ngOnInit() {
      this.groupListForm = this.formBuilder.group({
          groups: new FormArray([], minSelectedCheckboxes(1))
      });

      this.groupService.getGroups()
        .subscribe((response) => {
          this.groups = response;
          this.groups.forEach((item) => {
              (this.groupListForm.controls.groups as FormArray).push(item);
          });
      });
  }