普通班级的普通父母 [英] Generic Parent For Generic Class

问题描述

为此，我使用一个虚构的示例.说，我有一个类似Widget的类:

I am using a fictional example for this. Say, I have a Widget class like:

abstract class Widget
{
Widget parent;
}

现在，我的其他类将从该Widget类派生，但是假设我想在定义派生类型时在该类中施加一些约束，以使只有特定的类型"的widget可以成为特定类型的父对象.小部件.

Now, my other classes would be derived from this Widget class, but suppose I want to put some constraint in the class while defining the derived types such that only a particular "type" of widget can be parent to a particular type of Widget.

例如，我从Widget类派生了另外两个小部件WidgetParent和WidgetChild.在定义子类时，我想将父类的类型定义为WidgetParent，这样我就不必在每次使用父类时都将其类型转换为父类.

For example, I have derived two more widgets from the Widget class, WidgetParent and WidgetChild. While defining the child class, I want to define the type of parent as WidgetParent, so that I dont have to type cast the parent every time I use it.

准确地说，我想做的是这样:

Precisely, what I would have liked to do is this:

// This does not works!
class Widget<PType>: where PType: Widget
{
    PType parent;
}

class WidgetParent<Widget>
{
    public void Slap();
}

class WidgetChild<WidgetParent>
{
}

这样，当我想访问WidgetChild的父级时，而不是这样使用它:

So that when I want to access the parent of WidgetChild, instead of using it this way:

WidgetParent wp = wc.parent as WidgetParent;
if(wp != null)
{
    wp.Slap();
}
else throw FakeParentException();

我想以这种方式使用它(如果可以使用泛型的话):

I want to use it this way(if I could use generics):

wc.parent.Slap();

推荐答案

通过仍然具有非通用类Widget并使Widget<T>从其派生，您应该能够使用获得的代码:

You should be able to use the code you've got by still having the non-generic class Widget and making Widget<T> derive from it:

public abstract class Widget
{
}

public abstract class Widget<T> : Widget where T : Widget
{
}

然后，您需要根据经验算出什么属于泛型类，哪些属于非泛型类……这可能是一个棘手的平衡行为.期望来回来回去相当多！

You then need to work out what belongs in the generic class and what belongs in the non-generic... from experience, this can be a tricky balancing act. Expect to go back and forth a fair amount!

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