CODEWITHSUNDEEP
c++templates
lindsey
lindsey

Reputation: 23

Returning node pointer using a template

Trying to search for a specific Node in a Tree, and I need to return a pointer to the Node when I've found it. The nodes are of a derived class type called BudgetEnvelope, and the error that I'm getting reads:

Cannot initialize return object of type BudgetEnvelope with an lvalue of type Node<BudgetEnvelope>

template <class T>
T* Tree<T>::find( Node<T> * ptr, T value){
    if(ptr != NULL){
        if(ptr->value == value){
            return ptr;    <------error is on this line
        }
        else{
            if(value < ptr->value){
                return find(ptr->left, value);
            }
            else{
                return find(ptr->right, value);
            }
        }
    }
    else{
        return NULL;
    }
}

My understanding was that since the nodes are of the same type as the pointer that I am returning, that it should work. How can I resolve this?

Edit: More information. When I change the return type to Node<T>*, the file where I am using this method gives me another error. 

void EnvelopeBox::deposit(int id, double amount){
    BudgetEnvelope searchKey = *new BudgetEnvelope(id, "searchKey");
    BudgetEnvelope* keyPtr = envelopes.find(searchKey);     <----same error
    keyPtr->deposit(amount); 
}

The deposit method is defined inside the BudgetEnvelope class, not Node, so if I change keyPtr to be the same type Node<T>*, I can't access the deposit method.

Upvotes: 1

Views: 589

Answers (2)

Justin Lam
Justin Lam

Reputation: 799

I think you want to return Node<T>* not T* because ptr is of type Node<T>*

e.g.

Node<T>* Tree<T>::find( Node<T> * ptr, T value)

EDIT:

With the new information you provided, what you need to do is convert 

BudgetEnvelope* keyPtr = envelopes.find(searchKey);

to

Node<BudgetEnvelope>* keyPtr = envelopes.find(searchKey);

then to access the data inside, you do the following:

BudgetEnvelope myValue = keyPtr->Value;
myValue.deposit(amount)

What you need to do is access the data inside the node. Alternatively, you can return ptr->Value from your find function.

Upvotes: 2

perencia
perencia

Reputation: 1552

ptr is a pointer to type Node<T> and the function returns a pointer to type T. Types T and Node<T> are different.

If you want to return a T* you should return whatever method in your Node class returns a pointer to the value contained in that Node. Otherwise, which i think is what you want, change the signature of T* Tree<T>::find( Node<T> * ptr, T value) to return Node<T>*, as Justin suggested.

Upvotes: 2

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