java - 这是在 Java 中实现装饰器或多继承的新方法吗？

Question

我想知道是否找到了在 Java 中实现装饰器设计模式的替代方法？这是否可能是一种类似于 Java 中多重继承的新方法？有没有更好的方法来实现下面的问题？

我针对以下问题提供了一个最小的示例(想象一个简单的游戏引擎):

• Actor:是一个基本的 Actor，它有一个位置(在屏幕上)和一个可见性标志
• 某些 Actor 是可损坏的，这意味着它们可以通过生命值、施加伤害和在必要时摧毁它们(使基础 Actor 隐形)的方法来扩展。
• 某些 Actor 是物理，这意味着它们可以施加重力等力，从而有效地改 rebase 础 Actor 的位置。
• 某些 Actor 是可损坏且物理的，因此它们应该执行某种多重继承或应用 2 个装饰器(使用装饰器模式)。 EnemyActor 就是一个例子，它当然还有自己的方法。

这是我的实现(最小化):

public class Actor {
    int posX;
    int posY;
    boolean visible = true;
}

public class DamagableActorDecoration {
    float health = 10;
    private final Actor base;

    public DamagableActorDecoration(Actor base) {
        this.base = base;
    }

    void applyDamage (float dmg) {
        health -= dmg;
        if (health<=0)
            base.visible = false;
    }

    boolean isDestroyed () {
        return health<=0;
    }
}

public class PhysicalActorDecoration {
    private final Actor base;

    public PhysicalActorDecoration(Actor base) {
        this.base = base;
    }

    public void applyGravity () {
        base.posY--;
    }
}

public interface Damagable {
    DamagableActorDecoration d();
}

public interface Physical {
    PhysicalActorDecoration p();
}

public class EnemyActor extends Actor implements Damagable, Physical{
    @Override
    public DamagableActorDecoration d() {
        return new DamagableActorDecoration(this);
    }
    @Override
    public PhysicalActorDecoration p() {
        return new PhysicalActorDecoration(this);
    }

    public void showExplodingParticleSystem (){}
}

现在我可以创建一个扩展 Actor 的敌人，它有自己的方法，而且也是可损坏的和物理的。例如，像这样使用它:

public class Runner {
    public static void main(String[] args) {
        EnemyActor enemy1 = new EnemyActor();

        // basic actor behavior : appear
        enemy1.visible=true;

        // basic actor behavior : move forward
        enemy1.posX++;

        // damagable actor behavior : receive damage
        enemy1.d().applyDamage(0.7f);

        // physical actor behavior : fall down
        enemy1.p().applyGravity();

        // damagable actor behavior : be destroyed
        if (enemy1.d().isDestroyed())
        {
            // enemy actor behavior : explode into pieces
            enemy1.showExplodingParticleSystem();
        }
    }
}

Answer 1

你所做的事情介于委托(delegate)和组合之间。在我看来，“Damageable”和“Physical”应该独立运行，并将“EnemyActor”委托(delegate)委托(delegate)给它们，而不是将接口(interface)委托(delegate)委托(delegate)给装饰器。我通过删除不必要的间接级别对其进行了一些清理。

编辑:我忘了提及。当您玩视频游戏时，有时性能是最重要的。如果我们谈论的是由用户事件触发的操作，那么性能并不重要，但是如果我们谈论的是在循环中多次发生的操作 - 最好放弃并使用 Actor 来增强直接可访问的属性。

public class EnemyActor extends Actor implements Damageable, Physical {

    private final DamageableActorDecoration damageDecorator;
    private final PhysicalActorDecoration physicalDecorator;

    public EnemyActor() {
        damageDecorator = new DamageableActorDecoration(this);
        physicalDecorator = new PhysicalActorDecoration(this);
    }

    @Override
    public void applyDamage(float dmg) {
        damageDecorator.applyDamage(dmg);
    }

    @Override
    public boolean isDestroyed() {
        return damageDecorator.isDestroyed();
    }

    @Override
    public void applyGravity() {
        physicalDecorator.applyGravity();
    }
}

public class Actor {
    int posX;
    int posY;
    boolean visible = true;
}

public interface Damageable {
    void applyDamage(float dmg);

    boolean isDestroyed();
}

public class DamageableActorDecoration implements Damageable {
    float health = 10;
    private final Actor base;

    public DamageableActorDecoration(Actor base) {
        this.base = base;
    }

    @Override
    void applyDamage(float dmg) {
        health -= dmg;
        if (health <= 0)
            base.visible = false;
    }

    @Override
    boolean isDestroyed() {
        return health <= 0;
    }
}

public interface Physical {
    void applyGravity();
}

public class PhysicalActorDecoration implements Physical {
    private final Actor base;

    public PhysicalActorDecoration(Actor base) {
        this.base = base;
    }

    @Override
    public void applyGravity() {
        base.posY--;
    }
}