Thaichor Seng is a junior developer currently working on a restaurant menu application using Ruby on Rails. The document discusses metaprogramming in Ruby, which is writing code that writes code. It provides examples of metaprogramming methods like define_method(), method_missing(), class_eval(), and eval(). These methods allow dynamically adding methods to classes at runtime rather than during class definition.

2. Name: Thaichor Seng
Position: Junior Developer at Yoolk.Inc
I‟m currently working on creating
Restaurant Menu application
using Ruby on Rails.

3. • Sugar Syntax
• Dynamic Language
• English Like
• Lots of built-in methods
• Metaprogramming

4. Metaprogramming is writing code that writes code.
Here are some method using for metaprogramming:
• define_method()
• method_missing()
• class_eval()
• eval()

5. class MyClass
define_method :my_method do |my_arg|
my_arg * 3
end
# def my_method(my_arg)
# my_arg * 3
# end
end
obj = MyClass.new
obj.my_method(2) # => 6

6. class Currency
def initialize(value)
@value = value
end
[:usd, :riel, :yen, :bat].each do |method|
define_method “to_#{method}” do
“#{@value.to_s} #{method.to_s}”
end
end
end
c = Currency.new(14)
c.to_usd # 14 usd
c.to_riel # 14 riel

7. class Lawyer
end
nick = Lawyer.new
nick.talk_simple
NoMethodError: undefined method „talk_simple' for
#<Lawyer:0x3c848>

8. class Lawyer
def method_missing(method, *args)
puts "You called: #{method}(#{args.join(', ')})"
end
end
nick = Lawyer.new
nick.talk_simple # You called talk_simple()
Nick.talk(a, b) # You called talk(a, b)

9. class MyOpenStruct
def initialize
@attributes = {}
end
def method_missing(name, *args)
attribute = name.to_s
if attribute =~ /=$/
@attributes[attribute.chop] = args[0]
else
@attributes[attribute]
end
end
end
icecream = MyOpenStruct.new
icecream.flavor = "vanilla“ # nil
icecream.flavor # vanilla

10. def add_method_to(a_class)
a_class.class_eval do
def m
'Hello!'
end
end
end
add_method_to String
"abc".m # => "Hello!“

11. map = { "update" => "deploy:update" ,
"restart" => "deploy:restart" ,
"cleanup" => "deploy:cleanup" }
map.each do |old, new|
eval "task(#{old.inspect}) do
warn "[DEPRECATED] `#{old}' is deprecated. Use `#{new}' instead."
find_and_execute_task(#{new.inspect})
end"
end

12. The End