Angular 5 - Caching Service Does not work with router linking
I have the following caching service. DataService merely uses HttpClient module to return JSON data.
@Injectable({
providedIn: "root"
})
export class CategoryService extends DataService {
constructor(public http: HttpClient) {
super(environment.baseUrl + "category", http);
}
private cache$: Observable<Category>;
public get categories() {
if (!this.cache$) {
this.cache$ = this.requestCategories().pipe(
shareReplay(10)
);
}
return this.cache$;
}
private requestCategories(): Observable<Category> {
return this.getAll(); // this is implemented in DataService
}
I have a component which puts the categories returned in a dropdown list. I use the selector to add this to a web page. This works as expected. The first time thru the service, there is no cached data, so it is fetched and stored, and the next time the cache is used.
I call the get property in the service from the category component thusly:
ngOnInit() {
this.categories$ = this.categoryService.categories;
}
But aye, here's the rub: if I route to this component, say from a navigation bar, the service ALWAYS goes back to get new data. I.e., it is never cached. Here is the HTML for the router link:
<a class="nav-link" routerLink="/category">Category</a>
Bottom line, Conan, why does the service always go back to get new data, rather than use the cache?
Happy Thanksgiving!!!
angular edited Nov 21 '18 at 17:32
Yashwardhan Pauranik
2,12611729
asked Nov 21 '18 at 17:24
ScottScott
66311230
add a comment |
I have the following caching service. DataService merely uses HttpClient module to return JSON data.
@Injectable({
providedIn: "root"
})
export class CategoryService extends DataService {
constructor(public http: HttpClient) {
super(environment.baseUrl + "category", http);
}
private cache$: Observable<Category>;
public get categories() {
if (!this.cache$) {
this.cache$ = this.requestCategories().pipe(
shareReplay(10)
);
}
return this.cache$;
}
private requestCategories(): Observable<Category> {
return this.getAll(); // this is implemented in DataService
}
I have a component which puts the categories returned in a dropdown list. I use the selector to add this to a web page. This works as expected. The first time thru the service, there is no cached data, so it is fetched and stored, and the next time the cache is used.
I call the get property in the service from the category component thusly:
ngOnInit() {
this.categories$ = this.categoryService.categories;
}
But aye, here's the rub: if I route to this component, say from a navigation bar, the service ALWAYS goes back to get new data. I.e., it is never cached. Here is the HTML for the router link:
<a class="nav-link" routerLink="/category">Category</a>
Bottom line, Conan, why does the service always go back to get new data, rather than use the cache?
Happy Thanksgiving!!!
angular edited Nov 21 '18 at 17:32
Yashwardhan Pauranik
2,12611729
asked Nov 21 '18 at 17:24
ScottScott
66311230
add a comment |
I have the following caching service. DataService merely uses HttpClient module to return JSON data.
@Injectable({
providedIn: "root"
})
export class CategoryService extends DataService {
constructor(public http: HttpClient) {
super(environment.baseUrl + "category", http);
}
private cache$: Observable<Category>;
public get categories() {
if (!this.cache$) {
this.cache$ = this.requestCategories().pipe(
shareReplay(10)
);
}
return this.cache$;
}
private requestCategories(): Observable<Category> {
return this.getAll(); // this is implemented in DataService
}
I have a component which puts the categories returned in a dropdown list. I use the selector to add this to a web page. This works as expected. The first time thru the service, there is no cached data, so it is fetched and stored, and the next time the cache is used.
I call the get property in the service from the category component thusly:
ngOnInit() {
this.categories$ = this.categoryService.categories;
}
But aye, here's the rub: if I route to this component, say from a navigation bar, the service ALWAYS goes back to get new data. I.e., it is never cached. Here is the HTML for the router link:
<a class="nav-link" routerLink="/category">Category</a>
Bottom line, Conan, why does the service always go back to get new data, rather than use the cache?
Happy Thanksgiving!!!
angular edited Nov 21 '18 at 17:32
Yashwardhan Pauranik
2,12611729
asked Nov 21 '18 at 17:24
ScottScott
66311230
I have the following caching service. DataService merely uses HttpClient module to return JSON data.
@Injectable({
providedIn: "root"
})
export class CategoryService extends DataService {
constructor(public http: HttpClient) {
super(environment.baseUrl + "category", http);
}
private cache$: Observable<Category>;
public get categories() {
if (!this.cache$) {
this.cache$ = this.requestCategories().pipe(
shareReplay(10)
);
}
return this.cache$;
}
private requestCategories(): Observable<Category> {
return this.getAll(); // this is implemented in DataService
}
I have a component which puts the categories returned in a dropdown list. I use the selector to add this to a web page. This works as expected. The first time thru the service, there is no cached data, so it is fetched and stored, and the next time the cache is used.
