Problem with template with static QMap

[marpasternak]

Hi, I have a problem with template in which I use QMap:

template
<
        class IdentifierType,
        class BytesToRead
>
class CommandHandler : public Command
{
public:
    explicit CommandHandler();
    ~CommandHandler();
 
    static bool registerCommand(const IdentifierType& identifier, Command* ptrToObject);
    static bool unregisterCommand(const IdentifierType& identifier);
    QPair<ResponseType::type, QByteArray> handleMessage(QByteArray* datagramPtr);
 
private:
    static QMap<IdentifierType, Command*> _associations;
};

template
<
        class IdentifierType,
        class BytesToRead
>
class CommandHandler : public Command
{
public:
    explicit CommandHandler();
    ~CommandHandler();

    static bool registerCommand(const IdentifierType& identifier, Command* ptrToObject);
    static bool unregisterCommand(const IdentifierType& identifier);
    QPair<ResponseType::type, QByteArray> handleMessage(QByteArray* datagramPtr);

private:
    static QMap<IdentifierType, Command*> _associations;
};

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template <class IdentifierType, class BytesToRead>
bool
CommandHandler<IdentifierType, BytesToRead>
::registerCommand(const IdentifierType& identifier, Command* ptrToObject)
{
    if(_associations.contains(identifier))
        return 0;
    else
    {
        _associations.insert(identifier, ptrToObject);
        return 1;
    }
}

template <class IdentifierType, class BytesToRead>
bool
CommandHandler<IdentifierType, BytesToRead>
::registerCommand(const IdentifierType& identifier, Command* ptrToObject)
{
    if(_associations.contains(identifier))
        return 0;
    else
    {
        _associations.insert(identifier, ptrToObject);
        return 1;
    }
}

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namespace TransportLayerType {
    enum type{
        V1 = 1
    };
}
 
typedef CommandHandler<TransportLayerType::type, quint8> TransportLayerHandler;

namespace TransportLayerType {
    enum type{
        V1 = 1
    };
}

typedef CommandHandler<TransportLayerType::type, quint8> TransportLayerHandler;

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And when I try to do this:

TransportLayerHandler::registerCommand(TransportLayerType::V1, new TransportLayerV1());

TransportLayerHandler::registerCommand(TransportLayerType::V1, new TransportLayerV1());

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I get:

undefined reference to `CommandHandler<TransportLayerType::type, unsigned char>::_associations'

Do you have any ideas?

Thanks for help, Marcin.

[stampede]

static template data member should be declared too (just like for regular, non-template classes), something like:

template<typename T, typename U>
QMap<T, Command*> CommandHandler<T,U>::_associations;

template<typename T, typename U>
QMap<T, Command*> CommandHandler<T,U>::_associations;

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Put it somewhere after the template definition.

[marpasternak]

Wow, it works! Thanks a lot!