ngClass doesn't refresh css class - css

Question

I have great fight with angular 4. I wan`t to make simple star rating component. My template looks like this :
<div class="card rating">
<div class="card-section">
<p class="ratings-card-header">{{name}}</p>
<div class="grid-x grid-margin-x">
<div class="rating-block cell small-12 medium-6 large-3"
*ngFor="let ratingItem of values; let ratingItemIndex = index">
<p class="ratings-type">{{ ratingItem.label }}</p>
<div class="rating-block-rating">
<a *ngFor="let a of getFakeArrayIteration(); let index = index" [ngClass]="time"
(click)="changeValue(ratingItem, index + 1)" >
<i [ngClass]="isStarSelected(index, ratingItem)">
</i>
</a>
</div>
</div>
</div>
</div>
And my controller class look like this:
import {Component, Input, OnInit} from '#angular/core';
import 'foundation-sites';
import {LabelledValue} from './star-rating-vaules';
#Component({
selector: 'star-rating',
templateUrl: './star-rating.component.html',
styleUrls: ['./star-rating.component.scss']
})
export class StarRatingComponent implements OnInit {
#Input() public name: string;
#Input() public maxValue: number;
#Input() public values: LabelledValue[];
private time: Date;
constructor() {
}
ngOnInit() {
console.log(this.values);
}
changeValue(item: LabelledValue, newValue: number) {
item.value = newValue;
this.time = new Date();
}
isStarSelected(index: number, item: LabelledValue): string {
if (index < item.value) {
return 'fas fa-2x fa-minus-square';
} else {
return 'far fa-2x fa-star';
}
}
getFakeArrayIteration(): any[] {
return new Array(this.maxValue);
}
}
export class LabelledValue {
public key: string;
public label: string;
public value: number;
}
Works on beginning. Set proper amount of stars. But if value changes, you cannot set less stars than initial value. I have no clue what`s wrong

Answer 1

Problem is caused because on first adding icon it is translated somehow to svg. After changes of state it is not a problem, but on beginning is unfortunately blocker of css change. Also I created new question: Prevent svg translation of fontawesome