enum ImportType: Int {
case First = 1
case None
case Original
}
var type: ImportType = .First
print(type) --------------------> This will output "First"
NSLog("%#", String(type) --------------------> I can't do this.
NSLog("%d", type.rawValue) --------------------> This will output "1"
Hi All,
I want to get similar result of NSLog as the print function, it more readable for people, but I can't found a way to do this, I got some result that need to do additional handling inside the enum, but I am using other body's source code and just want to collect some information directly.
Are there easy transform way to do what I want?
Thanks~~
Eric
print uses String.init(describing:) under the hood to convert whatever you give it to a String, so you can do that too:
NSLog("%#", String(describing: type))
But really though, the enum should conform to CustomStringConvertible:
enum ImportType: Int, CustomStringConvertible {
case First = 1
case None
case Original
var description: String {
switch self {
case .First:
return "First"
case .None:
return "None"
case .Original:
return "Original"
}
}
}
and you should not rely on this default behaviour of String(describing:), because its behaviour is not specified unless the type conforms to TextOutputStreamable, CustomStringConvertible or CustomDebugStringConvertible. See here for more info.
Consider the following code, where I declared an enum with sub enums inside of it.
enum LocalizeKey {
case message(Messages)
case buttons(Buttons)
enum Buttons: String {
case remove = "Remove"
case add = "Add"
}
enum Messages: String {
case success = "Success"
case failure = "Failure"
}
}
In a normal enum with no sub enums we can easily access .rawValue property and get the raw value of whatever case we picked.
For this case, i created a function like this just to check out what am i getting .
func keyString(for type: LocalizeKey) {
print(type)
}
keyString(for: .message(.failure)) // usage
Problem : there are no other properties than .self to access for this LocalizeKey enum .
What I am trying to achieve: perhaps you can relate by the naming, i am trying to wrap my localized keys, so i can access them easily based on the key type etc, and the rawValue that is refering to the actual key will go into the getLocalizedValue function .
Playground Output : using the function above the playground output was
message(__lldb_expr_21.LocalizeKey.Messages.failure)
Edit: without having to create a variable that switches self on every case, imagine if we had +400 key that would be a huge mess probably.
You need to switch on the type parameter and do pattern matching:
switch type {
case .message(let messages): return messages.rawValue
case .buttons(let buttons): return buttons.rawValue
}
You can also make this an extension of LocalizeKey:
extension LocalizeKey {
var keyString: String {
switch self {
case .message(let messages): return messages.rawValue
case .buttons(let buttons): return buttons.rawValue
}
}
}
You are going to have to switch somewhere. If there are only a handful of "sub-enums", it is probably the easiest to just write a switch manually:
func keyString(for type: LocalizeKey) {
switch type {
case .message(let message):
print(message.rawValue)
case .buttons(let button):
print(button.rawValue)
}
}
If you don't want to write this manually, you either have to change your data structure so it is not needed, or use a code generation tool that generates the boilerplate for you.
Although The mentioned answers do provide the solution, I'd mention the issue of the approach itself:
At this point, each new case (key) has to be added in your switch statement with an associated value, which seems to be undesired boilerplate coding; I assume that you could imagine how it will look like when having many cases in the enums.
Therefore, I'd recommend to follow an approach to be more dynamic instead of adding the value of each case manually in a switch statement. Example:
protocol Localizable {
var value: String { get }
}
extension RawRepresentable where Self: Localizable, Self.RawValue == String {
var value: String { return rawValue }
}
extension CustomStringConvertible where Self: RawRepresentable, Self.RawValue == String {
var description: String { return rawValue }
}
struct LocalizeKey {
enum Buttons: String, Localizable, CustomStringConvertible {
case remove = "Remove"
case add = "Add"
}
enum Messages: String, Localizable, CustomStringConvertible {
case success = "Success"
case failure = "Failure"
}
}
We are applying the same logic for your code, with some improvements to make it easier to maintain.
Based on that, you still able to implement your function as:
func keyString(for type: Localizable) {
print(type)
}
Usage:
keyString(for: LocalizeKey.Buttons.add) // Add
keyString(for: LocalizeKey.Messages.success) // Success
IMO, I find calling it this way seems to be more readable, straightforward rather than the proposed approach (keyString(for: .message(.failure))).
