Angular 2 - 使用带有可选字段的ngControl

Question

我很难在表单中使用*ngIf和ngFormModel来验证表单.

用例是这样的:根据用户输入,隐藏或停用表单中的某些特定字段.但是如果显示这些输入,则必须对它们进行验证.

当只需要基本验证时,我可以这样或那样做:

• 如果仅需要输入,则使用ngControl和使用A-OKrequired
• 如果需要特定格式,则可以使用该pattern属性.它不是Angular,但它有效.

但是为了实现更复杂的验证,我一直在尝试使用ngControl耦合ngFormModel来使用自定义检查.我使用了以下页面中的代码片段:

如何在angular2中添加表单验证模式(以及那里引用的链接)

Angular2表单:Validations,ngControl,ngModel等

我的代码如下:

HTML

<div>
  <h1>Rundown of the problem</h1>
  <form (ngSubmit)="submitForm()" #formState="ngForm" [ngFormModel]="myForm">
    <div class="checkbox">
      <label>
        <input type="checkbox" [(ngModel)]="model.hideField" ngControl="hideField"> Is the input below useless for you ?
      </label>
    </div>

    <div *ngIf="!model.hideField">
      <div class="form-group">
        <label for="optionalField">Potentially irrelevant field </label>
        <input type="text" class="form-control" [(ngModel)]="model.optionalField" ngControl="optionalField" required #optionalField="ngForm">
        <div [hidden]="optionalField.valid || optionalField.pristine" class="alert alert-warning">
          This input must go through myCustomValidator(), so behave.
        </div>
      </div>
    </div>

    <button type="submit" class="btn btn-primary" [disabled]="!formState.form.valid">I can't be enabled without accessing the input :(</button>
    <button type="submit" class="btn btn-default">Submit without using form.valid (boo !)</button>
  </form>
</div>

打字稿

import {Component, ChangeDetectorRef, AfterViewInit } from 'angular2/core';
import {NgForm, FormBuilder, Validators, ControlGroup, FORM_DIRECTIVES}    from 'angular2/common';

@Component({
  selector: 'accueil',
  templateUrl: 'app/accueil.component.bak.html',
  directives:[FORM_DIRECTIVES],
  providers: [FormBuilder]
})
export class AccueilComponent implements AfterViewInit {

  private myForm: ControlGroup;
  model: any;

  constructor(fb: FormBuilder, cdr: ChangeDetectorRef) {
    this.cdr = cdr ;

    this.model = {} ;
    this.myForm = fb.group({
      "hideField": [false],
      "optionalField": [this.model.optionalField, Validators.compose([this.myCustomValidator])]
    });
  }

  ngAfterViewInit() {
    // Without this, I get the "Expression has changed after it was checked" exception.
    // See also : https://stackoverflow.com/questions/34364880/expression-has-changed-after-it-was-checked
    this.cdr.detectChanges();
  }

  submitForm(){
    alert("Submitted !");
  }

  myCustomValidator(optionalField){
    // Replace "true" by "_someService.someCheckRequiringLogicOrData()"
    if(true) {
      return null;
    }

    return { "ohNoes": true };
  }
}

即使使用*ngIf从模板中删除输入,构造函数仍然引用该控件.这反过来阻止我使用[disabled] ="!formState.form.valid",这myForm是可以理解的无效.

我的目标是使用Angular 2吗？我确信这不是一个不常见的用例,但是再次根据我目前的知识,我无法看到我如何才能使它工作.

谢谢 !

Answer 1

您可以尝试做的是重置控件上的验证器.这意味着,当您希望由于状态更改而将一组新验证器绑定到控件时,您将重新定义验证器函数.

在您的情况下,当选中/取消选中复选框时,您希望发生以下情况:

1. 将输入设置为可选(不是必需的),但仍然针对您的自定义验证器进行验证.
2. 取消选中该复选框后,将控件的验证器恢复为原始状态.
3. 再次验证控件以便form.valid更新.

请参阅我的plnkr示例,该示例基于Angular.io的Forms Guide

if (optional)
   this.heroFormModel.controls['name'].validator = Validators.minLength(3);
else
   this.heroFormModel.controls['name'].validator =
        Validators.compose([Validators.minLength(3), Validators.required]);

this.heroFormModel.controls['name'].updateValueAndValidity();