Angular 等待多个 http 请求完成，然后触发最后一个

Question

我有 4 个 http 请求。第三个接收查找值，而第四个获取实际的表单数据。

他们是这样的：

   let medicalData = this.data.getCodes('medical').subscribe((data: {}) => {
     console.log('med');
       this.Medical = data;
        });
   let delayData = this.data.getCodes('delay').subscribe((data: {}) => {
    console.log('del');
          this.Delays = data;
           });
   let disabilityData = this.data.getCodes('disability').subscribe((data: {}) => {
    console.log('dis');
            this.Disability = data;
             });
   let districtData = this.data.getCodes('district').subscribe((data: {}) => {
    console.log('dist');
              this.District = data;
               });

如何让第 4 个 get 请求等到前三个请求完成？

提前致谢

Answer 1

您应该使用forkJoin来达到预期的效果。forkJoin在发出值之前等待所有可观察对象完成。例子：

forkJoin(
  this.data.getCodes('medical'),
  this.data.getCodes('delay'),
  this.data.getCodes('disability'),
  this.data.getCodes('district'),
).subscribe(([medicalData, delayData, disabilityData, districtData]) => {
  this.Medical = medicalData;
  this.Delays = delayData;
  this.Disability = disabilityData;
  this.District = districtData;

  // make your last http request here.
});