CODEWITHSUNDEEP
angularobservable
Jason
Jason

Reputation: 151

Angular Cannot read property 'subscribe' of null

I am getting the error

cannot read property 'subscribe' of null.

This is where the error is happening, this is called by the constructor of its class:

loadItems() {
    this.itemService.subscribeItems().subscribe(x => {
      this.items = x;
      console.log(x);
    });
}

It calls this services method, this is where the issue is I think. It may be to do with the return null

subscribeItems(): Observable<Item[]> {
    this.session.uid.subscribe(x => {
            return this.af.database.list('users/' + x + '/Items')
            .map(Item.fromJsonList);
    });
    return null;
}

the session service holds the uid which is updated when the user logs in: This part works ok.

_uid = new BehaviorSubject<string>('');
uid = this._uid.asObservable();

Upvotes: 1

Views: 17935

Answers (2)

user1233092
user1233092

Reputation: 33

this error is happening because an observable/a service function is null or returning null.

so whichever it is initialize it first.

eg

Items():Observable<any>
{ 
   let itemToReturn = new Observable();

   if(this.itemService.subscribeItems()){
       this.itemService.subscribeItems().subscribe(data => itemToReturn.next(data)); 
   }
   return itemToReturn; 
}

Calling this method or subscribing to it won't error since it always returns an initialized item.

Upvotes: 0

Avram Virgil
Avram Virgil

Reputation: 1210

Try this:

subscribeItems(): Observable<Item[]> {
    return this.session.uid.subscribe(x => {
            return this.af.database.list('users/' + x + '/Items')
            .map(Item.fromJsonList => Item.fromJsonList.json());
    });
    return null;
}

Upvotes: 1

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