C / C++ / MFC

Re: stl list&amp;amp;lt;&amp;amp;gt;::iterator for derived classes ?!?

5-Jan-06 12:49

Hi

i have a little problem using the list<>::iterator.

Assume you have a class CARS{ virtual void info();...}
and some public derived classes as GM{void info();...},BMW{void info();...}

<br />
...<br />
list<CARS> carpark;<br />
GM car1();<br />
GM car2();<br />
BMW car3();<br />
BMW car4();<br />
<br />
carpark..push_back(car1);<br />
carpark..push_back(car2);<br />
carpark..push_back(car3);<br />
carpark..push_back(car4);<br />
<br />
list<CARS>::iterator it;<br />
for(it=carpark.begin();it != carpark.end(); it++)<br />
{<br />
cout << it->info() << endl;<br />
}<br />
...<br />

so far so fine.

Now how to call the info() from GM or BMW using the iterator ??
(not the one from CARS)

THX

Tim

-- modified at 17:50 Thursday 5th January, 2006

Christian Graus5-Jan-06 12:58

5-Jan-06 12:58

It should just be called for you automatically. That's the point of an overrided method.

However, if all cars have a type, then it should be stored in a variable that exists in the base class, and the GetType method should exist only in the base class. The derived classes should just set that variable.

Christian Graus - Microsoft MVP - C++

-- modified at 17:58 Thursday 5th January, 2006

tbrake5-Jan-06 13:08

5-Jan-06 13:08

Hallo

THX so far, but how do i do this with the GetType Methode and how can this help me calling the method of the derived class ??

Tim

Christian Graus5-Jan-06 13:11

5-Jan-06 13:11

#include <string>

class CAR
{
private:
std::string type;
public:
std::string GetType();
}

class BMW
{
public:
BMW() { type = "BMW"; }
}

and so on. you don't need to use std::string, obviously.

Christian Graus - Microsoft MVP - C++

tbrake5-Jan-06 13:29

5-Jan-06 13:29

HI
OK have somthing like this but how to call the individual info() method ??

Tim

Christian Graus5-Jan-06 13:32

5-Jan-06 13:32

Well, my way, there is no individual info method. However, in either case, you should find you're calling it in your original code. If not, perhaps you need to store a pointer instead of a class instance, perhaps it's being downcast by std::list at the moment ?

Christian Graus - Microsoft MVP - C++

tbrake5-Jan-06 13:43

5-Jan-06 13:43

OK
THX alot

Will write my own list and iterator
That might be no problem then i just liked to know how to use list and iterator

CU

Christian Graus5-Jan-06 13:46

Re: stl list&amp;lt;&amp;gt;::iterator for derived classes ?!?

5-Jan-06 13:46

tbrake wrote:
Will write my own list and iterator

No, please don't do that. What I was suggesting was that you should perhaps try storing a CAR * instead of a CAR in std::list.

Christian Graus - Microsoft MVP - C++

Christian Graus5-Jan-06 13:55

Re: Get Status of Comm Port

5-Jan-06 13:55

OK, I've done some testing:

this works:

#include <string>
#include <iostream>
#include <list>

class CAR
{
public:
virtual char * GetInfo() { return "BASE"; };
};

class BMW: public CAR
{
char * GetInfo() { return "BMW"; }
};

class Gemini :public CAR
{
char * GetInfo() { return "Gemini"; }
};

class Benz :public CAR
{
char * GetInfo() { return "Benz"; }
};

int _tmain(int argc, _TCHAR* argv[])
{
std::list<CAR*> cars;
cars.push_back(new BMW());
cars.push_back(new BMW());
cars.push_back(new Gemini());
cars.push_back(new Benz());

std::list<CAR*>::iterator it = cars.begin();

while(it != cars.end())
{
std::cout << (*it)->GetInfo() << std::endl;
++it;
}

int i;
std::cin >> i;
return 0;
}

but if you don't store pointers in the list, then it does indeed downcast to the base class.

Christian Graus - Microsoft MVP - C++

Get Status of Comm Port

tj_cts5-Jan-06 10:00

tj_cts

5-Jan-06 10:00

Hello all,
(My first post)

I am developing an application for WinCE 3.0 for a Pocket PC 2000 device in C++ using MFC / WinAPI.

