Common types - uniffi-bindgen for React Native

For usage in Rust on how to use uniffi’s proc-macros, see the uniffi-rs book for Procedural Macros: Attributes and Derives.

This section is about how the generated Typescript maps onto the Rust idioms available.

A useful way of organizing this is via the types that can be passed across the FFI.

Simple scalar types

	Rust	Typescript
Unsigned integers	`u8`, `u16`, `u32`	`number`	Positive numbers only
Signed integers	`i8`, `i16`, `i32`	`number`
Floating point	`f32`, `f64`	`number`
64 bit integers	`u64`, `i64`	`bigint`	MDN
Strings	`String`	`string`	UTF-8 encoded

Other simple types

	Rust	Typescript
Byte array	`Vec<u8>`	`ArrayBuffer`	MDN
Timestamp	`std::time::SystemTime`	`Date`	aliased to `UniffiTimestamp`
Duration	`std::time::Duration`	`number` ms	aliased to `UniffiDuration`

Structural types

	Rust	Typescript
Optional	`Option<T>`	`T \| undefined`
Sequences	`Vec<T>`	`Array<T>`	Max length is 2**31 - 1
Maps	`HashMap<K, V>` `BTreeMap<K, V>`	`Map<K, V>`	Max length is 2**31 - 1

Enumerated types

	Rust	Typescript
Enums	`enum`	`enum`	Flat enums
Tagged Union Types	`enum`	Tagged unions	Enums with properties
Error enums	`enums`	`Error`

Struct types

	Rust	Typescript
Objects	`struct Foo {}`	`class Foo`	class objects with methods
Records	`struct Bar {}`	`type Bar = {}`	objects without methods
Error objects	`struct Baz {}`	`Error`	object is a property of the `Error`