继承设计问题 [英] Inheritance Design Question
问题描述
我想提供一个抽象类来派生所有节点。在示例中，
基类中的Parent是Type Node，但在自定义类中我希望Parent返回Type CustomNode。当NodeNode由
辅助类访问时，Node Parent始终为null。这是一个糟糕的设计，我确定
这是一个常见的问题，我只是遗漏了一些东西。
注意：我使用虚拟为父，因为抽象不会编译。
公共抽象类节点
{
公共虚拟节点父级
{
get {return null; }
}
public virtual bool IsLastChild
{
get {return this._isLastChild; }
}
private bool _isLastChild = false;
}
公共类CustomNode：Node
{
public new CustomNode Parent
{
get {return this._customNode; }
}
private CustomNode _customNode = null;
}
I want to provide an abstract class to derive all nodes from. In the example
below Parent in the base class is of Type Node, but in the custom class I
want Parent to return a Type CustomNode. When CustomNode is accessed by a
helper class as Node Parent is always null. Is this a poor design, Im sure
it''s a common problem and I am just missing something.
Note: I use virtual for Parent because abstract will not compile.
public abstract class Node
{
public virtual Node Parent
{
get { return null; }
}
public virtual bool IsLastChild
{
get { return this._isLastChild; }
}
private bool _isLastChild = false;
}
public class CustomNode : Node
{
public new CustomNode Parent
{
get { return this._customNode; }
}
private CustomNode _customNode = null;
}
推荐答案
你需要在派生类中使用覆盖而不是新的。
Thomas P. Skinner [MVP]
"迈克" < MI ******** @ com.nospam>在留言中写道
新闻：O7 **************** @ TK2MSFTNGP11.phx.gbl ...
You need to use override rather than new in the derived class.
Thomas P. Skinner [MVP]
"Mike" <mi********@com.nospam> wrote in message
news:O7****************@TK2MSFTNGP11.phx.gbl...
我想要提供一个抽象类来派生所有节点。在下面的
示例中，基类中的Parent是Type Node，但在自定义类中我希望Parent返回Type CustomNode。当一个
辅助类访问CustomNode时，Node Parent始终为null。这是一个糟糕的设计，我确定
这是一个常见的问题，我只是缺少一些东西。
注意：我使用virtual for Parent，因为abstract不会编译。
公共抽象类Node
公共虚拟节点Parent
{
get {return null; }
}公共虚拟布尔IsLastChild
{
获取{return this._isLastChild; }
}
私有bool _isLastChild = false;
}
公共类CustomNode：Node
公共新的CustomNode Parent {
get {return this._customNode;私有CustomNode _customNode = null;
}
I want to provide an abstract class to derive all nodes from. In the
example
below Parent in the base class is of Type Node, but in the custom class I
want Parent to return a Type CustomNode. When CustomNode is accessed by a
helper class as Node Parent is always null. Is this a poor design, Im
sure
it''s a common problem and I am just missing something.
Note: I use virtual for Parent because abstract will not compile.
public abstract class Node
{
public virtual Node Parent
{
get { return null; }
}
public virtual bool IsLastChild
{
get { return this._isLastChild; }
}
private bool _isLastChild = false;
}
public class CustomNode : Node
{
public new CustomNode Parent
{
get { return this._customNode; }
}
private CustomNode _customNode = null;
}
更改时覆盖不起作用返回类型，我想返回
CustomNode派生自Node。
Override does not work when changing the return Type, I want to return
CustomNode which derives from Node.
" Mike" < MI ******** @ com.nospam>在消息中写道
news：e9 ************** @ TK2MSFTNGP14.phx.gbl ...
"Mike" <mi********@com.nospam> wrote in message
news:e9**************@TK2MSFTNGP14.phx.gbl...
覆盖不起作用更改返回类型，我想返回
CustomNode派生自Node。
Override does not work when changing the return Type, I want to return
CustomNode which derives from Node.
你真的应该返回Node。如果你知道它是CustomNode，你可以自由地把它投射到CustomNode。
David
You really should return Node. You are free to cast it to CustomNode if you
know it is a CustomNode.
David
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