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?
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
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.
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
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
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