How to create an enum where few cases contains extra properties - ios

Question

I need 4 file objects to upload. Few files have date, few files have image. What is the data structure should I use?
I tried to create an enum
enum File: String, CaseIterable {
case a = "A"
case b = "B"
case c = "C"
case d = "D"
var size: String//enum cannot contain stored properties
}
I tried to create a struct
struct File {
var name: String//for 4 files
var size: String//only for A and B
var image: UIImage// only for C and D
}

Answer 1

This could help you-
enum File: String, CaseIterable {
case a = "A"
case b = "B"
case c = "C"
case d = "D"
static let sizeMapper: [File: String] = [
.a: "Size A",
.b: "Size B"
]
static let nameMapper: [File: String] = [
.a: "Name A",
.b: "Name B",
.c: "Name C",
.d: "Name D"
]
static let imageMapper: [File: UIImage] = [
.c: UIImage(),
.d: UIImage()
]
var size: String {
return File.sizeMapper[self] ?? ""
}
var name: String {
return File.nameMapper[self] ?? ""
}
var image: UIImage {
return File.imageMapper[self] ?? UIImage()
}
}
call it like this-
let size = File.a.size
print(size)
let name = File.a.name
print(name)
let image = File.c.image
print(image)

Answer 2

The error says it all:
enum cannot contain stored properties
Ideally you're the one to provide values to your enum's properties. Meaning they should be read-only. You can however make a new instance of your enum.
Here's an example:
enum File: String, CaseIterable {
case a = "A"
case b = "B"
case c = "C"
case d = "D"
var size: String {
switch self {
case .a: return "Some size for A"
case .b: return "Some size for B"
case .c: return "Some size for C"
case .d: return "Some size for D"
}
}
}
let fileA = File(rawValue: "A")
let fileB = File(rawValue: "B")
let size = fileA.size //Some size for A
let size = fileB.size //Some size for B

Answer 3

If you answer is "How to create an enum with extra properties", then you can write something like this:
enum File {
case containingDate(fileName: String, date: Date)
case containingImage(fileName: String, image: UIImage)
}
Also, note that enum with raw types (in your case it is String) can't contain extra parameters.
PS: to be honest, I don't see any advantages of using enums in your situation

Answer 4

You should use both enum and struct here:
// Enum with associated values for differences
enum FileType {
case withDate(date: Date)
case withImage(image: UIImage)
}
// Struct to bind common
struct File {
var name: String
var fileType: FileType
}
And then you can have your files defined:
extension File {
// Files with date
static let a = File(name: "a", fileType: .withDate(date: Date()))
static let b = File(name: "b", fileType: .withDate(date: Date()))
// Files with image
static let c = File(name: "c", fileType: .withImage(image: UIImage()))
static let d = File(name: "d", fileType: .withImage(image: UIImage()))
}
And for simple way to access date and image you can declare those handy extensions:
extension FileType {
var date: Date? {
if case let .withDate(date) = self {
return date
} else {
return nil
}
}
var image: UIImage? {
if case let .withImage(image) = self {
return image
} else {
return nil
}
}
}
extension File {
var date: Date? {
return fileType.date
}
var image: UIImage? {
return fileType.image
}
}
And then use it like this:
let date = File.a.date