In my application I use a Bluetooth CF card to communicate with a wireless printer. The drivers installed assign a COM port to the printer so I may
read / write to it using WinAPI calls for Files such as:

CreateFile( ... );<br />
ReadFile( ... );<br />
WriteFle( ... );

The wireless printer conserves battery by automatically turning off after a period of inactivity, so at times I must check to see if it is there before the user tries to print something.

The problem is that if I want to know anything about the file I must first get a handle with the CreateFile( ... ) function, which lags about 10-15 seconds before it times out if the printer is off, so usually the user is already trying to print something by the time I get back from that function call. Or if I make the user wait until I get back, they will get frustrated after so much time.

I tried using

CFile::GetStatus( ... )<br />

but it doesn't seem to work for COM ports, eg. I can call:
HANDLE hPrinter = CreateFile( _T("COM4:"),...);
and I get the handle but if I do this:
BOOL bIsPortAvailable = CFile::GetStatus( _T("COM4:"), ...);
I get FALSE back;

Is there a way to specify the timeout for the CreateFile( ... ) function or another way to check if that COM port is available?

Thanks Much,
T.J. Barbour

KellyR5-Jan-06 10:12

KellyR

5-Jan-06 10:12

You could try polling the printer to see when it's off. That way when a user tried to print, the status would already be off unless it just turned off a few seconds before the user tried to print.

I think you might get more responses if this post were moved to the WinCE forum? I've noticed lots and lots of function calls give me major lag on WinCE when they don't on WinXP, so you're more likely to get someone who knows how to solve the problem over there.

Kelly Ryan

Re: Get Status of Comm Port

tj_cts5-Jan-06 11:12

tj_cts

5-Jan-06 11:12

I'll look into that.

Polling is an option that I may persue, but we all know the disadvantages of polling : )

I appreciate the reply!

Thanks Much,

T.J. Barbour

Re: Get Status of Comm Port

Blake Miller5-Jan-06 13:31

Blake Miller

5-Jan-06 13:31

Maybe you can get the printer driver manufacturer to support WM_DEVICECHANGE then you can actually be notified that the power has come or gone...

Marriage slows down your coding, a baby slows it down even more!

How to submit information from an application?

kevincwong5-Jan-06 9:47

kevincwong

5-Jan-06 9:47

Hi,

I am working on an application that requires user to submit registration information to my company.

There are a couple options for me.
1) bring up an email & pre-type all registraion
information to the body but I am not sure
it's doable or not.

2) create a submit button and send the information
to our server but it requires some work in back end.

Is there any better way to do it? If not, is
that possible to pre-type the email?

Can someone give me some ideas/suggestions?

Thanks,

Kevin

Office Lineman5-Jan-06 10:19

Office Lineman

5-Jan-06 10:19

Sure. You could use MAPISendMail (PSDK) to send mail from the application. You could easily provide the registration information in your desired format within the message object, and just show the user a read-only copy (out of niceness).

To the same end, there are also third-party add-ins that you can add to your app to handle mail sending.

Remember, though, that if you want to process these incoming registration messages automatically, some SMTP servers change the content of email messages. For example, my office e-mail scans for viruses and adds a line indicating the messages has been scanned for viruses at the bottom of the message.

--
I've killed again, haven't I?

kevincwong6-Jan-06 12:50

kevincwong

6-Jan-06 12:50

Hi,

Thanks for your suggestion.

After reading http://www.codeproject.com/internet/cimapi.asp,
I am able to send email from my application.

However, it got a minor issue.

My email body is about 10 lines with about 200 characters.
I have "\r\n" to separate each line. The AfxMessageBox
displayed the text correctly, 10 separate lines.
But, the mail.Text ( ) concatenated my data to a
huge BIG string.

Do you know what caused the problem?

Thanks,

Kevin

Office Lineman6-Jan-06 13:19

Office Lineman

6-Jan-06 13:19

I just tried the CIMapi and the mail I sent with "\r\n" as a line separator came across as individual lines as expected.

Have you checked the email message source to see if your CRLFs are coming through at all and just not getting displayed?

--
I've killed again, haven't I?