Thread: Template-Related Problems

I'm having a problem with using templates, and since I'm completely at a loss as to what's wrong, I'm simply going to dump the (I think) relevant sections of code here.

Here is the problem code:

The bolded line is the one throwing the error.

Code:

#include <vector>
#include <algorithm>

using namespace std;

template<class client_type> class ServiceList {
public:
    /* blah blah blah... */

    // move a client off the to-serve list
    void signOut(client_type & targ) { signOut(&targ); };
    void signOut(client_type * const targ) {
        // find the given client pointer in our list
        vector<client_type *>::iterator where =
            find(client_list.begin(),client_list.end(), targ);

        // if it's in there, delete it!
        if (where != client_list.end())
                client_list.erase(where);
    };

     /* more blah... */
protected:
    // the list of pointers to clients
    vector<client_type *> client_list;
};

Here is the compiler error:

Code:

In file included from KeyDispatcher.hpp:7,
                 from ProtPlay.hpp:4,
                 from Follower.hpp:4,
                 from Follower.cpp:1:
ServiceList.hpp: In member function `void ServiceList<client_type>::signOut(client_type*)':
ServiceList.hpp:26: error: expected `;' before "where"
ServiceList.hpp:30: error: `where' undeclared (first use this function)
ServiceList.hpp:30: error: (Each undeclared identifier is reported only once for each function it appears in.)

The bolded line refers to the bolded bit in the code segment I posted.

By the way, I'm using Dev-C++ 4.9.9.2.

As I said, I don't know what's wrong at all. Help me, please?

And if you have some clever suggestions about the implementation in general, feel free to state them. This class is a template class to use in creating a message-dispatching class. Specifically, I'm currently using it to dispatch keyboard messages to a bunch of character queues. The class keeps a vector of pointers to the client character queues, and the child class of ServiceList will specify a function to actually dispatch the messages by iterating through the vector. I decided on a vector because I don't care (at least, not now) about signin/signout speeds, just the time it takes to dispatch a message.

So, yeah. You.Help(Me); ?

Try this:

Code:

        typename vector<client_type *>::iterator where =
            find(client_list.begin(),client_list.end(), targ);

gg

Thanks. It worked and is glorious.

So, could someone explain to me why typename was required?

Whenever you use a name that is dependent on a template parameter, you have to qualify the name using the typename keyword.

So in your example, the complete type name of "vector<client_type *>::iterator" is dependent on the the template parameter client_type and therefore needs to be qualified using typename.

More details:
http://www.gotw.ca/gotw/035.htm

gg