How to enable a submit button after multiple form fields have been verified.
-
I have seen this same question not too long ago on this forum. Not sure it was the same one asking though.
While Volker's code is absolutely right, personally, I find something like this more readable:
@
void YourDialog::checkLineEdits()
{
bool ok(true);
ok &= !ui->lineEdit1->text().isEmpty();
ok &= !ui->lineEdit2->text().isEmpty();
ok &= !ui->lineEdit3->text().isEmpty();
ok &= !ui->lineEdit4->text().isEmpty();ui->okButton->setEnabled(ok);}
@And I know people here are going to disagree with me. :-)
Of course, variations are possible too, for instance one where you iterate over all QLineEdits (no matter how many there are):@
void YourDialog::checkLineEdits()
{
bool ok(true);
QList<QLineEdit*> lineEditList = findChildren<QLineEdit*>();
foreach (QLineEdit* le, lineEditList)
ok &= !le->text().isEmpty();ui->okButton->setEnabled(ok);}
@ -
[quote author="peppe" date="1302002385"]It makes little sense to use bitwise operators on a bool, doesn't it? :P[/quote]
How would you do then? On linux you can use '*=' instead of '&=' if both operands are bool, but I was told by an expert that (at least some) windows compiler just cannot stand such a notation.
-
[quote author="peppe" date="1302002385"]It makes little sense to use bitwise operators on a bool, doesn't it? :P[/quote]
Ah, well, they just are very short. Just one bit to compare bitwise. It works nonetheless.
If you want to do it "right", I guess you'd have to do this:
@
void YourDialog::checkLineEdits()
{
bool ok(true);
ok = ok && !ui->lineEdit1->text().isEmpty();
ok = ok && !ui->lineEdit2->text().isEmpty();
ok = ok && !ui->lineEdit3->text().isEmpty();
ok = ok && !ui->lineEdit4->text().isEmpty();ui->okButton->setEnabled(ok);}
@Does that get more readable? Not really, I think.
P.S. I was expecting comments on this not being efficient, actually. :-)
-
[quote author="VCsala" date="1301955029"]The method Volker suggested is the safe way to do it and as I understand it uses some kind of state machine for storing the actual state of validity therefore it does not cause significant overhead even if your validation is resource hungry.[/quote]
There is no state machine involved. The code always checks all four line edits. There may be some short circuiting by the compiler, if the first check is false, the complete expression is false, so there is no need to calculate the rest.
-
[quote author="Volker" date="1302021381"][quote author="VCsala" date="1301955029"]The method Volker suggested is the safe way to do it and as I understand it uses some kind of state machine for storing the actual state of validity therefore it does not cause significant overhead even if your validation is resource hungry.[/quote]
There is no state machine involved. The code always checks all four line edits. There may be some short circuiting by the compiler, if the first check is false, the complete expression is false, so there is no need to calculate the rest.[/quote]
However, if you want to have more complex check on the input field (and not only checking if it is empty or not) and you use validator (which is a more generic solution for this use case) then you have validity states (and in this case the validation itself can be resource and time consuming). As I know even in this case the above pattern is safe as the states are recalculated only if the field has been changed.
