Change opacity of button

Ionic Framework ionic-v3
1

Hello,

I want to change the opacity of button depending on boolean value, which can be changed by the checkbox.
But don’t work, please help.

  <button class="isActive ? me-button : ''" ion-item (click)="change()">
    {{ person.id}}
  </button>

  .me-button{
opacity: 0.5;
    }
  }
2

use it like this:

[ngClass]="active? 'on' : 'off'"
3

Or:
[class.me-button]=“isActive”