对于多层嵌套的情况，比如二维数组，或者数组项class，或者class的属性是class，第二层的属性变化如何观察

class DateClass extends Date {
constructor(args: number | string) {
super(args)
}
}

@Observed
class ClassB {
public a: DateClass;

constructor(a: DateClass) {
this.a = a;
}
}

@Component
struct ViewA {
label: string = 'date';
@ObjectLink a: DateClass;

build() {
Column() {
Button(`child increase the day by 1`)
.onClick(() => {
this.a.setDate(this.a.getDate() + 1);
})
DatePicker({
start: new Date('1970-1-1'),
end: new Date('2100-1-1'),
selected: this.a
})
}
}
}

@Entry
@Component
struct ViewB {
@State b: ClassB = new ClassB(new DateClass('2023-1-1'));

build() {
Column() {
ViewA({ label: 'date', a: this.b.a })

Button(`parent update the new date`)
.onClick(() => {
this.b.a = new DateClass('2023-07-07');
})
Button(`ViewB: this.b = new ClassB(new DateClass('2023-08-20'))`)
.onClick(() => {
this.b = new ClassB(new DateClass('2023-08-20'));
})
}
}
}
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