In order to write generic code for an NSValueTransformer, I need to be able to check that an enum is of type String for example. Ie.:
enum TestEnum: String {
case Tall
case Short
}
I am expecially interested in a test that can be used with the guard statement. Something allong the line of:
guard let e = myEnum as <string based enum test> else {
// throw an error
}
Please note that not all enums have raw values. For eample:
enum Test2Enum {
case Fat
case Slim
}
Hence a check on the raw value type can not be used alone for this purpose.
EDIT
After some further investigation it has become clear that NSValueTransformer can not be used to transform Swift enums. Please see my second comment from matt's answer.
First, it's your enums, so you can't not know what type they are. Second, you're not going to receive an enum type, but an enum instance. Third, even if you insist on pretending not to know what type this enum is, it's easy to make a function that can be called only with an enum that has a raw value and check what type that raw value is:
enum E1 {
case One
case Two
}
enum E2 : String {
case One
case Two
}
enum E3 : Int {
case One
case Two
}
func f<T:RawRepresentable>(t:T) -> Bool {
return T.RawValue.self == String.self
}
f(E3.One) // false
f(E2.One) // true
f(E1.One) // compile error
Generics to the rescue :
func enumRawType<T>(of v:T)-> Any?
{ return nil }
func enumRawType<T:RawRepresentable>(of v:T)-> Any?
{
return type(of:v.rawValue)
}
enumRawType(of:E1.One) // nil
enumRawType(of:E2.One) // String.Type
enumRawType(of:E3.One) // Int.Type
I have an enum as follows
enum AccountForm: String {
case Profile
enum Content: String {
case Feedback
case Likes
}
enum Actions: String {
case Redeem
case Help
}
}
This represents a form, where profile content and actions are sections and the cases are rows.
These resolve to strings and work as expected
AccountForm.Profile.rawValue returns "Profile"
AccountForm.Content.Feedback.rawValue returns "Feedback"
However, I'd like AccountForm.Content.rawValue to return "Content"
Is this possible? Or is there a better way besides enums to achieve this?
I'm guessing you've got an answer to this by now but just in case you didn't try this:
enum AccountForm : String {
case profile
enum Content: String {
static let rawValue = "Content"
case feedback = "Feedback"
case likes = "Likes"
}
enum Actions : String {
static let rawValue = "Actions"
case redeem = "Redeem"
case help = "Help"
}
}
Static properties on both the Content and Actions enumerations should achieve what you want. A word of warning though. By calling the properties rawValue you're obviously implying the returned values are raw values when technically they aren't. If you can I'd think of a better name (maybe sectionTitle?).
Couple of other things to note.
First, you have to define the properties as static as it sounds like you want to call them on the enumeration type (e.g. AccountForm.Content.rawValue) rather than on an individual enumeration case (e.g. AccountForm.Content.feedback.rawValue). I'll leave you to decide whether that makes sense in your context.
Secondly, when Swift 3.0 arrives, the recommendation for enumeration cases is going to be that case labels follow a lowerCamelCase naming convention rather than the UpperCamelCase convention that was recommended in Swift 2.2.
I've followed the Swift 3.0 recommendation here but the result is that explicit raw-value assignments is needed as you won't be able to rely on using the implicit raw-value assignment mechanism assigning a string with an UpperCamelCase representation which is kind of annoying but those are the implications.
Anyway, hope it helps.
enum Typo {
case Bold
case Normal
case Italic
case All
}
enum Format: CustomStringConvertible {
case Header(Typo)
case Text(Typo)
var description:String {
switch self {
case .Header(let value) where value != .All:
return "Header.\(value)"
case .Header(let value) where value == .All:
return "Header"
case .Text(let value) where value == .All:
return "Text"
case .Text(let value) where value != .All:
return "Text.\(value)"
default:
return ""
}
}
}
let a:Format = .Header(.Bold)
let b:Format = .Text(.Italic)
Format.Header(.All) // Header
Format.Text(.Bold) // Text.Bold
Format.Text(.All) // Text
I want to associate two raw values to an enum instance (imagine an enum representing error types, I want Error.Teapot to have an Int type property code with value 418, and a String property set to I'm a teapot.)
Note the difference between raw values and associated values here—I want all Teapot instances to have a code of 418, I don't want a unique associated value for each Teapot instance.
