HarmonyOS 鸿蒙Next：@ObjectLink和@State的区别

// objectLinkNestedObjects.ets
let NextID: number = 1;

@Observed
class Bag {
public id: number;
public size: number;
constructor(size: number) {
this.id = NextID++;
this.size = size;
}
}
@Observed
class User {
public bag: Bag;
constructor(bag: Bag) {
this.bag = bag;
}
}
@Observed
class Book {
public bookName: BookName;
constructor(bookName: BookName) {
this.bookName = bookName;
}
}
@Observed
class BookName extends Bag {
public nameSize: number;
constructor(nameSize: number) {
// 调用父类方法对nameSize进行处理
super(nameSize);
this.nameSize = nameSize;
}
}
@Component
struct ViewC {
label: string = ‘ViewC1’;
// @ObjectLink bookName: BookName;
@State bookName: BookName = new BookName(0); // 修改点
build() {
Row() {
Column() {
Text(ViewC [${<span class="hljs-keyword"><span class="hljs-keyword">this</span></span>.label}] <span class="hljs-keyword"><span class="hljs-keyword">this</span></span>.bookName.size = ${<span class="hljs-keyword"><span class="hljs-keyword">this</span></span>.bookName.size})
.fontColor(’#ffffffff’)
.backgroundColor(’#ff3d9dba’)
.width(320)
.height(50)
.borderRadius(25)
.margin(10)
.textAlign(TextAlign.Center)
}
.width(320)
}
}
}
@Entry
@Component
struct ViewB {
@State child: Book = new Book(new BookName(0));
build() {
Column() {
ViewC({ label: ‘ViewC #3’, bookName: this.child.bookName })
.width(320)
Button(ViewB: <span class="hljs-keyword"><span class="hljs-keyword">this</span></span>.child.bookName.size add <span class="hljs-number"><span class="hljs-number">10</span></span>)
.width(320)
.backgroundColor(’#ff17a98d’)
.margin(10)
.onClick(() => {
this.child.bookName.size += 10
console.log(‘this.child.bookName.size:’ + this.child.bookName.size)
})
}
}
}<button style="position: absolute; padding: 4px 8px 0px; cursor: pointer; top: 8px; right: 8px; font-size: 14px;">复制</button>

读了指南里的“@Observed装饰器和@ObjectLink装饰器”一节后，对“嵌套对象”里的示例有了一个疑问，我把@ObjectLink修饰的变量换成@State来修饰，点击父组件的Button后子组件ViewC一样能刷新UI（如上面代码中的修改点），那么它俩的区别到底在哪里，请高人指教~