Javascript 如何在angular2中进行顺序http api调用？

我有多个api调用，其中依赖于另一个调用。如何使用rxjs实现这一点？

试试这个

this.serviceInst.firstAPIMethod()
    .flatMap(firstMethodResult => this.serviceInst.secondAPIMethod(firstMethodResult))
    .flatMap(secondMethodResult => this.serviceInst.thirdAPIMethod(secondMethodResult))
    .subscribe(thirdMethodResult => {
          console.log(thirdMethodResult);
     });

let inSequence = (tasks) => { // tasks being an array of functions returning promises
  return tasks.reduce((p, task) => p.then(task), Promise.resolve());
}

inSequence(tasks).then(() => {
  console.log('all requests done');
});