I call the get property in the service from the category component thusly:
ngOnInit() {
this.categories$ = this.categoryService.categories;
}
But aye, here's the rub: if I route to this component, say from a navigation bar, the service ALWAYS goes back to get new data. I.e., it is never cached. Here is the HTML for the router link:
<a class="nav-link" routerLink="/category">Category</a>
Bottom line, Conan, why does the service always go back to get new data, rather than use the cache?
Happy Thanksgiving!!!
angular angular edited Nov 21 '18 at 17:32
Yashwardhan Pauranik
2,12611729
asked Nov 21 '18 at 17:24
ScottScott
66311230
edited Nov 21 '18 at 17:32
Yashwardhan Pauranik
2,12611729
asked Nov 21 '18 at 17:24
ScottScott
66311230
edited Nov 21 '18 at 17:32
Yashwardhan Pauranik
2,12611729
edited Nov 21 '18 at 17:32
Yashwardhan Pauranik
2,12611729
edited Nov 21 '18 at 17:32
Yashwardhan Pauranik
2,12611729
2,12611729
asked Nov 21 '18 at 17:24
ScottScott
66311230
asked Nov 21 '18 at 17:24
ScottScott
66311230
asked Nov 21 '18 at 17:24
ScottScott
66311230
66311230
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
I assume the problem is with using shareReplay() operator. Thing is that when no subscriptions are left, the 'cached' data is flushed.
This is different with publishReplay(1).refCount() where the cache is kept even when the last subscriber unsubscribes.
This article describes it in detail:
https://blog.angularindepth.com/rxjs-how-to-use-refcount-73a0c6619a4e
The relevant section is What does shareReplay do
So, first try using publishReplay(1).refCount(). If this doesn't help, then you might want to save the data in the localStorage. Obviously, if you refresh the page all the in-memory cache will be gone anyway.
answered Nov 21 '18 at 17:36
Daniil Andreyevich BaunovDaniil Andreyevich Baunov
1,122528
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
I assume the problem is with using shareReplay() operator. Thing is that when no subscriptions are left, the 'cached' data is flushed.
This is different with publishReplay(1).refCount() where the cache is kept even when the last subscriber unsubscribes.
This article describes it in detail:
https://blog.angularindepth.com/rxjs-how-to-use-refcount-73a0c6619a4e
The relevant section is What does shareReplay do
So, first try using publishReplay(1).refCount(). If this doesn't help, then you might want to save the data in the localStorage. Obviously, if you refresh the page all the in-memory cache will be gone anyway.
answered Nov 21 '18 at 17:36
Daniil Andreyevich BaunovDaniil Andreyevich Baunov
1,122528
add a comment |
I assume the problem is with using shareReplay() operator. Thing is that when no subscriptions are left, the 'cached' data is flushed.
This is different with publishReplay(1).refCount() where the cache is kept even when the last subscriber unsubscribes.
This article describes it in detail:
https://blog.angularindepth.com/rxjs-how-to-use-refcount-73a0c6619a4e
The relevant section is What does shareReplay do
So, first try using publishReplay(1).refCount(). If this doesn't help, then you might want to save the data in the localStorage. Obviously, if you refresh the page all the in-memory cache will be gone anyway.
answered Nov 21 '18 at 17:36
Daniil Andreyevich BaunovDaniil Andreyevich Baunov
1,122528
add a comment |
I assume the problem is with using shareReplay() operator. Thing is that when no subscriptions are left, the 'cached' data is flushed.
This is different with publishReplay(1).refCount() where the cache is kept even when the last subscriber unsubscribes.
This article describes it in detail:
https://blog.angularindepth.com/rxjs-how-to-use-refcount-73a0c6619a4e
The relevant section is What does shareReplay do
So, first try using publishReplay(1).refCount(). If this doesn't help, then you might want to save the data in the localStorage. Obviously, if you refresh the page all the in-memory cache will be gone anyway.
answered Nov 21 '18 at 17:36
Daniil Andreyevich BaunovDaniil Andreyevich Baunov
1,122528
I assume the problem is with using shareReplay() operator. Thing is that when no subscriptions are left, the 'cached' data is flushed.
This is different with publishReplay(1).refCount() where the cache is kept even when the last subscriber unsubscribes.
This article describes it in detail:
https://blog.angularindepth.com/rxjs-how-to-use-refcount-73a0c6619a4e
The relevant section is What does shareReplay do
So, first try using publishReplay(1).refCount(). If this doesn't help, then you might want to save the data in the localStorage. Obviously, if you refresh the page all the in-memory cache will be gone anyway.
answered Nov 21 '18 at 17:36
Daniil Andreyevich BaunovDaniil Andreyevich Baunov
1,122528
answered Nov 21 '18 at 17:36
Daniil Andreyevich BaunovDaniil Andreyevich Baunov
1,122528
answered Nov 21 '18 at 17:36
Daniil Andreyevich BaunovDaniil Andreyevich Baunov
1,122528
answered Nov 21 '18 at 17:36
Daniil Andreyevich BaunovDaniil Andreyevich Baunov
1,122528
1,122528
add a comment |
add a comment |
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