angular-di

Included with Lifetime

$97 forever

ALWAYS use when working with Angular Dependency Injection, providers, services, inject tokens, or hierarchical injection in Angular applications.

General

What this skill does


# Angular Dependency Injection

**Version:** Angular 21 (2025)
**Tags:** DI, Services, Providers, Tokens, inject()

**References:** [DI Guide](https://angular.dev/guide/di) • [API](https://angular.io/api/core) • [inject()](https://angular.io/api/core/inject)

## API Changes

This section documents recent version-specific API changes.

- NEW: Functional injection with inject() — Preferred over constructor injection in modern Angular [source](https://medium.com/tenantcloud-engineering/understanding-dependency-injection-in-angular-constructor-injection-vs-5c75f0226f70)

- NEW: inject() with Optional decorator — `inject(Service, { optional: true })`

- NEW: inject() with SkipSelf — `inject(Service, { skipSelf: true })`

- NEW: Tree-shakable InjectionToken — `new InjectionToken<T>(desc, { providedIn: 'root' })`

## Best Practices

- Use providedIn: 'root' for singleton services

```ts
@Injectable({ providedIn: 'root' })
export class LoggerService {
  log(message: string) { console.log(message); }
}
```

- Use inject() function for cleaner code

```ts
@Component({})
export class MyComponent {
  private service = inject(MyService);
  private router = inject(Router);
}
```

- Use InjectionToken for non-class dependencies

```ts
export const API_URL = new InjectionToken<string>('apiUrl');

providers: [
  { provide: API_URL, useValue: 'https://api.example.com' }
]

constructor(@Inject(API_URL) private apiUrl: string) {}
```

- Use factory providers for complex instantiation

```ts
providers: [
  {
    provide: AuthService,
    useFactory: (http: HttpClient, config: AppConfig) => {
      return new AuthService(http, config.apiUrl);
    },
    deps: [HttpClient, APP_CONFIG]
  }
]
```

- Use multi providers for multiple implementations

```ts
providers: [
  { provide: HTTP_INTERCEPTORS, useClass: AuthInterceptor, multi: true },
  { provide: HTTP_INTERCEPTORS, useClass: LogInterceptor, multi: true }
]
```

- Use @Optional for optional dependencies

```ts
constructor(@Optional() private logger: LoggerService) {
  this.logger?.log('Optional dependency');
}
```

- Use @SkipSelf to avoid self-injection

```ts
constructor(@SkipSelf() @Optional() private parent: ParentService) {}
```

- Use forwardRef for circular dependencies

```ts
constructor(@Inject(forwardRef(() => ParentService)) private parent: ParentService) {}
```

- Use hierarchical injectors for scoping

```ts
// Component-level provider
@Component({
  providers: [MyService]
})
export class MyComponent {}

// Lazy-loaded module provider
@Injectable({ providedIn: MyModule })
export class MyService {}
```

- Use interface injection pattern

```ts
export interface CacheInterface {
  get(key: string): any;
}

export const CACHE_TOKEN = new InjectionToken<CacheInterface>('cache');
```

- Use providedIn: 'any' for lazy-loaded services

```ts
@Injectable({ providedIn: 'any' })
export class LazyService {}
```

Files: 5

Size: 4.2 KB

Complexity: 25/100

Category: General

Source: https://github.com/oguzhan18/angular-ecosystem-skills/tree/main/skills/angular-di

Related in General

modeling-omnistudio-epc-catalog

Included

Salesforce Industries CME EPC product-modeling skill for Product2-based catalog creation. Use when creating EPC products, configuring product attributes, building offer bundles with Product Child Items, or reviewing EPC DataPack JSON metadata for product catalog changes. TRIGGER when: user creates or updates Product2 EPC records, AttributeAssignment payloads, AttributeMetadata/AttributeDefaultValues, Offer bundles, or ProductChildItem relationships. DO NOT TRIGGER when: designing OmniScripts/FlexCards/Integration Procedures (use building-omnistudio-omniscript, building-omnistudio-flexcard, or building-omnistudio-integration-procedure), implementing Apex business logic (use generating-apex), or troubleshooting deployment pipelines (use deploying-metadata).

Generalscripts

relationship-science-coach

Included

Use this skill for direct, practical adult relationship coaching: couples conflict, repair, trust, marriage, dating, flirting, attachment patterns, emotional connection, sex, desire differences, eroticism, kink negotiation, affection, love languages, breakups, and long-term passion. Draw on Gottman, EFT and Hold Me Tight, attachment science, modern sex research, Perel, Nagoski, Kerner, Schnarch, Love and Stosny, and flexible love-language tools. Be concrete and low-hedge. Redirect only for imminent danger, abuse, coercive control, minors, non-consent, self-harm, stalking, or medical/legal/psychiatric decisions.

Generalscripts

building-sf-integrations

Included

Salesforce integration architecture and runtime plumbing with 120-point scoring. Use this skill to set up Named Credentials, External Credentials, External Services, REST/SOAP callout patterns, Platform Events, and Change Data Capture. TRIGGER when: user sets up Named Credentials, External Services, REST/SOAP callouts, Platform Events, CDC, or touches .namedCredential-meta.xml files. DO NOT TRIGGER when: Connected App/OAuth config (use configuring-connected-apps), Apex-only logic (use generating-apex), or data import/export (use handling-sf-data).

Generalscripts

venue-templates

Included

Access comprehensive LaTeX templates, formatting requirements, and submission guidelines for major scientific publication venues (Nature, Science, PLOS, IEEE, ACM), academic conferences (NeurIPS, ICML, CVPR, CHI), research posters, and grant proposals (NSF, NIH, DOE, DARPA). This skill should be used when preparing manuscripts for journal submission, conference papers, research posters, or grant proposals and need venue-specific formatting requirements and templates.

Generalscripts

let-fate-decide

Included

Draws the 12 Houses of the Zodiac Tarot spread to inject entropy into planning when prompts are vague, ambiguous, or casually delegated. Interprets the spread to guide next steps. Use when the user says 'let fate decide', 'YOLO', 'whatever', 'idk', or other nonchalant phrases, makes Yu-Gi-Oh references, or when you are about to arbitrarily pick between multiple reasonable approaches. Prefer over ask-questions-if-underspecified when the user's tone is casual or playful rather than precision-seeking.

Generalscripts

net-ops

Included

Cross-platform network troubleshooting (Windows, macOS, Linux) via local or remote shell. Use for: DNS broken, can't resolve hostnames, nslookup/dig works but apps fail, NRPT, WFP, scutil, /etc/resolver, systemd-resolved, /etc/resolv.conf, NetworkManager, VPN DNS leak residue (ProtonVPN/Mullvad/WireGuard/AnyConnect), AV/firewall blocking DNS or DoH, Tailscale DNS interaction, intermittent connectivity, remote diagnostics over SSH.

Generalscripts