我假设这个答案非常简单，但我有一个公共变量listSports我通过MapService将sports传递给我的组件。
我还希望将它传递给公共函数getMapData，该函数将Http get Observable返回给组件，但我似乎无法这样做？
@Injectable()
export class MapService {
// list of sports to export
listSports: string[] = ["baseball", "football", "paddle", "soccer", "boxing", "golf", "hockey",
"tennis", "volleyball", "skateboard", "kickball", "bowling", "pool", "offroad",
"running", "hiking", "skating", "dance", "hockey", "yoga", "wrestling", "squash", "swimming", "horseriding", "fishing",
"handball", "sailing", "shooting", "bike", "hunting", 'archery', 'karting', 'atv', "karting", "kayaking", 'climbing',
'cricket', 'motorcycle', 'rugby', 'judo', 'scuba', 'barre', 'atv', 'basketball', 'rowing', 'karate', 'mma', 'equestrian', 'gymnastics'
];
constructor(private http: Http) { }
//return event map data from server
getMapData(chosen?: string[]): Observable<marker.MapMarker[]> {
在这里失败，并没有传入this.listSports变量
let sportChoices: string[] = chosen !== undefined ? chosen : this.listSports;
// returns all we need to to make google map markers and populate out menus
return this.http.get('http://localhost:4000/api/events')
.map((result) => { ....
继续直到结束