如果子组件字段无效，如何禁用父组件表单提交按钮

Question

我正在使用模板驱动表单。

父组件HTML

<form #BasicForm="ngForm" (ngSubmit)="onBasicDetailsSubmit()" id="BasicForm">

  <app-input-text [(sharedVar)]="dashboardDetails.Text1" [isMandatory]="true" ></app-input-text>
  <app-input-text [(sharedVar)]="dashboardDetails.Text2" [isMandatory]="false"></app-input-text>

  <input type="submit" value="Save" [disabled]="!BasicForm.valid" class="btn btn-success">

</form>

子组件

TS

@Input() sharedVar: number;
@Input() isMandatory: boolean;

@Output() sharedVarChange = new EventEmitter();


change(newValue) {
  this.sharedVar = newValue;
  this.sharedVarChange.emit(newValue);
}

HTML

<input type="text" class="form-control" [(ngModel)]="sharedVar" (ngModelChange)="change($event)" [attr.required]="isMandatory">

提交按钮没有被禁用。我试过在子组件和父组件选择器中写 required，但它不起作用。请帮忙。

Answer 1

父组件HTML

<app-input-text [(sharedVar)]="dashboardDetails.Text1" (sharedVarChange)="sharedVarChangeHandle($event)" ...

父组件 TS

sharedVarChangeHandle($event) {
    // by evaluating the value passed you can update a variable (ex: disableSubmit)
}

父组件HTML

<input type="submit" value="Save" [disabled]="!disableSubmit" class="bt .....

Answer 2

子组件 ts

valid // this is a public variable

change(newValue) {
  this.sharedVar = newValue;
  this.sharedVarChange.emit(newValue);
  // here conditioanally update the **valid** variable (true or false)
}

Answer 3

当您使用 Template-Driven-Form 时，验证 Child components 的最佳方法是创建一个像这样的 custom-Directive，您将始终在要验证的每个字段中添加子组件表单：

你可以使用这个：

import {Directive, OnInit} from '@angular/core';
import {NgControl, NgForm, NgModel} from "@angular/forms";

/**
 * This attribute directive must be used to each input-field of a childComponent.
 * That input-field must contain a NgModel attribute, else the application must throw an error
 * Usage: (<input class="form-control" type="text" registerChildComponentToForm
 *          [(ngModel)]="testname" name="testname" required />
 */

@Directive({
    selector: '[registerChildComponentToForm]',
    providers: [NgModel]
})
export class RegisterTemplateFormModelDirective implements OnInit {

    constructor(private form: NgForm, private eltControl: NgControl) {
    }

    ngOnInit() {
        if (this.form && this.eltControl) {
            this.form.form.addControl(this.eltControl.name, this.eltControl.control);
        }
    }

}

然后在App-Module

中将其注册到declarations和exports

declarations: [
        RegisterTemplateFormModelDirective,
        ...
],
exports: [
        RegisterTemplateFormModelDirective,
        ...
]

假设你的 <app-input-text> 是这个 HTML 代码，那么你应该像这样使用 directive(registerChildComponentToForm):

<input id="iban" name="iban" [(ngModel)]="bank.iban" #ibanRef="ngModel" 
  [required]="isMandatory" registerChildComponentToForm/>

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