在创建一个类的结构体的时候，有可能报错：
A required parameter cannot follow an optional parameter.
onstructor(id: number,
itemName: string,
isPoison: boolean,
poisonOwner?: number,
isSelected: boolean) {

this.id = id;
this.itemName = itemName;
this.isPoison = isPoison;
this.poisonOwner = poisonOwner;
this.isSelected = isSelected;
}

具体原因：因为必选参数不能放在可选参数之后

修改方案：
constructor(id: number,
itemName: string,
isPoison: boolean,
isSelected: boolean,
poisonOwner?: number,
) {

this.id = id;
this.itemName = itemName;
this.isPoison = isPoison;
this.poisonOwner = poisonOwner;
this.isSelected = isSelected;
}