Can't delete a heap instance of my custom class (C++) - c++

Question

Here's what I've got:
class MyClass {
int holder;
public:
MyClass() {
holder = 5;
}
};
template<class T>
class First {
std::vector<T> items;
public:
First() {
T* tmp;
for (int i = 0; i < 20; i++) {
tmp = new T();
items.push_back(*tmp);
}
};
~First() {
for (int i = 0; i < 20; i++) {
delete items.at(i);
}
};
};
class Second {
std::vector<std::deque<First<MyClass>>> items;
public:
Second() {
std::deque<First<MyClass>>* tmp;
for (int i = 0; i < 10; i++) {
tmp = new std::deque<First<MyClass>>;
items.push_back(*tmp);
}
};
~Second() {
for (int i = 0; i < 10; i++) {
for (int j = 0; j < items.at(i).size(); j++) {
delete items.at(i).at(j); // this deletes the "First" instances
}
delete items.at(i); // this deletes the deque
}
};
};
In my main, I'm create an instance of Second and adding First instances to it (through methods that aren't included). At the end of main, I delete the instance of Second, which should delete all the instances of First and the deques. However, I'm getting the following errors:
error: cannot delete expression of type 'value_type' (aka 'MyClass')
error: cannot delete expression of type 'value_type' (aka 'First<MyClass>')
error: cannot delete expression of type 'value_type' (aka 'std::deque<First<MyClass>>')
Essentially, all my delete commands are throwing errors. What am I missing here? I need to manually implement a destructor because I created a bunch of stuff on the heap - correct?

Answer 1

You are never storing the result of the new expression. Your code should perhaps look like this:
First() {
T* tmp;
for (int i = 0; i < 20; i++) {
tmp = new T();
items.push_back(*tmp);
delete tmp; // result of "new" is still accessible here
}
}
~First() { }
Or like this:
First() {
for (int i = 0; i < 20; i++) {
items.push_back(T());
}
}
Or just like this:
First() : items(20) {}