แนวคิด OOP (Object-Oriented Programming) มีหลักการ 4 อย่างหลัก ๆ
- Encapsulation (การห่อหุ้มข้อมูล)
- Inheritance (การสืบทอดคุณสมบัติ)
- Polymorphism (พ้องรูป) ความสามารถในการใช้ชื่อ method เดียวกันในหลายรูปแบบ
- Abstraction (นามธรรม) การซ่อนความซับซ้อน และเปิดเผยเฉพาะสิ่งที่จำเป็น คือ รู้แค่ว่ามันทำได้ แต่ไม่ต้องรู้ว่าทำอย่างไร
ต่อไปนี้คือตัวอย่างโค้ด OOP พื้นฐานในหลายภาษา
1. Java
abstract class Animal {
protected String name;
public Animal(String name) {
this.name = name;
}
public abstract String speak();
}
class Dog extends Animal {
public Dog(String name) { super(name); }
public String speak() { return name + " says Woof!"; }
}
class Cat extends Animal {
public Cat(String name) { super(name); }
public String speak() { return name + " says Meow!"; }
}
public class Main {
public static void main(String[] args) {
Animal[] animals = { new Dog("Buddy"), new Cat("Milo") };
for (Animal a : animals) {
System.out.println(a.speak());
}
}
}
2. JavaScript
class Animal {
constructor(name) {
this._name = name;
if (new.target === Animal) throw new Error("Abstract class");
}
speak() {
throw new Error("Must override");
}
}
class Dog extends Animal {
speak() { return `${this._name} says Woof!`; }
}
class Cat extends Animal {
speak() { return `${this._name} says Meow!`; }
}
function main() {
const animals = [new Dog("Buddy"), new Cat("Milo")];
animals.forEach(a => console.log(a.speak()));
}
main();
3. TypeScript
abstract class Animal {
protected name: string;
constructor(name: string) { this.name = name; }
abstract speak(): string;
}
class Dog extends Animal {
speak(): string { return `${this.name} says Woof!`; }
}
class Cat extends Animal {
speak(): string { return `${this.name} says Meow!`; }
}
function main() {
const animals: Animal[] = [new Dog("Buddy"), new Cat("Milo")];
animals.forEach(a => console.log(a.speak()));
}
main();
4. Python
from abc import ABC, abstractmethod
class Animal(ABC):
def __init__(self, name):
self._name = name # Encapsulation
@abstractmethod
def speak(self):
pass
class Dog(Animal):
def speak(self):
return f"{self._name} says Woof!"
class Cat(Animal):
def speak(self):
return f"{self._name} says Meow!"
def main():
animals = [Dog("Buddy"), Cat("Milo")]
for a in animals:
print(a.speak())
if __name__ == "__main__":
main()
5. C#
abstract class Animal {
protected string name;
public Animal(string name) { this.name = name; }
public abstract string Speak();
}
class Dog : Animal {
public Dog(string name) : base(name) { }
public override string Speak() => $"{name} says Woof!";
}
class Cat : Animal {
public Cat(string name) : base(name) { }
public override string Speak() => $"{name} says Meow!";
}
class Program {
static void Main() {
var animals = new List<Animal> { new Dog("Buddy"), new Cat("Milo") };
animals.ForEach(a => Console.WriteLine(a.Speak()));
}
}
6. C++
class Animal {
protected:
string name;
public:
Animal(string name): name(name) {}
virtual string speak() = 0;
};
class Dog : public Animal {
public:
Dog(string name): Animal(name) {}
string speak() override { return name + " says Woof!"; }
};
class Cat : public Animal {
public:
Cat(string name): Animal(name) {}
string speak() override { return name + " says Meow!"; }
};
int main() {
vector<Animal*> animals = { new Dog("Buddy"), new Cat("Milo") };
for (auto a : animals) {
cout << a->speak() << endl;
delete a;
}
}
7. Kotlin
abstract class Animal(protected val name: String) {
abstract fun speak(): String
}
class Dog(name: String) : Animal(name) {
override fun speak() = "$name says Woof!"
