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Convert CString to char for use in Switch

Posted on 2003-12-06
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Last Modified: 2013-11-20
I know that I can't use a CString in a switch statement, but I only need to do a comparison against the first letter of the string.  I can not figure out how to take the letter from the CString and put it into a char so I can use it in switch statement.

This seems like a simple thing to do, but all searches on CString and char pull up char pointers and that is what I am trying to get away from.

Thanks in advance.
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Question by:APlusComp247
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LVL 86

Expert Comment

by:jkr
Comment Utility
>> I can not figure out how to take the letter from the CString
>>and put it into a char so I can use it in switch statement

Use

CString str ( "test");
char* pc = (LPCTSTR) str;

switch ( *pc) {

case 'a':

//...

break;

//....

case 't':

break;
};
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Expert Comment

by:jkr
Comment Utility
To elaborate on the above - the docs explain 'operator LPCTSTR()' as follows:

--------------->8-----------------------------

CString::operator LPCTSTR
operator LPCTSTR ( ) const;

Return Value

A character pointer to the string’s data.

Remarks

This useful casting operator provides an efficient method to access the null-terminated C string contained in a CString object. No characters are copied; only a pointer is returned. Be careful with this operator. If you change a CString object after you have obtained the character pointer, you may cause a reallocation of memory that invalidates the pointer.

--------------->8-----------------------------

So, if you have acces to the contents through a char*, you can dereference the pointer using '*pc'  to access the first character.
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Author Comment

by:APlusComp247
Comment Utility
This is part of the code that I am use

                szFileName = data.cFileName;
      szFirstLetter.Format("%s",szFileName.Left(1));
      szFirstLetter.MakeLower();
      char* cLetter = (LPCTSTR) szFirstLetter;
                        
      switch (*cLetter)
      {
      case 'a':
           m_nCount[1] ++;
      default:
             m_nCount[0] ++;
      }

I get the following error.

error C2440: 'initializing' : cannot convert from 'const char *' to 'char *'
        Conversion loses qualifiers

Thanks for the prompt reply
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Accepted Solution

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jkr earned 500 total points
Comment Utility
Ooops, make that read

const char* cLetter = (LPCTSTR) szFirstLetter;

and it will work. Since you are not going to manipulate the char*, this is the easiest solution.

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Author Comment

by:APlusComp247
Comment Utility
That works great!!!!   Thank you so much for you quick responces!
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Expert Comment

by:TiCpu
Comment Utility
Better would be :
char cLetter = sTextYouWantFirstLetter.GetAt(0);
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Author Comment

by:APlusComp247
Comment Utility
TiCpu
Thanks a lot for the post.  I am by no means a C++/MFC pro and really appreciate all the little shortcuts that I can pick up.  I really thought that there should be an easier way to do that, and sure enough you showed me.

Thanks again!
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Expert Comment

by:WilimarLynwood
Comment Utility
I'd use

CString str = "SomeString";

switch (str[0]) //0 so we point to the first char
{
     case 'S':
          //stuff
          break;
     default:
          //other stuff
          break;
}
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