从不同的类获取子类的实例

发布于 2024-12-22 23:48:44 字数 464 浏览 2 评论 0原文

我正在使用光滑的 2D 引擎和我自己的实体引擎编写一个游戏，以计算出 2D 侧向滚动条的细节。

我的代码当前的工作方式是这样的：

实体类保存实体信息。它可以有一种能力，比如动画、声音或运动。所有能力都是称为能力的抽象类的子类。

我在实体类中有一个方法，我希望获取特定能力的实例，以便我可以使用它的方法：

 public Ability getAbility(String id) {
    for(Ability abil : ablitites) {
        if(abil.getId().equalsIgnoreCase(id)) {
            return abil;
        }
    }
    return null;
}

但是，这仅返回超类能力的特定实例。我希望从不同的包或类中获取子类的实例。

执行此操作的代码示例将不胜感激。谢谢

原文

I am writing a game using the slick 2D engine and my own entity engine to work out the details of a 2D side scroller

The way my code currently works is like this:

Entity class holds entity information. It can have an Ability, something like Animation or sound or movement. All abilities are subclasses of an abstract class called Ability.

I have a method in the Entity class where I wish to get an instance of a specific ability, so that I can use its methods:

 public Ability getAbility(String id) {
    for(Ability abil : ablitites) {
        if(abil.getId().equalsIgnoreCase(id)) {
            return abil;
        }
    }
    return null;
}

However, this only returns a specific instance of the superclass, Ability. I wish to get an instance of the subclass from a different package or class.

A sample of code that does this would be appreciated. Thanks

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魔法少女 2024-12-29 23:48:44

我不完全理解你的问题，但我认为你应该看看 Casting< /a>.

我认为你应该像这样使用你的代码：
（当然，我不知道你的设计，所以我猜测一下）

Ability ability = getAbility("moveLeft");
if (ability instanceof MoveAbility)
{
    // Right here, we know it IS a MoveAbility because we checked it with
    // instanceof

    // So, we can cast it to a MoveAbility.
    MoveAbility moveAbility = (MoveAbility) ability;
    moveAbility.execute();
}

I don't completely understand your question but I think you should take a look to Casting.

I think you should use your code like this:
(Of course, I have no clue of your design, so I'm guessing a bit)

Ability ability = getAbility("moveLeft");
if (ability instanceof MoveAbility)
{
    // Right here, we know it IS a MoveAbility because we checked it with
    // instanceof

    // So, we can cast it to a MoveAbility.
    MoveAbility moveAbility = (MoveAbility) ability;
    moveAbility.execute();
}

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半山落雨半山空 2024-12-29 23:48:44

我认为你的代码已经在做你想做的事情了。如果您的 ablitites 集合已包含 Animation、Sound 和 Movement 对象的实例，那么这就是您的方法所要做的返回。它只是通过 Ability 引用返回它们。它无法返回超类 Ability 的实例，因为它是一个抽象类。您应该能够调用 Ability 中声明的常用方法，并看到您的方法返回的对象充当您请求的特定子类的实例。