}
class Cat(name: String) : Animal(name) {
override fun speak() = "$name says Meow!"
}
fun main() {
val animals = listOf(Dog("Buddy"), Cat("Milo"))
animals.forEach { println(it.speak()) }
}
8. Ruby
class Animal
def initialize(name)
@name = name
end
def speak
raise NotImplementedError
end
end
class Dog < Animal
def speak
"#{@name} says Woof!"
end
end
class Cat < Animal
def speak
"#{@name} says Meow!"
end
end
def main
animals = [Dog.new("Buddy"), Cat.new("Milo")]
animals.each { |a| puts a.speak }
end
main
9. PHP
<?php
abstract class Animal {
protected $name;
public function __construct($name) {
$this->name = $name;
}
abstract public function speak();
}
class Dog extends Animal {
public function speak() {
return "{$this->name} says Woof!";
}
}
class Cat extends Animal {
public function speak() {
return "{$this->name} says Meow!";
}
}
function main() {
$animals = [new Dog("Buddy"), new Cat("Milo")];
foreach ($animals as $animal) {
echo $animal->speak() . "\\n";
}
}
main();
?>
10. Dart
abstract class Animal {
final String _name;
Animal(this._name);
String speak();
}
class Dog extends Animal {
Dog(String name) : super(name);
@override
String speak() => '$_name says Woof!';
}
class Cat extends Animal {
Cat(String name) : super(name);
@override
String speak() => '$_name says Meow!';
}
void main() {
final animals = [Dog("Buddy"), Cat("Milo")];
for (final a in animals) {
print(a.speak());
}
}
11. Swift
class Animal {
private var name: String
init(name: String) {
self.name = name
}
func speak() -> String {
fatalError("Abstract method must be overridden")
}
}
class Dog: Animal {
override func speak() -> String {
return "\(name) says Woof!"
}
}
class Cat: Animal {
override func speak() -> String {
return "\(name) says Meow!"
}
}
func main() {
let animals: [Animal] = [Dog(name: "Buddy"), Cat(name: "Milo")]
for animal in animals {
print(animal.speak())
}
}
main()
12. Rust (ใช้ Trait แทน Class แบบปกติ)
trait Animal {
fn speak(&self) -> String;
}
struct Dog { name: String }
struct Cat { name: String }
impl Animal for Dog {
fn speak(&self) -> String {
format!("{} says Woof!", self.name)
}
}
impl Animal for Cat {
fn speak(&self) -> String {
format!("{} says Meow!", self.name)
}
}
fn main() {
let animals: Vec<Box<dyn Animal>> = vec![
Box::new(Dog { name: "Buddy".to_string() }),
Box::new(Cat { name: "Milo".to_string() })
];
for animal in animals {
println!("{}", animal.speak());
}
}
13. Scala
abstract class Animal(val name: String) {
def speak(): String
}
class Dog(name: String) extends Animal(name) {
def speak(): String = s"$name says Woof!"
}
class Cat(name: String) extends Animal(name) {
def speak(): String = s"$name says Meow!"
}
object Main {
def main(args: Array[String]): Unit = {
val animals: List[Animal] = List(new Dog("Buddy"), new Cat("Milo"))
animals.foreach(a => println(a.speak()))
}
}
14. Go (ไม่มี class แต่ใช้ struct + interface ทำ OOP ได้)
type Animal interface {
Speak() string
}
type dog struct { name string }
func (d dog) Speak() string { return d.name + " says Woof!" }
type cat struct { name string }
func (c cat) Speak() string { return c.name + " says Meow!" }
func main() {
animals := []Animal{dog{"Buddy"}, cat{"Milo"}}
for _, a := range animals {
fmt.Println(a.Speak())
}
}