[RN] React Native 使用 realm 数据库
React Native 使用 realm 数据库
realm 是一款专为移动 端开发的高性能数据库,其宣称自己是最快的 react-native 数据库。
realm 整体的优点有这么四点:
1.简单易用,
2.跨平台,
3.快速性能优越,
4.提供高级功能。realm 核心数据引擎用 C++ 打造,并不是建立在 SQLite 之上的 ORM。因此性能就是比普通的 ORM 要快很多,甚至比单独无封装的 SQLite 还要快。同时因为是 ORM,本身在设计时也针对移动设备(iOS、Android),所以简单易用,学习成本很低。
一、安装依赖
npm i -S realm
Link
react-native link
二、使用
1)先定义工具文件
RealmUtil.js
import Realm from 'realm'; /***表定义区**/ export const HistoryTableName = 'History'; export const CityTableName = 'City'; const HistorySchema = { name: HistoryTableName, primaryKey: 'id', properties: { id: 'int', name: 'string', } }; const CitySchema = { name: CityTableName, primaryKey: 'city_id', properties: { city_id: 'int', city_name: 'string', } }; const instance = new Realm({ schema: [ HistorySchema, CitySchema, ], deleteRealmIfMigrationNeeded: true, inMemory: false, }); /***表使用区**/ export function writeToRealm(obj,tabName) { return new Promise((resolve, reject) => { instance.write(() => { instance.create(tabName, obj, true) resolve(true) }) }) } export function queryAllFromRealm(tabName) { return new Promise((resolve, reject) => { let obj = instance.objects(tabName); let objStr = JSON.stringify(obj); resolve(JSON.parse(objStr)) }) } export function clearAllFromRealm(tabName) { return new Promise((resolve, reject) => { instance.write(() => { let arrays = instance.objects(tabName); instance.delete(arrays); resolve(true) }) }) } export function clearRowFromRealm(id,tabName) { return new Promise((resolve, reject) => { instance.write(() => { let arrays = instance.objects(tabName); let row = arrays.filtered(' + id); instance.delete(row); resolve(true) }) }) }
2)调用文件
import React, {Component} from "react"; import {StyleSheet, Text, ToastAndroid, TouchableHighlight, View,} from 'react-native'; import { HistoryTableName, CityTableName, clearAllFromRealm, queryAllFromRealm, writeToRealm, clearRowFromRealm } from "./RealmUtil"; export default class TestRealm extends Component { componentWillMount() { } //表1操作 _addData() { clearAllFromRealm(HistoryTableName); let row1 = {"id": 1, "name": "战狼1"}; writeToRealm(row1, HistoryTableName).then(() => { ToastAndroid.show('写入完成1', ToastAndroid.SHORT); }); let row2 = {"id": 2, "name": "战狼2"}; writeToRealm(row2, HistoryTableName).then(() => { ToastAndroid.show('写入完成2', ToastAndroid.SHORT); }); } _readAllData() { queryAllFromRealm(HistoryTableName).then((list) => { for (let key in list) { ToastAndroid.show('id:' + list[key].id + ',name:' + list[key].name, ToastAndroid.SHORT); } }); } _updateData() { let row2 = {"id": 2, "name": "北京222"}; writeToRealm(row2, HistoryTableName).then(() => { ToastAndroid.show('修改完成', ToastAndroid.SHORT); }); } _delRowData() { //删除第一行 clearRowFromRealm(1, HistoryTableName).then(() => { ToastAndroid.show('删除完成', ToastAndroid.SHORT); }); } //表2操作 _addData2() { clearAllFromRealm(CityTableName); let row1 = {"city_id": 1, "city_name": "上海"}; writeToRealm(row1, CityTableName).then(() => { ToastAndroid.show('2写入完成1', ToastAndroid.SHORT); }); let row2 = {"city_id": 2, "city_name": "北京"}; writeToRealm(row2, CityTableName).then(() => { ToastAndroid.show('2写入完成2', ToastAndroid.SHORT); }); } _readAllData2() { queryAllFromRealm(CityTableName).then((list) => { for (let key in list) { ToastAndroid.show('城市ID:' + list[key].city_id + ',城市名:' + list[key].city_name, ToastAndroid.SHORT); } }); } render() { return ( <View style={{flex: 1}}> <View style={{padding: 10}}><Text>表1操作</Text></View> <TouchableHighlight onPress={() => this._delRowData()} #a5a5a5"> <Text>删除第一行</Text> </TouchableHighlight> <TouchableHighlight onPress={() => this._addData()} #a5a5a5"> <Text>增加数据</Text> </TouchableHighlight> <TouchableHighlight onPress={() => this._updateData()} #a5a5a5"> <Text>修改数据</Text> </TouchableHighlight> <TouchableHighlight onPress={() => this._readAllData()} #a5a5a5"> <Text>读取全部数据</Text> </TouchableHighlight> <View style={{padding: 10, marginTop: 10}}><Text>表2操作</Text></View> <TouchableHighlight onPress={() => this._addData2()} #a5a5a5"> <Text>增加数据</Text> </TouchableHighlight> <TouchableHighlight onPress={() => this._readAllData2()} #a5a5a5"> <Text>读取全部数据</Text> </TouchableHighlight> </View> ); } } const styles = StyleSheet.create({ button: { margin: 3, backgroundColor: 'white', padding: 10, borderBottomWidth: StyleSheet.hairlineWidth, borderBottomColor: '#cdcdcd' }, });
三、如何查看数据文件
笔者是在Genymotion模拟器里测试的
思路是使用 adb 命令 ,先 复制到本地 windows 下,然后用 Realm Studio 打开 realm 文件即可!
复制步骤如下:
1)先连接远程
adb remount
2)查看对应目录下文件
adb ls /data/data/com.testdemo/files
看到结果如下:
000041f9 00001000 5cece0e8 .
000041e9 00001000 5cece048 ..
000041c0 00001000 5cece0e8 default.realm.management
00008180 00316390 5cece0e7 ReactNativeDevBundle.js
00008180 00000498 5cece0fe default.realm.lock
00008180 00004000 5cece0fc default.realm
00001180 00000000 5cece0fc default.realm.note
3)对,没错,然后复制 default.realm 出来就行
adb pull /data/data/com.testdemo/files/default.realm d:/m
注意: com.testdemo 为自己的包名,要对应的修改 。 最后的 d:/m 为 自己要复制的win目录。
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本文原文地址:https://www.cnblogs.com/wukong1688/p/10935043.html
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今日心得:
苦难