Angular Typescript中的对象继承

我试图在angular中使用typescript扩展一个类，但出现以下错误：

 export class Product {

  constructor(public id?: number, public name?: string,
     public brand?: string, public expiry?: Date) {

  }
}

export class StockItem extends Product {
  constructor(public id?: number, public name?: string,
     public brand?: string, public expiry?: Date, public category?: string,
     public price?: number, public quantity?: number,
     public sold?: number, public description?: string,
     public status?: boolean, public expired?: boolean,
     public addedOn?: Date)

      super(id, name, brand, expiry);
}

错误行：

src/app/models/data.model.ts(96,6): error TS2369: A parameter property is only allowed in a constructor implementation.
src/app/models/data.model.ts(96,28): error TS2369: A parameter property is only allowed in a constructor implementation.
src/app/models/data.model.ts(97,6): error TS2369: A parameter property is only allowed in a constructor implementation.
src/app/models/data.model.ts(97,31): error TS2369: A parameter property is only allowed in a constructor implementation.
src/app/models/data.model.ts(98,6): error TS2369: A parameter property is only allowed in a constructor implementation.
src/app/models/data.model.ts(99,6): error TS2391: Function implementation is missing or not immediately following the declaration.

---

您缺少构造函数体的

{}

，该构造函数体应包含对super的调用：

export class Product {

constructor(public id?: number, public name?: string,
    public brand?: string, public expiry?: Date) {

}
}
export class StockItem extends Product {
    constructor(id?: number, name?: string,
        brand?: string, expiry?: Date, public category?: string,
        public price?: number, public quantity?: number,
        public sold?: number, public description?: string,
        public status?: boolean, public expired?: boolean,
        public addedOn?: Date) {

        super(id, name, brand, expiry);
    }
}

---

也不需要重新声明基类声明的字段（即，我从

id

、

name

、

brand

和

expiration

中删除了

public

修饰符，因为它们已经在基类型中声明）

括号不见了吗？关于stockitem构造函数