know if a text (or char) field is empty

[maxpesa]

hello, i'm new here, i searched in the forum if this question was asked before but i found nothing (maybe it is too simple?). So, i want to know if a text field (or a char) is empty (for example a Edit or a Memo).
another question, in c/c++, a string's end comes from the '\0' character, is te same in lazarus?

[taazz]

1) check if a string variable is empty

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if MyStringVar = '' then writeln('Empty String') else WriteLn('Not an empty string');
2) String type has a hidden length field which keeps the actually length and can be used regardless of character but since the win api expects zero terminated strings it also has a #0 at the end of each string.

[maxpesa]

i already tried it, with

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if (Edit3.Text='') then ShowMessage('!!!')ut i don't get a message

[howardpc]

You'd better show more code then.

Also note that the sysutils unit defines

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EmptyStr: string = '';
NullStr: PString = @EmptyStr
Using these can aid code clarity.

[maxpesa]

sysutils is in the uses

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procedure TForm1.TrovaFenotipoClick(Sender: TObject);
var fgen1,fgen2,ffiglio:fenotipo;
begin
str:=Edit4.Text;
 if (Edit3.Text='') //genitore-genitore
  then
   begin
    showmessage('!!!');
    duegenitori(Edit1.Text,Edit2.Text);
   end;                        

[taazz]

i already tried it, with

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if (Edit3.Text='') then ShowMessage('!!!')ut i don't get a message

I can only assume that the program flow never reached that line at all or the Edit3.text has one more space characters.
Try something simple eg make that the only line on a button's click event and add a break point to make sure that the line does executes. You can also write something like

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var
  CompRes : Boolean;
begin
  CompRes := (Edit3.text = '');
  If CompRes then ShowMessage('!!!');
and place a break point on the if line, observe the CompRes value by moving the mouse pointer on the CompRes.

[maxpesa]

YAY, now it works, i didn't change anything, i used the debugger and it worked, i don't now why, but it works
thanks taazz