React-native this.props回调函数中为空

Question

我正在尝试在我的 class 中实现 Facebook 登录。我创建了一个按钮组件，但是当我调用 Facebook api 并尝试发送一个注册函数时，我得到了未定义的道具。这是我的组件：

import React, { Component } from 'react';
import { View, StyleSheet } from 'react-native';
import { LoginManager, AccessToken, GraphRequest, GraphRequestManager } from 'react-native-fbsdk';
import Icon from 'react-native-vector-icons/FontAwesome';
import { connect } from 'react-redux';
import AsyncStorage from '@react-native-async-storage/async-storage';
import {register} from '../Actions/authActions';

class Login extends Component {
    constructor(props) {
        super(props);
    }

    _fbAuth = () => {
        LoginManager.logInWithPermissions(['public_profile','email']).then(function(result){
            if(result.isCancelled){
                console.log('loging cancelled')
            }
            else {
                AccessToken.getCurrentAccessToken().then((data) => {
                    let accessToken = data.accessToken;
                    let facebookId = data.userID;
                    const responseInfoCallback = (error, result) => {
                        if (error) {
                            alert('Error logging in with Facebook');
                        }
                        else {
                            console.log('Props here are empty', this.props);
                            this.props.registerSubmit({
                                "customerName": result.name,
                                "customerTel": '000000000',
                                "customerEmail": result.email,
                                "customerPassword": facebookId
                            }).then(response => {
                                console.log('RESPONSE', response);
                                if (response && response.Success) {
                                    this.props.navigation.navigate('App');
                                    AsyncStorage.setItem('customerEmail', data.email);
                                    AsyncStorage.setItem('customerPassword', data.password);
                                } else {
                                    this.props.navigation.navigate('Auth');
                                }
                            });
                        }
                    }
                    const infoRequest = new GraphRequest('/me', {
                        accessToken: accessToken, 
                        parameters: {
                            fields: {
                                string: 'name,picture,email'
                            }}
                        }, responseInfoCallback);
                    new GraphRequestManager().addRequest(infoRequest).start();
                });
            }}, function (error) {
                console.log('Error logging with facebook');
            });
     }


    render() {
    return (
        <View style={styles.container}>
        <Icon.Button name="facebook" backgroundColor="#3b5998" onPress={this._fbAuth.bind(this)} style={styles.signInButton}>
          Facebook login
        </Icon.Button>
    </View>
    )
}
};

const mapDispatchToProps = (dispatch) => {
    // Action
    return {
        // Login
        registerSubmit: (data) => dispatch(register(data)),
    };
};

const styles = StyleSheet.create({
container: {
  flex: 1,
  justifyContent: 'center',
  alignItems: 'center',
},
signInButton: {
  width: 358,
  height: 48
}
});

export default connect(null, mapDispatchToProps)(Login);

当我进入回调函数时 this.props 是空的，因此 registerSubmit 是未定义的。这是我第一个使用 class 组件的项目，我通常使用钩子。我做错了什么？

Answer 1

当你运行这一行：

LoginManager.logInWithPermissions(['public_profile','email']).then(function(result){

新的 function (result) { 作用域有自己的 this。

为了访问组件的 this，您可以在回调外部保存对它的引用，然后在回调内部使用它：

const componentProps = this.props
LoginManager.logInWithPermissions(['public_profile','email']).then(function(result){

或者，您可以为回调使用“箭头函数”，它没有自己的 this，如下所示：

LoginManager.logInWithPermissions(['public_profile','email']).then(result => {

（注意我们不再使用 function 关键字）

React-native this.props回调函数中为空

React-native this.props is empty in callback function

react-native

fbsdk

react-redux