Svelte基础
Svelte高阶
上下文API
特殊元素
接下来
SvelteKit基础
Shared modules
API routes
$app/state
Errors and redirects
Advanced SvelteKit
Page options
Link options
Advanced routing
Advanced loading
Environment variables
Conclusion
小主还可以使用bind:this绑定到组件实例本身哦。
这在需要以编程方式与组件交互（而不是通过提供更新的 props）的罕见情况下非常有用。回顾我们在前几节练习中的画布应用，添加一个清除屏幕的按钮会很不错。
首先，让我们从 Canvas.svelte 中导出一个函数：
Just as you can bind to DOM elements, you can bind to component instances themselves with
bind:this. This is useful in the rare cases that you need to interact with a component programmatically (rather than by providing it with updated props). Revisiting our canvas app from a few exercises ago, it would be nice to add a button to clear the screen. First, let’s export a function fromCanvas.svelte:
Canvas
let canvas = $state();
let context = $state();
let coords = $state();
export function clear() {
context.clearRect(0, 0, canvas.width, canvas.height);
}然后，创建一个对组件实例的引用：
Then, create a reference to the component instance:
App
let selected = $state(colors[0]);
let size = $state(10);
let showMenu = $state(true);
let canvas;App
<Canvas bind:this={canvas} color={selected} size={size} />最后，添加一个调用 clear 函数的按钮：
Finally, add a button that calls the
clearfunction:
App
<div class="controls">
<button class="show-menu" onclick={() => showMenu = !showMenu}>
{showMenu ? 'close' : 'menu'}
</button>
<button onclick={() => canvas.clear()}>
clear
</button>
</div>1
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<script>
import Canvas from './Canvas.svelte';
import { trapFocus } from './actions.svelte.js';const colors = ['red', 'orange', 'yellow', 'green', 'blue', 'indigo', 'violet', 'white', 'black'];
let selected = $state(colors[0]);
let size = $state(10);
let showMenu = $state(true);
</script>
<div class="container">
<Canvas color={selected} size={size} /> {#if showMenu}<div
role="presentation"
class="modal-background"
onclick={(event) => { if (event.target === event.currentTarget) {showMenu = false;
}
}}
onkeydown={(e) => { if (e.key === 'Escape') {showMenu = false;
}
}}
>
<div class="menu" use:trapFocus>
<div class="colors">
{#each colors as color}<button
class="color"
aria-label={color} aria-current={selected === color} style="--color: {color}" onclick={() => {selected = color;
}}
></button>
{/each}</div>
<label>
small
<input type="range" bind:value={size} min="1" max="50" />large
</label>
</div>
</div>
{/if}<div class="controls">
<button class="show-menu" onclick={() => showMenu = !showMenu}> {showMenu ? 'close' : 'menu'}</button>
</div>
</div>
<style>
.container {position: fixed;
left: 0;
top: 0;
width: 100%;
height: 100%;
}
.controls {position: absolute;
left: 0;
top: 0;
padding: 1em;
}
.show-menu {width: 5em;
}
.modal-background {position: fixed;
display: flex;
justify-content: center;
align-items: center;
left: 0;
top: 0;
width: 100%;
height: 100%;
backdrop-filter: blur(20px);
}
.menu {position: relative;
background: var(--bg-2);
width: calc(100% - 2em);
max-width: 28em;
padding: 1em 1em 0.5em 1em;
border-radius: 1em;
box-sizing: border-box;
user-select: none;
}
.colors {display: grid;
align-items: center;
grid-template-columns: repeat(9, 1fr);
grid-gap: 0.5em;
}
.color {aspect-ratio: 1;
border-radius: 50%;
background: var(--color, #fff);
transform: none;
filter: drop-shadow(2px 2px 3px rgba(0,0,0,0.2));
transition: all 0.1s;
}
.color[aria-current="true"] {transform: translate(1px, 1px);
filter: none;
box-shadow: inset 3px 3px 4px rgba(0,0,0,0.2);
}
.menu label {display: flex;
width: 100%;
margin: 1em 0 0 0;
}
.menu input {flex: 1;
}
</style>