Creating a type array for the interface in Angular 11

Question

Creating a type array for the interface in Angular 11

A newly created interface named Test in Angular 11 contains the following properties:

 export interface Test {
      id:number;
      name:string;
    }

After exporting the interface, an array named ProvinceAllStudent was created to store test data.

import { Test } from './../../../student/Models/test';
import { Component, OnInit } from '@angular/core';
import { Province } from 'src/app/student/Models/Province.model';
@Component({
  selector: 'app-general-statistic',
  templateUrl: './general-statistic.component.html',
  styleUrls: ['./general-statistic.component.css']
})
export class GeneralStatisticComponent implements OnInit {
Provinces:any[];
ProvinceAllStudent:Test[]=[];

  constructor(
) { }

  ngOnInit(): void {
 this.CalculateProvinceStudents()
  }
  CalculateProvinceStudents()
  {
     for(let j=0;j<5;j++)
     {
      this.ProvinceAllStudent[j].id=j;
      this.ProvinceAllStudent[j].name='A';
     }
  }

}

An error occurred when running the application:

core.js:6210 ERROR TypeError: Cannot set properties of undefined (setting 'id') at GeneralStatisticComponent.CalculateProvinceStudents (general-statistic.component.ts:23)

angular typescript

Answer 1

Answer №1

When trying to assign a value to a property of this.ProvinceAllStudent[j], an exception is thrown because this.ProvinceAllStudent[j] is undefined. (undefined does not have the id and name properties)

One suggestion is to use the push method of the array. For example:

for (let j = 0; j < 5; j++) {
  this.ProvinceAllStudent.push({ id: j, name: 'A' });
}

Alternatively, you can add elements by index like this:

for(let j = 0; j < 5; j++) {
  this.ProvinceAllStudent[j] = {id: j, name: 'A'};
}

Answer 2

When trying to assign a value to a property of this.ProvinceAllStudent[j], an exception is thrown because this.ProvinceAllStudent[j] is undefined. (undefined does not have the id and name properties)

One suggestion is to use the push method of the array. For example:

for (let j = 0; j < 5; j++) {
  this.ProvinceAllStudent.push({ id: j, name: 'A' });
}

Alternatively, you can add elements by index like this:

for(let j = 0; j < 5; j++) {
  this.ProvinceAllStudent[j] = {id: j, name: 'A'};
}

Answer 3

Answer №2

To make changes to an object in the array, it is necessary to first initialize the object.

this.ProvinceAllStudent.push({
  id: k,
  name: 'B'
})

Answer 4

To make changes to an object in the array, it is necessary to first initialize the object.

this.ProvinceAllStudent.push({
  id: k,
  name: 'B'
})

Creating a type array for the interface in Angular 11

Answer №1

Answer №2

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