Collections with basic types.md

Collections with basic types

Collections with elements of basic types (except String) require a wrapper.

Explanations

Kotlin primitive types specified in generics are turned into special wrappers over primitive types:

• List<Byte> -> [KotlinByte]
• List<UByte> -> [KotlinUByte]
• List<Short> -> [KotlinShort]
• List<UShort> -> [KotlinUShort]
• List<Int> -> [KotlinInt]
• List<UInt> -> [KotlinUInt]
• List<Long> -> [KotlinLong]
• List<ULong> -> [KotlinULong]
• List<Float> -> [KotlinFloat]
• List<Double> -> [KotlinDouble]
• List<Boolean> -> [KotlinBoolean]

There are two exceptions to this rule (similar to optional primitive types):

• List<String> -> [String]
• List<Char> -> [Any]

To pass Swift types (not literals) as arguments to a Kotlin function, you will have to write mappings:

CollectionWithPrimitiveTypesKt.intList(list: [1, 2, 3]) // ok
let result2: [KotlinInt] = [1, 2, 3] + CommonTypesKt.listType(list: [1, 3, 4]) // ok

// Mapping
let li2: [KotlinInt] = CommonTypesKt.listType(
    list: intList.map({ p in KotlinInt(value: Int32(p)) })
)

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