react-native – 在ReactNative中,Async Await方法在这两个方面

发布时间：2020-12-15 05:07:51 所属栏目：百科来源：网络整理

导读：等待verifyUserSignInSuccess的verifyUser等待等待用户的userSnapshot 这里有两个函数,它们在ReactNative应用程序的正确性,内存,时间方面会更有效： export function verifyUser() { return async dispatch = { dispatch(verifyUserSignInRequest()); try {

等待verifyUserSignInSuccess的verifyUser等待等待用户的userSnapshot

这里有两个函数,它们在ReactNative应用程序的正确性,内存,时间方面会更有效：

export function verifyUser() {
  return async dispatch => {
    dispatch(verifyUserSignInRequest());
    try {
      const user = await firebase.auth().onAuthStateChanged();

        if (user) {
          let userRef = "/user/" + user.uid;
          const userSnapshot = await firebase
            .database()
            .ref(userRef)
            .once("value");
          dispatch(verifyUserSignInSuccess(userSnapshot.val()));
        } else {
          dispatch(verifyUserSignInFailure(USER_NOT_SIGNED_IN));
        }
    } catch (e) {
      dispatch(verifyUserSignInFailure(e.message));
    }
  };
}

或嵌套异步等待：

export function verifyUser() {
  return async dispatch => {
    dispatch(verifyUserSignInRequest());
    try {
      await firebase.auth().onAuthStateChanged(async user => {
        if (user) {
          let userRef = "/user/" + user.uid;
          await firebase
            .database()
            .ref(userRef)
            .once("value")
            .then( () => {
              dispatch(verifyUserSignInSuccess(userSnapshot.val()));
            });
        } else {
          dispatch(verifyUserSignInFailure(USER_NOT_SIGNED_IN));
        }
      });
    } catch (e) {
      dispatch(verifyUserSignInFailure(e.message));
    }
  };
}

根据 documentation,onAuthStateChanged()函数返回

The unsubscribe function for the observer.

所以你可以：

var unsubscribe = firebase.auth().onAuthStateChanged((user) {
    // handle it for changes signed in,signed out,or when the user's ID token changed in situations such as token expiry or password change 
});

然后：

退订();注册观察员.

onAuthStateChanged是一个Observer,它在用户登录,注销或在令牌到期或密码更改等情况下更改用户的ID令牌时调用观察者.所以第二个是最好的解决方案.每次登录或更改.

` let userRef = "/user/" + user.uid;
          await firebase
            .database()
            .ref(userRef)
            .once("value")
            .then( () => {
              dispatch(verifyUserSignInSuccess(userSnapshot.val()));
            });
        } else {
          dispatch(verifyUserSignInFailure(USER_NOT_SIGNED_IN));
        }`

交叉检查是正确的是用户是否有效.我不认为有内存比较是必需的.

（编辑：李大同）

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