Flutter数据库管理插件realm的使用

警告

请注意，我们宣布了Atlas Device Sync + Realm SDKs的弃用，自2024年9月起。更多详情请参阅：

• SDK弃用
• Device Sync弃用

对于不包含同步功能的realm-dart版本，请安装版本20或查看community分支。

简介

Realm是一个直接在手机、平板电脑或可穿戴设备中运行的移动数据库。本仓库包含了Flutter™和Dart™的Realm SDK源代码。

功能特性

• 移动端优先：Realm是第一个从零开始构建以直接运行于手机、平板电脑和可穿戴设备中的数据库。
• 简单：Realm面向对象的数据模型易于学习，不需要ORM，并且API可以让你编写更少的代码，在几分钟内启动并运行应用程序。
• 现代：支持最新的Dart和Flutter版本，并采用严格的空安全机制。
• 快速：在常见的操作上比原始SQLite更快，同时保持极其丰富的功能集。
• MongoDB Atlas Device Sync：简化了用户、设备和后端之间数据的实时同步。可以通过模板应用免费开始使用，并创建云端后端。

快速入门

导入Realm并定义数据模型

import 'package:realm/realm.dart';

part 'app.realm.dart';

@RealmModel()
class _Car {
  late String make;
  late String model;
  int? kilometers = 500;
}

生成RealmObject类

dart run realm generate

打开Realm并添加对象

var config = Configuration.local([Car.schema]);
var realm = Realm(config);

var car = Car("Tesla", "Model Y", kilometers: 5);
realm.write(() {
  realm.add(car);
});

查询对象

var cars = realm.all<Car>();
Car myCar = cars[0];
print("My car is ${myCar.make} model ${myCar.model}");

cars = realm.all<Car>().query("make == 'Tesla'");

监听查询结果的变化

final cars = realm.all<Car>().query(r'make == $0', ['Tesla']);
cars.changes.listen((changes) {
  print('Inserted indexes: ${changes.inserted}');
  print('Deleted indexes: ${changes.deleted}');
  print('Modified indexes: ${changes.modified}');
});
realm.write(() => realm.add(Car('VW', 'Polo', kilometers: 22000)));

示例代码

以下是一个完整的示例demo，展示了如何在Flutter项目中使用Realm进行数据库管理。

main.dart

// Copyright 2021 MongoDB, Inc.
// SPDX-License-Identifier: Apache-2.0

// ignore_for_file: avoid_print

import 'dart:io';
import 'package:flutter/material.dart';
import 'package:realm/realm.dart';

part 'main.realm.dart';

@RealmModel()
class _Car {
  late String make;
  String? model;
  int? kilometers = 500;
  _Person? owner;
}

@RealmModel()
class _Person {
  late String name;
  int age = 1;
}

void main() {
  print("Current PID $pid");
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  late Realm realm;

  _MyAppState() {
    final config = Configuration.local([Car.schema, Person.schema]);
    realm = Realm(config);
  }

  int get carsCount => realm.all<Car>().length;

  @override
  void initState() {
    var myCar = Car("Tesla", model: "Model Y", kilometers: 1);
    realm.write(() {
      print('Adding a Car to Realm.');
      var car = realm.add(Car("Tesla", owner: Person("John")));
      print("Updating the car's model and kilometers");
      car.model = "Model 3";
      car.kilometers = 5000;

      print('Adding another Car to Realm.');
      realm.add(myCar);

      print("Changing the owner of the car.");
      myCar.owner = Person("me", age: 18);
      print("The car has a new owner ${car.owner!.name}");
    });

    print("Getting all cars from the Realm.");
    var cars = realm.all<Car>();
    print("There are ${cars.length} cars in the Realm.");

    var indexedCar = cars[0];
    print('The first car is ${indexedCar.make} ${indexedCar.model}');

    print("Getting all Tesla cars from the Realm.");
    var filteredCars = realm.all<Car>().query("make == 'Tesla'");
    print('Found ${filteredCars.length} Tesla cars');

    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Plugin example app'),
        ),
        body: Center(
          child: Text('Running on: ${Platform.operatingSystem}.\n\nThere are $carsCount cars in the Realm.\n'),
        ),
      ),
    );
  }
}

文档与资源

• Realm Flutter API Docs
• Realm Dart API Docs
• Realm Flutter Samples
• Realm SDK Documentation
• Quick Start documentation
• App Services Overview
• Device Sync Overview

通过上述内容，您可以快速上手并在Flutter项目中使用Realm进行高效的数据库管理。如果您有任何问题或需要进一步的帮助，请参考官方文档或访问GitHub上的项目页面。