How do I code and pass a (reference to a std::vector)?

Question

I can't seem to get this right.

class Tree
{
    Node*   root;
    vector& dict;
} 

class Node
{
    vector& dict;
    char*   cargo;
    Node    left;
    Node    right;
}

I want each instance of Tree to have it's own dict, and I want it to pass a reference to the dict to the node constructor, which would recursively pass the reference to each child node so that each Node can enter a pointer to itself in the dict.

I'm having a lot of trouble with the syntax to:

• get the vector initialized
• pass a reference to the vector to the Node constructor
• receive the reference in the Node constructor

I know this stuff is pretty basic. I'm teaching myself c++.

Thanks

Answer 1

You can initialize a reference only in an initialization list of a constructor. For instance,

Tree::Tree( vector<type>& d ) : dict(d) 
{
  ...
}

Answer 2

You haven't specified what you've tried that isn't working, but I suspect you are having trouble in the constructors because a reference can't be assigned to; you have to initialize it.

Also, when you use std::vector, you have to use a template parameter for the element type. So you can't just use vector&, you need vector<Something>&, where Something is whatever the element type is.

So, you probably want something like this:

class Tree
{
private:
    Node* root;
    std::vector<Something>& dict;

public:
    Tree(Node* aRoot, std::vector<Something>& aDict): root(aRoot), dict(aDict) {}
};

class Node
{
private:
    std::vector<Something>& dict;
    char*cargo;
    Node left;
    Node right;

    Node(std::vector<Something>& aDict, char* aCargo): dict(aDict), cargo(aCargo) {}
};