Dart继承和超级构造函数 [英] Dart inheritance and super constructor

问题描述

我试图定义一个抽象父类 Event 和一个具体的子 PlaceChangeEvent ：

I am trying to define an abstract parent class Event and a concrete child PlaceChangeEvent:

abstract class Event {
    String name;
    DateTime occurredAt;
    int handleCount;

    Event(this.name, this.occurredAt, [this.handleCount = 0]);
}

class PlaceChangeEvent implements Event {
    Place place;

    PlaceChangeEvent(Place place) : super(place.name, DateTime.now());
}

PlaceChangeEvent 给我2个编译器警告：

The PlaceChangeEvent is giving me 2 compiler warnings:

• 第一个是类名本身：遗漏的成员：第二个是调用 super

< $ c>： 0位置参数期望，但2找到


• The first is on the class name itself: Missing inherited members: 'Event.name', 'Event.handleCount' and 'Event.occurredAt'
• The second is on the call to super: 0 positional arguments expected, but 2 found

我错了，我能做些什么来解决这个问题？我的意图是：

Where did I go wrong and what can I do to fix this? My intentions are to:

• 将名称 c> place.name ;和


• 使用当前日期/时间硬编码父级的 occurrenceAt 属性;

• Hardcode the parent's name with the place.name; and
• Hardcode the parent's occurredAt property with the current date/time'; and
• Initialize the parent's optional handleCount property to 0 by simply not providing it.

推荐答案

在这种情况下，你正在实现你的类而不是扩展它。实现你的类意味着你的子类必须提供相应的方法。实现意味着你的具体类应该有这些属性的getter和setter（或者只是定义那些属性）。它不会实际继承类中定义的那些，因为你不扩展 Event class

In this case, you're implementing your class rather than extending it. Implementation of your class means that your sub-class must provide the corresponding methods. The implementation means that your concrete class should have a getter and setter for those properties (or just define those properties themselves). It won't actually inherit the ones defined in the class because you are not extending the Event class

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