Harmony之路：实战起航（二）——数据模型与业务逻辑封装
引入
在上一篇中，我们搭建了清晰的项目结构，为应用奠定了坚实的架构基础。今天，我们将深入实战项目的核心——数据模型与业务逻辑封装。如果说项目结构是应用的骨架，那么数据模型就是血肉，业务逻辑则是神经中枢。合理的分层设计能让代码更易维护、测试和扩展，避免"面条式代码"的噩梦。
想象一下，当你的应用需要从本地存储切换到云端存储，或者需要支持多设备数据同步时，如果业务逻辑与数据源紧密耦合，修改成本将呈指数级增长。而通过今天学习的数据层抽象和业务逻辑封装，这些问题都能迎刃而解。
讲解
一、数据模型设计原则
在HarmonyOS应用中，数据模型设计遵循单一数据源（SSOT）原则，即每种数据类型都应该有且只有一个权威的数据源。这能确保数据一致性，避免数据冲突。
数据模型分层架构：
应用层
├── UI组件（页面、组件）
├── 业务逻辑层（ViewModel、Service）
└── 数据层├── 数据源抽象（Repository）├── 本地数据源（Preferences、数据库）└── 远程数据源（网络API）
二、实体类设计
首先定义应用的核心数据模型。以待办事项应用为例：
// models/Todo.ts
export interface Todo {id: string;title: string;description?: string;completed: boolean;createdAt: Date;updatedAt: Date;
}export interface TodoCreateParams {title: string;description?: string;
}
设计要点：
- 使用接口而非类，保持数据不可变性
- 区分实体类和创建参数类，避免污染实体属性
- 使用可选属性（?）标记非必填字段
三、数据源抽象层（Repository模式）
Repository模式是数据层设计的核心，它对外提供统一的数据访问接口，隐藏底层数据源的实现细节。
// data/repositories/TodoRepository.ts
export interface TodoRepository {getAll(): Promise<Todo[]>;getById(id: string): Promise<Todo | null>;create(todo: TodoCreateParams): Promise<Todo>;update(id: string, updates: Partial<Todo>): Promise<Todo>;delete(id: string): Promise<void>;toggleComplete(id: string): Promise<Todo>;
}
接口设计的优势：
- 支持多数据源（本地、网络、内存缓存）
- 便于单元测试（Mock实现）
- 支持热切换数据源（如离线优先策略）
四、本地数据源实现
4.1 使用Preferences存储
对于轻量级配置数据，使用Preferences是最佳选择：
// data/sources/LocalTodoSource.ts
import preferences from '@ohos.data.preferences';
import { Todo, TodoCreateParams } from '../models/Todo';export class LocalTodoSource {private static readonly STORE_NAME = 'todos';private static readonly KEY_TODOS = 'todos_list';private prefs: preferences.Preferences | null = null;async initialize(context: common.Context): Promise<void> {this.prefs = await preferences.getPreferences(context, LocalTodoSource.STORE_NAME);}async getAll(): Promise<Todo[]> {if (!this.prefs) throw new Error('Preferences not initialized');const json = await this.prefs.get(LocalTodoSource.KEY_TODOS, '[]');return JSON.parse(json.toString());}async saveAll(todos: Todo[]): Promise<void> {if (!this.prefs) throw new Error('Preferences not initialized');await this.prefs.put(LocalTodoSource.KEY_TODOS, JSON.stringify(todos));await this.prefs.flush();}
}
4.2 使用关系型数据库
对于结构化数据，关系型数据库更合适：
// data/sources/DatabaseTodoSource.ts
import relationalStore from '@ohos.data.relationalStore';
import { Todo, TodoCreateParams } from '../models/Todo';export class DatabaseTodoSource {private static readonly DB_NAME = 'todo.db';private static readonly TABLE_NAME = 'todos';private rdbStore: relationalStore.RdbStore | null = null;async initialize(context: common.Context): Promise<void> {const config: relationalStore.StoreConfig = {name: DatabaseTodoSource.DB_NAME,securityLevel: relationalStore.SecurityLevel.S1};this.rdbStore = await relationalStore.getRdbStore(context, config);// 创建表const sql = `CREATE TABLE IF NOT EXISTS ${DatabaseTodoSource.TABLE_NAME} (id TEXT PRIMARY KEY,title TEXT NOT NULL,description TEXT,completed INTEGER NOT NULL DEFAULT 0,createdAt TEXT NOT NULL,updatedAt TEXT NOT NULL)`;await this.rdbStore.executeSql(sql);}async getAll(): Promise<Todo[]> {if (!this.rdbStore) throw new Error('Database not initialized');const predicates = new relationalStore.RdbPredicates(DatabaseTodoSource.TABLE_NAME);const result = await this.rdbStore.query(predicates);const todos: Todo[] = [];while (result.goToNextRow()) {todos.push({id: result.getString(result.getColumnIndex('id')),title: result.getString(result.getColumnIndex('title')),description: result.getString(result.getColumnIndex('description')),completed: result.getLong(result.getColumnIndex('completed')) === 1,createdAt: new Date(result.getString(result.getColumnIndex('createdAt'))),updatedAt: new Date(result.getString(result.getColumnIndex('updatedAt')))});}return todos;}
