Svelte 商店功能更新

Question

Svlete 商店文档显示字符串或整数正在更新，但我没有在商店中找到任何动态函数。

我不明白如何将 getData 函数设置为可写函数以便将更改通知 html。

在下面的示例中，我希望在调用 updateKey 函数后显示 'b'。

您将在此处找到 REPL 中的最小代码：https://svelte.dev/repl/3c86bd48d5b5428daee514765c926e58?version=3.29.7

这里使用相同的代码以防 REPL 出现故障：

App.svelte:

<script>
import { getData } from './store.js';
import { updateKey } from './store.js';
setTimeout(updateKey, 1000);
</script>

<h1>{getData()}!</h1>

store.js

import {setContext} from 'svelte';
import {writable} from 'svelte/store';

var data = {
    'a': 'a',
    'b': 'b'
};

var key = 'a';

export const getData = function() {
    return data[key];
}

export const updateKey = () => {
    key = 'b';
}

目标是在商店中使用动态功能。

感谢阅读。

Answer 1

好吧，我认为您对 Svelte 中的工作方式仍然有些困惑...不确定如何最好地回答您的问题，所以这里有一些代码可以说明您想要实现的目标，以及一些注释。我希望它能帮助您更好地了解商店是如何组合在一起的。

App.svelte

<script>
    import { onMount } from 'svelte'
    import { key, data, updateKey } from './store.js'

    onMount(() => {
        // it's not safe to have an unchecked timer running -- problems would
        // occur if the component is destroyed before the timeout has ellapsed,
        // that's why we're using the `onMount` lifecycle function and its
        // cleanup function here
        const timeout = setTimeout(updateKey, 1000);
        
        // this cleanup function is called when the component is destroyed
        return () => {
            clearTimeout(timeout)
        }
    })

    // this will log the value of the `key` store each time it changes, using
    // a reactive expression (a Sveltism)
    $: console.log($key)
</script>

<!--
  NOTE: we're using the $ prefix notation to access _the value_ of the store,
        and not `data`, which would be _the store itself_ (an object with
        subscribe, set, etc.)
  -->
<h1>{$data}</h1>

store.js

import { writable, derived } from 'svelte/store'

const db = {
    'a': 'a',
    'b': 'b'
}

// a writable store with initial value 'a'
export const key = writable('a')

export const updateKey = () => {
    // a writable store has a `set` method to change its value
    key.set('b')
}

// you can use a derived store to compute derived values from
// the current value of other stores
//
// here, we're getting the value from the db when the value of
// the `key` store changes
export const data = derived([key], ([$key]) => db[$key])

Answer 2

如果我正确理解了你的问题，你希望能够更改由 getData() 执行的功能（逻辑）并且你希望在每个功能上更改 html 以进行更新

对于此用例，您需要创建自己的自定义商店

如下store.js

import { writable } from 'svelte/store';
// an object to hold our functions
const functions = {
        "funcA": () => {
            // do something
            return "whatevedata for a"
        },
        "funcB": () => {
            // do something
            return "the data of b"
        }
    }

// this how to create a custom store, taken from svelte documentation
function createCustomStore(defaultValue) {
    const { subscribe, set, update } = writable(defaultValue);
    return {
        subscribe,
        //custom function change func where suppliedValue the value you input to the store
        // set() is a default function for a store to change it's value
        changeFunc: (suppliedValue) => set(functions[suppliedValue]),
        reset: () => set(defaultValue)
    };
}

export const getData = createCustomStore(() => "default");


export const updateKey = () => {
        // this to update which function the store uses
        getData.changeFunc("funcB")
}

在App.svelte

<script>
    
    import { getData } from './store.js';
    import { updateKey } from './store.js';
    
    setTimeout(function() {
        updateKey()
    }, 1000);
    

</script>

<h1>{$getData()}</h1>

我们将 $ 添加到 getData，因为它是一个保存函数引用的存储，而 () 用于执行 getData 存储引用的任何函数。因为它是 getData 的每个值更改（函数更改）的存储，所以 html 将被更新

这里是一个repl的实现

Svelte 商店功能更新

Svelte store function update

javascript

svelte

svelte-store

svelte-3