Swift - Associated value or extension for an Enum - swift

Question

General question regarding swift enum.
I want to create an enum of "icon" and "associate" a value to the enum case
enum Icon {
case plane
case arrow
case logo
case flag
}
I want to create an associated image to the enum's value.
And also an associated color to the enum value
So for instance if it was possible to do something like:
extension Icon.plane {
var image = {
get {
return UIImage("plane.png")
}
}
var color = {
get {
return UIColor.greenColor()
}
}
}
var image = Icon.arrow.image // the image associated to the enum
var color = Icon.arrow.color // the color associated to the enum
Is this type of thing possible?

Answer 1

Unfortunately you cannot define static properties based on enum cases, but you can use computed properties and switch to return values for each case:
enum Icon {
case plane
case arrow
case logo
case flag
var image: UIImage {
switch self {
case .plane: return UIImage(named: "plane.png")!
case .arrow: return UIImage(named: "arrow.png")!
case .logo: return UIImage(named: "logo.png")!
case .flag: return UIImage(named: "flag.png")!
}
}
var color: UIColor {
switch self {
case .plane: return UIColor.greenColor()
case .arrow: return UIColor.greenColor()
case .logo: return UIColor.greenColor()
case .flag: return UIColor.greenColor()
}
}
}
// usage
Icon.plane.color

Answer 2

Using enums with associated values combined with switch statements you can be very flexible. A first example:
enum Icon {
case plane(img:UIImage, col:UIColor)
case arrow(img:UIImage, col:UIColor)
case logo(img:UIImage, col:UIColor)
case flag(img:UIImage, col:UIColor)
var values:(img:UIImage,col:UIColor) {
switch self {
case let .plane(image, color):
return (image,color)
case let .arrow(image, color):
return (image,color)
case let .logo(image, color):
return (image,color)
case let .flag(image, color):
return (image,color)
}
}
}
var a = Icon.plane(img: UIImage(named: "image.png")!, col: UIColor.blueColor())
a.values.col
a.values.img
and a second example:
enum Icon {
case plane(img:UIImage, col:UIColor)
case arrow(img:UIImage, col:UIColor)
case logo(img:UIImage, col:UIColor)
case flag(img:UIImage, col:UIColor)
var img:UIImage {
switch self {
case let .plane(image, color):
return image
case let .arrow(image, color):
return image
case let .logo(image, color):
return image
case let .flag(image, color):
return image
}
}
var col:UIColor {
switch self {
case let .plane(image, color):
return color
case let .arrow(image, color):
return color
case let .logo(image, color):
return color
case let .flag(image, color):
return color
}
}
}
var a = Icon.plane(img: UIImage(named: "image.png")!, col: UIColor.blueColor())
a.col
a.img
no need for extensions. And if you really do want static values, you could do this:
struct MyIcon {
static let plane = Icon.plane(img: UIImage(named: "image.png")!, col: UIColor.blueColor())
static let arrow = Icon.arrow(img: UIImage(named: "image.png")!, col: UIColor.blueColor())
static let logo = Icon.logo(img: UIImage(named: "image.png")!, col: UIColor.blueColor())
static let flag = Icon.flag(img: UIImage(named: "image.png")!, col: UIColor.blueColor())
}
MyIcon.arrow.col
which might be tidier than placing the fixed literal values inside a switch statement.

Answer 3

Shorter and safer code:
import UIKit
enum Icon: String {
case plane, arrow, logo, flag
var image: UIImage {
// If the image is not available, provide a default value so we dont force optional unwrapping
return UIImage(named: "\(self.rawValue).png") ?? UIImage()
}
var color: UIColor {
switch self {
case .plane: return UIColor.green
case .arrow: return UIColor.green
case .logo: return UIColor.green
case .flag: return UIColor.green
}
}
}
// Usage
Icon.plane.color
Icon.arrow.image

Answer 4

More cleaner and readable
enum Icon {
case plane
case arrow
case logo
case flag
var image: UIImage {
return value.image
}
var color: UIColor {
return value.color
}
private var value: (image: UIImage, color: UIColor) {
switch self {
case .plane: return (UIImage(named: "plane.png")!, UIColor.green)
case .arrow: return (UIImage(named: "arrow.png")!, UIColor.green)
case .logo: return (UIImage(named: "logo.png")!, UIColor.green)
case .flag: return (UIImage(named: "flag.png")!, UIColor.green)
}
}
}
// Use
Icon.plane.image
Icon.plane.color