How to create new recursive json object from interface in Angular 8

Question

I am trying to create a Json with the following format

{
  "via": [
    {
      "name": "Kittin",
      "vagon": [
        {"id":123},
        {"id":321}
        ]
    }
  ]
}

I use the following interface

app.interface.ts

interface RootObject {
  via: Via[];
}

interface Via {
  name: string;
  vagon: Vagon[];
}

interface Vagon {
  id: number;
}

But trying to use it returns the following error

app.component.ts

varData: IVias;

this.varData.via.push('foo');

// this.varData.via = 'foo';

core.js:6014 ERROR TypeError: Cannot read property 'via' of undefined

Thanks in advance for the help

Answer 1

As the message says, varData is undefined.

Probably because it's not initialized at the beginning of your script.

A simple fix would be:

this.varData = { 
   via : [],
}