尽管打印正确，但为什么我的函数返回 undefined

Question

代码

函数返回

  async getData(key, setHook) {
    try {
      await AsyncStorage.getItem(key).then((response) => {
        console.log("getData response: " + response); // prints out correctly
        setHook(response); // sets my hook as undefined?
      })
    } catch(e) {
      console.log("AsyncStorage getData: error: " + e);
    }
  }

函数接收


const key = 'key';

const Home = ( {navigation} ) =>  {
  ...
  const [totalBreaks, setTotalBreaks] = useState('0'); // the hook I use in the above function

 // on mount setCounter
 useEffect(() => {  
      setCounter();
 }, []);


 async function setCounter () {
    await asyncStorageInterface.getData(key, setTotalBreaks);
    console.log("total breaks: " + totalBreaks); // returns undefined on mount... when it shouldn't
    if(totalBreaks === null || totalBreaks === undefined) {
      await asyncStorageInterface.storeData(key, '0');
      await asyncStorageInterface.getData(key, setTotalBreaks);
    }
    console.log("total breaks: " + totalBreaks);
  }

问题

我不知道问题出在哪里...我花了将近 6 个小时来解决这个问题，有人可以帮我解决一下吗？如果可能的话，请深入解释问题所在，以便我可以将其记录在某个地方。谢谢

Answer 1

您的 totalBreaks 在您设置之前已被阅读。就这么简单：

const result = {};
const {val} = result;
result.val = 'foo';
console.log(val); // you will still get undefined.

这与异步无关

尽管打印正确，但为什么我的函数返回 undefined

Why is my function returning undefined despite printing out correctly

javascript

asynchronous

async-await

代码

函数返回

函数接收

问题