Angular2 RC：在创建ControlGroup后,使用addControls方法添加了

我有一个添加不同的字段(我添加新的控件,因为只是使用* ngIf将它们从模板中隐藏起来,因此不会从表单中将它们排除,因此导致表单无效)基于select选项中的选定选项.我正在使用Angular2中的表单的addControl方法向可用表单添加新控件.控件正在正确添加,但我不知道为什么这些添加的控件的值在用户输入后没有更新.以下是我向表单添加新控件的方法：

signUpForm: ControlGroup;

constructor(private fb: FormBuilder) { }

ngOnInit(): void {
    this.signUpForm = this.fb.group({
        firstName: ["",Validators.required],lastName: ["",group: ["",Validators.required]
    });
}

modifyControls(selectedGroup): number {
    if (selectedGroup == 1) {
        if (this.signUpForm.contains("studentID")) {
            this.signUpForm.removeControl("studentID");
        }
        this.signUpForm.addControl("teacherCode",new Control("",Validators.required));//need some custome validations
        this.signUpForm.addControl("teacherID",Validators.required));
        return 1;
    }
    else if (selectedGroup == 2) {
        if (this.signUpForm.contains("teacherCode")) {
            this.signUpForm.removeControl("teacherCode");
            this.signUpForm.removeControl("teacherID");
        }
        this.signUpForm.addControl("studentID",Validators.required));
        return 2;
    }
}

看起来角度不能识别那些新的领域.我认为它与AbstractControl有关,但文档缺乏这一点.以下是问题的快照,即动态添加的控件未被角度拾取.

为了显示问题,我在下面的plunker中创建了一个简单的例子(请转到版本2来复制此问题).

https://plnkr.co/edit/RI4JL4Pnf2LrJ3TsxsSt?p=preview

我做错了什么以及如何使其适用于当前的设置？
实现相同行为的其他选择有哪些？

谢谢您的帮助

解决方法：

modifyControls(selectedGroup) {
    if (selectedGroup == 1) {
        this.signUpForm.controls['teacherCode'].validator = Validators.required;
        this.signUpForm.controls['teacherCode'].updateValueAndValidity();
        this.signUpForm.controls['teacherID'].validator = Validators.required;
        this.signUpForm.controls['teacherID'].updateValueAndValidity(); 
        this.signUpForm.controls['studentID'].validator = null;
        this.signUpForm.controls['studentID'].updateValueAndValidity();
    }
    else if (selectedGroup == 2) {
        this.signUpForm.controls['teacherCode'].validator = null;
        this.signUpForm.controls['teacherCode'].updateValueAndValidity();
        this.signUpForm.controls['teacherID'].validator = null;
        this.signUpForm.controls['teacherID'].updateValueAndValidity();
        this.signUpForm.controls['studentID'].validator = Validators.required;
        this.signUpForm.controls['studentID'].updateValueAndValidity(); 

    }
}

this.signUpForm.addControl("teacherCode",(c:Control) => { 
          if(this.signUpForm.controls['teacherID'].value) {
            return Validators.required(c);
          }
        })
    );