[英]Using switchMap on POST Request for Observable in Angular App
在我的Angular應用程序中,我具有一個函數,該函數接受各種用戶選擇的過濾器值,並相應地返回數據。 通過事件發射器將這些值從一個組件傳遞到另一個組件,將這些值傳遞到函數中,如下所示:
<data-list [records]="records"
(sendLocation)="onFilterReceived($event, type = 'location')"
(sendZipcode)="onFilterReceived($event, type = 'zipcode')"
(sendFirstName)="onFilterReceived($event, type = 'firstName')"
(sendLastName)="onFilterReceived($event, type = 'lastName')"
(sendLanguage)="onFilterReceived($event, type = 'language')"
(sendBranch)="onFilterReceived($event, type = 'branch')">
</data-list>
然后,我接受這些值,對其進行處理,然后向API發送POST請求以獲取返回的過濾數據:
public onFilterReceived(value, type)
{
let selections = this.filtersService.processByTypes(value, type);
this.route.params.subscribe(
(params: any) => {
this.page = params['page'];
}
);
let fn = resRecordsData => {
this.records = resRecordsData;
let data = resRecordsData.data;
};
this.filtersService.getByFilters(
this.page - 1, this.pagesize, this.language = selections.language, this.location = selections.location,
this.zipcode = selections.zipcode, this.firstName = selections.firstName, this.lastName = selections.lastName,
this.branch = selections.branch, fn);
}
在此處調用的filterService函數如下所示:
filters = { language: [], location: [], zipcode: [], firstName: [], lastName: [], branch: [] };
public processByTypes(value, type) {
if (value && type) { this.filters[type] = value; }
return this.filters;
}
public getByFilters(page, pagesize, language?, location?, zipcode?, firstName?, lastName?, branch?, fn?: any) {
return this.apiService.post({
req: this.strReq, reqArgs: { page, pagesize, stage, language, location, zipcode, firstName, lastName, branch }, callback: fn });
}
此處調用的API POST函數如下所示:
public post(params: {
req: string,
reqArgs?: any,
reqBody?: any,
callback?: IRequestCallback
}): Observable<Response>
{
params['reqType'] = 'post';
return this.runHttpRequest(params);
}
我遇到的問題是,每次onFilterReceived()函數接收到一個過濾器值時,都會觸發POST請求,因此對於基本未更改的過濾器值,我最終會收到7或8個POST請求。 所以我想做的就是收集這些值,並且只發出一個 POST請求。
現在POST請求返回一個可觀察到的消息,因此我的想法是我應該能夠使用switchMap之類的操作來處理此問題。 這聽起來可行嗎? 這是第一個問題。 第二個問題是關於正確使用語法。
我嘗試將switchMap鏈接到POST請求的末尾,如下所示:
public getByFilters(page, pagesize, stage?, language?, location?, zipcode?, firstName?, lastName?, branch?, fn?: any) {
return this.apiService.post({
req: this.strReq, reqArgs: { page, pagesize, stage, language, location, zipcode, firstName, lastName, branch }, callback: fn }).switchMap;
}
...但是那沒有用。 沒有錯誤,但是沒有用,因為我仍然看到多個POST請求發出。
我能正確理解switchMap嗎? 如果要將鏈鏈接到POST請求操作上,語法需要什么樣?
我將嘗試編寫一個簡化的示例,希望您能從中得到啟發。 您應該具有過濾器當前狀態的主題。 將其切換到api調用,您可以投入debounceTime來給用戶時間來快速進行連續更改。
將使用較新的管道運算符。
filter$:Subject<any> = new Subject();
data:any;
destroy$:Subject<void> = new Subject();
ngOnInit() {
this.filter$.pipe(
takeUntil(destroy$), // stop and cleanup when component gone
debounceTime(400),
switchMap(filter => this.service.post(filter)) // switch one stream to another
).subscribe(data => this.data = data)
}
onFilterReceived(value, type)
{
let selections = this.filtersService.processByTypes(value, type);
this.filter$.next(selections);
}
ngOnDestroy() { this.destroy$.next() }
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