angular6 中的串行 api 调用

Question

I have parent component with two child component. Every off child components have OnInit api call with some date that will show in that components.

Can I call this api's serially? So first load api 1 and thent api 2?

Answer 1

Use Concat

Concat will combine two observables into a combined sequence, but the second observable will not start emitting until the first one has completed.

let first = Observable.timer(10,500).map(r => {
  return {source:1,value:r};
}).take(4);
let second = Observable.timer(10,500).map(r => {
  return {source:2,value:r};
}).take(4);
first.concat(second).subscribe(res => this.concatStream.push(res));

Ref: http://www.syntaxsuccess.com/viewarticle/combining-multiple-rxjs-streams-in-angular-2.0

Answer 2

This can be achieved using ForkJoin, which will allow Http call trigged async and parallel. Here is the Code

const apiCalls = [
   service.method1(),
   service.method2(),
];

return forkJoin(apiCalls).map((results)=>{
    console.log(results);
    return results;
});

Note: both method1() & method2() will return Observable.