責(zé)任鏈模式

使多個(gè)對(duì)象都有機(jī)會(huì)處理請(qǐng)求，從而避免請(qǐng)求的發(fā)送者和接收者之間發(fā)生耦合。此模式將這些對(duì)象連成一條鏈，并沿著這條鏈傳遞請(qǐng)求，直到有一個(gè)對(duì)象處理它為止。最初的定義出現(xiàn)于《設(shè)計(jì)模式》（Addison-Wesley，1994）。

何時(shí)使用責(zé)任鏈模式

1. 有多個(gè)對(duì)象可以處理請(qǐng)求，而處理程序只有在運(yùn)行時(shí)才能確定。
2. 向一組對(duì)象發(fā)送請(qǐng)求，而不想顯式指定處理請(qǐng)求的特定處理程序。

在游戲中RPG使用責(zé)任鏈模式

創(chuàng)建AttackHanlder父類

class AttackHandler: NSObject {
    
    private var nextAttackHandler: AttackHandler?
    
    init(nextAttackHandler: AttackHandler?) {
        self.nextAttackHandler = nextAttackHandler
    }
    
    func handleAttack(attack: Attack) {
        nextAttackHandler?.handleAttack(attack: attack)
    }

}

創(chuàng)建三個(gè)子類

class MetalArmor: AttackHandler {

    override func handleAttack(attack: Attack) {
        if attack.isKind(of: SwordAttack.classForCoder()) {
            print("No demage from a sword attack!")
        } else {
            print("I don't know this attack: \(attack.classForCoder)")
            super.handleAttack(attack: attack)
        }
    }
}

客戶端代碼

  
        let avatar = Avatar(nextAttackHandler: nil)
        let metalArmoredAvatar = MetalArmor(nextAttackHandler: avatar)
        let superAvatar = CrystalShield(nextAttackHandler: metalArmoredAvatar)
        
        let swordAttack = SwordAttack()
        superAvatar.handleAttack(attack: swordAttack)
        
        let magicFireAttack = MagicFireAttack()
        superAvatar.handleAttack(attack: magicFireAttack)
        
        let lightningAttack = LightingAttack()
        superAvatar.handleAttack(attack: lightningAttack)

GitHub地址