denisdefreyne

class Employee
  # …
  def ==(other)
    super || (
      self.class == other.class &&
      [email protected]? &&
      @id == other.id
    )
  end
end

denisdefreyne

class Employee
  attr_reader :id
  attr_reader :name

  def initialize(id, name)
    @id = id
    @name = name
  end
end

denisdefreyne

class Point
  # …
  def ==(other)
    self.class == other.class &&
      @x == other.x &&
      @y == other.y
  end
end

denisdefreyne

Float::NAN == Float::NAN   # => false

denisdefreyne

a != b          # => true
a != "rabbit"   # => true

denisdefreyne

a = Point.new(4, 6)
b = Point.new(3, 7)
a_also = Point.new(4, 6)

a == a        # => true
a == b        # => false
a == "soup"   # => false
a == a_also   # => true

denisdefreyne

class Point
  # …
  def ==(other)
    self.class == other.class &&
      @x == other.x &&
      @y == other.y
  end
end

denisdefreyne

a = Point.new(4, 6)
b = Point.new(3, 7)
a_also = Point.new(4, 6)

a == a        # => true
a == b        # => false
a == "soup"   # => false
a == a_also   # => false?!

denisdefreyne

class Point
  attr_reader :x
  attr_reader :y

  def initialize(x, y)
    @x = x
    @y = y
  end
end

denisdefreyne

geb = Book.find_by(title: "Gödel, Escher, Bach")
also_geb = Book.find_by(isbn: "978-0-14-028920-6")

geb == also_geb   # => true