如何解决在Angular中链接RESTful端点调用
我在SO上看到了无数的帖子,它们似乎围绕着我要完成的工作而跳舞,但是没有一个达到目标。所以....这是另一篇有关在Angular中链接RESTful端点调用的文章。这是我的简化示例:
给出学生,课程和注册的数据模型:
interface Student {
id: number;
studentName: string;
}
interface Course {
id: number;
courseName: string;
}
interface Enrollment {
studentId: number;
courseId: number;
}
...并在我的Angular服务中提供以下方法:
getEnrollmentsForStudent(studentId: number): Observable<Enrollment[]> {
return this.http.get<Enrollment[]>('http://url/enrollment?id='+studentId);
}
我需要编写具有以下签名的第二种方法:
getCoursesForStudent(studentId: number): Observable<Course[]> {
...
}
,它使用getEnrollmentsForStudent方法中的Enrollment数组来获取所有相关的Course对象(这里是StackBlitz)。我敢肯定,有一些RxJS运算符的魔术组合可以做到这一点,但是我已经竭尽全力试图解决这个问题。
编辑:这是我的Angular服务的最小可复制示例:
import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable,of } from 'rxjs';
interface Student {
id: number;
studentName: string;
}
interface Course {
id: number;
courseName: string;
}
interface Enrollment {
studentId: number;
courseId: number;
}
@Injectable()
export class RegistrationService {
constructor(private http: HttpClient) { }
getEnrollmentsForStudent(studentId: number): Observable<Enrollment[]> {
return this.http.get<Enrollment[]>('http://url/enrollment?id=studentId');
}
getCoursesForStudent(studentId: number): Observable<Course[]> {
// 1. get Enrollments for student using getEnrollemtnsForStudent
// 2. for each enrollment,get the course
// 3. return array of Course objects
return null;
}
}
解决方法
您将要使用switchMap。我不知道您获取课程的端点是什么样的,所以我猜测是将ID数组作为查询字符串发送...
您getCoursesForStudent
调用getEnrollmentsForStudent
方法,并通过switchMap
传递其注册数组,并使第二个API调用返回第二个调用的Observable。
https://stackblitz.com/edit/angular-chain-observables-ck6oyt?file=src/app/registration.service.ts
getCoursesForStudent(studentId: number): Observable<Course[]> {
// 1. get Enrollments for student using getEnrollemtnsForStudent
// 2. for each enrollment,get the course
// 3. return array of Course objects
return this.getEnrollmentsForStudent(studentId).pipe(switchMap(enrollments => {
const enrollmentIds = enrollments.map(e => e.courseId);
// Not sure what your API expects to get an array of IDs,just guessing here...
return this.http.get<Course[]>(`http://url/courses?ids_in=${enrollmentIds}`);
}));
}
版权声明:本文内容由互联网用户自发贡献,该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 dio@foxmail.com 举报,一经查实,本站将立刻删除。