How to store custom class in QHash?

[Misenko]

Hi

I have written a class User. Its a simple class which stores some information about user. Here is a code:

user.h

#ifndef USER_H
#define USER_H
 
#include <QObject>
#include <QString>
#include <QHostAddress>
#include <QDateTime>
#include <QDataStream>
 
class User : public QObject
{
    Q_OBJECT
 
public:
    User();
    User(QString &firstName, QString &lastName);
    User(const User &newUser);
    ~User();
    void setIpAddress(const QHostAddress &newIpAddress);
    void setConnectionDateTime(const QDateTime &newConnectionDateTime);
    void setFirstName(const QString &newFirstName);
    void setLastName(const QString &newLastName);
    QString firstName() const {return userFirstName;}
    QString lastName() const {return userLastName;}
    QHostAddress ipAddress() const {return userIpAddress;}
    QDateTime connectionDateTime() const {return userConnectionDateTime;}
    quint16 userSize() const;
    bool operator==(const User & other) const;
private:
    QString userFirstName;
    QString userLastName;
    QHostAddress userIpAddress;
    QDateTime userConnectionDateTime;
};
 
Q_CORE_EXPORT QDataStream & operator<<(QDataStream & out, const User &user);
Q_CORE_EXPORT QDataStream & operator>>(QDataStream & in, User &user);
 
#endif // USER_H

#ifndef USER_H
#define USER_H

#include <QObject>
#include <QString>
#include <QHostAddress>
#include <QDateTime>
#include <QDataStream>

class User : public QObject
{
    Q_OBJECT

public:
    User();
    User(QString &firstName, QString &lastName);
    User(const User &newUser);
    ~User();
    void setIpAddress(const QHostAddress &newIpAddress);
    void setConnectionDateTime(const QDateTime &newConnectionDateTime);
    void setFirstName(const QString &newFirstName);
    void setLastName(const QString &newLastName);
    QString firstName() const {return userFirstName;}
    QString lastName() const {return userLastName;}
    QHostAddress ipAddress() const {return userIpAddress;}
    QDateTime connectionDateTime() const {return userConnectionDateTime;}
    quint16 userSize() const;
    bool operator==(const User & other) const;
private:
    QString userFirstName;
    QString userLastName;
    QHostAddress userIpAddress;
    QDateTime userConnectionDateTime;
};

Q_CORE_EXPORT QDataStream & operator<<(QDataStream & out, const User &user);
Q_CORE_EXPORT QDataStream & operator>>(QDataStream & in, User &user);

#endif // USER_H

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user.cpp

#include "user.h"
#include <QByteArray>
#include <QDataStream>
 
User::User()
	:userFirstName(""), userLastName("")
{
 
}
 
User::User(QString &firstName, QString &lastName)
	:userFirstName(firstName), userLastName(lastName)
{
 
}
 
User::User(const User &newUser)
{
	userFirstName = newUser.firstName();
	userLastName = newUser.lastName();
	userIpAddress = newUser.ipAddress();
	userConnectionDateTime = newUser.connectionDateTime();
}
 
User::~User()
{
 
}
 
void User::setIpAddress(const QHostAddress &newIpAddress)
{
	userIpAddress = newIpAddress;
}
 
void User::setConnectionDateTime(const QDateTime &newConnectionDateTime)
{
	userConnectionDateTime = newConnectionDateTime;
}
 
void User::setFirstName(const QString &newFirstName)
{
	userFirstName = newFirstName;
}
 
void User::setLastName(const QString &newLastName)
{
	userLastName = newLastName;
}
 
quint16 User::userSize() const
{
	QByteArray *array = new QByteArray;
	QDataStream stream(array, QIODevice::WriteOnly);
	stream << userFirstName << userLastName << userIpAddress << userConnectionDateTime;
	quint16 size = array->size();
	return size;
}
 
bool User::operator==(const User & other) const
{
	bool state;
	if (userFirstName == other.firstName() && userLastName == other.lastName())
		state = true;
	else
		state = false;
 
	return state;
}
 
QDataStream &operator<<(QDataStream & out, const User &user)
{
	out << user.firstName() << user.lastName() << user.ipAddress() << user.connectionDateTime();
	return out;
}
 
