Adding multiple lines in UILabel - ios

Question

I am trying to make a times table app with user's input value. Whenever I try to print result on a label, it just prints the last line and not a full table.
How can I append text in UILabel? Here is my code:
if let textBox = textField.text{
let textBoxNum = Int(textBox)
if let number = textBoxNum{
if number > 0{
let i = 1
while i <= 20{
label.text = "\(number) x \(i) = \(number * i)"
}
}
else{
label.text = "Please enter a positive whole number"
}
}
else{
label.text = "Please enter a positive whole number"
}
}

Answer 1

The assignment operator = just reassigns a new value to the text of your label. You need to add on to the existing text using the Compound Assignment Operator call addition assignment operator += which will assign new value by adding it to the existing value.
let a:String = "Hello"
print(a) // Hello
a += " World!"
print(a) // Hello World!
This same terminology will be applied to your case where you will use += on the text property of the label.
if let textBox = textField.text{
let textBoxNum = Int(textBox)
if let number = textBoxNum{
if number > 0{
let i = 1
while i <= 20{
label.text += "\(number) x \(i) = \(number * i)\n"
// Use of compound operator here will append the text so you have
// to use a new line escape character to print the text properly.
}
}
else{
label.text = "Please enter a positive whole number"
}
}
else{
label.text = "Please enter a positive whole number"
}
}
More about operators here:
https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/BasicOperators.html

Answer 2

Additional to the other answers (using += and \n for line breaks):
If you use a label, you'll have to set the number of lines to zero, which will allow unlimited number of lines:
label.numberOfLines = 0
But you might better want a UITextField to display multi-line text, which allows the user to scroll up and down if the text gets too long. You would only have to disable the editing / keyboard popping up, something like:
class TheViewController: UIViewController, UITextFieldDelegate {
override func viewDidLoad() {
super.viewDidLoad()
self.theTextField.delegate = self
}
func textFieldShouldBeginEditing(textField: UITextField) -> Bool {
return false
}
}