Rxjs-具有keyup事件的DistinctUntilChanged() [英] Rxjs - DistinctUntilChanged() with keyup event

问题描述

我正在使用Rxjs 6，该Rxjs 6根据表单字段中的(键")事件过滤Firebase返回的可观察对象.

I'm using Rxjs 6 which filters an observable returned by Firebase based on (keyup) event in a form field.

当用户在表单字段中没有值的情况下继续按退格键时，出现了一个问题，那就好像可观察的对象会不断刷新.

I have an issue when the user keeps pressing backspace while there is no value in the form field, then it looks like the observable is constantly refreshed.

使用DistinctUntilChanged()添加管道似乎无效:

Adding a pipe with DistinctUntilChanged() doesn't seem to be effective:

打字稿过滤功能:

updateFilter2() {
    const val = this.filteredValue.toLowerCase().toString().trim();

    if (this.filteredValue) {
        this.loadingIndicator = true;
        this.rows = this.svc.getData()
            .pipe(
                distinctUntilChanged(),
                debounceTime(300),
                map(_co => _co.filter(_company =>
                    _company['company'].toLowerCase().trim().indexOf(val) !== -1 || !val
                    ||
                    _company['name'].toLowerCase().trim().indexOf(val) !== -1 || !val
                    ||
                    _company['gender'].toLowerCase().trim().indexOf(val) !== -1 || !val
                )),
                tap(res => {
                    this.loadingIndicator = false;
                })
            );
    }
    else {
        this.rows = this.svc.getData()
            .pipe(distinctUntilChanged())
        this.loadingIndicator = false;
    }

    this.table.offset = 0;
}

HTML模板:

<mat-form-field style="padding:8px;">
    <input
            type='text'
            matInput
            [(ngModel)] = "filteredValue"
            style='padding:8px;margin:15px auto;width:30%;'
            placeholder='Type to filter the name column...'
            (input)='updateFilter2()'
    />
</mat-form-field>

我有一个Stackblitz重现此行为: https://stackblitz.com/edit/angular-nyqcuk

I have a Stackblitz reproducing the behaviour: https://stackblitz.com/edit/angular-nyqcuk

还有其他解决方法吗?

谢谢

推荐答案

问题是，ALLWAYS总是生成getData.您首先查看更改，然后切换映射以获取数据.因此，您必须具有可观察到的变化.使用"FormControl"，而不是[[ngModel)]的输入 因此，在您的.html

The problem is that ALLWAYS make getData. You first look at changes, then switchmap to get Data. So you must have a Observable of changes. Use a "FormControl", not an input with [(ngModel)] So, in your .html

<input type="text" [formControl]="search">

代码必须为

  search= new FormControl();       //Declare the formControl

  constructor() {}

  ngOnInit() {
    this.search.valueChanges.pipe(
         debounceTime(400),
         distinctUntilChanged(),
         tap((term)=>{
              //here the value has changed
              this.loadingIndicator = true;
         }),
         switchMap(filteredValue=> {
              //We not return the value changed, 
              return this.svc.getData().pipe(
                     map(_co => {
                         return _co.filter(...)
                     }),
                     tap(()=>{
                         this.loadingIndicator=false;
                     }))
          })).subscribe(result=>{
             this.result=result
          })
  }

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