Is there a better way than adding computed properties to the enum that switched on self to look up the appropriate value?
You have a couple options. But neither of them involve raw values. Raw values are just not the right tool for the task.
Option 1 (so-so): Associated Values
I personally highly recommend against there being more than one associated value per enum case. Associated values should be dead obvious (since they don't have arguments/names), and having more than one heavily muddies the water.
That said, it's something the language lets you do. This allows you to have each case defined differently as well, if that was something you needed. Example:
enum ErrorType {
case teapot(String, Int)
case skillet(UInt, [CGFloat])
}
Option 2 (better): Tuples! And computed properties!
Tuples are a great feature of Swift because they give you the power of creating ad-hoc types. That means you can define it in-line. Sweet!
If each of your error types are going to have a code and a description, then you could have a computed info property (hopefully with a better name?). See below:
enum ErrorType {
case teapot
case skillet
var info: (code: Int, description: String) {
switch self {
case .teapot:
return (418, "Hear me shout!")
case .skillet:
return (326, "I'm big and heavy.")
}
}
}
Calling this would be much easier because you could use tasty, tasty dot syntax:
let errorCode = myErrorType.info.code
No, an enum cannot have multiple raw values - it has to be a single value, implementing the Equatable protocol, and be literal-convertible as described in the documentation.
I think the best approach in your case is to use the error code as raw value, and a property backed by a prepopulated static dictionary with the error code as key and the text as value.
I created a way of simulating this (No different than what Marcos Crispino suggested on his answer). Far from a perfect solution but allows us to avoid those nasty switch cases for every different property we want to get.
The trick is to use a struct as the "properties/data" holder and using it as a RawValue in the enum itself.
It has a bit of duplication but it's serving me well so far. Every time you want to add a new enum case, the compiler will remind you to fill in the extra case in the rawValue getter, which should remind you to update the init? which would remind you to create the new static property on the struct.
Gist
Code to the Gist:
enum VehicleType : RawRepresentable {
struct Vehicle : Equatable {
let name: String
let wheels: Int
static func ==(l: Vehicle, r: Vehicle) -> Bool {
return l.name == r.name && l.wheels == r.wheels
}
static var bike: Vehicle {
return Vehicle(name: "Bicycle", wheels: 2)
}
static var car: Vehicle {
return Vehicle(name: "Automobile", wheels: 4)
}
static var bus: Vehicle {
return Vehicle(name: "Autobus", wheels: 8)
}
}
typealias RawValue = Vehicle
case car
case bus
case bike
var rawValue: RawValue {
switch self {
case .car:
return Vehicle.car
case .bike:
return Vehicle.bike
case .bus:
return Vehicle.bus
}
}
init?(rawValue: RawValue) {
switch rawValue {
case Vehicle.bike:
self = .bike
case Vehicle.car:
self = .car
case Vehicle.bus:
self = .bus
default: return nil
}
}
}
VehicleType.bike.rawValue.name
VehicleType.bike.rawValue.wheels
VehicleType.car.rawValue.wheels
VehicleType(rawValue: .bike)?.rawValue.name => "Bicycle"
VehicleType(rawValue: .bike)?.rawValue.wheels => 2
VehicleType(rawValue: .car)?.rawValue.name => "Automobile"
VehicleType(rawValue: .car)?.rawValue.wheels => 4
VehicleType(rawValue: .bus)?.rawValue.name => "Autobus"
VehicleType(rawValue: .bus)?.rawValue.wheels => 8
No, you cannot have multiple raw values associated with an enum.
In your case, you could have the raw value to be equal to the code, and have an associated value with the description. But I think the computed properties approach is the best option here.
One workaround if you wanted to have many static properties for a YourError could be to import a property list; you could set the root object to a dictionary, with your enum raw value as the key for each object, allowing you to easily retrieve static structured data for the object.
This has an example of importing and using a plist: http://www.spritekitlessons.com/parsing-a-property-list-using-swift/
That might be overkill for simply an error description, for which you could just use a hardcoded static function with a switch statement for your enum values, that returns the error string you need. Simply place the static function in the same .swift file as your enum.
