C ++ template syntax error
My C ++ is a little rusty, working in Java and C # for the past year and a half. I have a silly little error that I just can't figure out.
I have shortened the code as much as possible.
#include <list>
template<class T> class Subscriber
{
virtual void published( T t ) = 0;
};
template <class T> class PubSub
{
private:
std::list< Subscriber<T>* > subscribers;
public:
void publish( T t );
};
template<class T> void PubSub<T>::publish( T t )
{
for( std::list< Subscriber<T>* >::iterator i = subscribers.begin(); i != subscribers.end(); ++i )
i->published( t );
}
When I try to compile this (by including this header file in my code file) I get the following error:
../util/pubsub.h: In member function ‘void PubSub<T>::publish(T)’:
../util/pubsub.h:18: error: expected `;' before ‘i’
../util/pubsub.h:18: error: ‘i’ was not declared in this scope
What am I missing here?
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for( typename std::list< Subscriber<T>* >::iterator i = subscribers.begin(); i != subscribers.end(); ++i )
You need it typename
because it iterator
is a dependent name. The compiler must check the type of the template T
before it knows if it is a iterator
type or a value. In these cases, it is assumed to be the value unless you add typename
.
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