Angular2:使用 [(ngModel)] 和 [ngModelOptions]=“{standalone: true}"；链接到对模型属性的引用

问题描述

假设我有一个 Mailtype 类型的打字稿对象，如下所示:

Let's say I have a typescript object of type Mailtype like following:

export class Mailtype {
  constructor(
    public name?: string,
    public locale?: string,
    public email?: string,
    public properties? : Property[]
  ) {  }
}

它的属性"在哪里?字段是一个属性类型的数组:

Where its "properties" field is an array of type Property:

export class Property {
  constructor(
    public name?: string,
    public type?: string,
    public example?: string,
    public required?: boolean,
    public masked?: boolean
  ) {  }
}

现在在我的组件中，我有一个 Mailtype 对象，并且 html 有一个表单元素，用于编辑和添加到 Mailtype 的属性数组中:

Now in my component I have a single Mailtype object and the html has a form element used for editing and adding to the properties array of the Mailtype:

<form>
   <tr *ngFor="let property of model.properties; let i=index">
          <td>
            <input type="text" [(ngModel)]="property.name" required>
          </td>
  </tr>
  <button (click)="onAddProperty()">Add property</button>
</form>

组件:

export class MailtypeComponent {
  model : Mailtype;
  constructor() {
    this.model = new Mailtype('','','',[]);
    this.model.properties.push(new Property());
  }

  onAddProperty() {
    this.model.properties.push(new Property());
  }
}

我想知道是否不允许使用 [(ngModel)] 链接到参考属性"到数组中的数组元素，尤其是在我迭代数组的同时?因为上面的代码会抛出如下错误:

I was wondering if I'm not allowed to use [(ngModel)] to link to a reference "property" to the array element in the array, especially at the same time I'm iterating the array? Because it throws the following error for the above code:

ORIGINAL EXCEPTION: If ngModel is used within a form tag, either the name attribute must be set
                      or the form control must be defined as 'standalone' in ngModelOptions.

                      Example 1: <input [(ngModel)]="person.firstName" name="first">
                      Example 2: <input [(ngModel)]="person.firstName" [ngModelOptions]="{standalone: true}">

所以它建议我使用 [ngModelOptions]={standalone: true}" 或向 html 添加名称字段.看起来 [ngModelOptions]={standalone: true}" 在这种情况下有效.standalone: true 实际上是什么意思，因为我找不到任何关于它的文档?

So it's suggesting I use either [ngModelOptions]="{standalone: true}" or add a name field to the html. And it looks like [ngModelOptions]="{standalone: true}" works in this case. What does standalone: true actually mean since I cannot find any documentation about it?

推荐答案

使用 @angular/forms 当您使用 标签时，它会自动创建一个 .

Using @angular/forms when you use a <form> tag it automatically creates a FormGroup.

对于每个包含的 ngModel 标记的 它将创建一个 FormControl 并将其添加到 FormGroup> 以上创建；这个 FormControl 将使用属性 name 命名到 FormGroup 中.

For every contained ngModel tagged <input> it will create a FormControl and add it into the FormGroup created above; this FormControl will be named into the FormGroup using attribute name.

示例:

<form #f="ngForm">
    <input type="text" [(ngModel)]="firstFieldVariable" name="firstField">
    <span>{{ f.controls['firstField']?.value }}</span>
</form>

说到这里，你的问题的答案如下.

Said this, the answer to your question follows.

当您将其标记为 standalone: true 时，这不会发生(它不会被添加到 FormGroup).

When you mark it as standalone: true this will not happen (it will not be added to the FormGroup).

参考:https://github.com/angular/angular/issues/9230#issuecomment-228116474

这篇关于Angular2:使用 [(ngModel)] 和 [ngModelOptions]=“{standalone: true}"；链接到对模型属性的引用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！