Quickstart

Setup

Install

rust can be installed like any other Dart package.

Dart:

dart pub add rust

Flutter:

flutter pub add rust

or add directly to your pubspec.yaml:

dependencies:
  rust: <version>

Imports

rust follows the same library structure and naming as Rust's core library.

To that extent, each library can be imported individually

import 'package:rust/result.dart';

or all libraries

import 'package:rust/rust.dart';

General Notes

All of rust's classes and methods are well documented in the docs, but being an implementation of Rust's core library, you can also refer to Rust core if anything is unclear. The functionally is the same.

The Basics

Result and Option

Result<T, E> is a sum type used for returning and propagating errors - Ok and Err.

Option<T> represents a value that can be either some value of type T (Some<T>) or None. It is used "in place" of T? (implemented as a zero cost extension type of T?).

These types can be easily chained with other operations or pattern matched.

The Rust ? Operator and Early Return Key Notion

Result<T,E> and Option<T> both support early return key notation, which has the same function as the rust ? operator. It returns from the scope if an Err or None is encountered, otherwise it retrieves the inner value.

Result example:

Result<double, String> divideBy(int num, int divisor) => divisor == 0 ? Err("Divide by zero error") : Ok(num / divisor); 
Result<double, String> func(int x) => Result(($) { // Early Return Key
   // The function will return here
   int val = divideBy(x, 0)[$] + 10;
   return Ok(val);
 });

 void main(){
    assert(func(5) == Err("Divide by zero error"));
 }

List and Arr

Arr (array) is a compliment to List, representing a fixed sized List. Having a separate Arr type fixes runtime exceptions for trying to grow a non-growable List. It also has zero runtime cost, as it is an extension type of List and is more efficient than a growable List. With Arr, type intent is clear for maintainers and developers are able think about code performance more critically.

var array = Arr(null, 10);
array = Arr.constant(const [1,2,3,4,5]);
array = Arr.generate(10, (i) => i);
for(final entry in array){
    // do something
}
var (slice1, slice2) = array.splitSlice(3);

Iter

rust implements the entirety of Rust's stable and unstable Iterator methods. There are a lot of methods here that many Dart developers may not be familiar with. Definitely worth a look - docs

List<int> list = [1, 2, 3, 4, 5];
Iter<int> filtered = list.iter().filterMap((e) {
  if (e % 2 == 0) {
    return Some(e * 2);
  }
  return None;
});
expect(filtered, [4, 8]);

Iter functions the same as a Rust Iterator. For Dart developers, you can think of it as the union of Dart's Iterator and Iterable. check here for more info.

Slice

A Slice is a contiguous sequence of elements in a List or Arr. Slices are a view into a list without allocating and copying to a new list, thus slices are more efficient than creating a new List with .sublist() e.g. list.sublist(x,y).

var list = [1, 2, 3, 4, 5];
var slice = Slice(list, 1, 4); // or `list.slice(1,4)`
expect(slice, [2, 3, 4]);
var taken = slice.takeLast();
expect(taken, 4);
expect(slice, [2, 3]);
slice[1] = 10;
expect(list, [1, 2, 10, 4, 5]);

Slice also has a lot of efficient methods for in-place mutation within and between slices - docs

Whats Next?

Checkout any of the other sections in the book for more details and enjoy!