java - 容器和元素之间触发事件的解决方案？

Question

我有一堂这样的课:

public class Graph {
    Map<NodeKey,Node> nodes;

    List<RelationKey,Relation> relations;

    public void addNode(Node node){
        nodes.put(node.key,node);
    }

    public void addRelation(Relation relationship){
        relations.add(relation.key,relation);
    }

//getter and setter
}
public class Node {
    Map<RelationKey,Relation> relations;

    public void addRelationship(Relation relation){
        relations.put(relation.key,relation);
    }
//getter and setter
}

当调用node.addRelationship(Relationlation)时，Graph如何调用它的方法:addRelation(Relationrelation)。我可以在 Node 类中添加 Graph 属性，但它似乎与 OOP 中的 HAS-A 关系不太接近

Answer 1

您可以像这样使用观察者模式:

class Node extends Observable {

    public Node(Observer observer){
        addObserver(observer);
    }

    public void addRelationship(Relation relation){
        relations.put(relation.key,relation);
        setChanged();
        notifyObservers(relation);
    }
}


class Graph implements Observer {
    @Override
    public void update(Observable o, Object arg) {
        Relation relation = (Observable)arg;
        relations.add(relation.key,relation);
    }
}