Set a maximum number value for a text field - xcode

Question

I'm making an app where students enter their grade in a specific text field. I want them to enter a number from 0 to 100. I was just wondering how do we set a maximum NUMBER value for a textfield.
I'm assuming I'm supposed to make some type of action but I'm not sure what action type to use or the code to set a maximum value.
Any help would be very appreciated :) !!

Answer 1

You can use a UIPickerView if you want to present a limited number of fixed answers: http://sourcefreeze.com/ios-uipickerview-example-using-swift/. But if you want to have them enter it in a textbox, you can validate the input in the textFieldDidEndEditing method like so:
func textFieldDidEndEditing(textField: UITextField) {
if textField.text.toInt() < 0 || textfield.text.toInt() > 100 {
//Here you can present an alert, change the input or clear the field.
}
}

Answer 2

An alternative is to make the score 0 when negative and 100 when the user enters something more than 100. This allows you to enter fractional score like 72.5:
class ViewController: UIViewController, UITextFieldDelegate {
#IBOutlet weak var textField: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
self.textField.delegate = self
}
func textFieldShouldEndEditing(textField: UITextField) -> Bool {
// Make sure the user entered a number
guard let score = Double(textField.text!) else {
let alert = UIAlertController(title: "Invalid Score", message: "Score must be a number from 0 to 100", preferredStyle: .Alert)
alert.addAction(UIAlertAction(title: "OK", style: .Default, handler: nil))
self.presentViewController(alert, animated: true, completion: nil)
return false
}
if score < 0 {
textField.text = "0"
} else if score > 100 {
textField.text = "100"
}
return true
}
}

Answer 3

internal func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
if ((self.inputTextField?.text)!.characters.count > 10 && range.length == 0)
{
return false
//return false // return NO to not change text
}else{
return true
}
}
Note: Import text field UITextFieldDelegat.