Dr Nic
drnicwilliams.com
DIY Syntax

$ irb
>> $KCODE = \"u\"
>> \"\\303\\274\"
=> \"ü\"

Isn’t this nicer?
>> U00FC
=> \"ü\"

$ sudo gem install charesc
$ irb
>> $KCODE = \"u\"
>> require 'rubygems'
>> require 'charesc'
>> \"charesc is made by Martin D#{U00FC}rst\"
=> \"charesc is made by Martin Dürst\"
>> U00FC
=> \"ü\"
>> \"\\303\\274\"
=> \"ü\"
charesc

Active
Records
SELECT * FROM conferences WHERE (start_date > '2007-06-07')
# But, much nicer is...

Active
Records
SELECT * FROM conferences WHERE (start_date > '2007-06-07')
# But, much nicer is...
Conference.find(:all,
:conditions => [‘start_date > ?’,Date.today])

Active Records
SELECT conferences.\"id\" AS t0_r0,
conferences.\"name\" AS t0_r2, ...,
conference_sessions.\"id\" AS t1_r0,
conference_sessions.\"conference_id\" AS t1_r1, ...
FROM conferences
LEFT OUTER JOIN conference_sessions
ON conference_sessions.conference_id = conferences.id
WHERE (start_date < '2007-05-26')
# But, definitely easier and nicer is...

Active Records
SELECT conferences.\"id\" AS t0_r0,
conferences.\"name\" AS t0_r2, ...,
conference_sessions.\"id\" AS t1_r0,
conference_sessions.\"conference_id\" AS t1_r1, ...
FROM conferences
LEFT OUTER JOIN conference_sessions
ON conference_sessions.conference_id = conferences.id
WHERE (start_date < '2007-05-26')
# But, definitely easier and nicer is...
Conference.find(:all,
:conditions => ['start_date < ?', Date.today],
:include => :conference_sessions)

Sexy
Syntax
ActiveRecords
- no SQL
... + marshalling
to objects

Sexy
Syntax
Convenient
Code

Schemas
create_table :conferences do |t|
t.fkey :user
t.string :name, :limit => 50
t.text :description
t.date :start_date, :end_date
t.auto_dates
end
# instead of...
I can never
remember
SQL syntax

Schemas
create_table :conferences do |t|
t.fkey :user
t.string :name, :limit => 50
t.text :description
t.date :start_date, :end_date
t.auto_dates
end
# instead of...
Look up SQL on
I can never
remember
SQL syntax

Composite
Primary Keys
ProductHistory.find(:first, :conditions =>
['id = ? and start_date = ?', 56, Date.new(2000,5,5)])
# rather...
What about
Ruby syntax
improving on
other Ruby
syntax?

Composite
Primary Keys
ProductHistory.find(:first, :conditions =>
['id = ? and start_date = ?', 56, Date.new(2000,5,5)])
# rather...
ProductHistory.find(56, Date.new(2000,5,5))
What about
Ruby syntax
class ProductHistory < ActiveRecord::Base improving on
other Ruby
set_primary_keys :id, :start_date syntax?
end

What’s this do? #1
Nice syntax
can quickly tell
you want the
code will does
@user.conference_sessions_for(@conference)

What’s this do? #1
Nice syntax
can quickly tell
you want the
code will does
@user.conference_sessions_for(@conference)
# Returns all ConferenceSessions
# for a user at a conference

What’s this do? #2
@conference_attendees.map_id_and_login_and_full_name

What’s this do? #2
@conference_attendees.map_id_and_login_and_full_name
# map {|att| [att.id, att.login, att.full_name]}

What’s this do? #3
User.find(params[:id])

What’s this do? #3
@to_user = @target_db::User.find(params[:id])
User.find(params[:id])

What’s this do? #3
@to_user = @target_db::User.find(params[:id])
User.find(params[:id])
@to_user.update(@from_db::User.find(params[:id]))

What’s this do? #3
@to_user = @target_db::User.find(params[:id])
User.find(params[:id])
@to_user.update(@from_db::User.find(params[:id]))
# Copies a User from one database to another
# see Magic Multi-Connection
# http://magicmodels.rubyforge.org

Let’s see how they
work...

What’s this do? #1
Nice syntax
can quickly tell
you want the
code will does
@user.conference_sessions_for(@conference)

What’s this do? #1
Nice syntax
can quickly tell
you want the
code will does
@user.conference_sessions_for(@conference)
# Returns all ConferenceSessions
# for a user at a conference

What’s this do? #1
class User < ActiveRecord::Base
has_many :conference_sessions
def conference_sessions_for(conference)
conference_sessions.find(:all,
:conditions => ['conference_id = ?', conference])
end
end
No meta-magic, but it gives nice syntax

What’s this do? #2
@attendees.map_by_id_and_login_and_full_name
# map {|att| [att.id, att.login, att.full_name]}

Cute ways to use #map
@users = User.find(:all)
@users.map {|user| user.login}
# => ['drnic', 'topfunky', 'dhh']

Cute ways to use #map
@users = User.find(:all)
@users.map {|user| user.login}
# => ['drnic', 'topfunky', 'dhh']
@users.map &:login
# => ['drnic', 'topfunky', 'dhh']

Cute ways to use #map
@users = User.find(:all)
@users.map {|user| user.login}
# => ['drnic', 'topfunky', 'dhh']
@users.map &:login
# => ['drnic', 'topfunky', 'dhh']
# but it gets ugly when you chain them...
@users.map(&:login).map(&:size)
# => [5, 8, 3]

Cute ways to use #map
# So, instead of...
@users.map(&:login).map(&:size)
# We might like...
@users.map_login.map_size

Remember find_by_xxx ?
def method_missing(method_id, *arguments)
pattern = /^find_(all_by|by)_([_a-zA-Z]\\w*)$/
if match = pattern.match(method_id.to_s)
finder = determine_finder(match)
# from active_record/base.rb, line 1190

Dissecting the request
def method_missing(method, *args, &block)
pattern = /(map|select|...)_by_([\\w\\_]+\\??)/
if (match = method.match(pattern))
iterator, callmethod = match[1], match[2]
# changed ‘find’ to ‘map’
# or select, reject, each, collect...

