当使用过滤数据时，ion-select不会呈现选定的值

Question

我遇到了离子选择动态数据过滤的奇怪错误。在我的应用程序中，用户应该在注册期间选择三个安全问题，因此这些问题不能相同。我有一系列问题：

 questions: Array<{isSelected: boolean;question: string}> = [
    {isSelected: false, question: 'What is your pet’s name?'},
    {isSelected: false, question: 'What is the first name of the person you first kissed?'},
    {isSelected: false, question: 'Who was your childhood hero?'},
    {isSelected: false, question: 'What was your first grade friend last name?'},
    {isSelected: false, question: 'Where did you celebrate your 20th birthday?'},
    {isSelected: false, question: 'In what city or town does your nearest sibling live?'},
    {isSelected: false, question: 'What time of the day were you born?'}];

我的注册表格的这一部分如下所示：

    <ion-item>
      <ion-label floating>Select security question*</ion-label>
      <ion-select [(ngModel)]="regModel.SecurityQuestions[i].Question" name="Question"
                  [selectOptions]="sqSelectOptions"
                  (ionChange)="chooseQuestion(regModel.SecurityQuestions[i].Question)">
        <ion-option *ngFor="let sqOption of questions|filterSQ" value="{{sqOption.question}}"> {{sqOption.question}}
        </ion-option>
      </ion-select>
    </ion-item>

    <ion-item>
      <ion-label floating>Your answer*</ion-label>
      <ion-input type="text" required [(ngModel)]="regModel.SecurityQuestions[i].Answer" name="Answer"></ion-input>
    </ion-item>

  </div>

我使用(ionChange)="chooseQuestion(regModel.SecurityQuestions[i].Question)来跟踪所选的选项：

 chooseQuestion(s: string) {
    console.log(this.TAG + 'chooseQuestion: event value: ' + s);
    this.questions.filter(res => res.question == s).map(res => res.isSelected = true);
    //todo rewrite this 
    this.questions.filter(res => res.isSelected == true &&
    res.question != this.regModel.SecurityQuestions[0].Question &&
    res.question != this.regModel.SecurityQuestions[1].Question &&
    res.question != this.regModel.SecurityQuestions[2].Question)
      .map(res => res.isSelected = false);
    this.questions_filtered = this.questions.filter(res => res.isSelected == false);

    console.log(this.TAG + 'chooseQuestion: questions: ' + JSON.stringify(this.questions));
    console.log(this.TAG + 'chooseQuestion: questions_filtered: ' + JSON.stringify(this.questions_filtered));
  }

根据日志逻辑工作正常。我第一次使用questions_filtered来提供离子选择和遇到问题的问题：选择的选项不会显示在UI字段中。然后我尝试使用管道作为过滤数据的推荐方式，同样影响。 我将不胜感激任何建议。谢谢。

更新

为了澄清这个案例，我添加了一些记录并重写了一点代码。本例中的三个问题中有两个有管道，最后一个没有。我得到正确的值，但没有实际显示。

更新

我仍然不知道为什么 @ misha130 提出的解决方案没有给出任何结果。所以我试着去挖掘Chrome检查器，发现这个部分没有被调用。（我复制了突出显示的部分，但我不确定它是否正确）http://plnkr.co/edit/n4wv2UUdLtCmt4enYuVS?p=catalogue

Answer 1

Angular2不会检测数组及其子对象的更改。要在视图中实际生效，您必须调用更改检测

import { ChangeDetectorRef } from '@angular/core';

// Inject to constructor
constructor(public cd:ChangeDetectorRef){}

// as per your example call it on in your ionChange method
chooseQuestion(s: string) {
  this.cd.detectChanges();
}

有关详细信息：http://blog.thoughtram.io/angular/2016/02/22/angular-2-change-detection-explained.html