Angular - shared service between components doesn't work

I have a service where I declare my variable. In my component I use this variable to put data into it.

Service:

@Injectable()
export class DataService {

    public msgs = [];

    constructor() { }       

}

Now I use this variable in my component:

export class MessagesComponent implements OnInit {   

    constructor(private dataService: DataService){}

    ngOnInit() {   
        this.getData();   
    }

    getData(){
        let msgs = [];

        if (diffr <= this.geomessage[i].range) {
            this.geomessage[i].dist = diffr;
            msgs.push(this.geomessage[i]);
            //console.log("this message: ", this.geomessage[i]); //DEBUG
        }
        this.dataService.msgs = msgs;

    }    
}    

I have only posted the necessary code.The this.dataService.msgs het filled with messages this works fine. When I got to another component the data of this.dataService.msgs still exists but when i Get back tot the Messagescomponent the this.dataService.msgs is undefined till i fill it again but I need the data that was in it. Does somebody know how to do this?

Thx