Variants (A | B | ...)

A Variant is a type of either one of the values defined in it's declaration. Example:

interface Math extends HybridObject {
  distance(value: number | Point): number
}

tip

While variants are still very efficient, they need runtime-checks for type conversions, which comes with a tiny overhead compared to all other statically defined types. If possible, avoid variants.

Custom Alias Names

Each variant is a unique type in Swift/Kotlin - for example: string | number becomes Variant_String_Double.

Since the generated names are hard to read, it is recommended to declare type-aliases with custom names instead:

Bad ❌

export interface Math extends HybridObject {
  calculate(): string | number
}

Good ✅

export type MathOutput = string | number
export interface Math extends HybridObject {
  calculate(): MathOutput
}

This will then use the easier-to-read type-alias name instead of Variant_String_Double:

nitrogen/generated/ios/HybridMathSpec.swift

public protocol HybridMathSpec: HybridObject {
  func calculate() -> Variant_String_Double
  func calculate() -> MathOutput
}