}
五、网络数据源实现
// data/sources/RemoteTodoSource.ts
import http from '@ohos.net.http';
import { Todo, TodoCreateParams } from '../models/Todo';export class RemoteTodoSource {private static readonly BASE_URL = 'https://api.example.com/todos';private httpClient: http.HttpClient;constructor() {this.httpClient = http.createHttp();}async getAll(): Promise<Todo[]> {const response = await this.httpClient.request(`${RemoteTodoSource.BASE_URL}`,{ method: http.RequestMethod.GET });if (response.responseCode !== 200) {throw new Error(`HTTP ${response.responseCode}: ${response.result}`);}return JSON.parse(response.result.toString());}async create(todo: TodoCreateParams): Promise<Todo> {const response = await this.httpClient.request(`${RemoteTodoSource.BASE_URL}`,{method: http.RequestMethod.POST,header: { 'Content-Type': 'application/json' },extraData: JSON.stringify(todo)});if (response.responseCode !== 201) {throw new Error(`HTTP ${response.responseCode}: ${response.result}`);}return JSON.parse(response.result.toString());}
}
六、Repository实现
将多个数据源组合成统一的Repository：
// data/repositories/TodoRepositoryImpl.ts
import { Todo, TodoCreateParams } from '../models/Todo';
import { TodoRepository } from './TodoRepository';
import { LocalTodoSource } from '../sources/LocalTodoSource';
import { RemoteTodoSource } from '../sources/RemoteTodoSource';export class TodoRepositoryImpl implements TodoRepository {private localSource: LocalTodoSource;private remoteSource: RemoteTodoSource;private isOnline: boolean = false;constructor(context: common.Context) {this.localSource = new LocalTodoSource();this.remoteSource = new RemoteTodoSource();// 初始化本地数据源this.localSource.initialize(context);// 监听网络状态this.checkNetworkStatus();}async getAll(): Promise<Todo[]> {if (this.isOnline) {try {const todos = await this.remoteSource.getAll();await this.localSource.saveAll(todos);return todos;} catch (error) {console.warn('Failed to fetch from remote, falling back to local', error);}}return this.localSource.getAll();}async create(todo: TodoCreateParams): Promise<Todo> {const newTodo: Todo = {id: this.generateId(),title: todo.title,description: todo.description,completed: false,createdAt: new Date(),updatedAt: new Date()};if (this.isOnline) {try {const created = await this.remoteSource.create(todo);await this.localSource.saveTodo(created);return created;} catch (error) {console.warn('Failed to create on remote, saving locally', error);}}await this.localSource.saveTodo(newTodo);return newTodo;}private generateId(): string {return `${Date.now()}-${Math.random().toString(36).substr(2, 9)}`;}private async checkNetworkStatus(): Promise<void> {// 实际项目中应使用@ohos.net.connection监听网络状态this.isOnline = true; // 简化实现}
}
七、业务逻辑层封装
业务逻辑层负责处理复杂的业务规则，将数据层与UI层解耦：
// business/TodoService.ts
import { Todo, TodoCreateParams } from '../models/Todo';
