0plus1 0plus1 - 1 year ago 134
TypeScript Question

Property '' does not exist on type 'Object'. Observable subscribe

I have just started with Angular2 and I've got an issue I cannot really understand.

I have some mock data created as such:

export const WORKFLOW_DATA: Object =
"testDataArray" : [
{ key: "1", name: "Don Meow", source: "cat1.png" },
{ key: "2", parent: "1", name: "Roquefort", source: "cat2.png" },
{ key: "3", parent: "1", name: "Toulouse", source: "cat3.png" },
{ key: "4", parent: "3", name: "Peppo", source: "cat4.png" },
{ key: "5", parent: "3", name: "Alonzo", source: "cat5.png" },
{ key: "6", parent: "2", name: "Berlioz", source: "cat6.png" }

Which is then imported in a service and "observed"

import { Injectable } from '@angular/core';

import { WORKFLOW_DATA } from './../mock-data/workflow'
import {Observable} from "rxjs";

export class ApiService {

constructor() { }

getWorkflowForEditor(): Observable<Object>
return Observable.of( WORKFLOW_DATA );


I then have a component which, in the constructor:

constructor( private apiService: ApiService)
this.apiService.getWorkflowForEditor().subscribe( WORKFLOW_DATA => {
console.log( WORKFLOW_DATA);
console.log( WORKFLOW_DATA.testDataArray );
} );

The first console.log logs an Object of type Object which contains the testDataArray property.

The second console.log, results in an error at compile time:

Property 'testDataArray' does not exist on type 'Object'.

While still logging an array of objects [Object, Object, ..] as intended.

I really do not understand why, I am sure I am doing something wrong, I would love an explanation.

Thank you for any help!

Answer Source

When you tell typescript:


You are telling it that WORKFLOW_DATA is a plain object with no attributes. When you later try to access WORKFLOW_DATA.testDataArray the compiler thinks you misusing the type.

If you want type checking on WORKFLOW_DATA you need to create an interface that describes your object.

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