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rails engines
rails-engines.org
James Adam
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“Hello”
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a bit of background
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for many clients
we build applications
simultaneously
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common
functional
aspects
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User Control
Auditing
Reporting
Job Scheduling
Charts & Graphs
Data Storage
Help Systems
Content Management
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many applications
many aspects
lots of code
✕
lots of maintenance
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i am lazy
i am a
conscientious
developer
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Reuse is overrated
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Reuse is essential
... it just depends on the context
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e.g.
a simple
help system
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db/migrate/001_add_help.rb
class AddHelp < ActiveRecord::Migration
def self.up
create_table :help_pages do |t|
t.column :key, :string
t.column :title, :string
t.column :content, :text
end
end
def self.down
drop_table :help_pages
end
end
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models/help_page.rb
class HelpPage < ActiveRecord::Base
end
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helpers/help_helper.rb
module HelpHelper
def help_link(key=nil)
key ||= params[:controller] + ‘/’ +
params[:action]
page = HelpPage.find_by_key(key)
unless page.nil?
link_to(‘[help]’, {:controller => ‘help’,
:action => ‘show’,
:id => page},
{:class => ‘help_link’})
end
end
end
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and in our application:
MeatSword :: Basket
Please find your basket contents below. <%= help_link %>
<% @cart.items.each do |item| %> <%= render :partial => ‘cart/item’ %> <%= link_to(‘[X]’, :action => ‘remove’, :id => item) %> <%= help_link ‘remove_item’ %> <% end %>Slide 16
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public/stylesheets/help.css
a.help_link {
text-decoration: underline;
color: #0F0;
font-size: 0.8em;
}
a.help_link:hover {
text-decoration: none;
color: #000;
background-color: #0F0;
}
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generators
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rails generators
$ script/generate model HelpPage
create app/models/help_page.rb
create test/fixtures/help_pages.yml
create test/unit/help_page_test.rb
$ script/generate controller Help
create app/controllers/help_controller.rb
create app/helpers/help_helper.rb
create test/functional/... # and so on
$ script/generate scaffold HelpPage Help
create app/views/help/show.rhtml
create app/views/help/edit.rhtml # ... etc
generators
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a package of
code templates
processed by ERb
generators
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script/generate my_help_system
our help generator
generators
Text
create app/models/help_page.rb
create app/controllers/help_controller.rb
create app/helpers/help_helper.rb
create app/views/help/show.rhtml
create app/views/help/edit.rhtml
create app/views/help/list.rhtml
create app/views/help/_form.rhtml
create db/migrations/001_add_help.rb
create lib/help_system.rb
create lib/tasks/help.rake
create public/stylesheets/help.css
create test/unit/help_test.rb
create test/fixtures/help_pages.yml
$
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generators
complete
subsystem
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generators
share with
rubygems
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meanwhile, in our app:
class HelpPage < ActiveRecord::Base
# only words containing the
# letter ‘x’ are important
def summarize(limit=20)
content.split.select { |word|
word.include?(’x’)
}.flatten[0..limit].join
end
end
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generators
difficult to
maintain
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plugins
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plugins
init.rb
start-up
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plugins
install.rb
post-install
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plugins
lib/
added to $LOAD_PATH
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plugins
shareable
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sharing with
svn:externals
plugins
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$ svn propset svn:externals \
‘my_plugin svn://server/my_plugin’ \
vendor/plugins
property 'svn:externals' set
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No content
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$ svn update vendor/plugins
A vendor/plugins/my_plugin/monkey.rb
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monkey.rb monkey.rb monkey.rb
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plugins
maintainable
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help plugin
help.rb help_helper.rb help_controller.rb
show.rhtml help.css 001_add_help.rb
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plugins
only code
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engines
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a login system?
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huge, monolithic,
apocalyptic
high-level
components?
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easy way to annoy
DHH?
