使用[]和insert（）插入std :: unordered_map有什么区别？

Question

I want to add unordered_map to my app to store values as <string,object> pairs. I wanted to add element to map in function, return pointer to this object, do some logic and later retrieve this value.

Unfortunately I cannot do as planned, because it looks like my reference is loosing somehow connection. This is how insertion is currently done:

std::unordered_map<std::string, EdgeS> edges;

// Some extra stuff

EdgeS* Node::insertEdge(Node* to)
{
    EdgeS edge = edges[to->name];
    if(!edge.to)
        edge.to = to;
    edge.frequency++;
    edge.packets_number++;
    return &edge;
}

As you can see I am using operator[] , but when later I am trying to use this map's object it looks like it is recreated and everything I've done on it has no effect.

I've been thinking also about insert , but I am not sure about difference. With operator good thing is that it doesn't matter if object exists or not I can still have reference to it. But apparently I cannot do anything with this object. So what is better in this case?

Answer 1

it looks like my reference is loosing somehow connection

You're not using a reference. You're making a copy:

EdgeS edge = edges[to->name];

If you want to use a reference, edge should have type EdgeS & .