调用通用成员的成员函数 [英] Calling member-function of generic member

问题描述

我有一个超类（GraphNode）和一个子类（AStarNode）。
两个人都可以成为另一个类的成员，这就是为什么我把它变成了一个泛型类（GraphEdge）的类。

喜欢调用超类的某些成员函数，但编译器会抱怨：

 方法addEdge（GraphEdge< T> ）是未定义的类型T 
  

我该如何解决这个问题，或者我的方法甚至可以吗？ p>

下面是一些更好地描述场景的代码：

  public class GraphNode { 
保护图表图形; 
 $ b $ public GraphEdge addEdge（）{
 //一些代码
} 
} 
 
公共类AStarNode扩展GraphNode {
受保护的GraphEdge前身; 
} 
 
 // from和to属性可以是AStarNode或GraphNode 
 public class GraphEdge< T>扩展实体{
 protected T from; 
保护T到; 
 
 public someMethod（）{
 from.addEdge（this）; 
} 
 
} 
  

解决方案

您的GraphEdge类使用可以是任何东西的泛型类型，而不仅仅是GraphNode。声明应该是

  public class GraphEdge< T extends GraphNode>扩展实体{
 protected T from; 
保护T到; 
} 
  

另外，由于GraphEdge是一个泛型类型，因此您不应该将它用作AStarNode中的原始类型：

  public class AStarNode扩展GraphNode {
 protected GraphEdge< PutSomeTypeHere>前任; 
} 
  

I've got a super-class (GraphNode) and sub-class (AStarNode). Both can be a member by another class thats why I turned the class which uses it into a generic class (GraphEdge).

Inside this class I'd like to call some member-functions of the super-class but the compiler complains that:

The method addEdge(GraphEdge<T>) is undefined for the type T

How can I fix this or is my approach even ok?

Here's some code that better describes the scenario:

public class GraphNode {
   protected Graph graph;

   public GraphEdge addEdge(){
   //some code
   }
}

public class AStarNode extends GraphNode {
   protected GraphEdge predecessor;
}

//The from and to properties can be either AStarNode or GraphNode
public class GraphEdge<T> extends Entity {
   protected T from;
   protected T to;

   public someMethod(){
       from.addEdge(this);
   } 

}

解决方案

Your GraphEdge class uses a generic type which could be anything, and not just GraphNode. The declaration should be

public class GraphEdge<T extends GraphNode> extends Entity {
   protected T from;
   protected T to;
}

Additionally, since GraphEdge is a generic type, you should not use it as a raw type in AStarNode:

public class AStarNode extends GraphNode {
    protected GraphEdge<PutSomeTypeHere> predecessor;
}

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