Ruby Advanced - Metaprogramming & Design Patterns

Metaprogramming adalah kemampuan program untuk menulis kode saat runtime.

Apa itu Metaprogramming?

Metaprogramming adalah teknik di mana kode Ruby dapat:

• Introspect dirinya sendiri
• Memodifikasi struktur class/module saat runtime
• Generate methods dinamis
• Memanipulasi object model

Mengapa Metaprogramming?

• Mengurangi code repetition (DRY)
• Membuat DSL (Domain-Specific Language)
• Framework magic (Rails menggunakan metaprogramming heavily)

Object Model Ruby

class Person
  def initialize(name)
    @name = name
  end
end

person = Person.new("Alice")

# Introspection
puts person.class              # Person
puts Person.superclass         # Object
puts Object.superclass         # BasicObject

# Check methods
puts person.methods.sort       # List all methods
puts person.respond_to?(:name) # false (no getter)

Open Classes

Ruby memungkinkan Anda membuka class yang sudah ada dan menambahkan methods:

# Menambahkan method ke String
class String
  def shout
    self.upcase + "!!!"
  end
end

puts "hello".shout  # "HELLO!!!"

⚠️ Monkey Patching Warning: Hati-hati mengubah core classes!

send Method

class Calculator
  def add(a, b)
    a + b
  end
  
  def subtract(a, b)
    a - b
  end
end

calc = Calculator.new

# Normal call
puts calc.add(5, 3)  # 8

# Dynamic call with send
operation = :add
puts calc.send(operation, 5, 3)  # 8

operation = :subtract
puts calc.send(operation, 10, 4)  # 6

public_send vs send

class Account
  def balance
    @balance
  end
  
  private
  
  def secret_method
    "Secret!"
  end
end

account = Account.new

# send can call private methods
puts account.send(:secret_method)  # "Secret!"

# public_send only calls public methods
# account.public_send(:secret_method)  # Error!