import { TodoRepository } from '../data/repositories/TodoRepository';export class TodoService {constructor(private repository: TodoRepository) {}async getTodos(): Promise<Todo[]> {return this.repository.getAll();}async addTodo(params: TodoCreateParams): Promise<Todo> {if (!params.title.trim()) {throw new Error('Title cannot be empty');}if (params.title.length > 100) {throw new Error('Title cannot exceed 100 characters');}return this.repository.create(params);}async toggleTodo(id: string): Promise<Todo> {const todo = await this.repository.getById(id);if (!todo) {throw new Error('Todo not found');}return this.repository.update(id, {completed: !todo.completed,updatedAt: new Date()});}async deleteTodo(id: string): Promise<void> {const todo = await this.repository.getById(id);if (!todo) {throw new Error('Todo not found');}return this.repository.delete(id);}
}
八、ViewModel层实现
ViewModel负责管理UI状态，响应式更新UI：
// viewmodels/TodoViewModel.ts
import { Todo, TodoCreateParams } from '../models/Todo';
import { TodoService } from '../business/TodoService';export class TodoViewModel {@State todos: Todo[] = [];@State loading: boolean = false;@State error: string | null = null;constructor(private todoService: TodoService) {}async loadTodos(): Promise<void> {this.loading = true;this.error = null;try {this.todos = await this.todoService.getTodos();} catch (err) {this.error = err instanceof Error ? err.message : 'Failed to load todos';} finally {this.loading = false;}}async addTodo(title: string): Promise<void> {this.error = null;try {await this.todoService.addTodo({ title });await this.loadTodos(); // 重新加载列表} catch (err) {this.error = err instanceof Error ? err.message : 'Failed to add todo';}}async toggleTodo(id: string): Promise<void> {try {await this.todoService.toggleTodo(id);// 本地更新，避免重新加载const index = this.todos.findIndex(todo => todo.id === id);if (index !== -1) {this.todos[index] = {...this.todos[index],completed: !this.todos[index].completed,updatedAt: new Date()};}} catch (err) {this.error = err instanceof Error ? err.message : 'Failed to toggle todo';}}
}
九、依赖注入与单例管理
为了便于管理和测试，使用单例模式管理服务实例：
// managers/ServiceManager.ts
import { TodoRepositoryImpl } from '../data/repositories/TodoRepositoryImpl';
import { TodoService } from '../business/TodoService';export class ServiceManager {private static instance: ServiceManager;private todoService: TodoService | null = null;private constructor() {}static getInstance(): ServiceManager {if (!ServiceManager.instance) {ServiceManager.instance = new ServiceManager();}return ServiceManager.instance;}getTodoService(context: common.Context): TodoService {if (!this.todoService) {const repository = new TodoRepositoryImpl(context);this.todoService = new TodoService(repository);}return this.todoService;}
}
十、UI层使用示例
// pages/TodoPage.ets
import { TodoViewModel } from '../viewmodels/TodoViewModel';
import { ServiceManager } from '../managers/ServiceManager';@Entry
@Component
struct TodoPage {private viewModel: TodoViewModel;aboutToAppear() {const todoService = ServiceManager.getInstance().getTodoService(getContext(this));this.viewModel = new TodoViewModel(todoService);this.viewModel.loadTodos();}build() {Column() {if (this.viewModel.loading) {LoadingComponent()} else if (this.viewModel.error) {ErrorComponent(this.viewModel.error)} else {TodoListComponent({todos: this.viewModel.todos,onToggle: (id: string) => this.viewModel.toggleTodo(id)})}}}
}
小结
通过本文的学习，我们掌握了HarmonyOS应用数据模型与业务逻辑封装的核心方法。分层架构让我们将数据存储、业务规则和UI展示彻底解耦，每个层各司其职：
数据层：负责数据持久化和网络通信，通过Repository模式提供统一接口
业务层：封装复杂的业务逻辑和验证规则，确保数据一致性
ViewModel层：管理UI状态，响应式更新界面
UI层：专注于界面展示和用户交互
这种架构设计带来了三大优势：
- 可测试性：每层都可以独立测试，Mock依赖项
- 可维护性：修改数据源或业务逻辑不影响其他层
- 可扩展性：轻松添加新功能或切换数据源
在下一篇文章中，我们将进入实战项目的第三环节——UI组件化与重构，教你如何将复杂的UI拆分为可复用的自定义组件，进一步提升代码质量和开发效率。敬请期待！