Is forward declaration a hack for bad, lazy programmers? - C / C++ / MFC Discussion Boards

Re: from the index pos in ch[],delete the the string of len

David Crow8-Apr-10 3:43

David Crow

8-Apr-10 3:43

wbgxx wrote:
...but the first function is error...

Which means what exactly?

wbgxx wrote:
...I don not know why...

Have you used the debugger to step through the code to find out why?

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Re: from the index pos in ch[],delete the the string of len

wbgxx8-Apr-10 4:00

wbgxx

8-Apr-10 4:00

Oh,I don not do this,sorry! I am freshman and does not use the debugger to step through the coder

cannot convert from 'double' to 'class _variant_t *

browneyes867-Apr-10 9:38

browneyes86

7-Apr-10 9:38

hello, i need help on this: the error i get is: error C2440: '=' : cannot convert from 'double' to 'class _variant_t *' on this line:

Filtered_Average[ik] = filtered_sum/95;

the portion of the code is:

vector<_variant_t*> Filtered_Average(9990);<br />
	for(k = 0; k < Filtered_Average.size(); ++k)<br />
	{<br />
		Filtered_Average[k] = new _variant_t();<br />
	}

......

	// calculate average of filtered data<br />
		<br />
		for (int ik = 1; ik<=N; ik++)<br />
		{<br />
			 double filtered_sum =  0.0;<br />
<br />
			for (int jk= 1; jk<=N2; jk++)	<br />
			{<br />
				  filtered_sum =  filtered_sum + (double)results2[ik][jk];<br />
			}<br />
<br />
				  Filtered_Average[ik] = filtered_sum/95;<br />
			}

Re: cannot convert from 'double' to 'class _variant_t *

Iain Clarke, Warrior Programmer7-Apr-10 10:03

Iain Clarke, Warrior Programmer

7-Apr-10 10:03

_variant_t& operator=(double dblSrc);

is valid, so you can convert from double to _variant_t. So, your problem is your trying to make a pointer equal a double.

Maybe:

*(Filtered_Average[ik]) = filtered_sum/95;

?

I'd also question the 95... if you know N2 = 95, then you don't need N2. If you don't know, then you can't use 95...

Iain.

I have now moved to Sweden for love (awwww).

Re: cannot convert from 'double' to 'class _variant_t *

Eugen Podsypalnikov7-Apr-10 10:04

Eugen Podsypalnikov

7-Apr-10 10:04

Try it

*(Filtered_Average[ik]) = filtered_sum/95;

virtual void BeHappy() = 0;

resolving a shortcut file name

Alan Kurlansky7-Apr-10 9:30

Alan Kurlansky

7-Apr-10 9:30

I would like to use a shortcut to point to a file in some other directory. In windows C++ how can I get at the target the shortcut is pointing to in order to then open that specific file?

Re: resolving a shortcut file name

Nuri Ismail7-Apr-10 10:10

Nuri Ismail

7-Apr-10 10:10

This[^] article might help. Smile | :)

Is forward declaration a hack for bad, lazy programmers?

Vaclav_7-Apr-10 7:16

Vaclav_

7-Apr-10 7:16

I am not sure where to post this , so it is here.
I am a lazy programmer and have a hard time keeping track of #include(s) nesting in my messy program.
I started to use "forward declaration" to mask #include files dependencies.
It works most of the time.
But is it a good practice?
Would it be going too far if I just forward declare all my classes in stdafx.h? Is portability main issue here or what is the issue?
Thanks for reading.
Vaclav

Re: Is forward declaration a hack for bad, lazy programmers?

C^hris L^osinger7-Apr-10 7:25

C^hris L^osinger

7-Apr-10 7:25

i don't like forward declarations, but i'm not exactly sure why. i always feel weird when i have to make one.

but, sometimes they're just plain necessary.

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Re: Is forward declaration a hack for bad, lazy programmers?

Moak7-Apr-10 7:48

Moak

7-Apr-10 7:48

Vaclav_Sal wrote:
I started to use "forward declaration" to mask #include files dependencies.

Like you said, if you want to minimise link dependecies it's a great tool. Change one header file and you will not have to recompile a rats tail of other object files, just because the class is used in protected/private methods of other classes. Generally I include only header files absolutely necessary to compile in header files... and put the rest into the individual source files. With bigger projects it can be a time saver.

Vaclav_Sal wrote:
Would it be going too far if I just forward declare all my classes in stdafx.h

I would personally use stdafx.h only to what it was intended for, speed up compilation time. For example have library and rarely changing header files in it. However I keep dependencies working without precompiled headers, in case I rip out a file/module and reuse it in another project. That's just my personal design taste, hope it helped. Smile | :)

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modified on Wednesday, April 7, 2010 1:54 PM

Re: Is forward declaration a hack for bad, lazy programmers?

