从组件内部检查Angular2表单是否有效 [英] Checking whether an Angular2 form is valid or not from within the component

问题描述

我正在尝试检查表单是否有效，以防止进一步执行.

I am trying to check whether a form is valid or not to prevent further execution if it is not.

这是我的表格:

<form (ngSubmit)="updateFirstName(firstNameForm)" #firstNameForm="ngForm" novalidate>
    <div class="form-group" ng-class="getCssClasses(formCtrl, formCtrl.firstName)">
        <div class="input-group">
            <input type="text"
                   ngControl="firstName"
                   #firstName="ngForm"
                   required
                   minlength="2"
                   maxlength="35"
                   pattern_="FIRST_NAME_PATTERN"
                   [ngModel]="currentUserAccount?.firstName"
                   (ngModelChange)="currentUserAccount ? currentUserAccount.firstName = $event : null"
                   placeholder="{{'FIRST_NAME_FORM.NEW_FIRST_NAME'| translate }}"
                   class="form-control"/>
        </div>

        <div [hidden]="firstName.valid">
            <div *ngIf="firstName?.errors?.minlength" class="control-label">{{'FIRST_NAME_FORM.MIN_LENGTH'| translate}}</div>
        </div>
    </div>
    <div class="form-group">
        <button type="submit" class="btn btn-primary pull-right" [disabled]="buttonDisabled">{{'FIRST_NAME_FORM.SUBMIT'| translate}}</button>
        <a [routerLink]="['/dashboard/useraccount']" class="btn btn-link pull-right text-right">{{'FORM_CANCEL' | translate}}</a>
    </div>
</form>

但是，当我提交无效的表单时，我在控制台中注意到NgForm的有效属性是true ...

However, when I submit an invalid form, I notice in the console that the valid attribute of NgForm is true...

 updateFirstName(firstNameForm) {
   console.log(firstNameForm);//the valid attribute of firstNameForm is true...
 }

有人可以让我知道为什么是这种情况吗?

Can anyone please let me know why this is the case?

推荐答案

您正在做模板驱动的表单.请参考这个简单的 plunk

You are doing template driven forms. Please refer to this simple plunk

<h1>Employee Form</h1>
<form #personForm="ngForm" (submit)="personFormSubmit(personForm)" novalidate>
    <div>
        <div>
            <input id="nameInput" type="text" name="name"
                   ngControl="name"
                   required
                   minlength="2"
                   maxlength="35"
                   [(ngModel)]="person.name" />
        </div>
    </div> 
    <div>
      <button type="submit">Submit</button>
    </div>
    <div style="color: red">{{validationMessage}}</div>
</form>

然后是控制器:

import { Component } from '@angular/core';
import { FORM_DIRECTIVES, ControlGroup, Control, Validators, FormBuilder, Validator, } from '@angular/common';
import 'rxjs/Rx';

export class Person {
    id: number;
    name: string;
}

@Component({
    selector: 'my-app',
    directives: [FORM_DIRECTIVES],
    templateUrl: 'app/app.component.html'
})
export class AppComponent {

    person: Person;
    validationMessage: string;

    constructor() {
        this.person = new Person();
        this.validationMessage = "";
    }

    personFormSubmit(personForm: ControlGroup) {
        if (personForm.valid) {
          this.validationMessage = "Form Is Valid";
        }
        else
        {
          this.validationMessage = "Form Is Not Valid";
        }
    }

}

如果要转向更复杂的动态验证，则最好转换为模型驱动的表单.与此朋克

If you want to move to more complex dynamic validation then it would be better to convert to Model driven Forms. As with this plunk

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