What's the correct way to use twoWay directive in vue2.0

Question

Since vue2.0 removes the "twoWay" parameter and "set" function in directive, how to set back the value to the model.

Vue1.0 code

Vue.directive('dire', {
    twoWay: true,
    bind() {
        ...
        this.set(...);
    }
}

Then what's the best way in vue2.0?