Ember computed propery uniq for an array from service not working

Hi i have a controller with a drop down which needs location data. I provide this data via a service. The service is working find I know it as dropLocation: alias('loaddropLocation') line works and show all the location with duplicates. But when i change the alias to uniq i expect to get unique array data. but it does not work.

import Ember from 'ember';
const {
    get,
    computed,
}= Ember;
const{
    uniq,
    alias
} = computed;
const {
    service,
} = Ember.inject;


export default Ember.Controller.extend({
  dropLocation: uniq('loaddropLocation'),//first-line
  Dropdata: service(),
  loaddropLocation: computed('Dropdata',function(){
        return get(this,'Dropdata').locations().then((locs) =>{
            return locs;
        });
  }),
})