chart-component-input-change.ts

@Component({
  // ...
})
export class ChartComponent implements AfterViewInit, OnDestroy {
   public dataLength: number = INIT_LENGTH;
   public isLoading: boolean = true;

   constructor(private dataService: DataService) { }

   public modelChange(newValue: number): void {
      this.dataLength = newValue;
      this.isLoading = true;
      this.dataService.updateDataLength(newValue);
   }
   
   // ...
}