CODEWITHSUNDEEP
arraysangulartypescriptobject
bellotas
bellotas

Reputation: 2461

Initializing array of objects - Angular

I have an array of objects and when I try to access to it, I get an error saying:

TypeError: Cannot set property 'ID' of undefined

My code is the following:

export class Carimplements OnInit {
  pieces: Piece[] = [];

  test(pos){
    this.pieces[pos].ID = "test";
  }
}

being Piece an object

export class Piece{
    ID: string;
    doors: string;
}

I call to test(pos) from the HTML with a valid position.

I guess that I am trying to access to the position X of an array that has not been initialized. How could I do it? Is it possible to create a constructor?

Upvotes: 15

Views: 80350

Answers (4)

Shashidhar Mayannavar
Shashidhar Mayannavar

Reputation: 560

let pieces: Piece[]  = [];

//initialize object before assigning value
test(pos){
    this.pieces[pos] = new Piece();
    this.pieces[pos].ID = "test";
  }

Upvotes: 1

TLP
TLP

Reputation: 1288

How about this?

export class Carimplements OnInit {
  pieces: Piece[] = [];

  test(pos){
    this.pieces[pos] = {ID: "test"};
  }
}

Upvotes: 1

Ekansh Rastogi
Ekansh Rastogi

Reputation: 2526

You can try the following method

 test(pos){
    if(pos < this.pieces.length)
      this.pieces[pos].ID = "test";
    else
      // throw error
  }

Upvotes: 0

martin
martin

Reputation: 96889

  • Correct syntax for defining array types in TypeScript is this:

    pieces: Piece[] = [];

  • The error is a runtime error. When you run your app you have an empty array pieces (but the variable still initialized with []) but you call test(whatever) which tries to access an array element whatever that doesn't exist.

    You can do for example this:

    pieces: Piece[] = [{
  ID: '1',
  doors: 'foo'
}];

    and then test this method with test(0).

Upvotes: 19

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