从PopOver更改标签的文本

Question

I have a main view which has a label named timeLabel and a button that calls a popover view.

In the popover view I can choose a time (hour and min), when I choose I want the label text to immediately changes to the selected hour (the label has an initial value : "22:00").

What I tried to do is create a function in the main view that changes the label's text:

func setNotiTimeHour(hour: Int) 
    var time = self.notiTimeLabel.text!.componentsSeparatedByString(":") //ERROR 

    var newTime = String(hour) + ":" + time[1]

    self.notiTimeLabel.text = newTime
}    
func setNotiTimeMin(min: Int) {
    var time = self.notiTimeLabel.text!.componentsSeparatedByString(":") //ERROR

    var newTime = time[0] + ":" + String(min)

    self.notiTimeLabel.text = newTime
}

And then I tried to calls these functions when the hour or minute is changes like this:

SettingsTableViewController().setNotiTimeHour(Int(hours))
SettingsTableViewController().setNotiTimeHour(Int(minutes))

When I call the function like this I get an error that says: "fatal error: unexpectedly found nil while unwrapping an Optional value"

I think it means the label has no value.

Why do I get this error, is there another way to change the label's text?

Answer 1

SettingsTableViewController() creates a new view controller. It does not use the instance you already have. That's why the label is nil .

You need to hand your popover controller a reference to the existing view controller, save it in a property, and then call that one. You may want to create a delegate protocol for this so this popover class can be presented from other view controllers besides SettingsTableViewController .