Iterating the request
# continued...
iterator, callmethod = match[1], match[2]
self.send(iterator) {|obj| obj.send callmethod }
# @array.map_by_foo
# callmethod => ‘foo’
# #foo invoked on each element of Array

Iterating many callmethods
# continued...
iterator, callmethod = match[1], match[2]
callmethods = callmethod.split('_and_')
callmethods.map do |callmethod|
self.send(iterator) {|obj| obj.send callmethod }
end
# @array.map_by_foo_and_bar
# callmethods => [‘foo’, ‘bar’]
# #foo and #bar invoked on each element of Array

map_by_method gem
# for complete source:
$ gem install map_by_method
$ mate $RUBYGEMS_PATH/map_by_method-0.6.0/lib/map_by_method.rb

map_by_method gem
# for complete source:
$ gem install map_by_method
$ mate $RUBYGEMS_PATH/map_by_method-0.6.0/lib/map_by_method.rb
# add the following to your ~/.irbrc
require 'map_by_method'

What’s this do? #3
User.find(params[:id])

What’s this do? #3
@to_user = @target_db::User.find(params[:id])
User.find(params[:id])

What’s this do? #3
@to_user = @target_db::User.find(params[:id])
User.find(params[:id])
@to_user.update(@from_db::User.find(params[:id]))

What’s this do? #3
@to_user = @target_db::User.find(params[:id])
User.find(params[:id])
@to_user.update(@from_db::User.find(params[:id]))
# Copies a User from one database to another
# see Magic Multi-Connection
# http://magicmodels.rubyforge.org

Magic
Multi-Connections
@db::User.find(params[:id])

MMC - alternate ideas
@db::User.find(params[:id])
# but I would have preferred...
User.find(params[:id]).from_db(@db)

MMC - alternate ideas
@db::User.find(params[:id])
# but I would have preferred...
User.find(params[:id]).from_db(@db)
# but we’d need FindProxies
# like AssociationProxies

But what does this mean?
@db::User

class creator helper
class Module
def create_class(class_name, superclass = Object, &block)
klass = Class.new superclass, &block
self.const_set class_name, klass
end
end
>> module Connection; end
>> Connection.create_class 'User'
=> Connection::User

class creator helper
class Module
def create_class(class_name, superclass = Object, &block)
klass = Class.new superclass, &block
self.const_set class_name, klass
end
end
>> module Connection; end
>> Connection.create_class 'User'
=> Connection::User
@db::User

But...the class...
“when to create it?”
When you ask for it!

const_missing
class Module
alias :old_const_missing :const_missing
def const_missing(const_id)
return old_const_missing(const_id) rescue nil
target_class = \"::\\#{const_id}\".constantize rescue nil
raise NameError.new(\"bad constant \\#{const_id}\") unless target_class
create_class(const_id, target_class)
end
end

const_missing
class Module
alias :old_const_missing :const_missing
def const_missing(const_id)
return old_const_missing(const_id) rescue nil
target_class = \"::\\#{const_id}\".constantize rescue nil
raise NameError.new(\"bad constant \\#{const_id}\") unless target_class
create_class(const_id, target_class)
end
end
magic multi-connections

Picks up root classes
class Person; end
module Remote
establish_connection :other
end
>> Remote::Person.superclass
=> Person

const_missing
class Module
def const_missing(const_id)
return old_const_missing(class_id) rescue nil
table_name = DrNicMagicModels::Schema.models[const_id]
raise NameError.new(\"bad constant #{const_id}\") unless table_name
create_class(class_id, ActiveRecord::Base) do
set_table_name table_name
end
end
end
“Does the class name match to a table name?”

const_missing
class Module
def const_missing(const_id)
return old_const_missing(class_id) rescue nil
table_name = DrNicMagicModels::Schema.models[const_id]
raise NameError.new(\"bad constant #{const_id}\") unless table_name
create_class(class_id, ActiveRecord::Base) do
set_table_name table_name
end
end
dr nic’s magic models
end
“Does the class name match to a table name?”

const_missing
>> U00FC
=> \"ü\"

const_missing
def const_missing(const)
if const.to_s =~ /^((U( [0-9ABCEF][0-9A-F]{3} # general BMP
| D[0-7][0-9A-F]{2} # excluding surrogates
| [1-9A-F][0-9A-F]{4} # planes 1-15
| 10 [0-9A-F]{4} # plane 16
)
)*
)
$/ix
unescaped = $1.split(/[Uu]/)[1..-1].collect do |hex| hex.to_i(16) end.pack('U*')

Sexy
Syntax
Convenient
Code

Enjoy En !
drnicwilliams.com
by Dr Nic