For instance,
static func codeForError(error : YourErrorType) -> Int {
switch(error) {
case .Teapot:
return "I'm a Teapot"
case .Teacup:
return "I'm a Teacup"
...
default:
return "Unknown Teaware Error"
}
}
This has the benefit (compared to the .plist solution) of better accomodating localization. However, a .plist could just contain a key used for retrieving the proper localization, instead of a error string, for this purpose.
For beginning, assuming you want to store a code and a message, you can use a struct for RawValue
struct ErrorInfo {
let code: Int
let message: String
}
Next step is to define the enum as being RawRepresentable, and use ErrorInfo as the raw value:
enum MyError: RawRepresentable {
typealias RawValue = ErrorInfo
case teapot
What remains is to map between instances of MyError and ErrorInfo:
static private let mappings: [(ErrorInfo, MyError)] = [
(ErrorInfo(code: 418, message: "I'm a teapot"), .teapot)
]
With the above, let's build the full definition of the enum:
enum MyError: RawRepresentable {
static private let mappings: [(ErrorInfo, MyError)] = [
(ErrorInfo(code: 418, message: "I'm a teapot"), .teapot)
]
case teapot
init?(rawValue: ErrorInfo) {
guard let match = MyError.mappings.first(where: { $0.0.code == rawValue.code && $0.0.message == rawValue.message}) else {
return nil
}
self = match.1
}
var rawValue: ErrorInfo {
return MyError.mappings.first(where: { $0.1 == self })!.0
}
}
Some notes:
you could use only the error code for matching, however this might result in inconsistent raw values if the messages differ
the amount of boilerplate code required to have raw values of some custom type might not outcome the benefits of using associated values.
Possible work around may to associate custom functions with enum
enum ToolbarType : String{
case Case = "Case", View="View", Information="Information"
static let allValues = [Case, View, Information]
func ordinal() -> Int{
return ToolbarType.allValues.index(of: self)!
}
}
Can be used as
for item in ToolbarType.allValues {
print("\(item.rawValue): \(item.ordinal())")
}
Output
Case: 0
View: 1
Information: 2
Possibly you can have additional functions to associate enum type to different values
This doesn't particularly answer your question, which was asking to find a better way than switching through self to look up the appropriate value but this answer may still be useful for someone looking in the future that needs a simple way to get a string from an enum which is defined as an integer type.
enum Error: UInt {
case Teapot = 418
case Kettle = 419
static func errorMessage(code: UInt) -> String {
guard let error = Error(rawValue: code) else {
return "Unknown Error Code"
}
switch error {
case .Teapot:
return "I'm a teapot!"
case .Kettle:
return "I'm a kettle!"
}
}
}
This way, we can get the errorMessage two ways:
With an integer (eg. that was returned as an error code from a server)
With an enum value (the rawValue we define for the enum)
Option 1:
let option1 = Error.errorMessage(code: 418)
print(option1) //prints "I'm a teapot!"
Option 2:
let option2 = Error.errorMessage(code: Error.Teapot.rawValue)
print(option2) //prints "I'm a teapot!"
In modern versions of Swift it's possible to get the string value of an enum case label, even without that enum being declared with a : String rawValue.
How to get the name of enumeration value in Swift?
So there is no longer a need to define and maintain a convenience function that switches on each case to return a string literal. In addition, this works automatically for any enum, even if no raw-value type is specified.
This, at least, allows you to have "multiple raw values" by having both a real : Int rawValue as well as the string used as the case label.
I think it just tricky, and I have create my own idea like below:
enum Gender:NSNumber
{
case male = 1
case female = 0
init?(strValue: String?) {
switch strValue {
case Message.male.value:
self = .male
case Message.female.value:
self = .female
default: return nil
}
}
var strValue: String {
switch self {
case .male:
return Message.male.value
case .female:
return Message.female.value
}
}
}
First of all, enums should only have one raw value. However if you want to have something that can use multiple raw values... there is a way to 'hack' this, but you have to make it codable and hashable yourself, implement custom init's etc.
enum MyCustomEnum: Codable, Hashable {
// duplicate every case with associated value of Codable.Type
case myFirstCase, _myFirstCase(Codable.Type)
case mySecondCase, _mySecondCase(Codable.Type)
case myThirdCase, _myThirdCase(Codable.Type)
case unknown(Any), _unknown(Codable.Type, Any) // handles unknown values
// define an allCases value to determine the only values your app 'sees'.
static var allCases: [Self] {
return [
.myFirstCase,
.mySecondCase,
.myThirdCase
// unknown(String) // you can add unknown as well, but this is too mask any unknown values.
