QSignalMapper

[amleto]

what do you think I meant when I wrote

//Q_OBJECT etc


in the class code?

It means you have to fill in some bits for yourself! Now, please go and have a try for yourself!

[Ali Reza]

excuse me

what about 2'nd problem? (call a function that is member of other class)

my mapper class is :

class LookUpResultHandler : QObject
{
    Q_OBJECT;
public:
    LookUpResultHandler(int); //constructor
 
private:
    int id;
 
public slots:
    void lookupresult(QHostInfo);
 
};

class LookUpResultHandler : QObject
{
    Q_OBJECT;
public:
    LookUpResultHandler(int); //constructor

private:
    int id;

public slots:
    void lookupresult(QHostInfo);

};

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and in a cpp file i wrote :

#include "lookupresulthandler.h"
 
LookUpResultHandler::LookUpResultHandler(int id):id(id)
 
void LookUpResultHandler::lookupresult(QHostInfo hi)
{
    HostLookUpResult(hi,id); //this function is not accessible here because this is member of another class (my main class)
}

#include "lookupresulthandler.h"

LookUpResultHandler::LookUpResultHandler(int id):id(id)

void LookUpResultHandler::lookupresult(QHostInfo hi)
{
    HostLookUpResult(hi,id); //this function is not accessible here because this is member of another class (my main class)
}

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and in my main cpp file i wrote :

LookUpResultHandler *lrh = new LookUpResultHandler(id);
            QHostInfo::lookupHost(rp.getHost(),lrh,SLOT(lookupresult(QHostInfo)));

LookUpResultHandler *lrh = new LookUpResultHandler(id);
            QHostInfo::lookupHost(rp.getHost(),lrh,SLOT(lookupresult(QHostInfo)));

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just according your approach !
BUT give me ERROR !!!
why?????

[wysota]

BUT give me ERROR !!!
why?????

You answered this question yourself -- because it is not accessible as it is member of another class. Adjust your code accordingly. It's a basic programming issue and you should be able to solve it with basic programming skills.

[Ali Reza]

hi Mr Wysota

i knew this code is wrong but Mr amleto say this is correct.
i'm wait to amleto to relpy me

thanks Mr wysota

[amleto]

you already know that method is from another class. So I leave up to you to figure out how to solve this issue.

by the way,

LookUpResultHandler::LookUpResultHandler(int id):id(id)

LookUpResultHandler::LookUpResultHandler(int id):id(id)

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That is not a valid constructor.

[wysota]

i knew this code is wrong but Mr amleto say this is correct.

It is correct (as far as the logic is concerned, at least). It is just different than your actual code. Usually this is called "pseudo-code". If you never heard that term before, search for it using your favourite web search engine.

[Ali Reza]

i add a QObject *ReturnHandle to second class. by the following:

class LookUpResultHandler : QObject
{
    Q_OBJECT;
public:
    LookUpResultHandler(QObject *,int);
 
private:
    int id;
    QObject *ReturnHandle;
 
public slots:
    void lookupresult(QHostInfo);
 
};

class LookUpResultHandler : QObject
{
    Q_OBJECT;
public:
    LookUpResultHandler(QObject *,int);

private:
    int id;
    QObject *ReturnHandle;

public slots:
    void lookupresult(QHostInfo);

};

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and in my main cpp file i wrote:

LookUpResultHandler *lrh = new LookUpResultHandler(this,id);
QHostInfo::lookupHost(rp.getHost(),lrh,SLOT(lookupresult(QHostInfo)));

LookUpResultHandler *lrh = new LookUpResultHandler(this,id);
QHostInfo::lookupHost(rp.getHost(),lrh,SLOT(lookupresult(QHostInfo)));

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and for definition of lookupresult, i wrote:

LookUpResultHandler::LookUpResultHandler(QObject *rh,int id):id(id) , ReturnHandle(rh){}
 
void LookUpResultHandler::lookupresult(QHostInfo hi)
{
    ReturnHandle->HostLookUpResult(hi,id);
}

LookUpResultHandler::LookUpResultHandler(QObject *rh,int id):id(id) , ReturnHandle(rh){}

void LookUpResultHandler::lookupresult(QHostInfo hi)
{
    ReturnHandle->HostLookUpResult(hi,id);
}

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but give me error on second line in my main cpp
the error is: 'QObject' is inaccessible base of 'LookupResultHandler'
my problem is this ! what can i do ??
if needed i attach my project ?

[amleto]

my first try would be this:

class LookUpResultHandler : public QObject

For future reference, if you are going to say 'line two gives me an error', it is probably somewhat helpful if you actually show line 2

[Ali Reza]

now i tried by "public : QObject"

but give the error:
the 'QObject' has no member that named 'HostLookUpResult'

[amleto]

have you looked at QObject docs? Please do. If you look at the docs and find a method named HostLookUpResult, then you may think about writing a bug report to Qt. Otherwise you may want to think about why your code is wrong, and what the ccompiler is telling you.

[Ali Reza]

dear amleto plz tell me how i call that function ?

[wysota]

dear amleto plz tell me how i call that function ?

Ali Reza, please tell me, how much experience with C++ do you have? As it seems you have completely none. All the "problems" here are related more to C++ than to Qt, the fact that we're talking about Qt classes here is completely irrelevant. Maybe you should read some book on C++ programming and spend a week or two on practising use of the language? It would really save you a lot of time.

[Ali Reza]

you are right Mr wysota
i am newbie to C++ and Qt. because i am a student with 16 years old. and you are instructor and master.
thanks for your advice

[anda_skoa]

1.you define a new class that named "MyMapper" that inherits "QObject". but this definition get me the following error:
" 'QObject' is an inaccessible base of 'MyMapper' ".

That's because of the private inheritance. Just dervice publically from QObject

Cheers,
_

[amleto]

well done on reading the thread

[Ali Reza]

finally i solved my problem by signal&slot mechanism .
thanks Mr amleto