Delphi Using Locate function in data source in memory table - delphi

Question

I need to check given value is already exists in the memory table, so i have tried following method.
function TForm4.findValueExists(id: Integer): Boolean;
var
state: Boolean;
begin
state := DBGrid1.DataSource.DataSet.Locate('code', id, []);
end;
here is the Search button procedure
procedure TForm4.butSearchClick(Sender: TObject);
var
id: Integer;
Name: String;
Sell: Double;
Qty: Integer;
Amount: Double;
OldQty: Integer;
RecordExist: Boolean;
begin
if txtprocode.Text <> '' then
begin
FDQuery1.Params.ParamByName('ID').Value := txtprocode.Text;
if FDQuery1.Active then
FDQuery1.Close;
FDQuery1.Open();
try
FDQuery1.First;
if not FDQuery1.Eof then
begin
id := FDQuery1.FieldByName('Id').AsInteger;
Name := FDQuery1.FieldByName('name').AsString;
Sell := FDQuery1.FieldByName('selling').AsFloat;
Qty := 1;
Amount := Sell * Qty;
if Form4.findValueExists(id) then
begin
FDMemTable1.Edit;
OldQty := DBGrid1.Fields[3].Value;
FDMemTable1.FieldByName('Qty').AsInteger := (OldQty + 1);
FDMemTable1.FieldByName('amount').AsFloat := (Sell * (OldQty + 1));
FDMemTable1.Post;
end
else
begin
FDMemTable1.InsertRecord([id, Name, Sell, Qty, Amount]);
end;
end;
finally
end;
end;
end;
unfortunately this method always gives me result as 'false'. but physically i can found matched result for given id.
here is UI
Guys i`m new to Delphi language.

Answer 1

You're not returning a value from your FindValueExists function, so you have absolutely no way of knowing if it locates the record or not. If you'd turn on compiler hints and warnings, the compiler would have pointed that fact out to you. (It would have informed you function findValueExists might not return a value, and also that Value assigned to 'state' is never used.)
Change your findValueExists so that it actually returns the result of the Locate call.
function TForm4.findValueExists(id: Integer): Boolean;
begin
Result := DBGrid1.DataSource.DataSet.Locate('code', id, []);
end;