Angular Typescript 对象属性显然不是未定义的，但属性是

Question

Im having a rather ridicolous problem.

An object from an subscribed observable has clearly data in it, while printing it to console, but in actual code typescript says its undefined. See for yourself:

initData(): void {

    this.backendService.getData().subscribe((depotDays: DepotDayAcc[]) => {

      console.log(depotDays)
      console.log(depotDays[0])
      console.log(depotDays[0].investment)
      console.log(depotDays[0]["day"])

      console.log('depotDays[0] == undefined', depotDays[0] == undefined)
      console.log('depotDays[0].investment == undefined', depotDays[0].investment == undefined)
    })
}

constructor(
    public day: Date,
    public investment: number = -1,
    public profit: number = 0,
    public value: number = 0,
    public percent: number = 0,
    public tickers: Set<string> = new Set<string>()) {
}

Answer 1

As ShamPooSham has noted in his comment, your data is all strings. You have an array of strings, not objects.

const depotDay = JSON.parse(depotDays[0]);
console.log(depotDay.investment);

Choices are to either fix the payload so it gets deserialised properly, or to deserialise each entry yourself.