Add a better introduction to what Components are.

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Reinis Mazeiks committed 2022-02-10 15:50:11 +02:00
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@@ -12,32 +12,10 @@ In short, a component is a special function that takes input properties and outp
### Real-world example
Take a look at a post on Reddit:
Let's use a Reddit post as an example:
![Reddit Post](../images/reddit_post.png)
We can build this post as a component, consisting of multiple subcomponents. It has several inputs:
- The score
- The number of comments
- How long ago it was posted
- The url short address
- The title
- The username of the original poster
If we wanted to sketch out these requirements in Rust, we would start with a struct:
```rust
struct PostData {
score: i32,
comment_count: u32,
post_time: Instant,
url: String,
title: String,
original_poster_name: String
}
```
If we look at the layout of the component, we notice quite a few buttons and pieces of functionality:
- Upvote/Downvote
@@ -52,7 +30,7 @@ If we look at the layout of the component, we notice quite a few buttons and pie
- View article
- Visit user
If we included all this functionality in one `rsx!` call it would be huge! Instead, let's break the post down into some core pieces:
If we included all this functionality in one `rsx!` call it would be huge! Instead, let's break the post down into Components:
![Post as Component](../images/reddit_post_components.png)
@@ -61,4 +39,4 @@ If we included all this functionality in one `rsx!` call it would be huge! Inste
- **MetaCard**: Original Poster, Time Submitted
- **ActionCard**: View comments, Share, Save, Hide, Give award, Report, Crosspost
In this chapter, we'll learn how to define our own components.
In this chapter, we'll learn how to define these components.
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@@ -7,7 +7,7 @@ Dioxus components are functions that accept Props as input and output an Element
- The inline_props macro
## Props
All properties that your components take must implement the `Props` trait. We can derive this trait on our own structs to define a Component's props.
The input of your Component must be passed in a single struct, which must implement the `Props` trait. We can derive this trait automatically with `#[derive(Props)]`.
> Dioxus `Props` is very similar to [@idanarye](https://github.com/idanarye)'s [TypedBuilder crate](https://github.com/idanarye/rust-typed-builder) and supports many of the same parameters.
@@ -20,16 +20,41 @@ There are 2 flavors of Props: owned and borrowed.
Owned Props are very simple – they don't borrow anything. Example:
```rust
#[derive(Props, PartialEq)]
struct MyProps {
name: String
// Remember: owned props must implement PartialEq!
#[derive(PartialEq, Props)]
struct VoteButtonProps {
score: i32
}
fn Demo(cx: Scope<MyProps>) -> Element {
todo!()
fn VoteButton(cx: Scope<VoteButtonProps>) -> Element {
cx.render(rsx!{
div {
div { "+" }
div { "{cx.props.score}"}
div { "-" }
}
})
}
```
Now, we can use the VoteButton Component like we would use a regular HTML element:
```rust
fn main() {
dioxus::desktop::launch(App);
}
fn App(cx: Scope) -> Element {
cx.render(rsx! (
VoteButton { score: 42 }
))
}
```
And we can see that the Component indeed gets rendered:
![Screenshot of running app. Text: "+ \ 42 \ -"](component_example_votes.png)
> The simplest Owned Props you can have is `()` - or no value at all. This is what the `App` Component takes as props. `Scope` accepts a generic for the Props which defaults to `()`.
>
> ```rust
@@ -42,7 +67,7 @@ fn Demo(cx: Scope<MyProps>) -> Element {
### Borrowed Props
Owning a string works well as long as you only need it in one place. But what if we need to pass a String from a `Post` Component to a `TitleCard` subcomponent? A naive solution might be to [`.clone()`](https://doc.rust-lang.org/std/clone/trait.Clone.html) the String, creating a copy of it – but this would be inefficient, especially for larger Strings.
Owning props works well if your props are easy to copy around - like a single number. But what if we need to pass a larger data type, like a String from an `App` Component to a `TitleCard` subcomponent? A naive solution might be to [`.clone()`](https://doc.rust-lang.org/std/clone/trait.Clone.html) the String, creating a copy of it for the subcomponent – but this would be inefficient, especially for larger Strings.
Rust allows for something more efficient – borrowing the String as a `&str`. Instead of creating a copy, this will give us a reference to the original String – this is what Borrowed Props are for!
@@ -61,7 +86,21 @@ fn TitleCard<'a>(cx: Scope<'a, TitleCardProps<'a>>) -> Element {
}
```
This lifetime `'a` tells the compiler that as long as `title` exists, the String it was created from must also exist. Dioxus will happily accept such a component.
This lifetime `'a` tells the compiler that as long as `title` exists, the String it was created from must also exist. Dioxus will happily accept such a component – we can now render it alongside our VoteButton!
```rust
fn App(cx: Scope) -> Element {
// For the sake of an example, we create the &str here.
// But you might as well borrow it from an owned String type.
let hello = "Hello Dioxus!";
cx.render(rsx! (
VoteButton { score: 42 },
TitleCard { title: hello }
))
}
```
![New screenshot of running app, now including a "Hello Dioxus!" heading.](component_example_title.png)
## Memoization