Using pipe in *ngFor, the page sometimes updates, sometimes not - meteor

Question

I am using angular2-meteor, I already use pure: false. But the pipe sometimes run, sometimes not. See my comments in the code for details of the problem.
Thanks
<div *ngFor="#user of (users|orderByStatus)">
{{user.status.online}}
</div>
users:Mongo.Cursor<Meteor.User>;
ngOnInit()
{
this.subscribe('users', () => {
this.autorun(() => {
this.users = Meteor.users.find();
});
}, true);
}
import {Pipe} from 'angular2/core';
#Pipe({
name: 'orderByStatus',
pure: false
})
export class OrderByStatusPipe {
transform(usersCursor:Mongo.Cursor<Meteor.User>):Array<Meteor.User> {
console.log("OrderByStatusPipe runs");
// (1) If I only do these two lines, the change of other users' status can show on the screen immediately.
// let users = usersCursor.fetch();
// return users;
// (2) If sort users by status, the page sometimes updates, sometimes not when user status change.
// If not update automatically, I click that part of screen, it will update then.
let users:Array<Meteor.User> = usersCursor.fetch();
users.sort((a, b) => {
return (a.status.online === b.status.online) ? 0 : (a.status.online ? -1 : 1);
});
return users;
}
}

Answer 1

UPDATE: The bug seems fixed.
I think the problem is related with angular2-meteor.
At last I found a working way using sort in when you try to get data from Mongo. So not using sort pipe any more.
But you cannot use users:Mongo.Cursor<Meteor.User> with *ngFor, need fetch() first and use Array<Meteor.User>, otherwise it will show this error when the order of list changes:
Cannot read property 'status' of undefined
But then the list won't update automatically in UI. So you need use NgZone.
So the final working code is like this:
<div *ngFor="#user of users)">
{{user.status.online}}
</div>
users:Array<Meteor.User>; // here cannot use users:Mongo.Cursor<Meteor.User>
constructor(private _ngZone:NgZone) {}
ngOnInit()
{
this.subscribe('users', () => {
this.autorun(() => {
this._ngZone.run(() => {
this.users = Meteor.users.find().fetch();
});
});
}, true);
}

Answer 2

I don't know exactly what is behind the calls Meteor.users.find() and usersCursor.fetch() but I think the retrieval of your users should be done outside the filter itself. I guess that one part is done in the filter (with usersCursor.fetch()?) and this could be the problem...