将对象推送到嵌套的 Typescript 数组中，得到错误：无法读取未定义的属性“推送”

Question

I've been looking around SO for a bit trying to solve this but my code seems to go a little beyond a standard "push object into array."

I have an interface that types a "Year" property with another interface as an array:

   export interface IUser {
        Nickname: string;
        FirstName: string;
        LastName: string;
        Email: string;
        EmergencyContact: string;
        EmergencyNumber: string;
        Year: Array<IYear>;
        IsTeacher: boolean;
        IsAdmin: boolean;
        Uid: string;
    }

    export interface IYear {
        CalendarYear: string;
        PassType: string;
        UserItinerary: IItinerary;
        WaiverStatus: boolean;
        Guests: Array<IGuest>;
        SignupDate: string;
    }

At a certain point I'm going to pass some formGroup data into the IYear typed property:

user: IUser = <IUser>{};

createUser(
    firstName: string,
    lastName: string,
    email: string,
    uid: string,
    isTeacher: boolean,
    passType: string) {
    const year: IYear = {
      CalendarYear: this.calendarYear,
      PassType: passType,
      UserItinerary: {} as IItinerary,
      WaiverStatus: false,
      Guests: [],
      SignupDate: this.dateTime
    }
    this.user.FirstName = firstName;
    this.user.LastName = lastName;
    this.user.Email = email;
    this.user.Uid = uid;
    this.user.IsTeacher = isTeacher;
    this.user.IsAdmin = false;
    this.user.Year.push(year);

    return this.user;
  }

The problem is, when I try to pass the 'year' property inside of createUser into the 'this.user.Year' array, I get the error

Cannot read property 'push' of undefined

I've tried explicitly passing in the values by key:

this.user.Year['CalendarYear'] = year.CalendarYear;

But that didn't work. Can anyone point out my mistake here?

Answer 1

The Year array in the user Object should be initialized to empty before pushing objects into it.

this.user.Year = [];

and then,

this.user.Year.push(year);

Answer 2

The reason you get the error is because you have to first initialize an array , and then you can push() values to it.

• Either initialize a new IUser with a year = [{your year}] , and then you can push more values to it.
• Or initialize a new IUser object with an empty array year, and then you can push values to it.

Answer 3

you have initialize your array before use it.

user: IUser = <IUser>{};    
createUser(
    firstName: string,
    lastName: string,
    email: string,
    uid: string,
    isTeacher: boolean,
    passType: string) {
    const year: IYear = {
      CalendarYear: this.calendarYear,
      PassType: passType,
      UserItinerary: {} as IItinerary,
      WaiverStatus: false,
      Guests: [],
      SignupDate: this.dateTime
    }
    this.user.FirstName = firstName;
    this.user.LastName = lastName;
    this.user.Email = email;
    this.user.Uid = uid;
    this.user.IsTeacher = isTeacher;
    this.user.IsAdmin = false;
    this.user.Year=[];
    this.user.Year.push(year);    
    return this.user;
  }

Answer 4

您需要确保Year存在于用户对象上，并且CalendarYear存在于Year对象上