Qt or C++ checking for NULL condition

Question

I am writing an application with a submit button but I want to check if the textfield has been filled if not do not submit.

Not quite sure how the code should go.

My code currently looks like

if(flightNumber == NULL)
{
   flightNumbertext.text.color = 'red';
}

I am designing this for a Qt Quick application written in QML.

Check the docs for the widget you're using for flightNumber. If it's a QLineEdit, for example, check its text() property. — vanza
– vanza, Commented Jun 30, 2011 at 7:19
hi please is there anyway I can check the input in an email field fulfills the conditions for being a valid email address. — Ismael
– Ismael, Commented Jun 30, 2011 at 7:24
I managed to edit the code and the following does work (flightNumber.text.length == 0) but leaves a loop hole in that it allows white spaces to be considered as values. Trying to use the isEmpty or iNull so far results in an error telling me flightNumber isn't a function which I kind of agree with but just can't figure out my way around this since using QTQuick — Ismael
– Ismael, Commented Jun 30, 2011 at 8:44

O.C. · Accepted Answer · 2011-06-30 07:20:36Z

4

QT's editing widgets use QString.

QString has many methods that you can use.

Use isEmpty or isNull methods of QString.

I hope this helps.

answered Jun 30, 2011 at 7:20

O.C.

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1 Comment

Ismael Over a year ago

I managed to edit the code and the following does work (flightNumber.text.length == 0) but leaves a loop hole in that it allows white spaces to be considered as values. Trying to use the isEmpty or iNull so far results in an error telling me flightNumber isn't a function which I kind of agree with but just can't figure out my way around this since using QTQuick

jwernerny · Accepted Answer · 2011-06-30 12:37:50Z

0

After a bit of playing, I think this will work for you

if (flightNumber.text.trim().length == 0) {
    flightNumbertext.text.color = 'red'; 
}

The function trim() is like QString::trimmed(). It removes both leading and trailing spaces from the string.

answered Jun 30, 2011 at 12:37

jwernerny

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