Kotlin map string to enum

[Solved]-How do I create an enum from a string in Kotlin?-kotlin

Kotlin enum classes have «static» function valueOf to get enum entry by string(like Java enums). Additionally they have «static» function values to get all enum entries. Example:

enum class MyEnum < Foo, Bar, Baz >fun main(args : Array)

If you want to create an enum value from one of its parameters, instead of the name, this funny code does a pretty decent job:

inline fun , V> ((T) -> V).find(value: V): T? < return enumValues().firstOrNull < this(it) == value >> 

This can be used like this:

enum class Algorithms(val string: String) < Sha1("SHA-1"), Sha256("SHA-256"), >fun main() = println( Algorithms::string.find("SHA-256") ?: throw IllegalArgumentException("Bad algorithm string: SHA-256") ) 

Reusable Exception Safe Solution

The default solution in Kotlin will throw an exception. If you want a reliable solution that works statically for all enums, try this!

Now just call valueOf(«value») . If the type is invalid, you’ll get null and have to handle it, instead of an exception.

inline fun > valueOf(type: String): T? < return try < java.lang.Enum.valueOf(T::class.java, type) >catch (e: Exception) < null >> 

Alternatively, you can set a default value, calling valueOf(«value», MyEnum.FALLBACK) , and avoid a null response. You can extend your specific enum to have the default be automatic

inline fun > valueOf(type: String, default: T): T < return try < java.lang.Enum.valueOf(T::class.java, type) >catch (e: Exception) < default >> 

Or if you want both, make the second:

inline fun > valueOf(type: String, default: T): T = valueOf(type) ?: default 

enum class MyEnum < Foo, Bar, Baz >val value = MyEnum.values().firstOrNull // results to MyEnum.Foo 

As bashor suggested, use MyEnum.valueOf() but please have in mind that it throws an exception if value can’t be found. I recommend using:

enum class MyEnum < Foo, Bar, Baz >try < myVar = MyEnum.valueOf("Qux") >catch(e: IllegalArgumentException)

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Источник

How do I create an enum from a string in Kotlin?

I have an enum with some instances Foo and Bar . If I have a string «Foo» , how can I instantiate a Foo enum from that? In C# it would be Enum.Parse(. ) , is there an equivalent in Kotlin? Currently, the best I have found is to create a factory that switches on all possible strings, but that is error prone and performs poorly for large enumerations.

for new comers. read this detailed tutorial on enums in Kotlin. developine.com/enum-classes-in-kotlin-example

5 Answers 5

Kotlin enum classes have «static» function valueOf to get enum entry by string(like Java enums). Additionally they have «static» function values to get all enum entries. Example:

enum class MyEnum < Foo, Bar, Baz >fun main(args : Array)

Is it possible to override this at all? For example, if I wanted to implemented my own version that was case insensitive.

It’s impossible, AFAIK it’s impossible Java too. Introducing own method isn’t suitable for your case?

Doing my own method is fine sure, but it would just be nice to use an existing method so that users don’t need to worry about what this valueOfIgnoringCase method is, they just use valueOf like normal

@Developine this links to a 5 billionth search winner for me. You should check if you site has malware.

As bashor suggested, use MyEnum.valueOf() but please have in mind that it throws an exception if value can’t be found. I recommend using:

enum class MyEnum < Foo Bar Baz >try < myVar = MyEnum.valueOf("Qux") >catch(e: IllegalArgumentException)

enum class MyEnum < Foo, Bar, Baz >val value = MyEnum.values().firstOrNull // results to MyEnum.Foo 

Reusable Exception Safe Solution

The default solution in Kotlin will throw an exception. If you want a reliable solution that works statically for all enums, try this!

Now just call valueOf(«value») . If the type is invalid, you’ll get null and have to handle it, instead of an exception.

inline fun > valueOf(type: String): T? < return try < java.lang.Enum.valueOf(T::class.java, type) >catch (e: Exception) < null >> 

Alternatively, you can set a default value, calling valueOf(«value», MyEnum.FALLBACK) , and avoid a null response. You can extend your specific enum to have the default be automatic

inline fun > valueOf(type: String, default: T): T < return try < java.lang.Enum.valueOf(T::class.java, type) >catch (e: Exception) < default >> 

Or if you want both, make the second:

inline fun > valueOf(type: String, default: T): T = valueOf(type) ?: default 

Источник

How do I create an enum from a string in Kotlin?

I have an enum with some instances Foo and Bar . If I have a string «Foo» , how can I instantiate a Foo enum from that? In C# it would be Enum.Parse(. ) , is there an equivalent in Kotlin? Currently, the best I have found is to create a factory that switches on all possible strings, but that is error prone and performs poorly for large enumerations.

5 Answers 5

Kotlin enum classes have «static» function valueOf to get enum entry by string(like Java enums). Additionally they have «static» function values to get all enum entries. Example:

enum class MyEnum < Foo, Bar, Baz >fun main(args : Array)

Is it possible to override this at all? For example, if I wanted to implemented my own version that was case insensitive.

It’s impossible, AFAIK it’s impossible Java too. Introducing own method isn’t suitable for your case?

Doing my own method is fine sure, but it would just be nice to use an existing method so that users don’t need to worry about what this valueOfIgnoringCase method is, they just use valueOf like normal

@Developine this links to a 5 billionth search winner for me. You should check if you site has malware.

As bashor suggested, use MyEnum.valueOf() but please have in mind that it throws an exception if value can’t be found. I recommend using:

enum class MyEnum < Foo, Bar, Baz >try < myVar = MyEnum.valueOf("Qux") >catch(e: IllegalArgumentException)

enum class MyEnum < Foo, Bar, Baz >val value = MyEnum.values().firstOrNull // results to MyEnum.Foo 

Reusable Exception Safe Solution

The default solution in Kotlin will throw an exception. If you want a reliable solution that works statically for all enums, try this!

Now just call valueOf(«value») . If the type is invalid, you’ll get null and have to handle it, instead of an exception.

inline fun > valueOf(type: String): T? < return try < java.lang.Enum.valueOf(T::class.java, type) >catch (e: Exception) < null >> 

Alternatively, you can set a default value, calling valueOf(«value», MyEnum.FALLBACK) , and avoid a null response. You can extend your specific enum to have the default be automatic

inline fun > valueOf(type: String, default: T): T < return try < java.lang.Enum.valueOf(T::class.java, type) >catch (e: Exception) < default >> 

Or if you want both, make the second:

inline fun > valueOf(type: String, default: T): T = valueOf(type) ?: default 

Источник