Ionic 3 angularjs check how many checkboxes are checked in a dynamic list

In my application I would like to show a certain number of checkboxes and check how many of them are checked before showing a button.
Other answers suggest to check for each checkbox using myCheckbox.isChecked(), but I do not now a priori how many of them I will have, since they represents tags that I fetch from a database, so they do not have a specific ID.
Is there a way to use an ngFor on the list?