Seed
A Rust framework for creating web apps
The best place to learn is the guide - this readme is an excerpt from it.
Quickstart
Setup
This framework requires you to install Rust - This will enable the CLI commands below:
You'll need a recent version of Rust: rustup update
The wasm32-unknown-unknown target: rustup target add wasm32-unknown-unknown
And wasm-bindgen: cargo install wasm-bindgen-cli
The theoretical minimum
To start, clone This quickstart repo,
run build.sh
or build.ps1
in a terminal, then start a dev server that supports WASM.
For example, with Python installed, run python serve.py
.
(Linux users may need to run python3 serve.py
.)
Once you change your package name, you'll
need to tweak the html file and build script, as described below.
A little deeper
Or, create a new lib with Cargo: cargo new --lib appname
. Here and everywhere it appears in this guide, appname
should be replaced with the name of your app.
If not using the quickstart repo, create an Html file that loads your app's compiled module, and provides an element with id to load the framework into. It also needs the following code to load your WASM module - Ie, the body should contain this:
The quickstart repo includes this file, but you will need to rename the two
occurances of appname
. (If your project name has a hyphen, use an underscore instead here) You will eventually need to modify this file to
change the page's title, add a description, favicon, stylesheet etc.
Cargo.toml
, which is a file created by Cargo that describes your app, needs wasm-bindgen
, web-sys
, and seed
added as depdendencies,
and crate-type
of "cdylib"
. (The version in the quickstart repo has these set up already) Example:
[]
= "appname"
= "0.1.0"
= ["Your Name <email@address.com>"]
= "2018"
[]
= ["cdylib"]
[]
= "^0.1.6"
= "^0.2.29"
= "^0.3.6"
# For serialization, eg sending requests to a server. Otherwise, not required.
= "^1.0.80"
= "^1.0.80"
= "1.0.33"
A short example
Here's an example demonstrating structure and syntax; it can be found in working form
under examples/counter
. Descriptions of its parts are in the
Guide section below. Its structure follows The Elm Architecture.
lib.rs:
extern crate seed;
use *;
use *;
// Model
// Setup a default here, for initialization later.
// Update
/// The sole source of updating the model; returns a fresh one.
// View
/// A simple component.
/// The top-level component we pass to the virtual dom. Must accept a ref to the model as its
/// only argument, and output a single El.
For truly minimimal example, see lib.rs in the quickstart repo
Building and running
To build your app, create a pkg
subdirectory, and run the following two commands:
cargo build --target wasm32-unknown-unknown
and
wasm-bindgen target/wasm32-unknown-unknown/debug/appname.wasm --no modules --out-dir ./pkg
where appname
is replaced with your app's name. This compiles your code in the target
folder, and populates the pkg folder with your WASM module, a Typescript definitions file,
and a Javascript file used to link your module from HTML.
You may wish to create a build script with these two lines. (build.sh
for Linux; build.ps1
for Windows).
The Quickstart repo includes these, but you'll still need to do the rename. You can then use
./build.sh
or .\build.ps1
If you run into permission errors on build.sh
, try this command
to allow executing the file:chmod +x build.sh
.
For development, you can view your app using a shimmed Python dev server described above.
(Set up this mime-type shim
from the quickstart repo, and run python serve.py
).
For details, reference the wasm-bindgen documention. In the future, I'd like the build script and commands above to be replaced by wasm-pack.
Running included examples
To run an example located in the examples
folder, navigate to that folder in a terminal,
run the build script for your system (build.sh
or build.ps1
), then start a dev server
as described above. Note that if you copy an example to a separate folder, you'll need
to edit its Cargo.toml
to point to the package on crates.io instead of locally: Ie replace
seed = { path = "../../"
with seed = "^0.1.0"
, and in the build script, remove the leading ../../
on the second
line.
About
Goals
-
Learning the syntax, creating a project, and building it should be easy - regardless of your familiarity with Rust.
