Svelte 提供了多種內(nèi)置元素。第一個(gè)，?<svelte:self>?，允許組件遞歸地包含自己。

它對(duì)于像文件夾樹(shù)視圖這樣的東西很有用，其中文件夾可以包含其他文件夾。在 ?Folder.svelte? 中，我們希望能夠做到這一點(diǎn)......

{#if file.type === 'folder'}
	<Folder {...file}/>
{:else}
	<File {...file}/>
{/if}

...但這是不可能的，因?yàn)槟K無(wú)法導(dǎo)入自身。相反，我們使用 ?<svelte:self>?：

{#if file.type === 'folder'}
	<svelte:self {...file}/>
{:else}
	<File {...file}/>
{/if}

示例代碼

• App.svelte

<script>
	import Folder from './Folder.svelte';

	let root = [
		{
			type: 'folder',
			name: 'Important work stuff',
			files: [
				{ type: 'file', name: 'quarterly-results.xlsx' }
			]
		},
		{
			type: 'folder',
			name: 'Animal GIFs',
			files: [
				{
					type: 'folder',
					name: 'Dogs',
					files: [
						{ type: 'file', name: 'treadmill.gif' },
						{ type: 'file', name: 'rope-jumping.gif' }
					]
				},
				{
					type: 'folder',
					name: 'Goats',
					files: [
						{ type: 'file', name: 'parkour.gif' },
						{ type: 'file', name: 'rampage.gif' }
					]
				},
				{ type: 'file', name: 'cat-roomba.gif' },
				{ type: 'file', name: 'duck-shuffle.gif' },
				{ type: 'file', name: 'monkey-on-a-pig.gif' }
			]
		},
		{ type: 'file', name: 'TODO.md' }
	];
</script>

<Folder name="Home" files={root} expanded/>

• File.svelte

<script>
	export let name;
	$: type = name.slice(name.lastIndexOf('.') + 1);
</script>

<style>
	span {
		padding: 0 0 0 1.5em;
		background: 0 0.1em no-repeat;
		background-size: 1em 1em;
	}
</style>

<span style="background-image: url(tutorial/icons/{type}.svg)">{name}</span>

• Folder.svelte

<script>
	import File from './File.svelte';

	export let expanded = false;
	export let name;
	export let files;

	function toggle() {
		expanded = !expanded;
	}
</script>

<style>
	span {
		padding: 0 0 0 1.5em;
		background: url(tutorial/icons/folder.svg) 0 0.1em no-repeat;
		background-size: 1em 1em;
		font-weight: bold;
		cursor: pointer;
	}

	.expanded {
		background-image: url(tutorial/icons/folder-open.svg);
	}

	ul {
		padding: 0.2em 0 0 0.5em;
		margin: 0 0 0 0.5em;
		list-style: none;
		border-left: 1px solid #eee;
	}

	li {
		padding: 0.2em 0;
	}
</style>

<span class:expanded on:click={toggle}>{name}</span>

{#if expanded}
	<ul>
		{#each files as file}
			<li>
				{#if file.type === 'folder'}
					<svelte:self {...file}/>
				{:else}
					<File {...file}/>
				{/if}
			</li>
		{/each}
	</ul>
{/if}