fixed dataTime range bug & clean code

src/app/data-grid-demo/data-grid-demo-home/data-grid-demo-home.component.ts

@@ -15,12 +15,14 @@ export class DataGridDemoHomeComponent implements OnInit, OnDestroy {
   columns = ['id','name', 'address', 'commands']
   merchantDataSource: IDataSource<IMerchant>;  
   private _dataSubscription: Subscription;
+  private _loading: Subscription;
   constructor(private  merchantService: MerchantService){
     this.merchantDataSource = this.createDataSource();
 
   }
   ngOnDestroy(): void {
     this._dataSubscription.unsubscribe();
+    this._loading.unsubscribe();
   }
 
   
@@ -46,7 +48,7 @@ export class DataGridDemoHomeComponent implements OnInit, OnDestroy {
   }
 
   ngOnInit() {
-    this.merchantDataSource.loading$.subscribe(isLoading => {
+    this._loading = this.merchantDataSource.loading$.subscribe(isLoading => {
       console.log('merchant data source event loading', isLoading);
     });