窗体 – FormGroup控件中的模型驱动窗体嵌套FormArray控件

this.form = fb.group({
  'teacher': [''],'schools': fb.array([
      fb.group({
        'school_name': [''],'school_description': [''],'events': fb.array([
          fb.group({
            'event_name': ['']
          })
        ])
      })
  ])
});
const control = (<FormArray>this.form.controls['schools']).controls[0]['events'];

如何获得嵌套数组控件’事件’？

const control = (<FormArray>this.form.controls['schools']).controls[0]['events'];