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# =================
# Spell: Open Class
# =================

# Modify an existing class.

class String
  def my_string_method
    "my method"
  end

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# ================
# Spell: Nil Guard
# ================

# Override a reference to nil with an “or.”

x = nil
y=x || "avalue" # =>"avalue"

# For more information: http://www.pragprog.com/titles/ppmetr/metaprogramming-ruby

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# ================
# Spell: Namespace
# ================

# Define constants within a module to avoid name clashes.

module MyNamespace
  class Array
    def to_s
      "my class"

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# ======================
# Spell: Named Arguments
# ======================

# Collect method arguments into a hash to identify them by name.

def my_method(args)
  args[:arg2]
end

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# ===================
# Spell: Mimic Method
# ===================

# Disguise a method as another language construct.

def BaseClass(name)
  name == "string" ? String : Object
end

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# =============================
# Spell: Lazy Instance Variable
# =============================

# Wait until the first access to initialize an instance variable.

class C
  def attribute
    @attribute = @attribute || "some value"
  end

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# ====================
# Spell: Kernel Method
# ====================

# Define a method in module Kernel to make the method available to all objects.

module Kernel
  def a_method
    "a kernel method"
  end

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# =================
# Spell: Flat Scope
# =================

# Use a closure to share variables between two scopes.

class C
  def an_attribute
    @attr
  end

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# ====================
# Spell: Dynamic Proxy
# ====================

# Forward to another object any messages that don’t match a method.

class MyDynamicProxy
  def initialize(target)
    @target = target
  end

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# =====================
# Spell: Dynamic Method
# =====================

# Decide how to define a method at runtime.

class C
end

C.class_eval do