Access Typescript Object Variables in Angular2 - json

Question

How do I display the id and title of the below Hero object?
The Hero interface below is mapped according to Firebase JSON response.
hero.component.ts
import {Component, Input} from 'angular2/core';
import {Hero} from '../model/hero';
#Component({
selector: 'hero-component',
template: `
{{hero | json }} this works. This display the Firebase JSON response as seen below
<br>
{{ Object.keys(hero)[0] }} this DOESN'T work
<br>
{{ hero[Object.keys(hero)[0]].title }}this also DOESN'T work
`
})
export class HeroComponent {
#Input()
hero:Hero;
}
hero.ts
export interface Hero {
[id: string]: {
createdAt: number;
isActive: boolean;
title: string;
updatedAt: number;
}
}
Firebase JSON response
{ "-KEMOfA5KFK98AXNhPY0": { "createdAt": 1459607745222, "isActive": true, "title": "Wind Hero", "updatedAt": 1459607745222 } }

Answer 1

update
instead of pipes: [KeysPipe]
use
#NgModule({
declarations: [KeysPipe],
exports: [KeysPipe],
}
export class SharedModule{}
#NgModule({
...
imports: [SharedModule],
})
original
You can't use Object.keys(hero)[0] in the template. No global references can be used, only members of the component.
Instead create a function on your component
getKeys(obj) {
return Object.keys(obj);
}
and then in the template
{{ getKeys(hero)[0] }}
Alternatively you can build a pipe that extracts the keys like for example https://stackoverflow.com/a/34074484/217408
#Pipe({ name: 'keys', pure: false })
export class KeysPipe implements PipeTransform {
transform(value: any, args: any[] = null): any {
return Object.keys(value);
}
}
then use it like
{{ (hero | keys)[0] }}
Don't forget to add the pipe to pipes: [KeysPipe] on the component where you want to use it or alternatively
bootstrap(App, [provide(PLATFORM_PIPES, {useValue: KeysPipe, multi:true})]);

Answer 2

Your code isn't working since Object isn't available in your component.
You could try something like this:
#Component({
selector: 'hero-component',
template: `
{{hero | json }} this works. This display the Firebase JSON response as seen below
<br>
{{ obj.keys(hero)[0] }} this DOESN'T work
<br>
{{ hero[obj.keys(hero)[0]].title }}this also DOESN'T work
`
})
export class HeroComponent {
#Input()
hero:Hero;
obj = Object;
}
or using a method like Günter suggested in his answer.