How to trim the empty spaces in VC++

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Hi All,

please help me how to trim whitespaces in VC++
In VC++ i am getting ImgFileName value as null. but i am getting empty space in the output so i am not able to get inside the if condition and moving to else part.

so i am not undersating how to write trim to remove whitespace

if( ImgFileName == NULL)
	
	*pbFileFound = FALSE;
else 
-----
----

What I have tried:

I am new to VC++. I am not able to understand how to perform trim in VC++

Posted 13-Jul-18 0:07am

suniti dinesh

Updated 13-Jul-18 0:47am

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Comments

Jochen Arndt 13-Jul-18 6:10am

What type is ImgFileName?
If that is a pointer to some kind of string, you can't trim it while it is NULL.

suniti dinesh 13-Jul-18 6:16am

Hi Jacon

ImgFileName type is

LPCTSTR ImgFileName

Jochen Arndt 13-Jul-18 6:19am

LPCTSTR is Long Pointer [to] Const T STRing.
The keyword here is const. Such strings can't be modified. You have to create a copy of the string and remove the spaces from that.

But a final answer requires knowing the context of your code (how it is called / preceeded and where and how should the string be used afterwards).

You can use the green 'Improve question' link to edit your question and add this information.

suniti dinesh 13-Jul-18 6:26am

Hi Jacon
Thank you so much for your Quick Reply.
yes it is a Const T STRing.

if the string is empty(IMGFileName) we have to make file found to false and we will close the application. in current scenario because of white space we are moving to else part and trying to open the file and we are not closing the application.

Jochen Arndt 13-Jul-18 6:38am

There is a difference between an empty string (usually indicated as "") and a NULL pointer to a string as explained by Griff.

But again:
Without knowing from where you got that string and what you want to do with it, it is impossible to answer.

2 solutions

Solution 1

NULL and whitespace aren;t that same at all: a NULL value means "there is nothing here", not even an empty string as represented by "", or a string full of whitespace " \n\n\n "
If ImgFileName is NULL, you can;t trim it - there is nothing to trim!

Think about it as cars: you have a parking space outside your house where you always park your car. One day you decide to go to the shops, and find your wife has moved the car - the space is empty. As a result, you cannot use the content of the parking space for anything - there is no car there to unlock, let alone drive!
The space is returning NULL - "No car here!" - so you must find out why it's NULL by speaking to your wife before you can try and do anything with the car.

Your code is the same: ImgFileName is telling you "there is no name here" - you need to look at why it's it null, not try to deal with it as if it wasn't.

Posted 13-Jul-18 0:17am

OriginalGriff

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suniti dinesh 13-Jul-18 6:34am

Hi OriginalGriff,
Thank you so much for your clear explanation. here the thing is like, if we don't have file in the specific location ImgFileName will be null and we will close the application. i have written logs and found that there is a white space in ImgFileName output, because of it we are trying to open the file instead of closing the application so we are getting error in my application.

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Jochen Arndt · Accepted Answer · 2018-07-13T00:47:00

You can use the CString class:

C++

// Added also a check for an empty string here
if (ImgFileName == NULL || *ImgFileName == _T('\x0'))
    *pbFileFound = FALSE;
else 
{
    // Create a CString copy from the string
    CString strFileName(ImgFileName);
    // Removes leading and trailing spaces from the string
    strFileName.Trim();
    // Optionally check again for empty string after trimming
    if (strFileName.IsEmpty())
        *pbFileFound = FALSE;
    else
    {
        // Can use strFileName to open the file
    }
}