Building Ruby gems

@steﬀoz stefanoverna.com What Gems are Building Ruby Gems

@steﬀoz stefanoverna.com What gems are

@steﬀoz stefanoverna.com •A Gem is a software package with a
name, version, and platform •Gems split out reusable functionality that others can use •Some gems also provide command line utilities Gems are build using the Rubygems tool (included with Ruby itself).

@steﬀoz stefanoverna.com Rubygems provides a gem executable that helps build,
download and install gems.

@steffoz stefanoverna.com % tree freewill freewill/ ├── lib/ │ └──
freewill.rb └── freewill.gemspec So, this is your first gem. Contains information about the gem’s files, test information, platform, version number, author’s email and name. Contains the code of the gem.

@steﬀoz stefanoverna.com % tree freewill freewill/ ├── bin/ │ └──
freewill ├── lib/ │ └── freewill.rb ├── test/ │ └── test_freewill.rb ├── README ├── Rakefile └── freewill.gemspec This is a more usual gem. Contains the executables of the gem. Contains the tests of the gem. Contains the docs of the gem. Helps automating gem release, testing and generate docs.

@steﬀoz stefanoverna.com Gem::Specification.new do |s| s.name = 'freewill' s.version =
'1.0.0' s.date = '2010-04-27' s.summary = "Freewill!" s.description = "I will choose Freewill!" s.authors = ["Nick Quaranto"] s.email = '[email protected]' s.homepage = 'http://example.com' s.files = ["lib/freewill.rb"] s.add_dependency 'activesupport' end

@steﬀoz stefanoverna.com › gem build freewill.gemspec Successfully built RubyGem Name:
freewill Version: 1.0.0 File: redpomo-1.0.0.gem › ls redpomo-1.0.0.gem

@steﬀoz stefanoverna.com Gems are just tarballs.

@steﬀoz stefanoverna.com › tar zxvf freewill-1.0.0.gem x data.tar.gz x metadata.gz
tar zxvf data.tar.gz x lib/freewill.rb [...] › gunzip metadata.gz › cat metadata --- !ruby/object:Gem::Specification name: redpomo version: !ruby/object:Gem::Version version: 0.0.7 prerelease: platform: ruby authors: - Stefano Verna autorequire: bindir: bin [...] All the gem ﬁles are placed in an inner data.tar.gz tarball A YAML serialized version of a Ruby class, containing all the gemspec infos.

@steﬀoz stefanoverna.com How to use gems

@steffoz stefanoverna.com require "foo/bar" Loads the given file, returning true
if successful and false if the feature is already loaded. If the filename does not resolve to an absolute path, it will be searched for in the directories listed in $LOAD_PATH.

@steﬀoz stefanoverna.com › irb irb(main)> puts $LOAD_PATH ~/.rbenv/versions/1.9.3-p0/lib/ruby/1.9.1 [...]

@steﬀoz stefanoverna.com gem install "rails" The install command installs local
or remote gems into the local gem repository.

@steﬀoz stefanoverna.com Rubygems patches Kernel#require with a pre-ﬁlter that adds
/lib directories of gems to your $LOAD_PATH

@steﬀoz stefanoverna.com › irb irb(main)> puts $LOAD_PATH ~/.rbenv/versions/1.9.3-p0/lib/ruby/1.9.1 [...] irb(main)>
require 'active_support' true irb(main)> puts $LOAD_PATH ~/.rbenv/versions/1.9.3-p0/lib/ruby/gems/1.9.1/gems/i18n-0.6.0/lib ~/.rbenv/versions/1.9.3-p0/lib/ruby/gems/1.9.1/gems/activesupport-3.2.3/lib ~/.rbenv/versions/1.9.3-p0/lib/ruby/1.9.1

@steﬀoz stefanoverna.com Lets build a gem!

@steﬀoz stefanoverna.com

@steﬀoz stefanoverna.com texticle comfortable-mexican-sofa lolita tranny cocaine smurf hoe whoa

@steﬀoz stefanoverna.com redditor

@steﬀoz stefanoverna.com > redditor > redditor hot|top|new|controversial > redditor hot
Programming > redditor top fffffffuuuuuuuuuuuu The Goal (we'll miss)

@steﬀoz stefanoverna.com What we need AKA The "Ruby Toolbox" phase

@steﬀoz stefanoverna.com 1 HTTP Client

@steﬀoz stefanoverna.com 1 HTTP Client RestClient Simple HTTP and REST
client for Ruby, inspired by microframework syntax for specifying actions.

@steﬀoz stefanoverna.com 1 require 'rest_client' response = RestClient.get 'http://example.com/resource' response.code
# 200 response.cookies # {"Foo"=>"BAR", "QUUX"=>"QUUUUX"} response.headers # {:content_type=>"text/html; charset=utf-8", :cache_control=>"private" ... response.to_s # \n<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01//EN\"\n \"http://www.w3.org/TR/html4/strict.dtd\">\n\n<html ....

