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官方文档：MVVM模式

[Q&A] 什么是MVVM

ArkUI采取MVVM = Model + View + ViewModel模式。

1. Model层：存储数据和相关逻辑的模型。
2. View层：在ArkUI中通常是@Component装饰组件渲染的UI。
3. ViewModel层：在ArkUI中，ViewModel是存储在自定义组件的状态变量、LocalStorage和AppStorage中的数据。
   

MVVM应用示例

开发一个电话簿应用，实现功能如下：

1. 显示联系人和设备（“Me”）电话号码 。
2. 选中联系人时，进入可编辑态“Edit”，可以更新该联系人详细信息，包括电话号码，住址。
3. 在更新联系人信息时，只有在单击保存“Save Changes”之后，才会保存更改。
4. 可以点击删除联系人“Delete Contact”，可以在联系人列表删除该联系人。

Model

Address，Person，AddressBook，MyArray

ViewModel

PersonView，phonesNumber，PersonEditView，AddressBookView

Vidw

PracExample

// ViewModel classes
let nextId = 0;@Observed
export class MyArray<T> extends Array<T> {constructor(args: T[]) {console.log(`MyArray: ${JSON.stringify(args)} `)if (args instanceof Array) {super(...args);} else {super(args)}}
}@Observed
export class Address {street: string;zip: number;city: string;constructor(street: string,zip: number,city: string) {this.street = street;this.zip = zip;this.city = city;}
}@Observed
export class Person {id_: string;name: string;address: Address;phones: MyArray<string>;constructor(name: string,street: string,zip: number,city: string,phones: string[]) {this.id_ = `${nextId}`;nextId++;this.name = name;this.address = new Address(street, zip, city);this.phones = new MyArray<string>(phones);}
}export class AddressBook {me: Person;friends: MyArray<Person>;constructor(me: Person, contacts: Person[]) {this.me = me;this.friends = new MyArray<Person>(contacts);}
}// 渲染出Person对象的名称和Observed数组<string>中的第一个号码
// 为了更新电话号码，这里需要@ObjectLink person和@ObjectLink phones，
// 不能使用this.person.phones，内部数组的更改不会被观察到。
// 在AddressBookView、PersonEditView中的onClick更新selectedPerson
@Component
struct PersonView {@ObjectLink person: Person;@ObjectLink phones: MyArray<string>;@Link selectedPerson: Person;build() {Flex({ direction: FlexDirection.Row, justifyContent: FlexAlign.SpaceBetween }) {Text(this.person.name)if (this.phones.length) {Text(this.phones[0])}}.height(55).backgroundColor(this.selectedPerson.name == this.person.name ? Color.Pink : "#ffffff").onClick(() => {this.selectedPerson = this.person;})}
}@Component
struct phonesNumber {@ObjectLink phoneNumber: MyArray<string>build() {Column() {ForEach(this.phoneNumber,(phone: ResourceStr, index?: number) => {TextInput({ text: phone }).width(150).onChange((value) => {console.log(`${index}. ${value} value has changed`)this.phoneNumber[index!] = value;})},(phone: ResourceStr, index: number) => `${this.phoneNumber[index] + index}`)}}
}// 渲染Person的详细信息
// @Prop装饰的变量从父组件AddressBookView深拷贝数据，将变化保留在本地, TextInput的变化只会在本地副本上进行修改。
// 点击 "Save Changes" 会将所有数据的复制通过@Prop到@Link, 同步到其他组件
@Component
struct PersonEditView {@Consume addrBook: AddressBook;/* 指向父组件selectedPerson的引用 */@Link selectedPerson: Person;/*在本地副本上编辑，直到点击保存*/@Prop name: string = "";@Prop address: Address = new Address("", 0, "");@Prop phones: MyArray<string> = [];selectedPersonIndex(): number {return this.addrBook.friends.findIndex((person: Person) => person.id_ == this.selectedPerson.id_);}build() {Column() {TextInput({ text: this.name }).onChange((value) => {this.name = value;})TextInput({ text: this.address.street }).onChange((value) => {this.address.street = value;})TextInput({ text: this.address.city }).onChange((value) => {this.address.city = value;})TextInput({ text: this.address.zip.toString() }).onChange((value) => {const result = Number.parseInt(value);this.address.zip = Number.isNaN(result) ? 0 : result;})if (this.phones.length > 0) {phonesNumber({ phoneNumber: this.phones })}Flex({ direction: FlexDirection.Row, justifyContent: FlexAlign.SpaceBetween }) {Text("Save Changes").onClick(() => {// 将本地副本更新的值赋值给指向父组件selectedPerson的引用// 避免创建新对象，在现有属性上进行修改this.selectedPerson.name = this.name;this.selectedPerson.address = new Address(this.address.street, this.address.zip, this.address.city)this.phones.forEach((phone: string, index: number) => {this.selectedPerson.phones[index] = phone});})if (this.selectedPersonIndex() != -1) {Text("Delete Contact").onClick(() => {let index = this.selectedPersonIndex();console.log(`delete contact at index ${index}`);// 删除当前联系人this.addrBook.friends.splice(index, 1);// 删除当前selectedPerson，选中态前移一位index = (index < this.addrBook.friends.length) ? index : index - 1;// 如果contract被删除完，则设置me为选中态this.selectedPerson = (index >= 0) ? this.addrBook.friends[index] : this.addrBook.me;})}}}}
}@Component
struct AddressBookView {@ObjectLink me: Person;@ObjectLink contacts: MyArray<Person>;@State selectedPerson: Person = new Person("", "", 0, "", []);aboutToAppear() {this.selectedPerson = this.me;}build() {Flex({ direction: FlexDirection.Column, justifyContent: FlexAlign.Start }) {Text("Me:")PersonView({person: this.me,phones: this.me.phones,selectedPerson: this.selectedPerson})Divider().height(8)ForEach(this.contacts, (contact: Person) => {PersonView({person: contact,phones: contact.phones as MyArray<string>,selectedPerson: this.selectedPerson})}, (contact: Person): string => {return contact.id_;})Divider().height(8)Text("Edit:")PersonEditView({selectedPerson: this.selectedPerson,name: this.selectedPerson.name,address: this.selectedPerson.address,phones: this.selectedPerson.phones})}.borderStyle(BorderStyle.Solid).borderWidth(5).borderColor(0xAFEEEE).borderRadius(5)}
}@Entry
@Component
struct PracExample {@Provide addrBook: AddressBook = new AddressBook(new Person("卧龙", "南路 9", 180, "大连", ["18*********", "18*********", "18*********"]),[new Person("小华", "东路 9", 180, "大连", ["11*********", "12*********"]),new Person("小刚", "西边路 9", 180, "大连", ["13*********", "14*********"]),new Person("小红", "南方街 9", 180, "大连", ["15*********", "168*********"]),]);build() {Column() {AddressBookView({me: this.addrBook.me,contacts: this.addrBook.friends,selectedPerson: this.addrBook.me})}}
}