Question

Have a simple program, where I can insert a string into a statically defined array of strings of size 20.

This program worked just fine, until I was assigned to change it to use templates, so the code (with modificaiton) would support intergers or strings.

Using the Class “Shelf” in the included header, I can no longer declare the following object int main(), “Shelf book;” –as the compiler tells me book has not been declared and I’m missing Template Arguments.

#include<iostream>
#include<string>

#define shelfSize 20
template<class T>
class Shelf{
   public:
       Shelf();//default constructor
       void insert(T&);
   private:
       string bookshelf[shelfSize];
       int counter;
};
template< class T>
Shelf<T>::Shelf(){
    for(int i=0; i <shelfSize; i++)
        bookshelf[i]="";
    counter=0;
}
template< class T>
void Shelf<T>::insert(T &booknum){
    bookshelf[counter] = booknum;
    counter++;
}
int main(){
   Shelf book;
   string isbn="";
   cout<<"Enter ISBN Number you wish to enter into the Array: "<<endl;
   getline(cin, isbn);
   book.insert(isbn);
   return 0;
 }

Obviously, I watered down my program greatly and want to focus on what’s actually giving me an issue.

So as I said I get the following errors:

Missing Template arguements before “book”;
expect “;” before “book”.
“book” undeclared.

Answer 1

You need to specify a parameter to T. Templates need to be instantiated with the datatype passed as a parameter, like so:

Shelf<std::string> book;