QDataStream &operator>>(QDataStream & in, User &user)
{
	QString firstName;
	QString lastName;
	QHostAddress address;
	QDateTime dateTime;
 
	in >> firstName >> lastName >> address >> dateTime;
 
	user.setFirstName(firstName);
	user.setLastName(lastName);
	user.setIpAddress(address);
	user.setConnectionDateTime(dateTime);
	return in;
}

#include "user.h"
#include <QByteArray>
#include <QDataStream>

User::User()
	:userFirstName(""), userLastName("")
{

}

User::User(QString &firstName, QString &lastName)
	:userFirstName(firstName), userLastName(lastName)
{
	
}

User::User(const User &newUser)
{
	userFirstName = newUser.firstName();
	userLastName = newUser.lastName();
	userIpAddress = newUser.ipAddress();
	userConnectionDateTime = newUser.connectionDateTime();
}

User::~User()
{

}

void User::setIpAddress(const QHostAddress &newIpAddress)
{
	userIpAddress = newIpAddress;
}

void User::setConnectionDateTime(const QDateTime &newConnectionDateTime)
{
	userConnectionDateTime = newConnectionDateTime;
}

void User::setFirstName(const QString &newFirstName)
{
	userFirstName = newFirstName;
}

void User::setLastName(const QString &newLastName)
{
	userLastName = newLastName;
}

quint16 User::userSize() const
{
	QByteArray *array = new QByteArray;
	QDataStream stream(array, QIODevice::WriteOnly);
	stream << userFirstName << userLastName << userIpAddress << userConnectionDateTime;
	quint16 size = array->size();
	return size;
}

bool User::operator==(const User & other) const
{
	bool state;
	if (userFirstName == other.firstName() && userLastName == other.lastName())
		state = true;
	else
		state = false;
	
	return state;
}

QDataStream &operator<<(QDataStream & out, const User &user)
{
	out << user.firstName() << user.lastName() << user.ipAddress() << user.connectionDateTime();
	return out;
}

QDataStream &operator>>(QDataStream & in, User &user)
{
	QString firstName;
	QString lastName;
	QHostAddress address;
	QDateTime dateTime;
	
	in >> firstName >> lastName >> address >> dateTime;
	
	user.setFirstName(firstName);
	user.setLastName(lastName);
	user.setIpAddress(address);
	user.setConnectionDateTime(dateTime);
	return in;
}

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In the other part of my program I am trying to put this class into QHash like this:

QHash<User, QTcpSocket *> connections;

QHash<User, QTcpSocket *> connections;

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But when I try to compile it i get the error message:

../../../Qt_4.3.4/include/QtCore/../../src/corelib/tools/qhash.h instantiated from `bool QHash<Key, T>::contains(const Key&) const [with Key = User, T = QTcpSocket*]'
../../../Qt_4.3.4/include/QtCore/../../src/corelib/tools/qhash.h no matching function for call to `qHash(const User&)'

What shoud I do to make possible to add this class into QHash?

Thanks.

[wysota]

QObjects can't be copied and QHash requires the key class to be mutable and have the qHash() function defined. From what I see you violated both requirements

Your class doesn't seem to benefit from being a QObject subclass and furthermore the serialization mechanism probably won't work with it either. I suggest you remove the QObject legacy and implement qHash for your class.

If you require your class to be a QObject, then I suggest storing pointers to those objects instead of objects themselves in the hash.

[Misenko]

Thanks.

Ok, I can remove the QObject legacy but how to implement qHash for my class? Can you write a little example?

[wysota]

As far as I remember there is a nice example in the docs. In general the function should return an integer for any object of your class - always the same integer for the same object content and different integers for different content with an equal spread of values among the object space.