Angular 6如何通过管道进行http调用
我有一个HTTP服务,它使用HttpClient进行API调用:Angular 6如何通过管道进行http调用,angular,angular2-observables,Angular,Angular2 Observables,我有一个HTTP服务,它使用HttpClient进行API调用: //provider.service.ts export interface Lesson { id?: number, name: string, type: LessonType, teacher_data: string, student_data: string } export class ProviderService { constructor(private htt
//provider.service.ts
export interface Lesson {
id?: number,
name: string,
type: LessonType,
teacher_data: string,
student_data: string
}
export class ProviderService {
constructor(private http: HttpClient) {}
postLesson(form): Observable<Lesson> {
const body = this.getFormUrlEncoded(form.value);
return this.http.post<Lesson>('/api/lesson/', body, this.postHttpOptions);
}
}
它工作得很好,一切都很好。现在我想做一个LessonService,让所有http调用都通过该服务。它将缓存结果、在更改时发出等
我是这样写的:
//updated lessons.component.ts
onSubmit():void {
this.LessonsService.createLesson(this.lessonForm).subscribe(result=> {
console.log(result);
//do my stuff
});
}
//lessons.service.ts
export class LessonsService {
constructor(private http: ProviderService) {}
@Output() lessonChange: EventEmitter<Lesson> = new EventEmitter();
public createLesson(form): Observable<Lesson> {
let observable = this.http.postLesson(form);
observable.pipe(
map(result => {
//this code is not executed, I do not understand why
this.lessonChange.emit(result);
return result;
})
);
return observable;
}
}
//更新了lessons.component.ts
onSubmit():void{
this.LessonsService.createLesson(this.lessonForm).subscribe(结果=>{
控制台日志(结果);
//做我的事
});
}
//课程服务
导出类LessonsService{
构造函数(专用http:ProviderService){}
@Output()lessonChange:EventEmitter=neweventemitter();
公共课程(形式):可观察{
让observable=this.http.postLesson(form);
可见光管(
映射(结果=>{
//这段代码没有执行,我不明白为什么
此.lessonChange.emit(结果);
返回结果;
})
);
可观测收益;
}
}
我想在从HTTP提供程序获得结果时发出一个事件。我做错了什么?有两种方法可以做到这一点,一种是将
管道
放入变量声明中,并使用点击
而不是映射
export class LessonsService {
@Output() lessonChange: EventEmitter<Lesson> = new EventEmitter();
public createLesson(form): Observable<Lesson> {
let observable = this.http.postLesson(form).pipe(
tap(result => {
//this code is not executed, I do not understand why
this.lessonChange.emit(result);
return result;
})
);
return observable;
}
}
导出类LessonsService{
@Output()lessonChange:EventEmitter=neweventemitter();
公共课程(形式):可观察{
让observable=this.http.postLesson(form.pipe)(
点击(结果=>{
//这段代码没有执行,我不明白为什么
此.lessonChange.emit(结果);
返回结果;
})
);
可观测收益;
}
}
另一种方法是创建对变量的订阅
export class LessonsService {
@Output() lessonChange: EventEmitter<Lesson> = new EventEmitter();
public createLesson(form): Observable<Lesson> {
let observable = this.http.postLesson(form);
observable.subscribe(result => {
//this code is not executed, I do not understand why
this.lessonChange.emit(result);
return result;
);
return observable;
}
}
导出类LessonsService{
@Output()lessonChange:EventEmitter=neweventemitter();
公共课程(形式):可观察{
让observable=this.http.postLesson(form);
可观察。订阅(结果=>{
//这段代码没有执行,我不明白为什么
此.lessonChange.emit(结果);
返回结果;
);
可观测收益;
}
}
我个人会选择后者,这样可以确保事件只在成功时发出。在第二种方法中,将有两个http调用,不是吗?第一个将在组件订阅时执行,第二个将在service@RustamGaneyev这是可能发生的,但是如果你使用Angular这样的库,这是最好的方法o这样做。
export class LessonsService {
@Output() lessonChange: EventEmitter<Lesson> = new EventEmitter();
public createLesson(form): Observable<Lesson> {
let observable = this.http.postLesson(form);
observable.subscribe(result => {
//this code is not executed, I do not understand why
this.lessonChange.emit(result);
return result;
);
return observable;
}
}