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Ruby Metaprogramming
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Sergio Gil
March 25, 2012
Programming
11
2.7k
Ruby Metaprogramming
Slides from my talk at #codemotion #es (Madrid, March 24th 2012).
http://codemotion.es/
Sergio Gil
March 25, 2012
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Transcript
Ruby Metaprogramming Sergio Gil (@porras)
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require 'excel' require 'sql' Excel.load('file.xls').each do |row| SQL.insert(row) end
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require 'html' require 'http' page = HTML.load(HTTP.get('http://example.com/')) page.links.each do |link|
HTTP.get(link).save end
class Company def projects HTTP::Request.new('/projects').get end def people HTTP::Request.new('/people').get end
def clients HTTP::Request.new('/clients').get end ... end
Yukihiro Matsumoto ‘Matz’, Ruby creator
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Metaprogramming
defining metaprogramming
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Classes Instances Methods Variables Constants Modules
Classes Instances Methods Variables Constants Modules
Memory
Classes Instances Methods Variables Constants Modules
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>> str = "hola" => "hola"
>> str = "hola" => "hola" >> str.methods => [...,
:reverse, ...]
>> str = "hola" => "hola" >> str.methods => [...,
:reverse, ...] >> def str.reverse "adios" end
>> str = "hola" => "hola" >> str.methods => [...,
:reverse, ...] >> def str.reverse "adios" end >> str.reverse
>> str = "hola" => "hola" >> str.methods => [...,
:reverse, ...] >> def str.reverse "adios" end >> str.reverse => "adios"
Ruby Object Model: The Musical
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It’s all about DRYness
class Company def projects HTTP::Request.new('/projects').get end def people HTTP::Request.new('/people').get end
... end
class Company def projects get('/projects') end def people get('/people') end
... private def get(url) HTTP::Request.new(url).get end end
Is that all?
Let Ruby create your methods for you
class Company [:projects, :people, ...].each do |method| eval %Q{ def
#{method} HTTP::Request.new('/#{method}').get end } end end
class Company [:projects, :people, ...].each do |method| define_method method do
HTTP::Request.new("/#{method}").get end end end
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It’s all about expresivity
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module HTTP def get(*methods) methods.each do |method| define_method method do
HTTP::Request.new("/#{method}").get end end end end
module HTTP def get(*methods) methods.each do |method| define_method method do
HTTP::Request.new("/#{method}").get end end end end class Company extend HTTP get :projects, :people, ... end
“I Taw a Putty DSL...”
class Company extend HTTP get :projects, :people, ... end
It’s all about flexibility
class Company def method_missing(method, *args, &blk) HTTP::Request.new("/#{method}").get end end
class Company def method_missing(method, *args, &blk) HTTP::Request.new("/#{method}").get end end
It’s all common sense
metaprogramming == programming
same trade-offs apply
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“Cleverness cannot win. The only weapons we have are simplicity
and convention” http://alarmingdevelopment.org/?p=422
Thank you :)