how to return a template list in C ?-CodePudding

I am learning C in school and in my homework, my task is to create the FooClass for these:

int main()
{
    int x[] = {3, 7, 4, 1, 2, 5, 6, 9};
    FooClass<int> ui(x, sizeof(x) / sizeof(x[0]));

    std::string s[] = {"Car", "Bike", "Bus"};
    FooClass<std::string> us(s, sizeof(s) / sizeof(s[0]));
}

then modify the code so it can write out the size of the lists and the elements of the lists.

I managed to write the code for the size function. But I am struggling with the element part, getting an

error: missing template arguments before '.' token.

Here is my code so far:

template <typename T>
class FooClass
{
private:
    T *items;
    int itemsSize;
    bool mergeOn;

public:
    FooClass(T items[], int itemsSize)
    {
        items = new T[itemsSize];
        this->itemsSize = itemsSize;
    };

    int getItemsSize()
    {
        return this->itemsSize;
    }

    void print(const FooClass <T>& items)
    {
        for (int i=0; i< items.getItemsSize();   i)
        {
            std::cout<<items[i]<<std::endl;
        }
    }
};

int main()
{
    int x[] = {3, 7, 4, 1, 2, 5, 6, 9};
    FooClass<int> ui(x, sizeof(x) / sizeof(x[0]));

    std::string s[] = {"Car", "Bike", "Bus"};
    FooClass<std::string> us(s, sizeof(s) / sizeof(s[0]));

    std::cout<<ui.getItemsSize()<<std::endl;
    FooClass.print(us); //this is where I get the compilation error.
}

How should I implement the print function?

CodePudding user response：

Your constructor is not copying the source elements into the array that it allocates. And, you need a destructor to free the allocated array when you are done using it.

And, your print() method is not static, so it should act on this instead of taking a FooClass object as a parameter.

Try this:

template <typename T>
class FooClass
{
private:
    T *m_items;
    int m_itemsSize;
    bool m_mergeOn;

public:
    FooClass(T items[], int itemsSize)
    {
        m_items = new T[itemsSize];
        for (int i = 0; i < itemsSize;   i) {
            m_items[i] = items[i];
        }
        m_itemsSize = itemsSize;
    };

    ~FooClass()
    {
        delete[] m_items;
    }

    int getItemsSize() const
    {
        return m_itemsSize;
    }

    void print() const
    {
        for (int i = 0; i < m_ItemsSize;   i)
        {
            std::cout << m_items[i] << std::endl;
        }
    }
};

int main()
{
    int x[] = {3, 7, 4, 1, 2, 5, 6, 9};
    FooClass<int> ui(x, sizeof(x) / sizeof(x[0]));

    std::cout << ui.getItemsSize() << std::endl;
    ui.print();

    std::string s[] = {"Car", "Bike", "Bus"};
    FooClass<std::string> us(s, sizeof(s) / sizeof(s[0]));

    std::cout << us.getItemsSize() << std::endl;
    us.print();
}