Generic Function to Output to UITextField or UILabel - ios

Question

I am trying to write a function in Swift 2 for iOS that processes some text and writes it to either a UITextField or a UILabel. Currently, I have the following that works:
#IBOutlet weak var textField: UITextField!
#IBOutlet weak var textLabal: UILabel!
​func writeSomeText(string: String, toOutput: UITextField) {
// do some text processing
toOutput.text = // processed string
}
​func writeSomeText(string: String, toOutput: UILabel) {
// do some text processing
toOutput.text = // processed string
}
As you see, right now I am overloading the function, essentially duplicating it for both UITextField and UILabel, and since I have a bunch of text processing that is exactly the same, I am duplicating code.
Is there any way to write a function using generics to achieve this with one function definition?

Answer 1

try look at this approach ...
import UIKit
protocol P {
func foo(str: String)->String
}
extension P {
func foo(str: String)->String {
// do some processing
let res = str
return res
}
}
extension UILabel:P {
func bar(str: String) {
self.text = foo(str)
}
}
extension UITextField:P {
func bar(str: String) {
self.text = foo(str)
}
}
let l = UILabel()
l.text = "alfa"
l.bar("ALFA")
let t = UITextField()
t.text = "beta"
t.bar("BETA")
print(l.text, t.text) // Optional("ALFA") Optional("BETA")
by the way, you don't need protocol P at all :-), it is there just as a 'namespace' (not to have a global func foo)
another approach is to define some common protocol and extend UILabel and UITextField
import UIKit
protocol P: class {
var text: String? {get set}
}
extension UILabel: P {}
extension UITextField: P {}
func writeSomeText<T:P>(string: String, toOutput: T ){
// do some text processing
toOutput.text = string
}
let l = UILabel()
writeSomeText("label", toOutput: l)
l.text // "label"
let tv = UITextView()
tv.text = "text"
// but
writeSomeText("text view", toOutput: tv) // error: cannot invoke 'writeSomeText' with an argument list of type '(String, toOutput: UITextView)'
later you can extend other classes with text property, if you want ... without changing implementation of func writeSomeText

Answer 2

A Swifty way (without Generics) would be
#objc
protocol UITextOutputProtocol: class {
func setOutputText(text: String)
}
extension UITextField : UITextOutputProtocol {
func setOutputText(text: String) {
self.text = text
}
}
extension UILabel : UITextOutputProtocol {
func setOutputText(text: String) {
self.text = text
}
}
class ViewController: UIViewController {
//An outlet Collection containing Labels and TextField
#IBOutlet var texts: [UITextOutputProtocol]!
//An example function that will be replicating a text in all controls
func setTexts() {
for text in texts {
text.setOutputText("example Text")
}
}
UPDATE:
As UILabel and UITextField are now implementing protocol UITextOutputProtocol the following code will work.
#IBOutlet weak var textField: UITextField!
#IBOutlet weak var textLabel: UILabel!
​func writeSomeText(string: String, toOutput: UITextOutputProtocol) {
// do some text processing
toOutput.setOutputText("example Text") // change the text here for your processed string
}
func doSomeProcessingOnText(text:String) {
writeSomeText(text, textField)
writeSomeText(text, textLabel)
}
}

Answer 3

This is a little bit of a hack since UITextField and UILabel don't conform any shared protocols for text editing, but you could use KVO:
func writeSomeText(string: String, output: AnyObject) {
// do some text processing
if output.respondsToSelector("text") {
output.setValue(string, forKey: "text")
}
}
respondsToSelector checks to make sure the object you're passing in has a property text before continuing setting a value to that key. This check is used to prevent a crash a runtime if you pass in an object that is not KVO compliant for the key text`.