template error message c++
I have the following header file:
#ifndef DATABASE_H
#define DATABASE_H
#include <vector>
#include <iostream>
#include <string>
#include "record.h"
using namespace std;
template <class value>
class Database {
public:
void write (ostream& out, DBScope scope) const;
Database <value>() {};
~Database();
private:
vector <Record<value> > records;
};
#include "database.tem"
#endif
database.tem:
template <class value>
void Database<value>::write (ostream& out, DBScope scope) const {
class vector <Record <value> >::iterator itr = records.begin();
switch (scope) {
case AllRecords:
for (; itr != records.end(); itr++) out << itr;
break;
case SelectedRecords:
for (; itr != records.end(); itr++) {
if (itr.isSelected) out << itr;
}
break;
}
}
I was running this header a long with another file and produced this error message, noting that in my header file I have another file called database.tem which is #include "database.tem"
into my database.h
file:
database.tem: In member function 'void Database<value>::write (std:: ostream&, DBScope) const [with value = int]':
database.tem: In member function 'void Database<value>::write(std::ostream&, DBScope) const [with value = int]':
interactive.cpp:285: instantiated from 'bool WriteCommand(Database<value>&) [with value = int]'
interactive.cpp:127: instantiated from 'bool DispatchCommand(CommandT, Database<value>&) [with value = int]'
interactive.cpp:74: instantiated from 'void MainLoop(Database<value>&) [with value = int]'
interactive.cpp:99: instantiated from here
database.tem:6: error: conversion from '__gnu_cxx::__normal_iterator<const Record<int>*, std::vector<Record<int>, std::allocator<Record<int> > > >' to non-scalar type '__gnu_cxx::__normal_iterator<Record<int>*, std::vector<Record<int>, std::allocator<Record<int> > > >' requested
interactive.cpp:285: instantiated from 'bool WriteCommand(Database<value>&) [with value = int]'
interactive.cpp:127: instantiated from 'bool DispatchCommand(CommandT, Database<value>&) [with value = int]'
interactive.cpp:74: instantiated from 'void MainLoop(Database<value>&) [with value = int]'
interactive.cpp:99: instantiated from here
database.tem:11: error: no match for 'operator<<' in 'out << itr'
I have no idea what this messsage is talking about, can someone help开发者_C百科 me
The first error has to do that the method is const, hence records
is const, and reconds.begin()
returns a const_iterator
.
template <class value>
void Database<value>::write (ostream& out, DBScope scope) const {
vector <Record <value> >::const_iterator itr = records.begin();
The second error means that you probably meant to dereference the iterator:
for (; itr != records.end(); itr++) out << *itr;
It looks like you have only posted a partial error message but the error is probably that you need to write itr->isSelected rather than itr.isSelected.
Also it's preferable to use ++itr instead of itr++ when using iterators.
What you are trying to print is iterator object, not the value it refer to:
out << itr;
Replace that with
out << *itr;
Also make sure that class Record has either method or function defined:
ostream& out operator <<(ostream& out); // method
ostream& out operator <<(ostream& out, const Record &); //function
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