Angular Simple Directive ngIf

Question

I do not know how to write my condition in angular and I can not find an equate example.

How i can listen to my material selection ?

How I write a ngIf condition ?

{{referentielToDisplay.speSS}} have a equal value of one of my toppingList, i want to write :

if ReferentielToDisplay. speSS is equal to an item selected in the material selection so: display this card

*ngIf="referentielToDisplay.speSS === topping"

Component.html

<mat-form-field style="width:100%" appearance="outline">
  <mat-label>Sélectionner une spécialité</mat-label>
  <mat-select placeholder="Toppings" [formControl]="toppings" multiple="true" >
    <mat-option *ngFor="let topping of toppingList" [value]="topping" >{{topping}}</mat-option>
  </mat-select>
</mat-form-field>

<div  *ngFor="let referentielToDisplay  of referentielsToDisplay | async" >
<mat-card *ngIf="referentielToDisplay.speSS === topping">
{{referentielToDisplay.nomSS}}
</mat-card>
</div>

Component.ts

toppings = new FormControl( );
toppingList: string[] = ['Multi-spécialité','Hématologie', 'Neurologie', 'Urologie', 'Digestif', 'Endocrinologie',  'Pneumologie', 'ORL','Dermatologie', 'Sein-Gynecologie'];

Answer 1

*ngIf="toppings.value.includes(referentielToDisplay.speSS)" 

It's not totaly the solution but it is the way !!