Angular 2和Angularfire2中的三向绑定 [英] Three way binding in Angular 2 and Angularfire2
问题描述
我正在尝试使用AngularFire 2(2.0.0-beta.2)将输入元素与Angular.js 2(2.0.0-rc.4)中的Firebase数据库绑定三路.
I am trying to three-way bind an input element to firebase database in Angular.js 2 (2.0.0-rc.4), using AngularFire 2 (2.0.0-beta.2).
我有一个非常简单的html,例如:
I have a very simple html like:
<form (ngSubmit)="onSubmit()" #commentForm="ngForm">
<input [(ngModel)]="model.author" type="input" name="author" required>
</form>
在我的组件中,要将此输入的内容保存和检索到firebase中,我有一个类似的实现:
In my component, to save and retrieve contents of this input to firebase, I have an implementation like this:
export class CommentFormComponent implements OnInit, AfterViewInit {
@ViewChild("commentForm") form;
// http://stackoverflow.com/questions/34615425/how-to-watch-for-form-changes-in-angular-2
firebaseInitComplete = false;
model: Comment = new Comment("", "");
firebaseForm: FirebaseObjectObservable<Comment>;
constructor(private af: AngularFire) { }
ngAfterViewInit() {
this.form.control.valueChanges
.subscribe(values => {
// If we haven't get the initial value from firebase yet,
// values will be empty strings. And we don't want to overwrite
// real firebase value with empty string on page load
if (!this.firebaseInitComplete) { return; }
// If this is a change after page load (getting initial firebase value) update it on firebase to enable 3-way binding
this.firebaseForm.update(values);
});
}
ngOnInit() {
this.firebaseForm = this.af.database.object("/currentComment");
// Listen to changes on server
this.firebaseForm.subscribe(data => {
this.firebaseInitComplete = true; // Mark first data retrieved from server
this.model = data;
});
}
}
上面的代码可以正常工作,当用户实时键入内容时,我能够读取Firebase的初始值并更新Firebase上的值.
The code above works, I am able to read initial firebase value and update value on firebase when user type something in real time.
但是拥有手动逻辑来检查this.firebaseInitComplete
并添加ngAfterViewInit
来监听更改感觉有点不对劲,我只是在破解它才能正常工作.
But having a manual logic to check for this.firebaseInitComplete
and adding ngAfterViewInit
to listen for changes feels a little bit wrong and I am just hacking it to work.
在组件内部使用更少逻辑的情况下,是否存在更好的三向绑定实现?
Is there a better implementation of three-way binding with less logic inside component?
推荐答案
七个月后,我为您提供了一个答案..扩展的ngModel语法..
Seven months later and I have an answer for you.. extended ngModel syntax..
<input [ngModel]='(model|async)?.author' (ngModelChange)="model.update({author: $event})">
[]块是一个getter,而()块是一个setter.由于模型的吸气剂实际上是在拆开FirebaseObjectObservable的包装,因此您必须使用FirebaseObjectObservable的绑定进行设置.
The [] block is a getter and the () block is a setter. Since the model's getter is actually unwrapping the FirebaseObjectObservable, you have to use the FirebaseObjectObservable's binding to set it.
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