C : Initialize template variable in struct-CodePudding

UPDATE: The issue was stemming from the fact that the Passenger class does not have a default constructor. I don't understand why that breaks the list implementation though. If someone could leave a comment explaining this to me, I'd appreciate it a lot!

OG Post:

Hello fellow stackoverflowers. I'm working on a simple university assignment but have run into a problem I can't seem to wrap my head around to solve. I'm new to C and I'm learning now that implementing generics is not as straightforward in C as it is in Java. Inside my LinkedList class there is a struct Node:

struct Node {
    T data;
    Node *next;
}; // Node

Simple enough. And when I create a list of integers in my main.cpp, the implementation functions as it should.

int main() {
    LinkedList<int> integers;
    integers.append(1);
    integers.append(2);
    integers.append(3);
    // append, prepend, get, insert, and remove 
    // functions all work as they should.
} // main

I also have a Passenger class. The problem occurs when I attempt to create a list of Passenger instances.

int main() {
    LinkedList<Passenger> passengers;
    Passenger passenger1("LastName1", "FirstName1", 0);
    Passenger passenger2("LastName2", "FirstName2", 1);
    passengers.append(passenger1);
    passengers.append(passenger2);
} // main

The error messages read exactly as follows:

./LinkedList.hpp:21:10: error: implicit default constructor 
for 'LinkedList<Passenger>::Node' must explicitly initialize 
the member 'data' which does not have a default constructor

./LinkedList.cpp:26:23: note: in implicit default constructor 
for 'LinkedList<Passenger>::Node' first required here:
    Node *newNode = new Node;

The append function in the LinkedList class is the following:

template<class T>
void LinkedList<T>::append(T data) {
    Node *newNode = new Node;
    newNode->data = data;
    newNode->next = NULL;
    if (head == NULL) {
        newNode->next = head;
        this->head = newNode;
    } else {
        Node *ptr = head;
        while (ptr->next != NULL) {
           ptr = ptr->next;
        } // while
        ptr->next = newNode;
    } // if
    length  ;
} // append

Thank you so much to anyone who helps me out here!

CodePudding user response：

It appears that you call:

    Node *newNode = new Node;

Which is equivalent to

    Passenger *newNode = new Passenger;

Which appears to be invalid because Passenger does not have a no argument constructor. I suspect you could fix this by doing:

    Node *newNode = new Node(data, nullptr);