Swift / iOS - UIButton Sender with more information - ios

Question

Lets say you have a calculator you're building for iOS in Swift. When a user taps an operation (division, addition, subtraction, etc) I'd like to avoid having a separate method to handle each.
Instead, i'd prefer to have a factory which, based on the sender, determines the correct OperationType sub-class to use (Subtraction, Multiplication, etc)
My question is: is it proper practice to store information directly on the UI Button in Xcode? For instance, on the Addition button (+), if I tagged it with Addition, I could then use that information to load the Addition class.
Similarly, for each digit, i would prefer to have one function which handles a user pushing any digit. However, to determine the sender, it seems somewhat sloppy to use sender.title, since it binds the visual title of the digit, to the code. Is it then appropriate to provide tags to deal with this, or is there another system of handling this?

Answer 1

You can certainly do that, and sometimes it makes for a clean design. View objects have a tag property (an Int.) You can put a switch statement on your action method(s) that switches on the tag value. Generally you should use tag values starting from 1 or greater, since 0 is the default tag value.
If you need more than an integer value you can either save your values into an array that you index into with the tag value or you can use associative storage to actually store objects attached to your buttons. Do a search on "Cocoa associated objects" for more information on that technique. Or you can take a look at a demo project I put on github: https://github.com/DuncanMC/AssocitiveStorageDemo (Written in Objective-C, but the technique is the same in Swift)

Answer 2

override func viewDidLoad() {
super.viewDidLoad()
let button1 = UIButton(frame: CGRect(x: 0, y: 0, width: 200, height: 200));
let button2 = UIButton(frame: CGRect(x: 0, y: 250, width: 200, height: 200));
button1.backgroundColor = UIColor.greenColor();
button2.backgroundColor = UIColor.yellowColor();
button1.addTarget(self, action: "buttonTaped:", forControlEvents: .TouchUpInside);
button2.addTarget(self, action: "buttonTaped:", forControlEvents: .TouchUpInside);
button1.tag = 0;
button2.tag = 1;
self.view.addSubview(button1);
self.view.addSubview(button2);
}
func buttonTaped(button:UIButton){
switch(button.tag){
case 0:
print("button 1 taped");
break;
case 1:
print("button 2 taped");
break;
default:
break;
}
}

Answer 3

You can use the tag property
func buttonClicked(sender:AnyObject) {
let button = sender as! UIButton
if button.tag == 0 {
...
}
else if button.tag == 1 {
...
}
}