Why am I getting “undefined is not an object (eval

问题:

Whenever I try to run my iOS simulator, I'm getting that error. All modules are installed, file path to my picture is correct, no errors being thrown within my IDE except for the one that's appearing in my simulator. Picture below of error.

Here's Login.js:

import React, {Component} from 'react';
import {StyleSheet, TextInput, Text, TouchableOpacity, KeyboardAvoidingView} from 'react-native';

class Login extends Component {
    onButtonPress() {
        this.props.navigator.push({
            id: 'CreateAccount'
        });
    }

    render() {
        return(
            <KeyboardAvoidingView behavior={"padding"} style={styles.container}>
                    <TextInput
                        style={styles.input}
                        returnKeyType={"next"}
                        keyboardType={"email-address"}
                        autoCorrect={false}
                        placeholder={"Email"}
                    />

                    <TextInput
                        style={styles.input}
                        returnKeyType={"go"}
                        placeholder={"Password"}
                        secureTextEntry
                    />

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

                    <TouchableOpacity onPress={this.onButtonPress.bind(this)}>
                        <Text style={styles.loginAndCA}>Create Account</Text>
                    </TouchableOpacity>
            </KeyboardAvoidingView>
        );
    }
}

const styles = StyleSheet.create({
    container: {
        padding: 20 // Length of text input boxes.
    },

    input: {
        backgroundColor: '#DAE5FF',
        padding: 20,
        paddingHorizontal: 15,
        marginBottom: 10,
        borderRadius: 15
    },

    loginAndCA: {
        fontSize: 40,
        textAlign: 'center',
        color: 'white',
        fontFamily: 'Bodoni 72 Smallcaps',
        paddingHorizontal: 10
    }
});

export default Login;

Here's BackGround.js:

import React, {Component} from 'react';
import {StyleSheet, Image, View, Text} from 'react-native';
import Login from './Login';

class BackGround extends Component {
    render() {
        return(
            <View style={styles.first}>
                <Image style={styles.container} source={require('../pictures/smoke.jpg')}>
                    <View style={styles.second}>
                         <View>
                            <Text style={styles.title}>My App</Text>
                         </View>
                        <Login/>
                    </View>
                </Image>
            </View>
        );
    }
}

const styles = StyleSheet.create({
    container: {
        flex: 1,
        alignItems: 'center',
        width: null,
        height: null,
        backgroundColor: 'rgba(0,0,0,0)'
    },

    first: {
        flex: 1
    },

    second: {
       paddingTop: 290 // Moves both <TextInput> boxes down.
    },

    title: {
        fontSize: 34,
        textAlign: 'center',
        justifyContent: 'center',
        flexDirection: 'row',
        fontFamily: 'Bodoni 72'
    }

    // movementTitle: {
    //     paddingBottom: 34
    // }
});

export default BackGround;

Here's CreateAccount.js:

import React, {Component} from 'react';
import {Text} from 'react-native';

class CreateAccount extends Component {
    render() {
        return(
            <Text>Must get to this page</Text>
        );
    }
}

export default CreateAccount;

Here's index.ios.js:

import React, {Component} from 'react';
import {View, StyleSheet, AppRegistry} from 'react-native';
import {Navigator} from 'react-native-deprecated-custom-components';
import BackGround from './components/BackGround';
import Login from "./components/Login";
import CreateAccount from "./components/CreateAccount";

export default class App extends Component {
    render() {
        return(
            <View style={styles.back}>
              <BackGround/>
              <Navigator
                  initialRoute={{id: 'Login'}}
                  renderScene={this.navigatorRenderScene}
              />
            </View>
        );
    }

    navigatorRenderScene() {
        _navigator = navigator;
        switch(route.id) {
            case 'Login':
                return (<Login navigator={navigator} title="Login"/>);
            case 'CreateAccount':
                return (<CreateAccount navigator={navigator} title="Create Account" />);
        }
    }
}

const styles = StyleSheet.create({
    back: {
        flex: 1
    }
});

AppRegistry.registerComponent('dendroApp', () => dendroApp);

回答1:

React recently removed PropTypes from their core library as of React 15.5.

Add the line

import PropTypes from 'prop-types';

And call your proptypes directly from that.

回答2:

It seems PropTypes is undefined. I don't see it declared anywhere in your code. You have to import it via a separate module as shown in the documents: PropTypes.

Update:

Perhaps a library you are using is using the now deprecated/non-supported React.PropTypes. I recommend using a more up to date library or actually going into the library and updating the package so it uses the new PropTypes from the separate package instead of React.PropTypes. This should fix your problem

回答3:

Yes definitely, if you upgrade react: 15 or higher then you have to add import PropTypes from 'prop-types';

But recently I faced the same issue in "react": "16.0.0-beta.5" after I changed

"dependencies": {
        "react": "16.0.0-alpha.12"
    },
    "devDependencies": {
        "react-test-renderer": "16.0.0-alpha.12"
    }

Then it found working fine. Hope it helps!