nusco

class Bird
  def fly
    "Wheee!"
  end
end

class Duck < Bird
end

donald = Duck.new

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module Bird
  def fly
    "Wheee!"
  end
end

class Duck
  include Bird
end

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# =======================
# Spell: Object Extension
# =======================

# Define Singleton Methods by mixing a module into an object’s singleton class.

obj = Object.new

module M
  def my_method

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# ======================
# Spell: Class Extension
# ======================

# Define class methods by mixing a module into a class’s singleton class
# (a special case of Object Extension - http://gist.github.com/534667).

class C; end

module M

nusco

# =======================
# Spell: Singleton Method
# =======================

# Define a method on a single object.

obj = "abc"

class << obj
  def my_singleton_method

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# ==================
# Spell: Monkeypatch
# ==================

# Change the features of an existing class.

"abc".reverse # => "cba"

class String
  def reverse

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# =====================
# Spell: Argument Array
# =====================

# Collapse a list of arguments into an array.

def my_method(*args)
  args.map {|arg| arg.reverse }
end

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# ===================
# Spell: Around Alias
# ===================

# Call the previous, aliased version of a method from a redefined method.

class String
  alias :old_reverse :reverse

  def reverse

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# ===================
# Spell: Ghost Method
# ===================

# Respond to a message that doesn’t have an associated method.

class C
  def method_missing(name, *args)
    name.to_s.reverse
  end

nusco

# ===================
# Spell: Blank Slate
# ===================

# Remove methods from an object to turn them into Ghost Methods (http://gist.github.com/534776).

class C
  def method_missing(name, *args)
    "a Ghost Method"
  end