React Native AsyncStorage => TypeError：无法读取未定义的属性“登录”

Question

This error occur while calling login function:

TypeError: Cannot read property 'login' of undefined

How to solve that problem error calling login() function. I called login() in AsyncStorage multiSet callback function. when I try to access the other property by using this keyword or without any keywords it occurs property not found.

facebookLogin() {
      LoginManager.logInWithPermissions(["public_profile","email","user_birthday","user_friends"]).then(
        function(result) {
          if (result.isCancelled) {
            console.log("Login cancelled");
          } else {
            console.log(
              "Login success with permissions: " +
                result.grantedPermissions.toString()
            );
            AccessToken.getCurrentAccessToken().then(
              (data) => {
                console.log(data.accessToken.toString());
                fetch('https://graph.facebook.com/v2.5/me?fields=email,name,friends,birthday&access_token=' + data.accessToken)
                .then((response) => response.json())
                .then((json) => { 
                  AsyncStorage.multiSet([
                    ['name', json.name.toString()], 
                    ['email', json.email.toString()], 
                    ['photo', 'http://graph.facebook.com/'+json.id+'/picture?type=square']], 
                    () => {
                      console.log("FACEBOOK Login Successeded..");
                      this.login();
                  });
                })
                .catch(() => {
                  console.log('ERROR GETTING DATA FROM FACEBOOK')
                });
              }
            );
          }
        },
        function(error) {
          console.log("Login fail with error: " + error);
        }
      );
    }

    login = () => {
      this.props.navigation.replace("Dashboard");
    }

Answer 1

Just replace your facebookLogin() {... }. with facebookLogin = () => {... }

With this fat arrow function. Hope this helps. feel free for doubts

Answer 2

Replace this code "this.login()" with "this.login"