How to write ng2-toasty in Helper class?

[hhntpp]

• I'm submitting a ...
  [x] bug report
  [x] feature request
  [ ] question about the decisions made in the repository

• Do you want to request a feature or report a bug?
  bug and feature

• What is the current behavior?
  I wanted to write a Helper class that has a function static addToast.
  But when it had been called, the toast didn't display. I pressed F12, the console didn't have error.
  If I write in component use it directly, it runs well.

• If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem via https://plnkr.co or similar.
  static addToast(success: boolean, message: string) {
  var toastyService: ToastyService;
  var toastyConfig: ToastyConfig;

    // create the instance of ToastOptions
    var toastOptions: ToastOptions = {
        title: '',
        msg: message,
        showClose: true,
        timeout: 2000,
    };
    toastyConfig = new ToastyConfig();
    toastyConfig.theme = 'bootstrap';
    toastyConfig.position = 'center-center';
    toastyService = new ToastyService(toastyConfig);
    if (success)
        toastyService.success(toastOptions);
    else
        toastyService.error(toastOptions);
  

  }

• What is the expected behavior?
  I want to intergrate ng2-toasty into a Helper class

• Please tell us about your environment:

• Angular version: 2.4.10
• Browser: Chrome 57.0.2987.133 (64-bit)