`ngrx` - how to implement the caching with `effects`

Question

I like to integrate the cache with my effects. but getting no result. the way i do may not correct.

any one correct me to fix the issue.

here is my code:

constructor(private courseService:CourseService, private actions:Actions,
    private store:Store<StateSetupConfig>){}

@Effect()
    EffLoadCourse = this.actions.pipe(
        ofType(LoadCourse.TYPE),
        withLatestFrom(this.store.pipe(select(subscribes.getCourses)),
            (action, courses) => {
                console.log('courses ::', courses)//getting logged,
                return courses
            }

        ),
       //but each time backend call initiated!!?
        mergeMap((action:LoadCourse) => this.courseService.getCourse().pipe(
            map((courses:ModelCourse[]) => (new LoadCourseSuccess(courses))),
            catchError(err => of(new LoadCourseFail(err)))
        ))

    )

the problem is, eventhough i back to the current page, I am getting backend call instead of supplying from store. where is wrong? what condition has to be added here?

Thanks in advance.

Answer 1

I come up with following solution: it works for me!!

@Effect()
        EffLoadCourse = this.actions.pipe(
            ofType(LoadCourse.TYPE),
            withLatestFrom(
                this.store.pipe(select(subscribes.getCourses)), //getting it from store
                (action:LoadCourse, courses: ModelCourse[]) => courses
            ),
            mergeMap((courses:ModelCourse[]) => {

                if(courses.length){
                    return of(courses).pipe(
                        map((courses:ModelCourse[]) => (new LoadCourseSuccess(courses))),
                        catchError(err => of(new LoadCourseFail(err)))
                    )
                }

                return this.courseService.getCourse().pipe(
                    map((courses:ModelCourse[]) => (new LoadCourseSuccess(courses))),
                    catchError(err => of(new LoadCourseFail(err)))
                )
            })
        )