类与对象 #

class Person:
  var name: String = ""
  var age: Int = 0
  
  def greet(): String = s"Hello, I'm $name"

val person = new Person
person.name = "Alice"
person.age = 25
println(person.greet())

class Person(name: String, age: Int):
  def greet(): String = s"Hello, I'm $name, $age years old"

val person = Person("Alice", 25)
println(person.greet())

val person = Person("Alice", 25)

class Person(val name: String, val age: Int)

val person = Person("Alice", 25)
println(person.name)
println(person.age)

class Person(var name: String, var age: Int)

val person = Person("Alice", 25)
person.name = "Bob"
person.age = 30

class Person(name: String, age: Int):
  def getName: String = name
  def getAge: Int = age

val person = Person("Alice", 25)

class Person(name: String, age: Int):
  private var _name = name
  private var _age = age
  
  def name_=(newName: String): Unit = _name = newName
  def name: String = _name
  
  def age_=(newAge: Int): Unit = _age = newAge
  def age: Int = _age

val person = Person("Alice", 25)
person.name = "Bob"
println(person.name)

class Calculator:
  def add(a: Int, b: Int): Int = a + b
  def subtract(a: Int, b: Int): Int = a - b
  def multiply(a: Int, b: Int): Int = a * b
  def divide(a: Int, b: Int): Option[Int] =
    if b != 0 then Some(a / b) else None

val calc = Calculator()
println(calc.add(10, 5))

class Counter:
  private var count = 0
  
  def increment(): Unit = count += 1
  def current: Int = count

val counter = Counter()
counter.increment()
println(counter.current)

class Math:
  def add(a: Int, b: Int): Int = a + b
  def add(a: Double, b: Double): Double = a + b
  def add(a: Int, b: Int, c: Int): Int = a + b + c

val math = Math()
math.add(1, 2)
math.add(1.5, 2.5)
math.add(1, 2, 3)

class BankAccount(initialBalance: Double):
  private var balance = initialBalance
  
  def deposit(amount: Double): Unit =
    if amount > 0 then balance += amount
  
  def withdraw(amount: Double): Unit =
    if amount > 0 && amount <= balance then balance -= amount
  
  def getBalance: Double = balance

val account = BankAccount(1000.0)
account.deposit(500.0)
account.withdraw(200.0)
println(account.getBalance)

class Animal:
  protected def makeSound(): String = "Some sound"

class Dog extends Animal:
  def bark(): String = makeSound()

val dog = Dog()
println(dog.bark())

package com.example

class MyClass:
  private[example] def internalMethod(): String = "internal"
  private[this] def instancePrivate(): String = "instance private"

object Counter:
  private var count = 0
  
  def increment(): Int =
    count += 1
    count
  
  def current: Int = count

Counter.increment()
Counter.increment()
println(Counter.current)

object MathUtils:
  def square(x: Double): Double = x * x
  def cube(x: Double): Double = x * x * x
  def factorial(n: Int): Int =
    if n <= 1 then 1 else n * factorial(n - 1)

println(MathUtils.square(5))
println(MathUtils.factorial(5))

object Direction:
  val North = "N"
  val South = "S"
  val East = "E"
  val West = "W"

println(Direction.North)

class Person(val name: String, val age: Int)

object Person:
  def apply(name: String): Person = Person(name, 0)
  def create(name: String, age: Int): Person = Person(name, age)

val p1 = Person("Alice")
val p2 = Person.create("Bob", 25)

class Person(val name: String, val age: Int)

object Person:
  def apply(name: String, age: Int): Person = new Person(name, age)

val person = Person("Alice", 25)

class Person(val name: String, val age: Int)

object Person:
  def apply(name: String, age: Int): Person = new Person(name, age)
  def unapply(person: Person): Option[(String, Int)] =
    Some((person.name, person.age))

val person = Person("Alice", 25)

person match
  case Person(name, age) => println(s"$name is $age years old")

class Account private (val id: String, var balance: Double)

object Account:
  private var nextId = 0
  
  def apply(initialBalance: Double): Account =
    nextId += 1
    new Account(s"ACC-$nextId", initialBalance)

val account = Account(1000.0)
println(account.id)

class Person(val name: String, val age: Int):
  def this(name: String) = this(name, 0)
  def this() = this("Unknown")

val p1 = Person("Alice", 25)
val p2 = Person("Bob")
val p3 = Person()

class Rectangle(val width: Double, val height: Double):
  def this(size: Double) = this(size, size)
  def this() = this(1.0)
  
  def area: Double = width * height

val r1 = Rectangle(10, 20)
val r2 = Rectangle(5)
val r3 = Rectangle()

class Person(
  val name: String = "Unknown",
  val age: Int = 0
)

val p1 = Person()
val p2 = Person("Alice")
val p3 = Person("Bob", 25)
val p4 = Person(age = 30)

class Config(
  val host: String = "localhost",
  val port: Int = 8080,
  val timeout: Int = 5000
)

val config = Config(port = 9090, host = "example.com")

class Person(val name: String, val age: Int):
  def withName(newName: String): Person = Person(newName, age)
  def withAge(newAge: Int): Person = Person(name, newAge)

val p1 = Person("Alice", 25)
val p2 = p1.withAge(26)

case class Person(name: String, age: Int)

val p1 = Person("Alice", 25)
val p2 = p1.copy(age = 26)

class Counter:
  private var count = 0
  
  def increment(): Int =
    count += 1
    count
  
  def current: Int = count
  
  def reset(): Unit =
    count = 0