面向對象編程（Object-Oriented Programming，OOP）是一種編程范式，它使用“對象”來表示現實世界中的事物，通過封裝、繼承和多態等特性來實現代碼的復用和模塊化。在Ruby中，面向對象編程的應用非常廣泛，以下是一些常見的應用場景：

1. 封裝（Encapsulation）

封裝是將對象的屬性和方法隱藏起來，只暴露必要的接口。這樣可以保護對象內部的狀態不被外部直接修改，提高代碼的安全性和可維護性。

class Car
  attr_reader :make, :model, :year

  def initialize(make, model, year)
    @make = make
    @model = model
    @year = year
  end

  def drive
    puts "Driving the #{@make} #{@model}..."
  end
end

car = Car.new("Toyota", "Corolla", 2020)
car.drive

2. 繼承（Inheritance）

繼承允許一個類（子類）繼承另一個類（父類）的屬性和方法。子類可以重寫或擴展父類的方法，實現代碼的復用。

class Vehicle
  attr_accessor :make, :model, :year

  def initialize(make, model, year)
    @make = make
    @model = model
    @year = year
  end

  def drive
    puts "Driving..."
  end
end

class Car < Vehicle
  def drive
    puts "Driving the #{@make} #{@model}..."
  end
end

bike = Vehicle.new("Honda", "CBR", 2021)
bike.drive

car = Car.new("Toyota", "Corolla", 2020)
car.drive

3. 多態（Polymorphism）

多態是指不同類的對象可以使用相同的接口。通過多態，可以在運行時根據對象的實際類型調用相應的方法，提高代碼的靈活性和可擴展性。

class Vehicle
  attr_accessor :make, :model, :year

  def initialize(make, model, year)
    @make = make
    @model = model
    @year = year
  end

  def drive
    puts "Driving..."
  end
end

class Car < Vehicle
  def drive
    puts "Driving the #{@make} #{@model}..."
  end
end

class Motorcycle < Vehicle
  def drive
    puts "Riding the #{@make} #{@model}..."
  end
end

vehicles = [Car.new("Toyota", "Corolla", 2020), Motorcycle.new("Honda", "CBR", 2021)]

vehicles.each do |vehicle|
  vehicle.drive
end

4. 模塊（Modules）

模塊是一種代碼復用的方式，可以將一組相關的函數和方法封裝在一個模塊中，然后在其他類中通過include關鍵字引入。

module Drivable
  def drive
    puts "Driving..."
  end
end

class Vehicle
  include Drivable

  attr_accessor :make, :model, :year

  def initialize(make, model, year)
    @make = make
    @model = model
    @year = year
  end
end

car = Vehicle.new("Toyota", "Corolla", 2020)
car.drive

5. 抽象類（Abstract Classes）

抽象類是不能實例化的類，通常用于定義一些通用的方法和屬性，供子類實現。

class Vehicle
  attr_accessor :make, :model, :year

  def initialize(make, model, year)
    @make = make
    @model = model
    @year = year
  end

  def drive
    raise NotImplementedError, "This method must be overridden in subclass"
  end
end

class Car < Vehicle
  def drive
    puts "Driving the #{@make} #{@model}..."
  end
end

class Motorcycle < Vehicle
  def drive
    puts "Riding the #{@make} #{@model}..."
  end
end

vehicles = [Car.new("Toyota", "Corolla", 2020), Motorcycle.new("Honda", "CBR", 2021)]

vehicles.each do |vehicle|
  vehicle.drive
end

通過這些面向對象編程的特性，Ruby可以編寫出結構清晰、易于維護和擴展的代碼。