Angular和TS承诺问题可能吗？

Question

此代码在服务器响应之前返回。我怎么让它等待？

public loadDropBoxItemsFromServer(preventSaveToCache: boolean = false): Promise<IDropboxItems> {

    let hcpid = this.authService.getUserInfo().userId;

    this.log("Loading d-box from server");
    CredDropboxProvider._loadDropboxFromServerPromises = new Promise((resolve, reject) => {
      this.http.get(this.appSettingsService.getApiUrl(`/CredDoc/list/${hcpid}`), this.appSettingsService.getHttpRequestOptions(this.authService))
        .map((response: Response) => {
          this.log("Got a response");
          this.log(response.json());
          return response.json();
        })
        .timeoutWith(this.appSettingsService.defaultHttpTimeout, Observable.throw(new HttpTimeoutError(this.appSettingsService.timeoutErrorText)))
        .subscribe((dropbox: IDropboxItems) => {
          this.log("Dropbox loaded from server");
          if (!dropbox.items) {
            dropbox.items = []
          }
          if (preventSaveToCache) {
            CredDropboxProvider._loadDropboxFromServerPromises = null;
            resolve(dropbox);
          } else {
            CredDropboxProvider._loadDropboxFromServerPromises = this.saveDropboxToCache(dropbox)
              .then((newDropbox: IDropboxItems) => {
                this.log("New Dropbox");
                console.log(newDropbox);
                CredDropboxProvider._loadDropboxFromServerPromises = newDropbox;
                resolve(newDropbox);
              })
              .catch(error => {
                CredDropboxProvider._loadDropboxFromServerPromises = null;
                reject(error);
              });
          }
        },
          this.appSettingsService.buildStandardHttpErrorHandler(reject)
        );
    });
    console.log("Returning ");
      **THIS IS RETURNING NULL BECAUSE IT RETURNS BEFORE THE DATA IS RETURNED **
      return CredDropboxProvider._loadDropboxFromServerPromises[hcpid];
  }

以上是在我的提供商和我的.ts文件中我称之为：

this.CredDropBox.loadDropBoxItemsFromServer().then((db: IDropboxItems) => {
  console.log("Loading DB Items");
  console.log(db);
  this.dropbox = db; ** THIS IS ALWAYS UNDEFINED **
});