@observable

Decorator that can be used on ES7- or TypeScript class properties to make them observable. The @observable can be used on instance fields and property getters. This offers fine-grained control on which parts of your object become observable.

import { observable, computed } from "mobx"

class OrderLine {
    @observable price = 0
    @observable amount = 1

    @computed get total() {
        return this.price * this.amount
    }
}

If your environment doesn't support decorators or field initializers, use decorate instead (see decorators for details).