162 lines
5.0 KiB
Markdown
162 lines
5.0 KiB
Markdown
# Hello World
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Let's put together a simple "hello world" desktop application to get acquainted with Dioxus.
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In this chapter, we'll cover:
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- Starting a new Dioxus project with Cargo
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- Adding Dioxus as a dependency
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- Launching our first component as the app root
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### A new project with Cargo
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First, let's start a new project. Rust has the concept of executables and libraries. Executables have a `main.rs` and libraries have `lib.rs`. A project may have both. Our `hello world` will be an executable - we expect our app to launch when we run it! Cargo provides this for us:
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```shell
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$ cargo new --bin hello-dioxus
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```
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Now, we can `cd` into our project and poke around:
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```shell
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$ cd hello-dioxus
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$ tree
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.
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├── Cargo.toml
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├── .git
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├── .gitignore
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└── src
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└── main.rs
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```
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We are greeted with a pre-initialized git repository, our code folder (`src`) and our project file (`Cargo.toml`).
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Our `src` folder holds our code. Our `main.rs` file holds our `fn main` which will be executed when our app is ran.
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```shell
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$ more src/main.rs
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```
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```rust
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fn main() {
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println!("Hello, world!");
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}
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```
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Right now, whenever our app is launched, "Hello world" will be echoed to the terminal.
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```shell
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$ cargo run
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Compiling hello-dioxus v0.1.0
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Finished dev [unoptimized + debuginfo] target(s) in 0.41s
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Running `target/debug/hello-dioxus`
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Hello, world!
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```
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Our `Cargo.toml` file holds our dependencies and project flags.
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```shell
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$ cat Cargo.toml
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```
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```toml
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[package]
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name = "hello-dioxus"
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version = "0.1.0"
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edition = "2018"
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# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
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[dependencies]
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```
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### Adding Dioxus as a dependency
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To use the Dioxus library, we'll want to add the most recent version of `Dioxus` to our crate. If you have `cargo edit` installed, simply call:
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```shell
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$ cargo add dioxus --features desktop
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```
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It's very important to add `dioxus` with the `desktop` feature for this example. The `dioxus` crate is a batteries-include crate that combines a bunch of utility crates together, ensuring compatibility of the most important parts of the ecosystem. Under the hood, the `dioxus` crate configures various renderers, hooks, debug tooling, and more. The `desktop` feature ensures the we only depend on the smallest set of required crates to compile and render.
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If you plan to develop extensions for the `Dioxus` ecosystem, please use the `dioxus` crate with the `core` feature to limit the amount of dependencies your project brings in.
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### Our first app
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Now, let's edit our `main.rs` file:
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```rust
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use dioxus::prelude::*;
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fn main() {
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dioxus::desktop::start(App, |c| c);
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}
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fn App((cx, props): Component<()>) -> Element {
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cx.render(rsx! (
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div { "Hello, world!" }
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))
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}
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```
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At this point, you could call `cargo run` and be greeted with a simple `Hello, World!` screen:
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### Dissecting our example
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This bit of code imports everything from the the `prelude` module. This brings into scope the right traits, types, and macros needed for working with Dioxus.
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```rust
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use dioxus::prelude::*;
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```
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This initialization code launches a Tokio runtime on a helper thread where your code will run. Then, the WebView renderer will be launched on the main-thread. Due to platform requirements, the main thread is blocked by your app's event loop.
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```rust
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fn main() {
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dioxus::desktop::start(App, |c| c);
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}
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```
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Finally, our app. Every component in Dioxus is a function that takes in `Context` and `Props` and returns an `Element`.
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```rust
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fn App((cx, props): Component<()>) -> Element {
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cx.render(rsx! {
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div { "Hello, world!" }
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})
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}
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```
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In cases where props need to borrow from their parent, you will need to specify lifetimes using the function syntax:
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```rust
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fn App<'a>(cx: Component<'a, ()>) -> Element<'a> {
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cx.render(rsx! {
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div { "Hello, world!" }
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})
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}
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```
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Writing `fn App((cx, props): Component<()>) -> Element {` might become tedious. Rust will also let you write functions as static closures, but these types of Components cannot have props that borrow data.
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```rust
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static App: Fc<()> = |(cx, props)| {
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cx.render(rsx! {
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div { "Hello, world!" }
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})
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};
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```
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### The `Context` object
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In React, you'll want to store data between renders with hooks. However, hooks rely on global variables which make them difficult to integrate in multi-tenant systems like server-rendering. In Dioxus, you are given an explicit `Context` object to control how the component renders and stores data.
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### The `rsx!` macro
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Next, we're greeted with the `rsx!` macro. This lets us add a custom DSL for declaratively building the structure of our app. The semantics of this macro are similar to that of JSX and HTML, though with a familiar Rust-y interface. The `html!` macro is also available for writing components with a JSX/HTML syntax.
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The `rsx!` macro is lazy: it does not immediately produce elements or allocates, but rather builds a closure which can be rendered with `cx.render`.
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