Angular 2 Dynamic Forms 如何根据另一个字段的值显示/隐藏一个字段

Question

环境：Angular 2 RC 4，Typescript。

我有一个Dynamic Angular forms的实现。我总共有 4 个字段 - dob、电子邮件、问题和答案

问题：

dob: new TextboxQuestion({
      key: 'dob',
      label: 'Date of Birth',
      value: '',
    }),


    email: new TextboxQuestion({
      key: 'email',
      label: 'Email Address',
      value: '',
      type: 'email',
    }),

    securityQuestion: new TextboxQuestion({
      key: 'challengeQuestion',
      label: 'Security Question',
      value: '',
      disabled: true
    }),
    securityAnswer: new TextboxQuestion({
      key: 'challengeAnswer',
      label: 'Write your answer',
      value: '',
    })

主/父组件的 html 片段

<dynamic-form (responsesEvt)="onFormSubmitResponseReceived($event);" [sections]="sections" class="col-md-8"></dynamic-form> 

动态表单组件

<form (ngSubmit)="onSubmit()" [formGroup]="form"> 
            <div *ngFor="let question of questions" class="form-row" >
                <df-question [question]="question" [form]="form" *ngIf="!section.hidden"></df-question>
            </div>

        <div class="row">
            <div class="col-md-5"></div>
            <div class="col-md-7 btn-row">
                <button type="submit" class="btn btn-primary pull-right" [disabled]="!form.valid">I agree with the Terms & Conditions</button>
                <!--<button type="submit" class="btn btn-primary pull-right" [disabled]="!form.valid || subbmittedalready">I agree with the Terms & Conditions</button>-->
                <button type="button" class="btn btn-default pull-right">Cancel</button>
            </div>
        </div>
    </form>

df-问题组件

<div [formGroup]="form">
  <div class="col-md-5"><label class="pull-right" [attr.for]="question.key"><span class="errorMessage">*&nbsp;</span>{{question.label}}</label></div>
  <div class="col-md-7" [ngSwitch]="question.controlType">
    <input *ngSwitchCase="'textbox'" [formControlName]="question.key" [id]="question.key" [type]="question.type" class="form-control"
      [placeholder]="question.placeHolder"
       />
  </div>
  <div class="col-md-5"></div>
</div>  

这是我的工作流程

Step 1 Initially at form load, only dob and email show up.
Step 2 User types in the dob and email. DOB and email are sent to the backend and if the info is correct, a "question" is returned.
Step 3 Now the question and answer fields appear (assuming that above step was successful). The question field is populated with the value returned from the server through the previous request
Step 4 User submits the form with dob, email, question and answer

关于如何使用动态表单实现这一点的任何想法？

我想我可以在 dob 之后以某种方式抛出一个事件，填写电子邮件，调用后端并得到问题。根据上述响应的成功/失败，使用变量隐藏/显示 questnio 和回答？

如果这是一个好方法，我怎么能感觉到用户已经填写了前两个字段并进行了后端调用。收到服务器响应后如何更新问题字段（特别是使用动态表单）？

如果没有，有没有更简单的方法来做到这一点？

Answer 1

我知道这是一个延迟的答案，但我认为这篇 Scotch.io 帖子基本上涵盖了您需要做的基础知识。

您创建一个表单组并根据字段的值交换验证，并在视图中隐藏使用 ngIfs 禁用的字段。