blocks|key|4510043|text|你所需要的是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4510044|enum+Foo:+String+{
+++case+a,+b,+c,+d
}

let+a+=+Foo(rawValue:+"a")
assert(a+==+Foo.a)

let++=+Foo(rawValue:+"")
assert(+==+nil)|code-block|syntax|javascript|4510045|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

All you need is:

<pre><code>enum Foo: String {
 case a, b, c, d
}

let a = Foo(rawValue: "a")
assert(a == Foo.a)

let = Foo(rawValue: "")
assert( == nil)
</code></pre>

blocks|key|2519|text|在Swift+4.2中，CaseIterable协议可用于带有rawValues的枚举，但字符串应与枚举大小写标签匹配：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2520|enum+MyCode+:+String,+CaseIterable+{

++++case+one+++=+"uno"
++++case+two+++=+"dos"
++++case+three+=+"tres"

++++static+func+withLabel(_+label:+String)+->+MyCode?+{
++++++++return+self.allCases.first{+"\($0)"+==+label+}
++++}
}|code-block|syntax|javascript|2521|用法：|2522|print(MyCode.withLabel("one"))+//+Optional(MyCode.one)
print(MyCode(rawValue:+"uno"))++//+Optional(MyCode.one)|2523|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

In Swift 4.2, the CaseIterable protocol can be used for an enum with rawValues, but the string should match against the enum case labels:

<pre><code>enum MyCode : String, CaseIterable {

 case one = "uno"
 case two = "dos"
 case three = "tres"

 static func withLabel(_ label: String) -&gt; MyCode? {
 return self.allCases.first{ "\($0)" == label }
 }
}
</code></pre>

usage:

<pre><code>print(MyCode.withLabel("one")) // Optional(MyCode.one)
print(MyCode(rawValue: "uno")) // Optional(MyCode.one)
</code></pre>

blocks|key|2390|text|在使用Int类型的枚举的情况下，可以这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2391|enum+MenuItem:+Int+{
++++case+One+=+0,+Two,+Three,+Four,+Five+//...+as+much+as+needs

++++static+func+enumFromString(string:String)+->+MenuItem?+{
++++++++var+i+=+0
++++++++while+let+item+=+MenuItem(rawValue:+i)+{
++++++++++++if+String(item)+==+string+{+return+item+}
++++++++++++i+%2B=+1
++++++++}
++++++++return+nil
++++}
}|code-block|syntax|javascript|2392|并使用：|2393|let+string+=+"Two"
if+let+item+=+MenuItem.enumFromString(string)+{
++++//in+this+case+item+=+1+
++++//your+code
}+|2394|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

In case with an enum with Int type you can do it so:

<pre><code>enum MenuItem: Int {
 case One = 0, Two, Three, Four, Five //... as much as needs

 static func enumFromString(string:String) -&gt; MenuItem? {
 var i = 0
 while let item = MenuItem(rawValue: i) {
 if String(item) == string { return item }
 i += 1
 }
 return nil
 }
}
</code></pre>

And use:

<pre><code>let string = "Two"
if let item = MenuItem.enumFromString(string) {
 //in this case item = 1 
 //your code
} 
</code></pre>

blocks|key|2605|text|Swift+4.2：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2606|public+enum+PaymentPlatform:+String,+CaseIterable+{
++++case+visa+=+"Visa+card"
++++case+masterCard+=+"Master+card"
++++case+cod+=+"Cod"

++++var+nameEnum:+String+{
++++++++return+Mirror(reflecting:+self).children.first?.label+??+String(describing:+self)
++++}

++++func+byName(name:+String)+->+PaymentPlatform+{
++++++++return+PaymentPlatform.allCases.first(where:+{$0.nameEnum.elementsEqual(name)})+??+.cod
++++}
}|code-block|syntax|javascript|2607|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Swift 4.2:

<pre><code>public enum PaymentPlatform: String, CaseIterable {
 case visa = "Visa card"
 case masterCard = "Master card"
 case cod = "Cod"

 var nameEnum: String {
 return Mirror(reflecting: self).children.first?.label ?? String(describing: self)
 }

 func byName(name: String) -&gt; PaymentPlatform {
 return PaymentPlatform.allCases.first(where: {$0.nameEnum.elementsEqual(name)}) ?? .cod
 }
}
</code></pre>

blocks|key|2752|text|根据djruss70的答案创建高度泛化的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2753|extension+CaseIterable+{
++++static+func+from(string:+String)+->+Self?+{
++++++++return+Self.allCases.first+{+string+==+"\($0)"+}
++++}
++++func+toString()+->+String+{+"\(self)"+}
}|code-block|syntax|javascript|2754|用法：|2755|enum+Chassis:+CaseIterable+{
++++case+pieridae,+oovidae
}

let+chassis:+Chassis+=+Chassis.from(string:+"oovidae")!
let+string:+String+=+chassis.toString()|2756|注意:不幸的是，如果枚举被声明为@objc，这将不起作用。据我所知，在Swift+5.3中，除了蛮力解决方案(一个switch语句)之外，没有办法让它与@objc枚举的解决方案一起工作。|2757|如果有人碰巧知道一种在@objc枚举上工作的方法，我会对答案非常感兴趣。|2758|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

