In Angular I have a service to access a cache. The service roughly works like this (but with a lot more asynchronous behavior).
@Injectable()
export class Cache {
cache : CacheTable;
constructor(
protected name : string
) {
this.cache = this.getTable(name);
}
put(id:string, data:any):void { this.cache.put(id, data); }
get(id:string):any { return this.cache.get(id); }
getTable(name : string) : CacheTable;
}
Now I have a number of services like UserService
that would like to have a Cache
corresponding to new Cache('user');
. Another service named ImageService
should work with an instance of Cache
corresponding to new Cache('image');
For this I would like to create a Factory to provide these:
// file: custom-caches.ts
import { Provider } from '@angular/core';
import { Cache } from '../cache/cache';
export let userCache : Provider = {
provide: Cache,
useFactory: () => new Cache('user')
};
export let imageCache : Provider = {
provide: Cache,
useFactory: () => new Cache('image')
};
How would I go about registering and using each of these services? As far as I can tell they're all registered as 'Cache
'.
// file: my.module.ts
@NgModule({
providers: [userCache, imageCache]
})
export class MyModule {}
(This relates to my other question)
As suggested by @ghetolay I used InjectionToken
and was able to successfully create multiple named providers as factoried instances:
// file: custom-caches.ts
import { Provider } from '@angular/core';
import { Cache } from '../cache/cache';
export const UserCache = new InjectionToken('userCache');
export let userCacheProvider : Provider = {
provide: UserCache,
useFactory: () => new Cache('user')
};
export const ImageCache = new InjectionToken('imageCache');
export let imageCacheProvider : Provider = {
provide: ImageCache,
useFactory: () => new Cache('image')
};
_
// file: my.module.ts
@NgModule({
providers: [userCacheProvider, imageCacheProvider]
})
export class MyModule {}
_
// file : UserService
@Injectable()
export class UserService {
constructor(
@Inject(UserCache) private cache : Cache
) {}
}
UserCache
and ImageCache
are now tokens for these provider instances.