CString.Append() in C++

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I have problems in a simple function that returns a string:

C++

if (format == style1)
    (value >= 0) ? str.Append(_T(">")) : str.Append(_T("<"));

I want to include another if condition without appending any symbols.ie;

C++

if (format == style2)
 (value >= 0) ? str.Append(_T(" ")) : str.Append(_T(" "));

But this does not work. Is there any other way to do this?

Edit: Added MFC tag as CString's an MFC class.

Posted 23-Apr-12 4:33am

Sumal.V

Updated 23-Apr-12 6:26am

Aescleal

v2

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nv3 23-Apr-12 11:24am

What exactly does not work? I guess, you will have to show us the entire function and tell us what you expect it do.

Sumal.V 23-Apr-12 11:56am

Well It is a very complicated code. Before the above shown code : There is :

String1.Format(_T("%%02d°%%02d'%%1.5lf\""), 3);
str.Format( String1, deg, min, sec);

This string is displayed in an edit box in the software. If the format type = style1, Then append '>' or '<'. If the format type = style2, I don't want to append any letter.

CPallini 23-Apr-12 12:44pm

Why don't you:
1. post the exact code
2. state clearly what is the expected behaviour
3. report the observed behaviour
?

Sumal.V 24-Apr-12 3:55am

if (Fmt == Latitude)
(val >= 0) ? str.Append(_T("N")) : str.Append(_T("S"));

else if (m_dirFmt == Longitude)
(val >= 0) ? str.Append(_T("E")) : str.Append(_T("W"));

else if (m_dirFmt == Bearing)
//Here I want to append nothing as bearing is just a degree value

Sumal.V 24-Apr-12 4:19am

All I want to know is can I append a blank space using CString.append?

Chuck O'Toole 24-Apr-12 9:53am

Of course and you did exactly that in your very first post. Now I'd like to point out that you never did answer the question of "What exactly do you mean when you say it doesn't work". Why do I get the feeling that appending the blank is not working for you yet it appears that the code you posted should do the job. So you will continue to go around and around on this until you either post the real code that doesn't work or explain what you see when you try to append the blank. Your debugger should be a lot of help on this.

Sumal.V 24-Apr-12 10:07am

Well edit box must have a different format that takes atleast one letter.If I dont append any letter, I get an error(User defined), that says Incorrect format. The problem is I'm working on somebody else's code.

For now I have appended a letter for that to work.
Thank u

Chuck O'Toole 24-Apr-12 10:19am

So, the "doesn't work" has nothing to do with the code itself, it's what you do with the variable when you're done. Apparently you try to sent the code to a custom edit control (derived from CEdit or other type control) and that custom control has some code to check for the validity of the string. You should focus on that control's code and maybe fit it to allow a trailing space or to allow space as a "letter".

Sumal.V 24-Apr-12 10:22am

Yeah the problem is with CEdit!! Will figure that out.

Thank u :)

Sumal.V 24-Apr-12 10:08am

And I'm not sure if I can post the actual code!! That would b wrong isn't it?

Chuck O'Toole 24-Apr-12 10:17am

You should only post small snippets of code that exhibits the problem you are having. Nobody is going to paw over dozens or more lines of code and very few will actually try to paste the code into a development eviornment and try to run it.

nv3 23-Apr-12 12:02pm

So what exactly does not work?

Richard MacCutchan 23-Apr-12 12:41pm

In your first case it will only append either character if format == style1, so the second test is redundant. Or maybe I misunderstood your question.

Chuck O'Toole 23-Apr-12 18:51pm

Echo all the above comments, you're going to have to carefully define "this does not work" because it sure looks like it should do something reasonable to us. Also, you said "I don't want to append any letter" in a reply above but you are willing to append " " (a blank character) so that does alter the string. Also, since both the true and false cases append a " " (blank) do you really want to go through the complications of the check for the value? Nothing in value will change the outcome, it will append a blank.

Sumal.V 24-Apr-12 3:55am

Exactly! I have no problems appending a character. But for one case I want to append nothing. ie:

if (Fmt == Latitude)
(val >= 0) ? str.Append(_T("N")) : str.Append(_T("S"));

else if (m_dirFmt == Longitude)
(val >= 0) ? str.Append(_T("E")) : str.Append(_T("W"));

else if (m_dirFmt == Bearing)
//Here I want to append nothing as bearing is just a degree value

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Aescleal · Accepted Answer · 2012-04-23T06:42:00

Solution 1

As every branch looks like it uses CString::Append why not simplify your code by doing something like:

C++

if (format == style1) str.Append( (value >= 0 ) ? "<" : ">" );

Or even go the conditional free route and use a lookup table:

C++

const *char appendable_strings[][] = { { "<", ">" }, { " ", " " } };

str.Append( appendable_strings[format][value < 0] );

and map format and style onto 0 based integers. The code will be smaller, probably faster and a lot easier to read. And stick it in a function so you've got a better idea what the compiler is whinging about when you do something incorrectly.

Cheers,

Ash

PS: Not sure the array indices are 'round the right way - I don't use arrays that often.

PPS: As another tip forget CString - std::string and std::ostringstream will perform all your formatting needs.

Edit: Caught Native Language Fail Exception

Edit II, the Horror Continues: Slung a conditional in as per Chuck's suggestion below and the fact that I'd missed the original poster wanting a space character appended for style2.

Posted 23-Apr-12 6:42am

Aescleal

Updated 23-Apr-12 15:06pm

v3

Comments

Chuck O'Toole 23-Apr-12 18:44pm

Basic logic flaw there. His condition is value >= 0. You can't use val (value) as the index because it can be *any* number, e.g. 999999 or -326 and that would be an unacceptable index for you "appendable_strings" array.

Chuck O'Toole 23-Apr-12 18:47pm

Another nit, assuming you did
int val = (value >= 0)
to change the bool to an int, you'd have to reverse the logic (0 = false = '>', 1 = true = '>') or reverse the conditional (value < 0). Then you can use the shorter code.
Just nitpicking, assuming the OP wanted to use your shortcut.

Aescleal 23-Apr-12 21:07pm

Thanks, modified the indexing to take your points into account.

Jochen Arndt 24-Apr-12 3:44am

It can be more simplified (and optimized) by using AppendChar().

Aescleal 24-Apr-12 5:22am

I got the impression from other comments he made that he wanted to be able to add arbitrary strings. If all he wants are characters then your way sounds fine.

Sumal.V 24-Apr-12 4:12am

I have no problem appending character/letter but for one case I want to return the string as it is : The code:
if(condition)
switch (degree)
{
case one:
str.Append(_T("0"));
break;

case two:
str.Append(_T("00"));
break;
}
if (Fmt == Latitude)
(val >= 0) ? str.Append(_T("N")) : str.Append(_T("S"));

else if (m_dirFmt == Longitude)
(val >= 0) ? str.Append(_T("E")) : str.Append(_T("W"));

else if (m_dirFmt == Bearing)
//Here I want to append nothing as bearing is just a degree value

}
return str;

Aescleal 24-Apr-12 5:24am

If I were you I'd chuck all code you've got away and create three new classes: angle, bearing and location. Then you want have to use complicated switches, conditionals and whatever else, all the formatting would be done based on the class you're formatting.

From what you've presented there it's a case of (slightly) simplified design at the expense of code complexity.

Jochen Arndt 24-Apr-12 5:30am

I still don't see where your problem is. Appending nothing is no case, it's just no code. If you want to append nothing with 'Bearing' (even not 'Degree'), just enclose the complete code by an if clause: if (m_dirFmt != Bearing)

CString.Append() in C++

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