当我尝试创建如下所示的 JSON 结构时,我遇到了一个问题:
所以为此我正在这样做:
class Aggregate{
average: Number;
count: String;
max: Number;
min: Number;
total: Number;
constructor(average,count,max,min,total) {
this.average= average;
this.count=count;
this.max=max;
this.min= min;
this.total=total;
}
}
var average = new Aggregate(43.833333333333336, 6, 90, 10, 263);
var aggregate = new Aggregate(0, undefined, 0, 0, 0);
var startDate=new Date("Tue Jul 05 2016 05:30:00 GMT+0530 (India Standard Time)");
var endDate=new Date("Tue Jul 05 2016 05:30:00 GMT+0530 (India Standard Time)");
interface date{
aggregate: Aggregate;
endDate: Date;
groupBy: String;
metricType: String;
quarters: Array<DateMetric>;
startDate: Date;
type: String;
quarter?: Number;
}
class DateMetric{
aggregate: Aggregate;
endDate: Date;
groupBy: String;
metricType: String;
quarters: Array<DateMetric>;
startDate: Date;
type: String;
quarter?: Number;
constructor();
constructor(obj: date);
constructor(obj?: any) {
this.aggregate= aggregate;
this.endDate=endDate;
this.groupBy=obj.groupBy;
this.metricType= obj.metricType;
this.quarters = obj.quarters;
this.startDate = startDate;
this.type = obj.type;
this.quarter =obj.quarter;
}
}
var b = new DateMetric();
b.aggregate = aggregate;
b.quarter=4
b.startDate = startDate;
var a = new DateMetric({ aggregate: average, endDate: endDate, groupBy: "datetime", metricType: "distance_metric", quarters: [b], startDate: startDate, type: "person" })
但这里我收到一条错误消息:无法读取未定义的属性“groupBy”
我不知道为什么会收到错误,因为构造函数中的 obj
应该包含创建对象 a
时传递的对象
如有任何帮助,我们将不胜感激。
最佳答案
像这样定义你的构造函数来消除错误。
constructor(obj: any | Date = {}) { }
这样,如果您创建一个实例而没有在构造函数中传递任何数据,则基本上您正在访问。
{}.groupBy; // ({} aka 'obj' is now defined)
使用现有代码,您也可以继续添加 if,如下所示:
constructor(obj: any | Date) {
if(!!obj) {
// do stuff
}
}
但是对于上面的示例,我认为第一个解决方案是最好的:)
关于javascript - 错误:Uncaught TypeError: Cannot read property 'groupBy' of undefined,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/39829749/