-
Complete documentation that always matches the current version. Getting examples working, and starting a project should be painless, and require nothing beyond this guide.
-
Expressive, flexible vew syntax that's easy to read and write.
A note on view syntax
This project takes a different approach to describing how to display DOM elements than others. It neither uses completely natural (ie macro-free) Rust code, nor an HTML-like abstraction (eg JSX or templates). My intent is to make the code close to natural Rust, while streamlining the syntax in a way suited for creating a visual layout with minimal repetition. The macros used here are thin wrappers for constructors, and don't conceal much. Specifically, the element-creation macros allow for accepting a variable number of arguments, and the attrs/style marcros are essentially HashMap literals, with wrappers that let el macros know how to distinguish them.
The lack of resemblance to HTML be offputting, but the learning curve is shallow, and I think the macro syntax used to create elements, attributes etc is close-enough to normal Rust syntax that it's easy to reason about how the code should come together, without compartmentalizing it into logic code and display code. This lack of separation in particlar is a subjective, controversial decision, but I think the benefits are worth it.
Where to start if you're familiar with existing frontend frameworks
The todomvc example is an implementation of the TodoMVC project, which has example code in my frameworks that do the same thing. Compare the example in this project to one on that page that uses a framework you're familiar with.
Suggestions? Critique? Submit an issue or pull request on Github
Influences
This project is strongly influenced by Elm, React, and Redux. The overall layout of Seed apps mimicks that of The Elm Architecture.
Why another entry in a saturated field?
There are already several Rust/WASM frameworks; why add another?
My goal is for this to be easy to pick up from looking at a tutorial or documentation, regardless of your
level of experience with Rust. I'm distinguising this package through clear examples
and documentation (see goals above), and using wasm-bindgen
internally. I started this
project after being unable to get existing frameworks to work
due to lack of documented examples, and inconsistency between documentation and
published versions. My intent is for anyone who's proficient in a frontend
framework to get a standalone app working in the browser within a few minutes, using just the
quickstart guide.
Seed approaches HTML-display syntax differently from existing packages: rather than use an HTML-like markup similar to JSX, it uses Rust builtin types, thinly-wrapped by a macro for each DOM element. This decision may not appeal to everyone, but I think it integrates more naturally with the language.
Why build a frontend in Rust over Elm or Javascript-based frameworks?
You may prefer writing in Rust, and using packages from Cargo vis npm. Getting started with this framework will, in most cases be faster, and require less config and setup overhead than with JS frameworks. You like the advantages of compile-time error-checking.
You may choose this approach over Elm if you're already comfortable with Rust, want the performance benefits, or don't want to code business logic in a purely-functional langauge.
Compared with React, you may appreciate the consistency of how to write apps: There's no distinction between logic and display code; no restrictions on comments; no distinction between components and normal functions. The API is flexible, and avoids OOP boilerplate.
I also hope that config, building, and dependency-management is cleaner with Cargo and wasm-bindgen than with npm.
Shoutouts
- The WASM-Bindgen team: For building the tools this project relies on
- Alex Chrichton, for being extraodinarily helpful in the Rust / WASM community
- The Elm team: For creating and standardizing the Elm architecture
- Denis Kolodin: for creating the inspirational Yew framework
- Utkarsh Kukreti, for through his Draco repo, helping me understand how wasm-bindgen's closure system can be used to update state.
- Tim Robinson, for being very helpful on the Rust Gitter.
Features to add
- High-level fetch API
- Lifecycle hooks
- SVG support
- More flexible routing
- Virtual DOM optimization
- High-level CSS-grid/Flexbox API ?
Bugs to fix
- Text renders above children instead of below
Reference
- wasm-bindgen guide
- Mozilla MDN web docs
- web-sys api (A good partner for the MDN docs - most DOM items have web-sys equivalents used internally)
- Rust book
- Rust standard library api
- Seed's API docs
- Learn Rust