Error when extending a template abstract class - c++

Question

I have this code for a Node based Queue implementation and I'm supposed to extends an abstract class called QueueInterface.
template<typename T>
struct QueueInterface {
public:
virtual ~QueueInterface(){};
virtual bool isEmpty() const = 0;
virtual void enqueue(const T value) = 0;
virtual void dequeue() throw(PreconditionViolationException) = 0;
virtual T peekFront() const throw(PreconditionViolationException) = 0;
};
template<typename T>
struct Queue : QueueInterface {
Queue();
~Queue();
bool isEmpty() const;
void enqueue(const T value);
void dequeue() throw(PreconditionViolationException);
T peekFront() const throw(PreconditionViolationException);
private:
Node<T>* front;
Node<T>* back;
};
I keep getting a expected class name before '{' token error even though I included the QueueInterface header file. Why is this happening?

Answer 1

QueueInterface is not a class. You can inherit from something that is not a struct or a class. This thing is what is called a templated class. You can recognize templates with the template<...> just before the templated class. You must specify a type so the compiler can create a class of that type.
In your case, you are trying to create a struct that is also a template. By looking at the overrides of the methods of your base classes, I guess you are trying to do this:
template<typename T>
struct Queue : QueueInterface<T> {
// notice that there ---^--- you are sending the required parameter
// defaulted members are good.
Queue() = default;
// override too.
bool isEmpty() const override;
void enqueue(const T value) override;
void dequeue() throw(PreconditionViolationException) override;
T peekFront() const throw(PreconditionViolationException) override;
private:
Node<T>* front;
Node<T>* back;
};