利用Suspense组件来包装请求

利用Suspense组件来包装请求

React的Suspense有个fallback，可以利用这个特性来处理未请求到数据时显式的内容，请求到数据后就显示结果。

import React, { useEffect, useState } from "react";

const f = fetchValue();

const Comp= (props) => {
  const value = f.read();
  return <div>{value}</div>;
};

export default Comp;

// 封装一个可以用于请求数据的工具函数
function fetchValue(promise) {
  let status = "pending";
  let result = null;
  // 此处模拟axios请求
  // promise.then()
  new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve("success");
    }, 2000);
  }).then(
    (r) => {
      status = "resolved";
      result = r;
    },
    (e) => {
      status = "rejected";
      result = e;
    }
  );
  return {
    read() {
      if (status === "resolved") {
        return result;
      }
      if (status === "rejected") {
        throw Promise.reject(null);
      }
      if (status === "pending") {
        throw Promise.resolve(null);
      }
    },
  };
}

UI上：

<Suspense fallback={<h1>正在加载...</h1>}>
  <Comp />
</Suspense>