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plugins.succ
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plugins + 1
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plugins.succ
(plus a little bit more that we
found REALLY useful)
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a mechanism
for sharing
MVC ‘slices’
between your apps
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class ArnoldController < ApplicationController
def terminator
@u = User.find_by_name(’Sarah Conner’)
@u.destroy
end
def total_recall
@quote = 'Get your ass to Mars!'
render :text => @quote
end
def twins
render :partial => ‘de_vito’,
:locals => { :julius => User.find
end
def sixth_day
User.find(:first).clone
end
end
ruby code
public
assets
<% for member in fellowship do %>
<%= member.name %>
<%= member.gift_from_galadrial
<%= member.ringbearer? %>
<% end %>
New member?
<%= form_tag :action => ‘add_dude’, :m <%= text_field :new_guy, :species %> <%= text_area :new_guy, :biography % <%= check_box :new_guy, :pawn_of_sau <%= end_form_tag %>
views, partials
class JazzMigration < ActiveRecord::Mi
def self.up
create_table :instruments do |t|
t.column :name, :string
t.column :type_id, :integer
t.column :family, :string
t.column :range, :integer, :defa
t.column :position_id, :integer,
end
Instrument.create_default_instrume
JazzPlayers.connect_to_instruments
end
def self.down
JazzPlayers.disconnect_from_instru
drop_table :instruments end
database
migrations
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intuitive
layout
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control your
environment
Engines.start :help,
:reporting,
:user_basics,
:user_interface
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shared
public assets
<%= engine_stylesheet :help %>
<%= engine_javascript :user_control %>
MeatSword.com
MeatSword :: Meat beyond Meat.
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migrations
rake db:migrate:engines
$
Migrated help
Migrated meat_sword
Migrated south
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... or just use them like
plugins
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developing
engines
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....guess
where
the files go
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init.rb
init_engine.rb
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generating an engine
$ script/generate engine Help
Author's name: James Adam
Author's email: james.adam@gmail.com
We can automatically generate a license for you:
0) MIT 1) GPL 2) LGPL 3) None
Please select a license: 0
create vendor/plugins/help
create vendor/plugins/help/README
create vendor/plugins/help/install.rb
create vendor/plugins/help/init_engine.rb
create vendor/plugins/help/app
create vendor/plugins/help/app/models
create vendor/plugins/help/app/controllers
create vendor/plugins/help/app/helpers
create vendor/plugins/help/app/views
create vendor/plugins/help/db
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client customisation
module HelpHelper
def help_link(key=nil) # overrides method in engine
key ||= params[:controller] + ‘/’ +
params[:action]
page = HelpPage.find_by_key(key)
if page.nil?
link_to(’Add help page?’, {:controller => ‘help’,
:action => ‘create’, :key => key})
else
link_to(‘More information...’, # different text
{:controller => ‘help’,
:action => ‘show’,
:id => page},
{:class => ‘info_link’})
end
end
end
/app/helpers/help_helper.rb
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extending & overriding
class HelpController < ApplicationController
def create # method NOT in engine
if request.post?
page = HelpPage.new(params[:new_page])
unless page.save
flash[:message] = ‘Oh noes!’
end
end
end
end
/app/controllers/help_controller.rb
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/app/views/help/show.rhtml
overriding views
NameOfThisParticularClient.com
Help » <%= @page.title %>
<%= render :partial => ‘index_links’ %>
<%= @page.content %>
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WARNING:
INCOMING
CUSS-WORD
WARNING:
INCOMING
CUSS-WORD
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WHAT
THE HELL
IS THIS
BLACK MAGIC
VOODOO?
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a set of small
extensions to Rails
http://svn.rails-engines.org/plugins/engines/
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dependencies_extensions.rb
overriding code
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action_view_extensions.rb
action_mailer_extensions.rb
overriding views
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action_view_extensions.rb
public assets
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migration_extensions.rb
migrations in plugins
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testing_extensions.rb
flexible fixtures
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ruby_extensions.rb
cheap configuration
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engines.rb
plugin management
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engines are a
mechanism for sharing
maintainable code
between your apps
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where from here?
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bundles
<%= require_bundle :help %>
MeatSword.org
More meat than you can shake a stick at.
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happy coexistence
with Rails Core
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feeding back to
plugin system
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opinionated
open source
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rails engines
rails-engines.org
James Adam
dev.rails-engines.org
www.rails-engines.org
api.rails-engines.org
issues/patches:
propaganda:
docs: