为什么我收到“未使用的默认导出”错误？

Question

I don't get how I'm getting unused default export error whenever I hover over export default emailChanged; in my index.js file. I'm assuming this is why my code won't run in the simulator.

Here's LoginForm.js :

import React, {Component} from 'react';
import {connect} from 'react-redux';
import {emailChanged} from 'TorusTeensApp/src/actions';
import {Text, StyleSheet, KeyboardAvoidingView, TextInput, TouchableOpacity} from 'react-native';

class LoginForm extends Component {
    onEmailChange(text) {
        this.props.emailChanged(text);
    }

    render() {
        return(
            <KeyboardAvoidingView style={styles.container}>
                <TextInput
                    style={styles.userInput}
                    onsubmitediting={() => this.passwordInput.focus()}
                    returnKeyType={"next"}
                    placeholder={"Email"}
                    label={"Email"}
                    keyboardType={"email-address"}
                    autoCorrect={false}
                    onChangeText={this.onEmailChange.bind(this)}
                    value={this.props.email}
                />

                <TextInput
                    style={styles.userInput}
                    ref={(userInput) => this.passwordInput = userInput}
                    returnKeyType={"go"}
                    placeholder={"Password"}
                    label={"Password"}
                    secureTextEntry
                />

                <TouchableOpacity style={styles.buttonContainer}>
                    <Text style={styles.buttonText}>Login</Text>
                </TouchableOpacity>

                <TouchableOpacity style={styles.buttonContainer}>
                    <Text style={styles.buttonText}>Create Account</Text>
                </TouchableOpacity>
            </KeyboardAvoidingView>
        );
    }
}

const styles = StyleSheet.create({
    container: {
        padding: 20 // creates a gap from the bottom
    },

    userInput: {
        marginBottom: 20,
        backgroundColor: '#9b42f4',
        height: 40
    },

    buttonContainer: {
        backgroundColor: '#41bbf4',
        paddingVertical: 10,
        marginBottom: 20
    },

    buttonText: {
        textAlign: 'center',
        color: '#FFFFFF'
    }
});

const mapStateToProps = state =>  {
    return {
        email: state.auth.email
    };
};

export default connect(mapStateToProps,
    (dispatch) => ({emailChanged: (text) => dispatch(emailChanged(text))}))(LoginForm);

Here's index.js :

import {EMAIL_CHANGED} from './types';

export const emailChanged = (text) => {
    return {
        type: 'EMAIL_CHANGED',
        payload: text
    };
};

onEmailChange = (text) => {
    this.props.emailChanged(text);
};

export default emailChanged;

Answer 1

In your index.js , you have exported the action emailChanged as a named export and you are again exporting the same as default . However you are only importing it as a named import. Thats the reason for your error.

Remove the default export for emailChanged .

import {EMAIL_CHANGED} from './types';

export const emailChanged = (text) => {
    return {
        type: 'EMAIL_CHANGED',
        payload: text
    };
};

onEmailChange = (text) => {
    this.props.emailChanged(text);
};

However, I assume that your intension was to export default onEmailChange function.

In that case change add

export default onEmailChange to the index.js file.

Answer 2

Because you used export default emailChanged , you can't get the value of emailChanged by destructing. Remove the export default emailChanged line in your index.js and you should be good.

Answer 3

Because you have the wrong import.

replace:

import {emailChanged} from 'TorusTeensApp/src/actions';

with:

import emailChanged from 'TorusTeensApp/src/actions';

Here's a better explanation: Difference between "import {Something} from somelib" and "import Something from somelib" React.js