Thanks so much Zlatko, this was very helpful. Your suggestion regarding the
AsyncPipe was also incredibly helpful.
Rich
On Wednesday, October 25, 2017 at 8:35:27 AM UTC-6, Zlatko Đurić wrote:
>
> Well, two things. For one, the way you define your property, *stock*,
> it's undefined when the thing is initialized. So, before the *dataService*
> gets
> the data back, it's undefined in the template, so yuou have
> *undefined.symbol* - so that's what fails.
>
> You can any of these:
>
> [...snip...]
> template: `Closing price for {{ stock?.symbol }} is {{ stock ?
> stock.close : '0' }}, while the opening was {{ stock && stock.opening || ''
> }} and high <span *ngIf="stock">{{ stock.high }}</span>`
> [...snip...]
>
> To solve your problem, pick any example. To learn how to solve the problem
> in the future, try to explain what each of these does.
>
> For some values (not this one though), you can also use *`{{ obj | async
> }}` * - it's called AsyncPipe in Angular, read up on it.
>
> 2 more things:
> - you fetch stuff in your constructor. That's not a good pattern, some
> things may not work as expected. Instead, do all of this init logic by
> implementing OnInit interface. It's pretty simple actually:
> import { Component, OnInit} from '@angular/core'
> @Component({
> selector:'my-cmp',
> template: 'Hi there',
> })
> export class MyCmp implements OnInit {
> constructor(private dataService: DataService) {} // in constructor,
> you basically only inject all the dependencies.
>
> ngOnInit() {
> // This runs when the component is fully initialized. You can do all
> the logic-related stuff here. If you also want to access view (template),
> implement AfterViewInit instead.
> this.dataService.getStocks().subscribe(stock => this.stock = stock);
> }
>
>
> Another tiny issue is that you declared *stock* as an array, not a single
> object.
>
> class MyComponent {
> obj: any; // that's an object. And it's undefined.
> obj2: any = {}; // that's also an object, initialized to {};
> obj3: any[]; // that's an array. But if you test
> this.obj3.length, it's gonna break because your array is empty.
> obj4: any[] = []; // also an array, but it's initialized when the
> object gets created. It's set to [] (empty array)
> ...
> }
>
> Hope this helps.
>
>
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