取消/Kill http api调用angular 2

取消 Angular 2 中的 HTTP API 调用

基础概念

在 Angular 2+ 中，当发起 HTTP 请求时，有时需要取消正在进行的请求。这在用户导航离开页面、组件销毁或手动取消操作时特别有用。

解决方案

Angular 的 HttpClient 返回的是 Observable，可以通过取消订阅来中止 HTTP 请求。

方法一：使用 Subscription

import { Component, OnDestroy } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Subscription } from 'rxjs';

@Component({
  selector: 'app-example',
  template: `
    <button (click)="makeRequest()">发起请求</button>
    <button (click)="cancelRequest()">取消请求</button>
  `
})
export class ExampleComponent implements OnDestroy {
  private subscription: Subscription;

  constructor(private http: HttpClient) {}

  makeRequest() {
    this.subscription = this.http.get('https://api.example.com/data')
      .subscribe(
        response => console.log(response),
        error => console.error(error)
      );
  }

  cancelRequest() {
    if (this.subscription) {
      this.subscription.unsubscribe();
      console.log('请求已取消');
    }
  }

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

方法二：使用 takeUntil 操作符（推荐）

import { Component, OnDestroy } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Subject } from 'rxjs';
import { takeUntil } from 'rxjs/operators';

@Component({
  selector: 'app-example',
  template: `
    <button (click)="makeRequest()">发起请求</button>
    <button (click)="cancelRequest()">取消请求</button>
  `
})
export class ExampleComponent implements OnDestroy {
  private destroy$ = new Subject<void>();

  constructor(private http: HttpClient) {}

  makeRequest() {
    this.http.get('https://api.example.com/data')
      .pipe(takeUntil(this.destroy$))
      .subscribe(
        response => console.log(response),
        error => console.error(error)
      );
  }

  cancelRequest() {
    this.destroy$.next();
    console.log('请求已取消');
  }

  ngOnDestroy() {
    this.destroy$.next();
    this.destroy$.complete();
  }
}

方法三：使用 AbortController（现代浏览器支持）

import { Component } from '@angular/core';
import { HttpClient, HttpHeaders } from '@angular/common/http';

@Component({
  selector: 'app-example',
  template: `
    <button (click)="makeRequest()">发起请求</button>
    <button (click)="cancelRequest()">取消请求</button>
  `
})
export class ExampleComponent {
  private abortController: AbortController;

  constructor(private http: HttpClient) {}

  makeRequest() {
    this.abortController = new AbortController();
    
    const options = {
      headers: new HttpHeaders(),
      signal: this.abortController.signal
    };

    this.http.get('https://api.example.com/data', options)
      .subscribe(
        response => console.log(response),
        error => {
          if (error.name === 'AbortError') {
            console.log('请求被取消');
          } else {
            console.error(error);
          }
        }
      );
  }

  cancelRequest() {
    if (this.abortController) {
      this.abortController.abort();
      console.log('请求已取消');
    }
  }
}