javascript - 如何在React Native Expo中使用Realm？

Question

我想在我的 React Native Expo 项目中使用 relamDb。我运行以下命令在我的项目中安装领域-

npm install --save 领域

安装时没有显示任何错误。安装后，在我的项目中我创建了两个类 - App.js 和 TodoListComponent.js

App.js

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

import TodoListComponent from './components/TodoListComponent';

export default class App extends React.Component {
  render() {
    return (
      <View style={styles.container}>
        <TodoListComponent/>
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
    alignItems: 'center',
    justifyContent: 'center',
  },
});

TodoListComponent.js

import React, { Component } from 'react';
import { View, FlatList, Text, TouchableOpacity, StyleSheet, Alert } from 'react-native';
import { updateTodoList, deleteTodoList, queryAllTodoLists } from '../databases/allSchemas';
import realm from '../databases/allSchemas';
import Swipeout from 'react-native-swipeout';

import HeaderComponent from './HeaderComponent';
import PopupDialogComponent from './PopupDialogComponent';
let FlatListItem = props => {
    const { itemIndex, id, name, creationDate, popupDialogComponent, onPressItem } = props;
    showEditModal = () => {
        popupDialogComponent.showDialogComponentForUpdate({
            id, name
        });
    }
    showDeleteConfirmation = () => {
        Alert.alert(
            'Delete',
            'Delete a todoList',
            [
                {
                    text: 'No', onPress: () => { },//Do nothing
                    style: 'cancel'
                },
                {
                    text: 'Yes', onPress: () => {
                        deleteTodoList(id).then().catch(error => {
                            alert(`Failed to delete todoList with id = ${id}, error=${error}`);
                        });
                    }
                },
            ],
            { cancelable: true }
        );
    };
    return (
        <Swipeout right={[
            {
                text: 'Edit',
                backgroundColor: 'rgb(81,134,237)',
                onPress: showEditModal
            },
            {
                text: 'Delete',
                backgroundColor: 'rgb(217, 80, 64)',
                onPress: showDeleteConfirmation
            }
        ]} autoClose={true}>
            <TouchableOpacity onPress={onPressItem}>
                <View style={{ backgroundColor: itemIndex % 2 == 0 ? 'powderblue' : 'skyblue' }}>
                    <Text style={{ fontWeight: 'bold', fontSize: 18, margin: 10 }}>{name}</Text>
                    <Text style={{ fontSize: 18, margin: 10 }} numberOfLines={2}>{creationDate.toLocaleString()}</Text>
                </View>
            </TouchableOpacity>
        </Swipeout >
    );
}
export default class TodoListComponent extends Component {
    constructor(props) {
        super(props);
        this.state = {
            todoLists: []
        };
        this.reloadData();
        realm.addListener('change', () => {
            this.reloadData();
        });
    }
    reloadData = () => {
        queryAllTodoLists().then((todoLists) => {
            this.setState({ todoLists });
        }).catch((error) => {
            this.setState({ todoLists: [] });
        });
        console.log(`reloadData`);
    }
    render() {
        return (<View style={styles.container}>
            <HeaderComponent title={"Todo List"}
                hasAddButton={true}
                hasDeleteAllButton={true}
                showAddTodoList={
                    () => {
                        this.refs.popupDialogComponent.showDialogComponentForAdd();
                    }
                }
            />
            <FlatList
                style={styles.flatList}
                data={this.state.todoLists}
                renderItem={({ item, index }) => <FlatListItem {...item} itemIndex={index}
                    popupDialogComponent={this.refs.popupDialogComponent}
                    onPressItem={() => {
                        alert(`You pressed item `);
                    }} />}
                keyExtractor={item => item.id}
            />
            <PopupDialogComponent ref={"popupDialogComponent"} />
        </View>);
    }
}
const styles = StyleSheet.create({
    container: {
        flex: 1,
        flexDirection: 'column',
        justifyContent: 'flex-start',
    },
    flatList: {
        flex: 1,
        flexDirection: 'column',
    }
});

在这些编码之后，当我运行应用程序时，它显示以下错误 -

缺少 Realm 构造函数。您是否运行了“react-native linkrealm”？请参阅https://realm.io/docs/react-native/latest/#missing-realm-constructor用于故障排除

我试图从下面的链接中找出问题-

https://github.com/realm/realm-js/issues/1407

https://github.com/realm/realm-js/issues/1340

但这些对我都没有帮助。因此，如果有人能帮助我了解如何在 React Native expo 项目中使用realmDb，那就太好了。

Answer 1

Expo 不支持领域。

您必须退出博览会，然后开始使用领域

请注意，根据文档，Expo 不支持 Realm。