Riffing on djruss70's answer to create highly generalized solution:
<pre><code>extension CaseIterable {
 static func from(string: String) -&gt; Self? {
 return Self.allCases.first { string == &quot;\($0)&quot; }
 }
 func toString() -&gt; String { &quot;\(self)&quot; }
}
</code></pre>
Usage:
<pre><code>enum Chassis: CaseIterable {
 case pieridae, oovidae
}

let chassis: Chassis = Chassis.from(string: &quot;oovidae&quot;)!
let string: String = chassis.toString()
</code></pre>
Note: this will unfortunately not work if the enum is declared @objc. As far as I know as of Swift 5.3 there is no way to get this to work with @objc enum's except brute force solutions (a switch statement).
If someone happens to know of a way to make this work for @objc enums, I'd be very interested in the answer.

blocks|key|2429|text|扩展Duncan+C的答案|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2430|extension+StringEnum:+StringLiteralConvertible+{

++++init(stringLiteral+value:+String){
++++++++self.init(rawValue:+value)!
++++}

++++init(extendedGraphemeClusterLiteral+value:+String)+{
++++++++self.init(stringLiteral:+value)
++++}

++++init(unicodeScalarLiteral+value:+String)+{
++++++++self.init(stringLiteral:+value)
++++}
}|code-block|syntax|javascript|2431|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Extending Duncan C's answer

<pre><code>extension StringEnum: StringLiteralConvertible {

 init(stringLiteral value: String){
 self.init(rawValue: value)!
 }

 init(extendedGraphemeClusterLiteral value: String) {
 self.init(stringLiteral: value)
 }

 init(unicodeScalarLiteral value: String) {
 self.init(stringLiteral: value)
 }
}
</code></pre>

blocks|key|2672|text|对于Int枚举及其字符串表示，我按如下方式声明枚举：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2673|enum+OrderState:+Int16,+CustomStringConvertible+{

++++case+waiting+=+1
++++case+inKitchen+=+2
++++case+ready+=+3

++++var+description:+String+{
++++++++switch+self+{
++++++++case+.waiting:
++++++++++++return+"Waiting"
++++++++case+.inKitchen:
++++++++++++return+"InKitchen"
++++++++case+.ready:
++++++++++++return+"Ready"
++++++++}
++++}

++++static+func+initialize(stringValue:+String)->+OrderState?+{
++++++++switch+stringValue+{
++++++++case+OrderState.waiting.description:
++++++++++++return+OrderState.waiting
++++++++case+OrderState.inKitchen.description:
++++++++++++return+OrderState.inKitchen
++++++++case+OrderState.ready.description:
++++++++++++return+OrderState.ready

++++++++default:
++++++++++++return+nil
++++++++}
++++}
}|code-block|syntax|javascript|2674|用法：|2675|order.orderState+=+OrderState.waiting.rawValue

let+orderState+=+OrderState.init(rawValue:+order.orderState)
let+orderStateStr+=+orderState?.description+??+""
print("orderStateStr+=+\(orderStateStr)")|2676|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

For Int enum and their String representation, I declare enum as follows:

<pre><code>enum OrderState: Int16, CustomStringConvertible {

 case waiting = 1
 case inKitchen = 2
 case ready = 3

 var description: String {
 switch self {
 case .waiting:
 return "Waiting"
 case .inKitchen:
 return "InKitchen"
 case .ready:
 return "Ready"
 }
 }

 static func initialize(stringValue: String)-&gt; OrderState? {
 switch stringValue {
 case OrderState.waiting.description:
 return OrderState.waiting
 case OrderState.inKitchen.description:
 return OrderState.inKitchen
 case OrderState.ready.description:
 return OrderState.ready

 default:
 return nil
 }
 }
}
</code></pre>

Usage:

<pre><code>order.orderState = OrderState.waiting.rawValue

let orderState = OrderState.init(rawValue: order.orderState)
let orderStateStr = orderState?.description ?? ""
print("orderStateStr = \(orderStateStr)")
</code></pre>

blocks|key|2769|text|我使用了这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2770|public+enum+Currency:+CaseIterable,+Codable+{
++++case+AFN+=+971+//+Afghani+(minor=2)
++++case+DZD+=+012+//+Algerian+Dinar+(minor=2)

...

++++private+static+var+cachedLookup:+[String:+Currency]+=+[:]
++++
++++init?(string:+String)+{
++++++++if+Self.cachedLookup.isEmpty+{
++++++++++++Self.cachedLookup+=+Dictionary(uniqueKeysWithValues:+Self.allCases.map+{+("\($0)",+$0)+})
++++++++}
++++++++
++++++++if+let+currency+=+Self.cachedLookup[string]+{
++++++++++++self+=+currency
++++++++++++return
++++++++}+else+{
++++++++++++return+nil
++++++++}
++++}
}|code-block|syntax|javascript|2771|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I used this:
<pre><code>public enum Currency: CaseIterable, Codable {
 case AFN = 971 // Afghani (minor=2)
 case DZD = 012 // Algerian Dinar (minor=2)

...

 private static var cachedLookup: [String: Currency] = [:]
 
 init?(string: String) {
 if Self.cachedLookup.isEmpty {
 Self.cachedLookup = Dictionary(uniqueKeysWithValues: Self.allCases.map { (&quot;\($0)&quot;, $0) })
 }
 
 if let currency = Self.cachedLookup[string] {
 self = currency
 return
 } else {
 return nil
 }
 }
}
</code></pre>

If I have an enum with the cases a,b,c,d is it possible for me to cast the string "a" as the enum?

In Swift, is it possible to convert a string to an enum?

Swift

如果我有一个大小写为a，b，c，d的枚举，是否可以将字符串"a“转换为枚举？

问在Swift中，可以将字符串转换为枚举吗？
EN

回答 8

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问在Swift中，可以将字符串转换为枚举吗？EN

回答 8

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问在Swift中，可以将字符串转换为枚举吗？
EN