Check if value is in array - DatePicker Swift

Question

I need to check if the hour selected by the user is outside of working hours. I am trying to achieve this result with a for in loop and switch statement, but I am not sure how to implement this. If var components matches a value in the timeRestricted array, it should break from the switch statement. Thanks for your help.

class FourthViewController: UIViewController {


@IBOutlet weak var myDatePicker: UIDatePicker!
                var currentTime = NSDate()
                let timeRestricted = [00,01,02,03,04,05,06,19,20,21,22,23]
                var dateComponents = NSDateComponents()
var dateFormatter:NSDateFormatter = NSDateFormatter()

@IBOutlet weak var someLabel: UILabel!


override func viewDidLoad() {

    super.viewDidLoad()

    dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm"

    // load current time as minimum date
    self.myDatePicker.minimumDate = NSDate(timeInterval: 1, sinceDate: currentTime)

    myDatePicker.addTarget(self, action: #selector(self.datePickerAction(_:)), forControlEvents: UIControlEvents.ValueChanged)


}


func datePickerAction(sender: UIDatePicker) {

    var timeSelected = sender.date
    var unitFlags: NSCalendarUnit = [.Hour]
    var components = NSCalendar.currentCalendar().components(unitFlags, fromDate: timeSelected)



    for components in timeRestricted {
        switch components {
        case timeRestricted[0...12]: print("update label")

        default: print(" record input data and segue to next screen")
        }



     }

  }

}

Answer 1

You have several misunderstandings in your code.

First, you have an NSDateComponent in your local variable components . Using for components in timeRestricted {...} introduces another local variable components , which would not be what you intend.

Second, you cannot use array as a case label. So, both for-in and switch-case does not fit for checking if an hour is included in the timeRestricted .

Maybe your datePickerAction needs to be something like this:

func datePickerAction(sender: UIDatePicker) {

    let timeSelected = sender.date
    let unitFlags: NSCalendarUnit = [.Hour]
    let components = NSCalendar.currentCalendar().components(unitFlags, fromDate: timeSelected)
    let hour = components.hour

    if timeRestricted.contains(hour) {
        print("update label")
    } else {
        print(" record input data and segue to next screen")
    }
}

---

Ok, let's see some other ways. One important thing in this case is that you need to retrieve hour value from the date components , so, the following codes replace the last 5 lines of my datePickerAction(_:) above.

Start with using for-in .

    var isInArray = false
    for restrictedHour in timeRestricted {
        if hour == restrictedHour {
            isInArray = true
            //We have no need to check the rest...
            break
        }
    }
    if isInArray {
        print("update label")
    } else {
        print(" record input data and segue to next screen")
    }

This code is very similar to what contains(_:) method does internally. And, you know, the for-in syntax introduces a new variable. You'd better avoid using the same name as any of the existing variables. Which makes many readers of your code confused, including yourself.

---

To use switch-case , you need to write all comma-separated values directly after the case keyword.

    switch hour {
    case 00,01,02,03,04,05,06,19,20,21,22,23:
        print("update label")
    default:
        print(" record input data and segue to next screen")
    }

---

The two above were some examples using basic Swift control statements. But the last example is a little bit advanced.

Define an overload for ~= operator (read as "matches"), somewhere at the top level (meaning outside of any class definitions nor such).

func ~= <T: Equatable>(lhs: [T], rhs: T) -> Bool {
    return lhs.contains(rhs)
}

Having this definition somewhere in your project, you can use array variables or constants for case label of switch statement.

    switch hour {
    case timeRestricted:
        print("update label")
    default:
        print(" record input data and segue to next screen")
    }

In this case, Swift uses that ~= operator, so, this is nearly the same as the first example using contains . So confusing that I wouldn't recommend.

---

With just knowing you can retrieve hour as an Int , and some basics about Swift language, you have got so many ways to do the same thing. Do it as you like.