]
}
static func == (lhs: MyCustomEnum, rhs: MyCustomEnum) -> Bool {
return lhs.stringValue == rhs.stringValue // can be either one of your custom raw values.
}
// add this per raw value. In this case one for Int and one for String
init(rawValue: Int) {
guard let value = Self.allCases.first(where:{ $0.intValue == rawValue }) else {
self = ._unknown(Int.self, rawValue)
return
}
switch value {
case .myFirstCase: self = ._myFirstCase(Int.self)
case .mySecondCase: self = ._mySecondCase(Int.self)
case .myThirdCase: self = ._myThirdCase(Int.self)
default: self = ._unknown(Int.self, rawValue)
}
}
init(rawValue: String) {
guard let value = Self.allCases.first(where:{ $0.stringValue == rawValue }) else {
self = ._unknown(String.self, rawValue)
return
}
switch value {
case .myFirstCase: self = ._myFirstCase(String.self)
case .mySecondCase: self = ._mySecondCase(String.self)
case .myThirdCase: self = ._myThirdCase(String.self)
default: self = ._unknown(Int.self, rawValue)
}
}
// add this per raw value. In this case one for Int and one for String
var intValue: Int {
switch self {
case .myFirstCase, ._myFirstCase(_): return 1
case .mySecondCase, ._mySecondCase(_): return 2
case .myThirdCase, ._myThirdCase(_): return 3
case .unknown(let value), ._unknown(_, let value): return value as? Int ?? -1 // you can also choose to let intValue return optional Int.
}
}
var stringValue: String {
switch self {
case .myFirstCase, ._myFirstCase(_): return "my first case"
case .mySecondCase, ._mySecondCase(_): return "my second case"
case .myThirdCase, ._myThirdCase(_): return "my third case"
case .unknown(let value), ._unknown(_, let value): return value as? String ?? "not a String" // you can also choose to let stringValue return optional String.
}
}
// determine the codable type using Mirror
private func getCodableType() -> Codable.Type? {
let mirrorOfModuleType = Mirror.init(reflecting: self)
guard let childOfModuleType = mirrorOfModuleType.children.first else { // no children, means no associated values.
return nil
}
let value = childOfModuleType.value // can be either Codable.Type, String or (Codable.Type & String)
if let rawValue = value as? Codable.Type {
return rawValue
} else {
guard let rawValue = value as? (Codable.Type, String) else {
// unknown(String), we don't know the rawValue as given, but try in this part of the code to guess what type fits best.
if self.stringValue != "\(self.intValue)" { // e.g. "1" might match 1 but "1.0" and 1 don't match
return String.self
} else {
return Int.self // return either a default value, or nil. It's your choice.
}
}
return rawValue.0
}
}
// confine to hashable using getCodableType
func hash(into hasher: inout Hasher) {
if self.getCodableType() is String.Type {
hasher.combine(self.stringValue)
} else { // if you don't call hasher.combine at all, you can expect strange issues. If you do not know the type, choose one that is most common.
hasher.combine(self.intValue)
}
}
// confine to Decodable
init(from decoder: Decoder) throws {
if let rawValue = try? Int.init(from: decoder) {
self.init(rawValue: rawValue)
} else if let rawValue = try? String.init(from: decoder) {
self.init(rawValue: rawValue)
} else {
throw DecodingError.valueNotFound(Self.self, DecodingError.Context(codingPath: [], debugDescription: "no matching value was found"))
}
}
// confine to Encodable using getCodableType
func encode(to encoder: Encoder) throws {
let rawValue = self.getCodableType()
if rawValue is String.Type {
try self.stringValue.encode(to: encoder)
} else if rawValue is Int.Type {
try self.intValue.encode(to: encoder)
} else {
// getCodableType returns nil if it does not know what value it is. (e.g. myFirstCase without associated value) If you want to support this as well, you can encode using one of your rawValues to the encoder.
throw EncodingError.invalidValue(Self.self, EncodingError.Context.init(codingPath: [], debugDescription: "this enum does not have a correct value", underlyingError: nil))
}
}
}
this code is scalable to any number of raw value as long as they are Codable