Help about *ngIf

Inside an .html file from a page of my app:

<ion-list * ngFor = “let item of items; let idx = index;”>
<ion-card * ngIf = “item.service_type == this.type”>

After this, how do I perform some action if * ngIf does not find anything?
In other languages I would simply put a variable and increment it if the loop entered the * ngIF ever, but I do not know how to do that in IONIC.

Could someone give me a basic example? Sorry for bad english and thank you!