Is it possible for a service to retrieve a component's template?

I am faced with a scenario where two services (A and B) need to communicate with each other. Service A is required to build a chart based on asynchronous data received from service B, which is used in other areas so it operates independently. I attempted to transfer the functionality from the component A to its service, but I have encountered difficulties in accessing the template of the component:

@Injectable()
export class HistoricGraphService {

... // implementation details

  onNewData() {
    const canvas = <HTMLCanvasElement>document.getElementById('historic-chart');
    const ctx = canvas.getContext('2d');
    ... logic to construct the chart using data, timestamp, and more
  }
}

The issue does not lie with the data itself, as the chart is generated successfully when this method is utilized in Component A. I am simply seeking to understand why the same approach cannot be applied to retrieve an element from my template.

Answer №1

To improve your code, consider making the following adjustments:

  1. Limit your service to fetching data and sending it back to your component
  2. Avoid directly accessing the document in your component. If necessary, reference elements like this:

Include this in your HTML:

 <canvas #historicChart></canvas>

In your Component:

@ViewChild('historicChart') historicChart: ElementRef;

After receiving the data in the component:

const ctx = (this.historicChart.nativeElement as HTMLCanvasElement).getContext('2d')

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