81.HarmonyOS NEXT 状态管理与响应式编程：@Observed深度解析

数据变化 -> 触发观察者 -> 更新依赖 -> 渲染UI

@Observed
class DataModel {
  public value: number = 0;
  
  constructor() {
    this.value = 0;
  }
  
  updateValue(newValue: number) {
    this.value = newValue;  // 触发响应式更新
  }
}

@Observed
class UserModel {
  // 1. 明确的数据结构
  private _name: string;
  private _age: number;
  
  // 2. 封装的访问方法
  get name(): string {
    return this._name;
  }
  
  // 3. 验证的更新方法
  setAge(age: number): boolean {
    if (age < 0 || age > 150) return false;
    this._age = age;
    return true;
  }
  
  // 4. 状态重置方法
  reset(): void {
    this._name = '';
    this._age = 0;
  }
}

@Component
struct UserProfile {
  @State private userModel: UserModel = new UserModel();
  
  build() {
    Column() {
      Text(this.userModel.name)
      Button('更新年龄')
        .onClick(() => {
          this.userModel.setAge(25);
        })
    }
  }
}

@Observed
class CartModel {
  private items: Array<ItemModel> = [];
  private total: number = 0;
  
  addItem(item: ItemModel): void {
    this.items.push(item);
    this.calculateTotal();
  }
  
  removeItem(id: string): void {
    this.items = this.items.filter(item => item.id !== id);
    this.calculateTotal();
  }
  
  private calculateTotal(): void {
    this.total = this.items.reduce((sum, item) => sum + item.price, 0);
  }
}

@Observed
class ItemModel {
  id: string;
  name: string;
  price: number;
  quantity: number;
  
  constructor(id: string, name: string, price: number) {
    this.id = id;
    this.name = name;
    this.price = price;
    this.quantity = 1;
  }
  
  updateQuantity(newQuantity: number): void {
    if (newQuantity > 0) {
      this.quantity = newQuantity;
    }
  }
}

@Observed
class ThemeModel {
  private _isDark: boolean = false;
  private _primaryColor: string = '#000000';
  private _fontSize: number = 14;
  
  get isDark(): boolean {
    return this._isDark;
  }
  
  toggleTheme(): void {
    this._isDark = !this._isDark;
    this.updateThemeColors();
  }
  
  private updateThemeColors(): void {
    if (this._isDark) {
      this._primaryColor = '#FFFFFF';
    } else {
      this._primaryColor = '#000000';
    }
  }
}

@Observed
class OptimizedModel {
  private updateQueue: Array<() => void> = [];
  private isUpdating: boolean = false;
  
  // 批量更新方法
  batchUpdate(updates: Array<() => void>) {
    this.updateQueue.push(...updates);
    
    if (!this.isUpdating) {
      this.isUpdating = true;
      Promise.resolve().then(() => {
        this.processUpdates();
      });
    }
  }
  
  private processUpdates() {
    while (this.updateQueue.length > 0) {
      const update = this.updateQueue.shift();
      update();
    }
    this.isUpdating = false;
  }
}