[英]Angular 2 converting to Promise
I want to fetch data from an API which works like a charm but i am struggling with filtering a single Report by a given id from an "Observable". 我想从像API一样工作的API中获取数据,但是我正努力通过“可观察”中的给定ID过滤单个报告。
Here are some snippets: 以下是一些摘要:
getAllReports(): Observable<Report[]> {
return this.http.get(this.reportUrl)
.map(res => res.json().results);
}
getReports(): void {
this.reportService.getAllReports()
.subscribe(
reports => this.reports = reports,
error => console.log(error)
);
}
getSingleReport(id: number): Promise<Report> {
return this.getAllReports()
.then(reports => reports.find(report => report.id === id));
// ^ "Property 'then' does not exist on type 'Observable<Report[]>'"
}
getSingleReport1(id: number): Promise<Report> {
this.getAllReports()
.subscribe(
reports => this.reports = reports,
error => console.log(error)
);
return this.reports.find(report => report.id === id);
// ^ "Type 'Report' is not assignable to type 'Promise<Report>'"
}
getAllReports()
is responsible for the communication with the API and returns an Ovserable getAllReports()
负责与API的通信并返回一个Ovserable getReports()
inserts the results from the API call in a reports: Report[]
aray getReports()
将API调用的结果插入reports: Report[]
getSingleReport()
should return a Promise<Report>
with the given Observable<Report[]>
getSingleReport()
应该返回一个Promise<Report>
和给定的Observable<Report[]>
getSingleReport1()
is my first try fixing the problem which unfortunately also doesn't work getSingleReport1()
是我的第一个尝试解决该问题的方法,不幸的是它也无法正常工作 Of course i know where the problems in 3 & 4 are but in don't know how to solve them. 我当然知道3和4中的问题在哪里,但不知道如何解决。
How can i accomplish a conversation from Report
or Observable<Report[]>
to Promise<Report>
. 我如何完成从
Report
或Observable<Report[]>
到Promise<Report>
的对话。
Any help is highly appreciated. 非常感谢您的帮助。
Thank you. 谢谢。
Use toPromise
operator like this: 像这样使用
toPromise
运算符:
getSingleReport(id: number): Promise<Report> {
return this.getAllReports()
.subscribe(reports => reports.find(report => report.id === id)).toPromise();
}
So i still didn't find a solution but i came up with a workaround i'll post here. 所以我仍然没有找到解决方案,但是我想出了一种解决方法,我将在此处发布。 I changed
getSingleReport(id: number): Promise<Report>
to getSingleReport(id: number): Report
. 我将
getSingleReport(id: number): Promise<Report>
更改为getSingleReport(id: number): Report
。
getSingleReport(id: number): Report {
this.getAllReports()
.subscribe(
reports => this.reports = reports,
error => console.log(error)
);
return this.reports.find(report => report.id === id);
}
This works but is still throwing the error TypeError: Cannot read property 'find' of undefined
. 此方法有效,但仍会
TypeError: Cannot read property 'find' of undefined
错误TypeError: Cannot read property 'find' of undefined
。 I'll probably fix it later today. 我可能会在今天晚些时候修复它。
UPDATE: 更新:
I got it perfectly working now but i decided to do it without a Promise. 我现在可以完美地工作了,但是我决定不做任何承诺。
report-detail.component.ts:
getReport(id: number) {
this.reportService.getSingleReport(id)
.subscribe(
report => this.report = report,
error => console.log(error)
);
}
report.service.ts:
getSingleReport(id: number): Observable<Report> {
const apiUrl = 'http://localhost:8080/Berichtsprogramm-API/getReport?api_key={TEMPORARY_APIKEY}&id=' + id;
return this.http.get(apiUrl)
.map(res => res.json());
}
This works for my case and finally i can be happy again. 这适用于我的情况,最后我可以再次感到高兴。
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