Copying "visualization_msgs::MarkerArray" as a vector

edit

I'm attemping to copy that message over the topic visualization_msgs::MarkerArray with a function like this:

void myclass::incomingPoints( const visualization_msgs::MarkerArray &waypoints ) 
{
    goals.reserve( waypoints->markers.size() );
    copy( waypoints->markers.begin(), waypoints->markers.end(), back_inserter( goals ) );
}

where:

std::vector<visualization_msgs::Marker> goals;

But trying to compile I get the error that says: .begin(), .size(), and .end() are not defined in the

visualization_msgs::Marker

error: base operand of ‘->’ has non-pointer type ‘const MarkerArray {aka const visualization_msgs::MarkerArray_<std::allocator<void>

}’ goals.reserve( waypoints->markers.size() );

and that's ok, because they are in the class vector defined. But how can I copy that array?

Regards