FactoryProvider
interface
stable
Configures the Injector
to return a value by invoking a useFactory
function.
provide
any
An injection token. (Typically an instance of Type
or InjectionToken
, but can be any
).
multi
boolean | undefined
When true, injector returns an array of instances. This is useful to allow multiple providers spread across many files to provide configuration information to a common token.
useFactory
Function
A function to invoke to create a value for this token
. The function is invoked with
resolved values of token
s in the deps
field.
deps
any[] | undefined
A list of token
s to be resolved by the injector. The list of values is then
used as arguments to the useFactory
function.
Usage Notes
const Location = new InjectionToken('location');
const Hash = new InjectionToken('hash');
const injector = Injector.create({
providers: [
{provide: Location, useValue: 'https://angular.io/#someLocation'},
{
provide: Hash,
useFactory: (location: string) => location.split('#')[1],
deps: [Location],
},
],
});
expect(injector.get(Hash)).toEqual('someLocation');
Dependencies can also be marked as optional:
const Location = new InjectionToken('location');
const Hash = new InjectionToken('hash');
const injector = Injector.create({
providers: [
{
provide: Hash,
useFactory: (location: string) => `Hash for: ${location}`,
// use a nested array to define metadata for dependencies.
deps: [[new Optional(), Location]],
},
],
});
expect(injector.get(Hash)).toEqual('Hash for: null');
Multi-value example
const locale = new InjectionToken<string[]>('locale');
const injector = Injector.create({
providers: [
{provide: locale, multi: true, useValue: 'en'},
{provide: locale, multi: true, useValue: 'sk'},
],
});
const locales: string[] = injector.get(locale);
expect(locales).toEqual(['en', 'sk']);
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