[英]typescript promise return after loop
I am trying to return after all the calls to an external service are done but my code is just flying through the for loop and returning. 在尝试完成对外部服务的所有调用后,我试图返回,但是我的代码只是通过for循环飞行并返回。 I cannot do a promise.all here as I need some values obtained in the loop. 我不能做一个promise.all,因为我需要在循环中获得一些值。 Is there an easy way to do this in typescript/angular2? 在typescript / angular2中有一种简单的方法吗?
var ret = [];
for (var l in users){
var userLicense = users[l].licenseNumber;
this.callExternalService(userLicense).subscribe(response=>{
ret.push(response+userLicense);
}
}
resolve(ret);
As you are already using observables, you can use a combination of forkJoin
and map
to achieve this: 由于您已经在使用可观察对象,因此可以结合使用forkJoin
和map
来实现:
var ret = [];
Observable.forkJoin(
users.map(
user => this.callExternalService(user.licenseNumber)
.map(response => response + user.licenseNumber)
)
).subscribe(values => {
ret = values;
resolve(ret);
})
You could try combineLatest
: 您可以尝试combineLatest
:
return Observable.combineLatest(
...users.map(user => this.callExternalService(user.licenseNumber)
.map(response => response + user.licenseNumber)),
(...vals) => vals);
This will return an observable of arrays of results from the service calls, which you can then subscribe to, convert to a promise with toPromise
if you prefer, etc. 这将从服务调用中返回可观察到的结果数组,然后您可以订阅这些结果,然后根据需要将其转换为toPromise
的promise等。
if you need to do some aggregation in the loop and pass it as part of return, you can add it into a Promise.all as Promise.resolve(aggregatedData) 如果您需要在循环中进行一些汇总并将其作为返回的一部分传递,则可以将其作为Promise.resolve(aggregatedData)添加到Promise.all中。
Something like that: 像这样:
function getData(ii) {
return new Promise(res => {
res(ii);
});
}
function getUserData(users) {
let promiseArray = [];
let aggregatedData = 0;
users.forEach(user => {
aggregatedData += user.id;
promiseArray.push(getData(user.id));
});
promiseArray.push(Promise.resolve(aggregatedData));
return Promise.all(promiseArray);
}
getUserData([{id:1}, {id:2}, {id:3}]).then(x=>console.log(x))
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