protected showFormErrors(loginForm: NgForm): void {
    const fields = Object.keys(this.formErrors);
    for (let fieldKey in fields) {
      if (!fields.hasOwnProperty(fieldKey)) {
        continue;
      }
      let field = fields[fieldKey];
      if (!loginForm.controls[field].valid) {
        let errors = loginForm.controls.login.errors;
        for (let key in errors) {
          if (!errors.hasOwnProperty(key)) {
            continue;
          }
          if (errors[key]) {
            this[field + 'Error'] = this.formErrors[field][key];
          }
        }

        return;
      }
    }
  }