Methods in

About Methods

Like properties, which store data in your structs and classes, you may also define methods which store functions in your struct or class.

Methods are defined in the same way as a regular function, only inside the body of the struct or class. Note that if a function changes the value of a property in a struct, it must be preceded by the mutating keyword. Additionally, if a property can be changed by a method, that property must be defined using var rather than let, just like regular variables.

struct CharacterStats {
  var health = 0.0
  var speed = 0
  var strength = 0

  mutating func takeHit(_ damage: Double) {
    health = max(0.0, health - damage)
  }
  func canLift(_ weight: Int) -> Bool {
    weight < strength * 100
  }
}

class GameCharacter {
  var stats = CharacterStats()
  var characterClass: String?
  var name: String?
  var active = false
  let id: String = makeRandomID()

  func takesDamage(_ damage: Double) {
    stats.takeHit(damage)
    if stats.health <= 0 {
      active = false
    }
  }
  func sayName() -> String {
    return "My name is \(name ?? "no one"), my class is \(characterClass ?? "undetermined")"
  }
  func lift(_ weight: Int) -> String {
    if stats.canLift(weight) {
      return "No problem!"
    } else {
      return "Ooof! No way."
    }
  }
}

These methods can be called using dot notation, just like properties.

var myChar = GameCharacter()
myChar.stats = CharacterStats(health: 72.8, speed: 19, strength: 6)
myChar.name = "Shadowfly"
myChar.characterClass = "spy"
myChar.active = true

myChar.active
// => true
myChar.sayName()
// => "My name is Shadowfly, my class is spy"
myChar.lift(750)
// => "Ooof! No way."
myChar.takesDamage(80)
myChar.active
// => false