Question

我尝试使用subscription.unsubsribe取消待处理的http请求，如下所示：

getAgentList(pageNumber: number, filter: string): any {
   let requestUrl: string = 'api/service/agents_search?ACCT=' 
   +this.accountId;

if ( this.subscription ) {
    this.subscription.unsubscribe();
}

this.subscription =  this.backEndCommService.getData(requestUrl)
.subscribe(
        (res: any) => {
        let serverResponse: ServerResponse = new 
        ServerResponse(this.accountId, pageNumber, res.search_results, 
        res.resultRows, res.pageSize, res.resultPages)
                this._agentListData.next(serverResponse);
            },   
       (err: HttpErrorResponse) => {
                let errorMessage: string;
                if (err instanceof TypeError) {
                    errorMessage = 'Script error: ' + err.message;
                } 
                console.log(errorMessage);
    });
}

我想知道如何将switchMap应用于此代码以杀死对URL的待处理请求（例如，当第一次搜索花费很多时间并且第二次输入时，自动完成搜索输入，我想要解除第一次。）感谢

Answer 1

基本示例：

export class MyComponent{
    private $filter: Subject<string> = new Subject<String>();

    constructor(){
        this.$filter
          .switchMap(filter => this.backEndCommService.getData(filter + this.baseUrl)
          .subscribe(res => {//do something})
    }

    getAgentList(filterValue: string){
        this.$filter.next(filterValue);
    }

}

要使用switchmap取消先前的请求，我们需要一个hot observable来输出我们的过滤器值。我们使用一个主题。每次我们从某个地方获得新价值？我们将它推向主题。

Answer 2

试过，它甚至没有出去服务器

getAgentList(pageNumber: number, filter: string): any {
    let requestUrl: string = 'api/service/agents_search?ACCT=' 
  +this.accountId;
    if (filter) {
        requestUrl = requestUrl + '&filter=' + filter;
    }
    if (pageNumber) {
        requestUrl = requestUrl + '&pageNumber=' + pageNumber;
    }
    this.$filter.next(requestUrl)

    this.$filter.switchMap(requestUrl => 
    this.backEndCommService.getData(requestUrl))
            .subscribe(
                (res: any) => {
                    let serverResponse: ServerResponse = new 
                    ServerResponse(this.accountId, pageNumber, 
                    res.search_results, 
                    res.resultRows, res.pageSize, res.resultPages)
                    this._agentListData$.next(serverResponse);
                },
               (err: HttpErrorResponse) => {

            console.log('handling error');
      });
}

此行switchMap（requestUrl =＆gt; this.backEndCommService.getData（requestUrl））没有进行调用悄无声息..... mmmm

Answer 3

看起来问题是addEventListener是在getAgentList(pageNumber: number, filter: string): any { let requestUrl: string = ‘...’ // assuming this.$filter is a Subject // subscription to it first this.$filter.switchMap(requestUrl => this.backEndCommService.getData(requestUrl)) .subscribe( (res: any) => { let serverResponse: ServerResponse = new ServerResponse(this.accountId, pageNumber, res.search_results, res.resultRows, res.pageSize, res.resultPages) this._agentListData$.next(serverResponse); }, (err: HttpErrorResponse) => { console.log('handling error') } ); // then call next() this.$filter.next(requestUrl) }之后完成的。可以把它想象成DOM上的this.$filter。添加侦听器后，或者在此情况下是订阅者，您将收到事件。

// these are going to be used as 2 bit fields,
// so we can only go to 3.
enum addresses
{
    x = 0,    // 00
    y = 1,    // 01
    z = 2,    // 10
    w = 3     // 11
};

int val_to_send;

// set the value to send, and shift it 2 bits left.
val_to_send = 1234;
// bit pattern:  0000 0100 1101 0010

// bit shift left by 2 bits
val_to_send = val_to_send << 2;
// bit pattern:  0001 0011 0100 1000

// set the address to the last 2 bits.
// this value is address w (bit pattern 11) for example...
val_to_send |= w;
// bit pattern: 0001 0011 0100 1011

send_value(val_to_send);

那可能就是这样。除非receive_value(&rx_value); // pick off the address by masking with the low 2 bits address = rx_value & 0x3; // address now = 3 (w) // bit shift right to restore the value rx_value = rx_value >> 2; // rx_value = 1234 again.是BehaviorSubject或ReplaySubject，否则我们可能会遇到其他问题。

如何使用switchMap取消挂起的http请求并仅进行最后一次订阅？

3 个答案: