I need to know how many children are in a <slot /> is this possible? For example:

我想知道一个<槽/>里有多少个孩子，这可能吗？例如：

// Parent.svelte
<script>
let count = 0 // how to get something like slot.children.count??
</script>
<slot />

// Child.svelte
<div>child</div>

Usage:

用途：

<Parent> // count inside parent should be set to 3
  <Child />
  <Child />
  <Child />
</Parent>

Not sure if I"m missing something obvious but I can't find this capability anywhere.

我不确定我是否遗漏了什么明显的东西，但我在任何地方都找不到这种功能。

After trying many different approaches without success, I have the rest of the functionality that needs to know the count working by just passing the count, but it really is not ideal:

在尝试了许多不同的方法都没有成功之后，我只需传递计数就可以知道计数的其余功能，但这真的不是很理想：

// Parent.svelte
<script>
  export let count
</script>
<slot />

And use like:

并使用如下方式：

<Parent count={3}>
  <Child />
  <Child />
  <Child />
</Parent>

But it would be much simpler to be able to calculate the child count to avoid mismatching between the amount of children and the count

但是，能够计算子计数以避免子数和计数之间的不匹配会简单得多

If the components can be coupled without causing issues elsewhere, you can define a context in the parent, get it in the child and make it "register" itself there.

如果组件可以耦合在一起而不会在其他地方引起问题，那么您可以在父级中定义上下文，将其放在子级中，并让它在那里“注册”自己。

Something along the lines of:

大概是这样的事情：

// in parent
// Use a store for reactivity
const count = setContext('count', writable(0));

<span>Child count: {$count}</span>

// in child
getContext('count').update(i => i + 1)

You could also query the DOM, though I would not recommend that.

您也可以查询DOM，尽管我不建议这样做。

There currently is no programmatic access to slot contents, except checking whether it was set at all.

目前没有对槽内容的编程访问，除了检查它是否被设置。