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I was originally going to put a PR to fix "has not side-effects", but I also re-read this sentence and realized it could be interpreted as saying a pure function returns its parameters, not a deterministic value based on its parameters.
37 lines
1.0 KiB
Plaintext
37 lines
1.0 KiB
Plaintext
---
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title: "Pure Components"
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---
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## Pure function definition
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A function is considered pure when the return values are deterministic given the same parameters, and it has no side-effects.
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## Pure components
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In the same sense component is pure when it does not have any state or side_effects and with the given props always returns the same `Html`.
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For example below is a pure component, for a given prop `is_loading` it will always result in same `Html` without any side effects.
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```rust
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use yew::{Properties, function_component, Html, html};
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#[derive(Properties, PartialEq)]
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pub struct Props {
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pub is_loading: bool,
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}
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#[function_component]
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fn HelloWorld(props: &Props) -> Html {
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if props.is_loading.clone() {
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html! { "Loading" }
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} else {
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html! { "Hello world" }
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}
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}
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```
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## Un-pure components
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Though you probably wonder how can a component even be un-pure if its just a function that is called every render and if it does not use any globals.
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This is where the next topic comes in - [hooks](./hooks)
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