可以返回不同类型的通用方法 [英] Generic method that can return different types

问题描述

我有一个基本的抽象类，该类旨在允许实现者返回不同的类型:

I have a base abstract class which is meant to allow implementors to return different types:

protected abstract T GetMyValue<T>();

我希望实现类能够执行以下操作:

I would like the implementing class to be able to do something like this:

T myResult;    
public override T GetMyValue<T>()
{

     return _myResult;
}

我希望呼叫者指定类型:

I would like the caller to specify the type:

int i = obj.GetMyValue<int>();

这可能吗?

推荐答案

一种选择就是将字段存储为对象.这将导致对结构进行装箱，但是没有更重要的更改，没有更好的方法.

One option would just be to store the field as an object. This will cause boxing for structs, but there isn't better way without a more significant change.

class Derived : Base
{
     private object o;

     protected override T GetMyValue<T>()
     {
        if (o is T)
           return (T)o;

        return default(T);
     }
}

除非抽象类本身是通用的，而不是特定的方法，否则您实际上不能拥有通用的字段.当然，这是一个重大的设计更改.现在，一种实现只能返回一种类型.像

You can't really have a generic field unless the abstract class is itself generic, not the specific method. Of course this is a significant design change. One implementation can now only return one type. Something like

abstract class BaseClass<T>
{
    protected abstract T GetMyValue();
}

class Derived : Base<int>
{
    private int i;

    protected override int GetMyValue()
    {
        return i;
    }
}

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