Detecting empty lines and absence of text in a UITextView in Swift - ios

Question

I have created a UITextView programmatically , and added a placeholder like so:
//textView
textView.frame = CGRectMake(viewSize.width * 0.05, contentView.frame.height - viewSize.width * 0.05, viewSize.width - viewSize.width * 0.05 * 2, -viewSize.height * 0.220833)
self.textView.delegate = self
self.textView.text = "Agregue una descripción..."
self.textView.textColor = UIColor.lightGrayColor()
self.textView.autocorrectionType = UITextAutocorrectionType.No
self.textView.layer.cornerRadius = 6
self.view.addSubview(textView)
and in the delegate functions:
func textViewDidBeginEditing(textView: UITextView) {
if textView.textColor == UIColor.lightGrayColor() {
textView.text = ""
textView.textColor = UIColor.blackColor()
}
}
func textViewDidEndEditing(textView: UITextView) {
if textView.text.isEmpty {
textView.text = "Agregue una descripción..."
textView.textColor = UIColor.lightGrayColor()
}
}
I have also tried to check string text to nil:
if textView.text == nil
And like this:
if textView.text == ""
None did detected the empty lines, and even the nil comparison was not detecting the absence of text after adding and deleting some chars.
So when the user enters text there is no problem, and when the user deletes all the text the placeholder comes back, but if you add a line or more without any text, the comparison to empty is not true, i need a way to detect that i have no text and also the lines added do not have text, because the newly introduced in Swift .isEmpty is not detecting empty lines added, nor any of the other comparison did.
How can i detect empty lines in my String?

Answer 1

Ask yourself whether the text is composed of only characters from the NSCharacterSet whitespaceAndNewlineCharacterSet (or whatever characters constitute emptiness in your mind - perhaps what you are after is newlineCharacterSet). The easiest way is to take its invertedSet and call rangeOfCharacterFromSet - if the result is {NSNotFound, 0} (Swift nil), this text is composed only of whitespace characters.
extension String {
var isBlank : Bool {
let s = self
let cset = NSCharacterSet.newlineCharacterSet().invertedSet
let r = s.rangeOfCharacterFromSet(cset)
let ok = s.isEmpty || r == nil
return ok
}
}
"howdy".isBlank // false
"".isBlank // true
"\n\n".isBlank // true

Answer 2

"quick and dirty" version of the code matt posted, without extending String:
func textViewDidEndEditing(textView: UITextView) {
let myAwesomeDescription = textView.text.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSe‌​t())
if myAwesomeDescription == "" {
//user did not modify empty box or text only consisted of space/newline characters, reset placeholder text and placeholder textColor
textView.text = "Agregue una descripción..."
textView.textColor = UIColor.lightGrayColor()
} else {
//textView holds a valid string, do stuff
}
}
What does myAwesomeDescription do? We refer to a great NSHipster article for that:
Stripping Whitespace
NSString -stringByTrimmingCharactersInSet: is a
method you should know by heart. It's most often passed NSCharacterSet
+whitespaceCharacterSet or +whitespaceAndNewlineCharacterSet in order to remove the leading and trailing whitespace of string input.
It's important to note that this method only strips the first and last
contiguous sequences of characters in the specified set.
That being said, this not only helps us dealing with Strings that have unnecessary leading or following spaces/newlines, but also with "empty" which in most definitions will mean that the String is just spaces/newlines only.