Inheritance

class3.rb

Gate Classes

# Class names must be capitalized.  Technically, it's a constant.
class Fred
  
  # The initialize method is the constructor.  The @val is
  # an object value.
  def initialize(v)
    @val = v
  end

  # Set it and get it.
  def set(v)
    @val = v
  end

  def to_s
    return "Fred(val=" + @val.to_s + ")"
  end

  # Since a simple access function is so common, ruby lets you declare one
  # automatically, like this:
  attr_reader :val
  # You can list any number of object variables. Separate by commas, and each
  # needs its own colon
  # attr_reader :fred, :joe, :alex, :sally
end

class Alice <Fred
  # We have a message, too.
  def initialize(n, m)
    super(n)
    @msg = m
  end

  # Takes the base result and changes the class name.
  def to_s
    ret = super
    ret.gsub!(/Fred/, 'Alice')
    return ret + ' ' + @msg + '!'
  end

  # The = allows the method to be used on the right, and the left of the
  # assignment is the parameter.
  def appmsg=(more)
    @msg += more
  end

  # Like attr_reader, if you want the data to be assignable.
  attr_writer :msg
end

a = Fred.new(45)
b = Alice.new(11, "So there")

print "A: a = ", a, "\n   b = ", b, "\n"

print "B: ", a.val, " ", b.val, "\n"

b.msg = "Never"
print "B: b = ", b, "\n"
b.appmsg = " In a million years"
print "C: b = ", b, "\n"

Inheritance

Gate Classes