A brief discussion on the implementation principle of useAsyncState in VueUse

useAsyncStateis a utility provided in the VueUse library that handles asynchronous state. This Hook allows you to handle the state of asynchronous operations in a synchronous manner in Vue components, such as loading, loading, errors, etc.

useAsyncStateThe implementation principle usually involves the following core concepts:

• Responsive system:One of the core features of Vue is its responsive system, which allows developers to declare changes in data to be automatically updated to the view.useAsyncStateThis system is used to ensure that the state changes of asynchronous operations can be reflected in the view in a timely manner.

• Hook mechanism:Vue 3 introduces the Composition API, where Hook is an important concept that allows developers to reuse logic without changing the component structure.useAsyncStateIt is a custom Hook that encapsulates the state management logic of asynchronous operations.

• Status Management：useAsyncStateUsually an object containing multiple states will be returned, for example:{ data, loading, error }. This allows components to access the state of each stage of asynchronous operation in a synchronous manner.

• Update queue:Vue uses asynchronous update queues to optimize performance and avoids multiple unnecessary renderings.useAsyncStateThis mechanism will be followed when updating the status to ensure that the status update is executed the next time the DOM is updated.

• Error handling: Asynchronous operation may fail.useAsyncStateAn error status is usually provided to facilitate the developer to handle exceptions.

To be specificuseAsyncStateImplementation, it may contain the following steps:

• Create responsive data: Using VuereactiveorrefCreate responsive data to store the state of asynchronous operations, such as loading (loading),data(data) and errors (error）。

• Handle asynchronous logic: Perform an asynchronous operation (usually usingasync/awaitgrammar). At different stages of asynchronous operation, the above responsive data is updated.

• Set up update listener: When the state changes, Vue's responsive system will automatically update the DOM.useAsyncStateListeners may be added when the status changes so that the corresponding view update logic is performed when the status is updated.

• Submit update: When all state changes are completed,useAsyncStateThe update will be submitted to Vue's asynchronous update queue to ensure that the update of the views is carried out in a reasonable order and timing.

• Error capture: If the asynchronous operation fails,useAsyncStateIt will catch exceptions and update the error status, and may provide a callback or error handling logic for users to use.

The above is a high-level introduction. The actual implementation may vary according to specific requirements and library design details. If you need to have an in-depth understandinguseAsyncStateFor specific implementations, you can view the source code of the VueUse library and analyze how it uses Vue's responsive system and other Composition APIs to manage asynchronous state.

Suppose we want to design a simple Vue component, which usesuseAsyncStateTo handle the situation of asynchronous acquisition of user data. This component displays a list of users, handling both loading and error states. Here is a basic implementation example:

First, make sure you have the VueUse library installed. If not installed, you can use npm or yarn to install it:

npm install vueuse# oryarn add vueuse

Then, you can create a Vue component like this:

<template>
  <div>
    <h1>User List</h1>
    <div v-if="loading">Loading users...</div>
    <div v-if="error">Error: {{  }}</div>
    <ul v-if="users">
      <li v-for="user in users" :key="">{{  }}</li>
    </ul>
  </div>
</template>
<script>
import { useAsyncState } from "vueuse";
export default {
  name: "UserList",
  setup() {
    // Use useAsyncState to handle the logic of asynchronously obtaining user data    const {
      data: users,
      loading,
      error,
    } = useAsyncState(
      async () => {
        // Here you can call the API to get data        // For example: const response = await fetch('/api/users');        // return ();        // For the sake of simple examples, we simulate an asynchronous operation        return new Promise((resolve) => {
          setTimeout(() => {
            resolve([
              { id: 1, name: "Alice" },
              { id: 2, name: "Bob" },
              { id: 3, name: "Charlie" },
            ]);
          }, 2000);
        });
      },
      {
        // The initial value of the loading state loading: false,        // The initial value of the error state        error: null,
      }
    );
    return { users, loading, error };
  },
};
</script>

In this example, we useuseAsyncStateTo handle asynchronous operations of obtaining user data. We define an asynchronous function that simulates an API call, returning a promise containing a list of users.useAsyncStateAccepts this asynchronous function and an initial state object that containsloadinganderrorTwo attributes.

In the template, weloadinganderrorstate to display different information. When the data is successfully obtained, we go throughusersArray and display the name of each user.

Note that this example is a simplified version, and in practice you may need to deal with more complex asynchronous logic and state management. Additionally, you may also need to install and configure the VueUse library, which usually involves introducing it into your projectvueuseAutomatic settings (for example, using the auto-import feature of Vite or Webpack).

Specific application

import { ref } from "vue";
import { useAsyncState } from "@vueuse/core";

function useGetLoadingStatus(fun: any, params?) {
  const { isLoading, isReady, state, execute } = useAsyncState(
    (args) => {
      return fun(params).then((res) => res);
    },
    {},
    { immediate: false }
  );
  const res: any = state;
  return {
    isLoading,
    isReady,
    res,
    execute,
  };
}

export default useGetLoadingStatus;

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