Building A Gem From Scratch

Building A Gem From Scratch Madison Ruby, 2011twitter: bphoganemail: brianhogan at napcs.com

Whats A Gem?twitter: bphoganemail: brianhogan at napcs.com

The (normal) Process • Come up with an idea • write some code • Release a gem • Beg people to write tests for youtwitter: bphoganemail: brianhogan at napcs.com

Our process • Come up with an idea and write some code • Throw all that code away • Rewrite it with tests as we go • Release it as a Gem • Enjoy fame and fortunetwitter: bphoganemail: brianhogan at napcs.com

Grabatar (a gem to grab Gravatar URLs) http://www.gravatar.com/avatar/ 6ef8cb7cd7cd58077f0b57e4fa49a969twitter: bphoganemail: brianhogan at napcs.com

Step one: Build tested, working codetwitter: bphoganemail: brianhogan at napcs.com

The basic structure of a Gem gemname.gemspec lib/ gemname version.rb anotherﬁle.rb gemname.rbtwitter: bphoganemail: brianhogan at napcs.com

Tests, Tests, Tests!twitter: bphoganemail: brianhogan at napcs.com

Test::Unit test someﬁle_test.rbtwitter: bphoganemail: brianhogan at napcs.com

Write the test test/grabatar_test.rb require test/unit require lib/grabatar class GrabatarTest < Test::Unit::TestCase def test_displays_version assert Grabatar::VERSION end endtwitter: bphoganemail: brianhogan at napcs.com

Implement the code lib/grabatar/version.rb module Grabatar VERSION = "0.0.2" endtwitter: bphoganemail: brianhogan at napcs.com

Add to the main Ruby ﬁle: lib/grabatar.rb require grabatar/versiontwitter: bphoganemail: brianhogan at napcs.com

Repeat.twitter: bphoganemail: brianhogan at napcs.com

Write the test ﬁrst... test/gravatar_helper.rb require test/unit require grabatar class GravatarTest < Test::Unit::TestCase def test_builds_gravatar_url g = Grabatar::Gravatar.new("bphogan@gmail.com") assert_equal "http://www.gravatar.com/avatar/ 6ef8cb7cd7cd58077f0b57e4fa49a969", g.avatar_url end endtwitter: bphoganemail: brianhogan at napcs.com

Then write the code lib/grabatar/gravatar.rb module Grabatar class Gravatar require digest/md5 def initialize(email) @email = email end def avatar_url hash = Digest::MD5.hexdigest(@email) "http://www.gravatar.com/avatar/#{hash}" end end endtwitter: bphoganemail: brianhogan at napcs.com

Step two: Make A Gemspectwitter: bphoganemail: brianhogan at napcs.com

Gemspecs are easy. grabatar.gemspec require lib/grabatar/version Gem::Specification.new do |s| s.name = "grabatar" s.version = Grabatar::VERSION s.summary = "Fetch avatar image URLs from Gravatar" s.authors = ["Brian Hogan"] s.email = ["bphogan@gmail.com"] s.files = [ "lib/grabatar.rb", "lib/grabatar/version.rb", "lib/grabatar/gravatar.rb", "lib/grabatar/railtie.rb", "lib/grabatar/view_helpers.rb" ] endtwitter: bphoganemail: brianhogan at napcs.com

The manifesttwitter: bphoganemail: brianhogan at napcs.com

bundle gem is bad for you s.files = `git ls-files`.split("n") s.test_files = `git ls-files -- {test,spec,features}/*`.split("n") s.executables = `git ls-files -- bin/*` .split("n").map{ |f| File.basename(f) }twitter: bphoganemail: brianhogan at napcs.com

What lies beneath • .DS_Store • thumbs.db • ~whatever.rb • whatever.mine.rb • Step 3: Rake • Test::Unit taskstwitter: bphoganemail: brianhogan at napcs.com

Craft your manifest by hand s.files = [ "lib/grabatar.rb", "lib/grabatar/version.rb", "lib/grabatar/gravatar.rb", "lib/grabatar/railtie.rb", "lib/grabatar/view_helpers.rb" ]twitter: bphoganemail: brianhogan at napcs.com

Build and install the gem $ gem build grabatar.gemspec $ gem install grabatar-0-0-1.gemtwitter: bphoganemail: brianhogan at napcs.com

Step 4: Rails gemstwitter: bphoganemail: brianhogan at napcs.com

Test ﬁrst test/view_helpers_test.rb require test/unit require grabatar/gravatar require grabatar/view_helpers class ViewHelpers < Test::Unit::TestCase include Grabatar::ViewHelpers def test_generates_avatar_url assert_equal "http://www.gravatar.com/avatar /6ef8cb7cd7cd58077f0b57e4fa49a969", gravatar_url_for("bphogan@gmail.com") end endtwitter: bphoganemail: brianhogan at napcs.com

Create a helper lib/grabatar/view_helpers.rb module Grabatar module ViewHelpers def gravatar_url_for(email) Grabatar::Gravatar.new(email).avatar_url end end endtwitter: bphoganemail: brianhogan at napcs.com

Railtiestwitter: bphoganemail: brianhogan at napcs.com

Include the Helper lib/grabatar/railtie.rb module Grabatar class Railtie < Rails::Railtie initializer "grabatar.view_helpers" do ActionView::Base.send :include, ViewHelpers end end endtwitter: bphoganemail: brianhogan at napcs.com

Only load the Railtie if we have Rails lib/grabatar.rb require grabatar/railtie if defined?(Rails)twitter: bphoganemail: brianhogan at napcs.com

Making a CLI tooltwitter: bphoganemail: brianhogan at napcs.com

Add a bin folder with the ﬁle!twitter: bphoganemail: brianhogan at napcs.com

The CLI program bin/grabatar #!/usr/bin/env ruby require grabatar puts "Grabatar v#{Grabatar::VERSION}" email = ARGV[0] if email.nil? puts "Usage: grabatar <youremail@server.com>" else g = Grabatar::Gravatar.new(email) puts g.avatar_url endtwitter: bphoganemail: brianhogan at napcs.com

Running it $ grabatar bphogan@gmail.com Grabatar v0.0.2 http://www.gravatar.com/avatar/6ef8cb7cd7cd58077f0b57e4fa49a969twitter: bphoganemail: brianhogan at napcs.com

Who wants code? http://github.com/napcs/grabatartwitter: bphoganemail: brianhogan at napcs.com

Thanks! http://spkr8.com/t/8181twitter: bphoganemail: brianhogan at napcs.com

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Building A Gem From Scratch

by Brian Hogan

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