Making Ionic2 Slides using Firebase data - firebase

Question

I stored profile data in firebase and
trying to retrieve them and show them in template with slides.
(I am making a matching service.)
But it seems the template is loaded before data is assigned to variable.
When I am just retrieving one data, not list,
it works fine.
I tried all the solutions on the goole,
like using 'NgZone', *ngIf, etc but nothing worked.
Please help me.
My Error message.
FindMatePage.html:21 ERROR Error: Error trying to diff '[object Object]'. Only arrays and iterables are allowed
at DefaultIterableDiffer.diff (core.es5.js:7083)
at NgForOf.ngDoCheck (common.es5.js:1699)~~
My find-mate.ts file.
export class FindMatePage implements OnInit{
#ViewChild('profileSlide') slider: Slides;
profileList = [] as Profile[];
constructor(public navCtrl: NavController, public navParams: NavParams,
private databaseService: DataServiceProvider, private auth:
AuthServiceProvider,
) {}
ngOnInit(){
this.auth.getActiveUser().getIdToken()
.then((token: string) => (
this.databaseService.fetchProfileList(token)
.subscribe((list: Profile[]) => {
if(list) {
this.profileList = list;
console.log(this.profileList)
} else {
this.profileList = [];
}
})
))//then ends
}
My find-mate.html file
<ion-content class="tutorial-page">
<ion-slides *ngIf="profileList" #profileSlide pager
(ionSlideDidChange)="slideChanged()">
<ion-slide>
<h2 class="profile-title">Ready to Play?</h2>
<button ion-button large clear icon-end color="primary">
Continue
<ion-icon name="arrow-forward"></ion-icon>
</button>
</ion-slide>
<ion-slide *ngFor="let profile of profileList">
<ion-buttons block>
<button ion-button color="primary">채팅하기</button>
</ion-buttons>
<ion-item> {{profile.username}}</ion-item>
<ion-item> {{profile.gym}</ion-item>
<ion-item> {{profile.goal}}</ion-item>
<ion-item> {{profile.level}}</ion-item>
</ion-slide>
My part of data-service.ts file
//프로필 목록 가져오기
fetchProfileList(token: string) {
return this.http.get('https://fitmate-16730.firebaseio.com/profile-list.json?auth=' + token)
.map((response: Response) => {
return response.json();
})
.do((profileList: Profile[]) => {
if (profileList) {
console.log(profileList);
return this.profileList = profileList;
} else {
return this.profileList = null;
}
});
}