William Winner7-Apr-10 11:41

William Winner

7-Apr-10 11:41

Quit editing quick answers and not changing anything...who wants to see a question from March brought back up to the top of the list just so you can get some editing points?!?

Offtopic

Moak7-Apr-10 11:57

Moak

7-Apr-10 11:57

William, I was retagging the questions for better findability.

In my opinion such changes should not bring back quick answers to the top of the "last changes" list and also give no editing points (actually they don't). You can report it here[^].

Cheers

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Re: Is forward declaration a hack for bad, lazy programmers?

Nemanja Trifunovic7-Apr-10 7:59

Nemanja Trifunovic

7-Apr-10 7:59

There is nothing wrong with forward declarations. In fact, some very well known and useful C++ idioms depend on that technique: Pimpl (opaque pointer)[^], for instance.

utf8-cpp

Re: Is forward declaration a hack for bad, lazy programmers?

Eugen Podsypalnikov7-Apr-10 9:24

Eugen Podsypalnikov

7-Apr-10 9:24

There was a good word said by Chris: "sometimes",
that is not associated for me with "stdafx.h"... Smile | :)

virtual void BeHappy() = 0;

CString convert error in Embedded Visual C++

CHYGO7-Apr-10 4:20

CHYGO

7-Apr-10 4:20

i want to convert the interger to a binary string in EVC.so i use the '_itot'.

<br />
UINT16 high16data = dwReadValue;<br />
CString high16string = _itot(high16data, high16string, 2);<br />

the error is:error C2664:'_itow':cannot convert parameter 2 from 'const unsigned short *'
how can i convert the parameter?(i do want to use the CString type not the char[] as showed in MSDN). so how to do it?

thanks for helping.

i 've tried ,then i have no regret

Re: CString convert error in Embedded Visual C++

eusto7-Apr-10 4:42

eusto

7-Apr-10 4:42

_itot does not accept a CString as parameter. you have to pass a TCHAR* as the second parameter. Why don't you use CString::Format?

Re: CString convert error in Embedded Visual C++

CHYGO7-Apr-10 5:18

CHYGO

7-Apr-10 5:18

CString::Format maybe a good choice,i'll try it tomorrow Smile | :)

i 've tried ,then i have no regret

Re: CString convert error in Embedded Visual C++

Eugen Podsypalnikov7-Apr-10 5:38

Eugen Podsypalnikov

7-Apr-10 5:38

CHYGO wrote:
i'll try it tomorrow

It will be a good day Smile | :)

virtual void BeHappy() = 0;

Re: CString convert error in Embedded Visual C++

CHYGO8-Apr-10 2:01

CHYGO

8-Apr-10 2:01

it is an good day Big Grin | :-D

i 've tried ,then i have no regret

ComboBox / Win32 [modified]

Fareed Rizkalla7-Apr-10 2:27

Fareed Rizkalla

7-Apr-10 2:27

LPWSTR URL;
ComboBox_GetText(hComboBox, URL, sizeof URL);

I'm writing this app where the user enters a URL in a ComboBox.
When he presses OK, the text in the ComboBox is retrieved to start processing.
Using Unicode!

Every time I enter a URL the program breaks and starts the debugger.
Running Visual Studio 2010.

Any help appreciated. Blush | :O

modified on Wednesday, April 7, 2010 8:43 AM

Re: ComboBox / Win32

CPallini7-Apr-10 2:31

CPallini

7-Apr-10 2:31

And what is your trouble about?

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Re: ComboBox / Win32

Fareed Rizkalla7-Apr-10 2:38

Fareed Rizkalla

7-Apr-10 2:38

Every time I enter a URL the program breaks and starts the debugger.
Running Visual Studio 2010.

Re: ComboBox / Win32

CPallini7-Apr-10 2:50

CPallini

7-Apr-10 2:50

You didn't provide the required buffer (URL doesn't point to a valid memory buffer).
Try

LPTSTR  URL;
int len = ComboBox_GetTextLength(hComboBox);
URL = new TCHAR[len+1];
ComboBox_GetText(hComboBox, URL, len+1);
//.. use URL
delete [] URL;

Re: ComboBox / Win32

Fareed Rizkalla7-Apr-10 3:15

Fareed Rizkalla

7-Apr-10 3:15

It works, but something weird happened.

The GetText method requested URL to be LPWSTR.
LPTSTR is multibyte, not unicode.
Any pointers what was the trick in fixing it?

Re: ComboBox / Win32

CPallini7-Apr-10 3:18

CPallini

7-Apr-10 3:18

Actually the ComboBox_GetText macro accpts a LPTSTR as you may see in the documentation [^].
Is there something I missed?
Smile | :)

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