ngpestelos

# see Metaprogramming Ruby, p. 108
class C
  def a_method
    "C#a_method"
  end

  def eigenclass
    class << self; self; end
  end
end

ngpestelos

# see Metaprogramming Ruby, p. 108

s1, s2 = "abc", "def"

s1.instance_eval do
  def swoosh!; reverse; end
end

s1.swoosh! # cba
s2.respond_to?(:swoosh!) # false

ngpestelos

# see Metaprogramming Ruby, p. 107

obj = Object.new
eigenclass = class << obj
  self
end
eigenclass.class # Class

def obj.my_singleton_method; end
eigenclass.instance_methods.grep(/my_/) # ["my_singleton_method"]

ngpestelos

class C; end

class << C
  def my_macro(arg)
    "my_macro(#{arg}) called"
  end
end

class C
  my_macro :x # my_macro(x) called

ngpestelos

# see Metaprogramming Ruby, p. 103

class MyClass
  def self.my_class_method; end
end

ngpestelos

# see Metaprogramming Ruby, p. 101

str = "just a regular string"

def str.title?
  self.upcase == self
end

str.title? # false
str.methods.grep(/title?/) # ["title?"]

ngpestelos

# see Metaprogramming Ruby, p. 93

def add_method_to(a_class)
  a_class.class_eval do
    def m; 'Hello!'; end
  end
end

add_method_to String
puts "foo".m # Hello!

ngpestelos

# see Metaprogramming Ruby, p. 92

result = class MyClass
  self
end

puts result # MyClass

ngpestelos

# see Metaprogramming Ruby, p. 80

def another_double
  p = Proc.new { return 10 }
  result = p.call
  return result * 2 # will not pass here
end

puts another_double

ngpestelos

# see Metaprogramming Ruby, p. 80
def double(callable_object)
  callable_object.call * 2
end

l = lambda { return 10 }
puts double(l) # 20