Why Modal constructor is always fired when Page constructor/ngOnInit only once ?

Hi there,
I want to show dynamic components with such like routes:
/mycomponent/myId/:myId

If this component is a modal, i can easily get param from constructor:
this.navParams.get(‘myId’);

But if this component is a normal page, i can get my param only at first call.
Next calls, constructor and ngOnInit are never fired.
I have to get param from ionViewWillEnter.

Is it the correct way ?
Modals and Pages don’t behave same way ?

Best regards