ios - 如何在 Swift 3 的子类中覆盖 Init()

Question

我仍然是 Swift 的初学者。我有一个类 NonPlayerCharacter 作为父类和一个从它继承的子类 Goblin。我在 NonPlayer 类中定义了 health 和 power，在 Goblin 类中定义了 weapon。然后我声明一个新变量，这样我就可以调用类 Goblin 并更改健康、力量和武器的值，但我看不到括号内的武器(我只看到健康和力量)。我试图创建一个 init 函数，但我得到了这个错误“从初始化程序返回之前，没有在所有路径上调用 Super.init ”。我在我的代码下面的评论中更清楚地解释了我的问题。

我在 Playground 上这个类

class NonPlayerCharacter 
{

  var health: Int
  var power: Int

init() {

    health = 0
    power = 0

}
 init(health: Int , power : Int) {
    self.health = health
    self.power = power

}

func attack () -> String
{
    return "attack from NonPlayer Character"

}    }

var NonPlayerMethod = NonPlayerCharacter(health: 100, power: 90)

 //and this is the SubClass: 

  class Goblin: NonPlayerCharacter
   {
  var weapon : Int = 0

  override func attack() -> String {
    return "attack from Goblin"
 }
 }



 var GoblinMethod = Goblin(health: 40, power: 12)
 GoblinMethod.weapon = 10
 GoblinMethod.attack()

  //I tried to make initialization like this in the SubClass** 


   class Goblin: NonPlayerCharacter
  {
   var weapon : Int = 0

   Init ( weapon: Int )
   {
   self.weapon = weapon 
   }
   }

   // so I can change the values like this :

   var GoblinMethod = Goblin( weapon: 30 , health: 20, power: 50) 

  // I got this error ( Super.init isn't called on all paths before returning from initializer )
 //I don't think I need to override Init as the weapon only in the SubClass.

Answer 1

所以你有两种方法来处理你的情况:

1 为您的子类创建一个自己的初始化器，调用 super 初始化器，然后像这样初始化武器属性

class Goblin: NonPlayerCharacter {
  var weapon : Int = 0

  init(health: Int, power: Int, weapon: Int) {
    super.init(health: health, power: power)
    self.weapon = weapon
  }

  override func attack() -> String {
    return "attack from Goblin"
  }
}

然后你就可以像这样创建一个地精了:

var goblin1 = Goblin(health: 30, power: 20, weapon: 50)

2 为您的子类创建一个方便的初始化器，以便能够决定您是只想从父类调用初始化器(设置健康和力量)还是像这样的便利初始化器(设置健康、力量和武器) :

class Goblin: NonPlayerCharacter {
  var weapon : Int = 0

  convenience init(health: Int, power: Int, weapon: Int) {
    self.init(health: health, power: power)
    self.weapon = weapon
  }

  override func attack() -> String {
    return "attack from Goblin"
  }
}

然后你就可以像这样创建一个地精了:

var goblin2 = Goblin(health: 30, power: 20, weapon: 50)

或者像这样:

var goblin3 = Goblin(health: 30, power: 20)

进一步阅读 here和 here