将可观察到的RxJS转换为承诺 [英] Converting RxJS Observable to a Promise
本文介绍了将可观察到的RxJS转换为承诺的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我正在尝试使用多个http调用将数据存储在本地存储中.我使用forkJoin等待所有调用完成,然后再恢复Promise.then
调用链.我该怎么做?
I'm trying to store data in local storage using multiple http calls. I use forkJoin to wait until all of the calls have been completed and then I want to resume my Promise.then
call chain. How do I do this?
updateCache() {
var cachesToUpdate;
return this.fetchServerTimestamps()
.then(res => {
var localTimestamps = this.getLocalTimestamps();
var serverTimestamps = this.getServerTimestamps();
//Compare timestamps and decide which cache data types to update
cachesToUpdate = this.cacheTypes.filter(function (cacheType) {
return localTimestamps ? localTimestamps[cacheType.timestamp] != serverTimestamps[cacheType.timestamp] : true;
});
}).then(res => {
//Request data and insert into cache
this.fetchData(cachesToUpdate)
.subscribe(res => {
res.forEach(function (item, index) {
this.insert(cachesToUpdate[index].messageType, JSON.stringify(item));
}.bind(this));
});
});
}
fetchData(cachesToUpdate): Observable<any> {
return forkJoin(cachesToUpdate.map(i => this.callservice.serverRead({ path: 'api/' + i.messageType })));
}
insert(key: string, value: string, compress = true) {
localStorage.setItem(key, compress ? LZString.compress(value) : value);
}
推荐答案
您可以使用Observable
https://github.com. com/Reactive-Extensions/RxJS/blob/master/doc/api/core/operators/topromise.md
this.fetchData(cachesToUpdate).toPromise().then(...)
编辑:作为 FriOne &注释中提到的 Lyubimov Roman ,请不要忘记
Edit: as FriOne & Lyubimov Roman mentioned in the comment, don't forget to
import 'rxjs/add/operator/toPromise';
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