在AngularJS中，我可以使用ng-model选项来撤销一个模型。
ng-model-options="{ debounce: 1000 }"
如何在Angular中释放一个模型?
我试着在文档里搜索debounce，但什么都没找到。
https://angular.io/search/#stq=debounce&stp=1
一个解决方案是编写我自己的debounce函数，例如:
import {Component, Template, bootstrap} from 'angular2/angular2';
// Annotation section
@Component({
selector: 'my-app'
})
@Template({
url: 'app.html'
})
// Component controller
class MyAppComponent {
constructor() {
this.firstName = 'Name';
}
changed($event, el){
console.log("changes", this.name, el.value);
this.name = el.value;
}
firstNameChanged($event, first){
if (this.timeoutId) window.clearTimeout(this.timeoutID);
this.timeoutID = window.setTimeout(() => {
this.firstName = first.value;
}, 250)
}
}
bootstrap(MyAppComponent);
我的html
<input type=text [value]="firstName" #first (keyup)="firstNameChanged($event, first)">
但我正在寻找一个内置函数，Angular中有吗?
如果你不想处理@angular/forms，你可以只使用RxJS Subject和变更绑定。
view.component.html
<input [ngModel]='model' (ngModelChange)='changed($event)' />
view.component.ts
import { Subject } from 'rxjs';
import { Component } from '@angular/core';
import 'rxjs/add/operator/debounceTime';
export class ViewComponent {
model: string;
modelChanged: Subject<string> = new Subject<string>();
constructor() {
this.modelChanged
.debounceTime(300) // wait 300ms after the last event before emitting last event
.distinctUntilChanged() // only emit if value is different from previous value
.subscribe(model => this.model = model);
}
changed(text: string) {
this.modelChanged.next(text);
}
}
这确实触发了变更检测。关于不触发变更检测的方法，请参阅Mark的回答。
更新
rxjs 6需要.pipe(debounceTime(300)， distinctUntilChanged())。
例子:
constructor() {
this.modelChanged.pipe(
debounceTime(300),
distinctUntilChanged())
.subscribe(model => this.model = model);
}
由于这个话题已经很老了，大多数答案在Angular 6-13和/或使用其他库中都不起作用。
这里有一个简短的RxJS Angular 6+解决方案。
首先导入必要的东西:
import { Component, OnInit, OnDestroy } from '@angular/core';
import { Subject, Subscription } from 'rxjs';
import { debounceTime, distinctUntilChanged } from 'rxjs/operators';
实现ngOnInit和ngOnDestroy:
export class MyComponent implements OnInit, OnDestroy {
public notesText: string;
public notesModelChanged: Subject<string> = new Subject<string>();
private notesModelChangeSubscription: Subscription
constructor() { }
ngOnInit() {
this.notesModelChangeSubscription = this.notesModelChanged
.pipe(
debounceTime(2000),
distinctUntilChanged()
)
.subscribe(newText => {
this.notesText = newText;
console.log(newText);
});
}
ngOnDestroy() {
this.notesModelChangeSubscription.unsubscribe();
}
}
用这种方式:
<input [ngModel]='notesText' (ngModelChange)='notesModelChanged.next($event)' />
附注:对于更复杂和有效的解决方案，您可能仍然需要检查其他答案。
RC.5更新
在Angular 2中，我们可以使用RxJS操作符debounceTime()对表单控件的valueChanges可观察对象进行deboundound:
import {Component} from '@angular/core';
import {FormControl} from '@angular/forms';
import {Observable} from 'rxjs/Observable';
import 'rxjs/add/operator/debounceTime';
import 'rxjs/add/operator/throttleTime';
import 'rxjs/add/observable/fromEvent';
@Component({
selector: 'my-app',
template: `<input type=text [value]="firstName" [formControl]="firstNameControl">
<br>{{firstName}}`
})
export class AppComponent {
firstName = 'Name';
firstNameControl = new FormControl();
formCtrlSub: Subscription;
resizeSub: Subscription;
ngOnInit() {
// debounce keystroke events
this.formCtrlSub = this.firstNameControl.valueChanges
.debounceTime(1000)
.subscribe(newValue => this.firstName = newValue);
// throttle resize events
this.resizeSub = Observable.fromEvent(window, 'resize')
.throttleTime(200)
.subscribe(e => {
console.log('resize event', e);
this.firstName += '*'; // change something to show it worked
});
}
ngDoCheck() { console.log('change detection'); }
ngOnDestroy() {
this.formCtrlSub.unsubscribe();
this.resizeSub .unsubscribe();
}
}
砰砰作响
上面的代码还包括一个如何限制窗口大小调整事件的示例，就像@albanx在下面的评论中所问的那样。
Although the above code is probably the Angular-way of doing it, it is not efficient. Every keystroke and every resize event, even though they are debounced and throttled, results in change detection running. In other words, debouncing and throttling do not affect how often change detection runs. (I found a GitHub comment by Tobias Bosch that confirms this.) You can see this when you run the plunker and you see how many times ngDoCheck() is being called when you type into the input box or resize the window. (Use the blue "x" button to run the plunker in a separate window to see the resize events.)
一个更有效的方法是你自己从事件中创建RxJS的可观察对象，在Angular的“区域”之外。这样，就不会在每次触发事件时调用更改检测。然后，在你的订阅回调方法中，手动触发变更检测——也就是说，你控制何时调用变更检测:
import {Component, NgZone, ChangeDetectorRef, ApplicationRef,
ViewChild, ElementRef} from '@angular/core';
import {Observable} from 'rxjs/Observable';
import 'rxjs/add/operator/debounceTime';
import 'rxjs/add/operator/throttleTime';
import 'rxjs/add/observable/fromEvent';
@Component({
selector: 'my-app',
template: `<input #input type=text [value]="firstName">
<br>{{firstName}}`
})
export class AppComponent {
firstName = 'Name';
keyupSub: Subscription;
resizeSub: Subscription;
@ViewChild('input') inputElRef: ElementRef;
constructor(private ngzone: NgZone, private cdref: ChangeDetectorRef,
private appref: ApplicationRef) {}
ngAfterViewInit() {
this.ngzone.runOutsideAngular( () => {
this.keyupSub = Observable.fromEvent(this.inputElRef.nativeElement, 'keyup')
.debounceTime(1000)
.subscribe(keyboardEvent => {
this.firstName = keyboardEvent.target.value;
this.cdref.detectChanges();
});
this.resizeSub = Observable.fromEvent(window, 'resize')
.throttleTime(200)
.subscribe(e => {
console.log('resize event', e);
this.firstName += '*'; // change something to show it worked
this.cdref.detectChanges();
});
});
}
ngDoCheck() { console.log('cd'); }
ngOnDestroy() {
this.keyupSub .unsubscribe();
this.resizeSub.unsubscribe();
}
}
砰砰作响
我使用ngAfterViewInit()而不是ngOnInit()来确保inputElRef被定义。
detectChanges()将在该组件及其子组件上运行变更检测。如果您更愿意从根组件运行变更检测(即，运行完整的变更检测检查)，则使用ApplicationRef.tick()代替。(我在plunker的注释中调用ApplicationRef.tick()。)注意，调用tick()将导致ngDoCheck()被调用。
