Primitives (number, boolean, bigint)

Primitive datatypes like number, boolean or bigint can use platform-native datatypes directly. For example, a JS number is always a 64-bit double in C++, a Double in Swift, and a Double in Kotlin.

TypeScript

interface Math extends HybridObject<{ … }> {
  add(a: number, b: number): number
}

Swift

class HybridMath: HybridMathSpec {
  func add(a: Double, b: Double) -> Double
}

Kotlin

class HybridMath: HybridMathSpec() {
  fun add(a: Double, b: Double): Double
}

C++

class HybridMath : public HybridMathSpec {
  double add(double a, double b);
}

Primitives are very efficient and can be passed with little to no overhead, especially between C++ and Swift, and C++ and Kotlin.

bigint

While a bigint is technically a primitive in JS, it is not fully representable by any standard library type in C++, Kotlin or Swift.

In Nitro, you can use bigint as either a signed, or unsigned 64-bit integer, which makes it a primitive, but limits it's range to those within 64-bit signed/unsigned values.

Int64

A 64-bit signed integer that ranges from -2^63 to 2^63-1.

TypeScript

interface Math extends HybridObject<{ … }> {
  add(a: Int64, b: Int64): Int64
}

Swift

class HybridMath: HybridMathSpec {
  func add(a: Int64, b: Int64) -> Int64
}

Kotlin

class HybridMath: HybridMathSpec() {
  fun add(a: Long, b: Long): Long
}

C++

class HybridMath : public HybridMathSpec {
  int64_t add(int64_t a, int64_t b);
}

UInt64

A 64-bit unsigned integer that ranges from 0 to 2^64-1. On 64-bit systems, this is the most convenient type to describe pointer addresses.

TypeScript

interface Math extends HybridObject<{ … }> {
  add(a: UInt64, b: UInt64): UInt64
}

Swift

class HybridMath: HybridMathSpec {
  func add(a: UInt64, b: UInt64) -> UInt64
}

Kotlin

class HybridMath: HybridMathSpec() {
  fun add(a: ULong, b: ULong): ULong
}

C++

class HybridMath : public HybridMathSpec {
  uint64_t add(uint64_t a, uint64_t b);
}

warning

A UInt64 cannot be stored in an AnyMap.

Anything larger

If you want to represent any bigint larger than UInt64/Int64's maximum value, or smaller than UInt64/Int64's minimum value, you must implement your own big integer type.

You can achieve this either by just passing the bigint as a string and deserializing it again on the native side, or by rolling your own type via Custom Types - in this case the JSIConverter can convert your custom big integer type from- and to a bigint.