Generic `getText()` function for UI elements in Swift - ios

Question

For a lot of actions, I need to check if the content of label.text, textView.text, textField.text etc. is nil.
So I created some extensions:
extension UILabel {
func getText() -> String {
return self.text ?? ""
}
}
extension UITextField {
func getText() -> String {
return self.text ?? ""
}
}
extension UITextView {
func getText() -> String {
return self.text ?? ""
}
}
The extensions are very redundant. A similar case is when I need to cast an Int, Double, Float etc. to another number format. What I want is a simple toInt() with a return of -1 or 0 when something went wrong.
So how can I create a generic function for the toString() or toInt()? I read about extensions and generics in the Apple documentation, but I didn't see a solution for my problem.
Finally, I tried to expand UIView with the same extension, because it's a superclass of UILabel etc., but I can't call getText().
So what is a good method to create generic extensions?

Answer 1

There are a couple of dubious things here: I wouldn't want any toInt() function to just return -1 or 0 when things went wrong. Swift has a good optionality system for a reason, and there are several obvious pitfalls introduced by returning -1 or 0. I also don't know what you plan to do for implementing getText() on a UIView. Lots of views don't have text. I don't know what this implementation would mean or do.
So I'll ignore those two details and focus on the primary question, which seems to be the redundancy of your extensions. There is a cleaner way, via protocol extensions, to cut down on duplication.
protocol TextProviding {
var text: String? { get }
}
extension TextProviding {
// Following your example here. I would prefer calling
// this a `var textOrEmpty: String` but same idea.
func getText() -> String {
return text ?? ""
}
}
// To conform additional types, you just need 1 line
extension UILabel: TextProviding { }
extension UITextField: TextProviding { }
EDIT: as some have pointed out, using the above code with extension UITextView: TextProviding { } will not work, because UITextView's text is a String!, not a String?. Unfortunately, this means if you want this to work for UITextView as well, you should rename the var text requirement to something else (and this means you will need a couple extra lines to manually conform UILabel and UITextField).
protocol TextProviding {
var string: String? { get }
}
extension TextProviding {
var stringOrEmpty: String {
return string ?? ""
}
}
extension UILabel: TextProviding {
var string: String? { return text }
}
extension UITextField: TextProviding {
var string: String? { return text }
}
extension UITextView: TextProviding {
var string: String? { return text }
}

Answer 2

For the first problem, you should only extend UIView and check whether its a label, a text field or a text view with if let.
extension UIView {
func getText() -> String {
if let label = self as? UILabel {
return label.text ?? ""
} else if let textField = self as? UITextField {
return textField.text ?? ""
} else if let textView = self as? UITextView {
return textView.text ?? ""
}
return ""
}
}
The advantage of this method over creating a protocol is that you can easily extend it, even if the text/title is retrievable with another method, for example, with a UIButton.
[...]
else if let button = self as? UIButton {
return button.title(for: .normal) ?? ""
}

Answer 3

This one-liner reduces redundant code (what you wanted) than all other answers posted here. No need for crazy condition-checks or multiple extensions.
extension UIView {
func getText() -> String? {
return self.responds(to: #selector(getter: UILabel.text)) ?
self.perform(#selector(getter: UILabel.text))?.takeUnretainedValue() as? String : nil
}
}

Answer 4

Create a protocol with an extension and then extend every class to adopt the protocol :)
protocol GetTextProtocol {
var text: String? {get}
func getText() -> String
}
extension GetTextProtocol {
func getText() -> String {
return self.text ?? ""
}
}
extension UILabel: GetTextProtocol {
var text: String? {
return self.text
}
}
extension UITextView: GetTextProtocol {
var text: String? {
return self.text
}
}