@steﬀoz stefanoverna.com 2 JSON Parser

@steﬀoz stefanoverna.com 2 JSON Parser JSON This is a implementation
of the JSON speciﬁcation according to RFC 4627

@steﬀoz stefanoverna.com 2 require 'json' JSON.parse '{ "foo": "bar" }'
# {"foo"=>"bar"} { foo: "bar" }.to_json # {"foo":"bar"}

@steﬀoz stefanoverna.com 3 URL Shortener

@steﬀoz stefanoverna.com 3 URL Shortener googl Google URL Shortener API
in Ruby

@steﬀoz stefanoverna.com 3 require 'googl' url = Googl.shorten('http://www.zigotto.com') url.short_url #
"http://goo.gl/ump4S" url.long_url # "http://www.zigotto.com/" url.qr_code # "http://goo.gl/ump4S.qr" url.info # "http://goo.gl/ump4S.info"

@steﬀoz stefanoverna.com 4 CLI Table Drawer

@steﬀoz stefanoverna.com 4 CLI Table Drawer command_line_reporter This gem makes
it easy to provide a report while your ruby script is executing

@steﬀoz stefanoverna.com 4 require 'command_line_reporter' include CommandLineReporter table :border =>
true do row :color => 'red' do column 'Name', :width => 20, :color => 'blue' column 'Address', :width => 20 column 'City', :width => 15 end row do column 'Caeser' column '1 Appian Way' column 'Rome' end row do column 'Richard Feynman' column '1 Golden Gate' column 'Quantum Field' end end

@steﬀoz stefanoverna.com 5 CLI

@steﬀoz stefanoverna.com 5 CLI thor A simple and efﬁcient tool
for building self- documenting command line utilities

@steﬀoz stefanoverna.com 5 class App < Thor map "-L" =>
:list desc "install APP_NAME", "install an app" method_options :version def install(name) version = options[:version] # do something end desc "list [SEARCH]", "list all the apps" def list(search = "") # list everything end end

@steﬀoz stefanoverna.com Exploration phase https://gist.github.com/2878853

@steﬀoz stefanoverna.com Ok, now let's make the world a better
place. Let's release redditor to the public!

@steﬀoz stefanoverna.com gem install ore

@steﬀoz stefanoverna.com mine redditor \ -D 'Browse Reddit from CLI'
\ -a 'Stefano Verna' \ -e '[email protected]' \ --markdown \ --yard \ --bin \ --bundler

@steﬀoz stefanoverna.com # redditor.gemspec gem.add_dependency 'activesupport' gem.add_dependency 'thor' gem.add_dependency 'command_line_reporter'
gem.add_dependency 'json' gem.add_dependency 'googl' gem.add_dependency 'rest-client' gem.add_dependency 'launchy'

@steﬀoz stefanoverna.com # lib/redditor/cli.rb require 'thor' module Redditor class CLI
< Thor desc "hot", "Shows the hottest stories on Reddit" def hot # COPY AND PASTE? HELL YEAH! end end end

@steﬀoz stefanoverna.com # bin/redditor #!/usr/bin/env ruby require 'redditor/cli' Redditor::CLI.start

@steﬀoz stefanoverna.com Done! rake build and go celebrate! https://gist.github.com/2878875

@steﬀoz stefanoverna.com Nope. You need to test it, bitch.

@steﬀoz stefanoverna.com Test Driven Development

@steﬀoz stefanoverna.com Behaviour Driven Development

@steﬀoz stefanoverna.com spec/fixtures/output/hot.txt

@steﬀoz stefanoverna.com # spec/acceptance/cli_usage_spec.rb require 'spec_helper' describe "CLI usage" do
describe "redditor hot" do it "returns the hottest news on Reddit" do redditor "hot" output.should == read_fixture("output/hot.txt") end end end

@steﬀoz stefanoverna.com def hot stories = Story.find(type: :hot) StoriesPrinter.output(stories) end
One class, one responsibility (MVC also)

@steﬀoz stefanoverna.com # spec/cli_spec.rb require 'spec_helper' require 'redditor/cli' describe Redditor::CLI
do describe ".hot" do it "fetches /hot.json stories, and prints them out" do stories = double("stories array") Redditor::Story.stub(:find).with(type: :hot).and_return(stories) Redditor::StoriesPrinter.should_receive(:output).with(stories) subject.hot end end end

do describe ".hot" do it "fetches /hot.json stories, and prints them out" do stories = double("stories array") Redditor::Story.stub(:find).with(type: :hot).and_return(stories) Redditor::StoriesPrinter.should_receive(:output).with(stories) subject.hot end end end double generic term for any kind of pretend object used in place of a real object for testing purposes. The name comes from the notion of a Stunt Double in movies.

do describe ".hot" do it "fetches /hot.json stories, and prints them out" do stories = double("stories array") Redditor::Story.stub(:find).with(type: :hot).and_return(stories) Redditor::StoriesPrinter.should_receive(:output).with(stories) subject.hot end end end

@steﬀoz stefanoverna.com The acceptance test is still failing. Acceptance tests
are reality checks.

@steﬀoz stefanoverna.com It's time to start a new inner loop
to think about what Story#find should do.

@steﬀoz stefanoverna.com # spec/story_spec.rb require 'spec_helper' require 'redditor/story' describe Redditor::Story
do describe "#find" do it "fetches stories for the specified filter, mapping them into Stories" do url = double("Reddit URL") raw_story = double("story hash") story = double("Story") Redditor::Story.stub(:url_for).with(foo: :bar).and_return(url) Redditor::Story.stub(:fetch).with(url).and_return([ raw_story ]) Redditor::Story.stub(:new).with(raw_story).and_return(story) result = Redditor::Story.find(foo: :bar) result.should have(1).story result.first.should == story end end end

@steﬀoz stefanoverna.com # lib/redditor/story.rb module Redditor class Story def self.find(filters)
fetch(url_for(filters)).map do |raw_story| Story.new(raw_story) end end end end

@steﬀoz stefanoverna.com The acceptance test is still failing. Now let's
deﬁne Story#url_for

@steﬀoz stefanoverna.com Maybe next time :) Until then, https://gist.github.com/2878916

Thanks! @steﬀoz U stefanoverna.com Y

Building Ruby gems

Building Ruby gems

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