javascript - 如何在 React-Native 中按顺序运行异步函数？

Question

我有一个这样的 Action :

export const loginUser = ({ email, password }) => {
  return (dispatch) => {
    dispatch({ type: LOGIN_USER });

    firebase.auth().signInWithEmailAndPassword(email, password)
      .then(user => {
        const { currentUser } = firebase.auth();
        firebase.database().ref(`users/${currentUser.uid}/userInfo`)
        .on('value', snapshot => {
          const userInfo = _.map(snapshot.val(), (val, uid) => {
            return { ...val, uid };
          });
          console.log(userInfo);
          dispatch({ type: USERINFO_FETCHED, payload: userInfo });
        });

        Actions.main();

        dispatch({
          type: LOGIN_USER_SUCCESS,
          payload: user
        });
      })
      .catch(() => {
        dispatch({
          type: LOGIN_USER_FAIL,
        });
      });
  };
};

这些函数无序运行，因为它们是异步函数。好吧，我们都知道。我想把这些功能整理一下。首先，我想运行并完成此代码:

const { currentUser } = firebase.auth();
        firebase.database().ref(`users/${currentUser.uid}/userInfo`)
        .on('value', snapshot => {
          const userInfo = _.map(snapshot.val(), (val, uid) => {
            return { ...val, uid };
          });
          console.log(userInfo);
          dispatch({ type: USERINFO_FETCHED, payload: userInfo });

完成后我想运行这一行:

Actions.main();

这可能吗？我做不到。谢谢您的回答...

Answer 1

简单的修复方法是，在 .on('value' 中尝试类似 Actions.main(); 这样的内容。

export const loginUser = ({ email, password }) => {
  return (dispatch) => {
    dispatch({ type: LOGIN_USER });

    firebase.auth().signInWithEmailAndPassword(email, password)
      .then(user => {
        const { currentUser } = firebase.auth();
        firebase.database().ref(`users/${currentUser.uid}/userInfo`)
        .on('value', snapshot => {
          const userInfo = _.map(snapshot.val(), (val, uid) => {
            return { ...val, uid };
          });
          console.log(userInfo);
          dispatch({ type: USERINFO_FETCHED, payload: userInfo });
          Actions.main();
        });
        dispatch({
          type: LOGIN_USER_SUCCESS,
          payload: user
        });
      })
      .catch(() => {
        dispatch({
          type: LOGIN_USER_FAIL,
        });
      });
  };
};