Okay, got it. Do exactly as I am saying as follows:
In your html code, replace the following line:
<ion-range dualKnobs="true" [(ngModel)]="dualValue2" min="21" max="72" step="3" snaps="true"></ion-range>
with this:
<ion-range dualKnobs="true" [(ngModel)]="knobValues" min="21" max="72" step="3" snaps="true"></ion-range>
And in your ts file, replace the following code:
knobValues:{
upper:100,
lower:50
}
with this:
knobValues: any = {
upper:100,
lower:50
}
It should work now.