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# how to calculate

Posted on 2007-03-22
606 Views
I would like to do some calculations on my form.
I have dbtext,currencyedit's and dbedit's.
Can you give me example how to calculate using these?
example:
I have a dbtext that gets a value from database.
Now I want that value to divide from a value in editbox
so a currency edit gives me the right sum..
just learning...
0
Question by:Vrtnar
• 8
• 7

LVL 21

Expert Comment

ID: 18770593
var a, b: Integer;
c: Double;

if TryStrToInt(dbtext.caption, a) and tryToInt(dbedit.text, b) then
c := b / a;

ziolko.
0

Author Comment

ID: 18770706
dont understand a thing...
I tried --
var a, b: Integer;
c: Double;
begin
if StrToInt(dbedit1.text, a) and StrToInt(edit14.text, b) then
currencyedit37.value := b / a;

and it dont work...please fro a nice explanation as I just learn
0

Author Comment

ID: 18770769
if TryStrToInt(dbedit1.Text,a) and TryStrToInt(edit14.text,b) then
currencyedit37.value:= a / b;
does not work either...
0

LVL 21

Expert Comment

ID: 18770798
TDBEdit has property called Text
TDBEdit has property called Caption
both properties are of type string which means they can contain literlas
so if you want to do any mth calculation you need to convert them

there are 3 most commonly used functions:
1. StrToInt() this func will throw exception if it's not possible to convert
sample

procedure S1;
var s: string;
i: Integer;
begin
s := 'hello world';
try
StrToInt(s, i);
except
ShowMessage('cannot convert hello world to integer value');
end;
end;

2. TryStrToInt() <- no error will be thrown

procedure S2;
var s: string;
i: Integer;
begin
s := 'hello world';
if not TryStrToInt(s, i) then
ShowMessage('cannot convert hello world to integer value');
end;

3. Val() <- no error will be thrown

procedure S3;
var s: string;
i: Integer;
val: Integer;
begin
s := 'hello world';
Val(s, i, code);
if code <> 0 then
ShowMessage('cannot convert hello world to integer value');
end;

ziolko.
0

LVL 21

Expert Comment

ID: 18770821
what kind of values you have in edits?

ziolko.
0

Author Comment

ID: 18770836
dbedit has no caption value but text.
in your 1st example to what do I assign   'c' ??
My 'c' should be a currency edit...
0

Author Comment

ID: 18770837
in edits I have numbers only...
0

LVL 21

Expert Comment

ID: 18770918
my mistake TBText has Caption...

this should work unless you have floating point values in edit or text
if TryStrToInt(dbedit1.Text,a) and TryStrToInt(edit14.text,b) then
currencyedit37.value:= a / b;

if you have floating point use TryStrToFloat()

ziolko.
0

Author Comment

ID: 18771054
dbedit1 is currency value in the database.
in edit14 i type in (freehand) number values.
I tried (on exit of the edit14):
procedure TPostavke.Edit14Exit(Sender: TObject);
var a, b: Integer;
c: Double;
begin
if TryStrToInt(dbedit1.Text,a) and TryStrToInt(edit14.text,b) then
currencyedit37.value:= a / b;
end;
It does not work..
If i substitute TryStrToInt with TryStrToFloat i get :
[Error] Unit3.pas(255): There is no overloaded version of 'TryStrToFloat' that can be called with these arguments

You see I have a value of '584,65 â‚¬' in my dbedit1.
Now I want to type (example number 2 in my editbox) and when I leave the edit my currency displays
292,325...
0

LVL 21

Accepted Solution

ziolko earned 125 total points
ID: 18771104
ok,

procedure TPostavke.Edit14Exit(Sender: TObject);
var a: Currency;
b: Double;
begin
if TryStrToCurr(dbedit1.Text,a) and TryStrToInt(edit14.text,b) then
currencyedit37.value:= a / b;
end;

ziolko.
0

Author Comment

ID: 18771208
procedure TPostavke.Edit14Change(Sender: TObject);
var a: Currency;
b: double;
begin
if TryStrToCurr(dbedit1.Text,a) and TryStrToInt(edit14.text,b) then
currencyedit37.value:= a / b;
end

I get :
[Error] Unit3.pas(256): Types of actual and formal var parameters must be identical
0

LVL 10

Expert Comment

ID: 18771616
0

LVL 21

Expert Comment

ID: 18771651
what the ...??

if TryStrToCurr(dbedit1.Text,a) and TryStrToFloat(edit14.text,b) then
currencyedit37.value:= a / b;

where did it go??

ziolko.
0

Author Comment

ID: 18773093
Dont seem to work...both ways...
0

Author Comment

ID: 18773543
I think i have figured what is the mistake here..
a queery that is the info provider for dbedit1 has the field
marked as 'currency' (it is currency in the database however)
But when I remove the field type as 'currency' in the
field rooster and set it to currency false the code :
var a: Currency;
b: integer;
begin
if TryStrToCurr(dbedit1.Text,a) and TryStrToInt(edit12.text,b) then
currencyedit37.value:= a / b;
works !
is this ok ??
0

LVL 21

Expert Comment

ID: 18778162
if it works it's ok:)

ziolko.
0

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