Enabling buttons when lineEdit has text

[Lykurg]

any solutions?

Yes, read about signals and slots in the documentation, seems you haven't understand the concept right.

Use textChanged() signal of the line edit, connect it to your slot, check the value and alter the state of your button.

[wagmare]

if (lineEdit_name->text() != " ") {
emit allfieldsfull();
}

also dont use like this condition ..

use
QString text = lineEdit_name->text();
if (!text.isEmpty())
emit allfieldsfull();

[Lykurg]

QString text = lineEdit_name->text();
if (!text.isEmpty())
emit allfieldsfull();

if (!lineEdit_name->text().isEmpty())
        emit allfieldsfull();

if (!lineEdit_name->text().isEmpty())
        emit allfieldsfull();

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Is even more better because of avoiding a temporary variable. But nonetheless in that case a signal is not necessary, because you can simply call your member function.

[wagmare]

if (!lineEdit_name->text().isEmpty())

yes i know this is more simpler ... but for newbie i explained clearly that we check in QString function ..

and see i use "also" .. to tell him in future u use conditions like this in different application ..
here using textChanged() signal is the better one ... i agree ...