 4. Publish new version 5. Update apps: $ cd /path/to/app; bundle update my_gem New Release
50. 1. Isolation from app code 2. Manage upgrades 3. Community support Pros…
51. Extraction encourages isolation; isolation encourages a simple interface; and, a simple interface is more maintainable. * “Encourages” is the operative word
52. 1. External dependencies to manage 2. Add’l development overhead 3. Community support Cons…
53. When is the “right time?”
54. It’s when the cost of maintaining an internal library, exceeds the cost of maintaining an external dependency.
55. https://rubygems.org/gems/trueman Simple truthy/falsy value manager
56. https://rubygems.org/gems/gravasaurus_hex The most basic gravatar url and hex generator
57. https://rubygems.org/gems/hash_diff Hash comparison gem
58. http://guides.rubygems.org/
59. github.com/acuppy @adamcuppy Find me on the inter webs
60. codingzeal.com @adamcuppy Adam Cuppy