Tare da gashin kawai Angular's hierarchical dependency injection yana aiki?

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Angular's DI shine **hierarchical**: injectors sun samar da bishiyar da ta nuna bishiyar gaida/module. Lokacin da wani gaida ya nema dogaro, Angular yana tafiya **sama** bishiyar injector har sai har aka sami provider — wanda ke lanawa ko ka sami shared singleton ko asali daban-daban per gaida. ## The injector hierarchy ```text Root injector (app-wide) ← providedIn: 'root' lives here (one singleton) └─ Module/Route injectors └─ Component injector ← providers: [...] in @Component └─ Child component injector ``` Shakowa tana farawa daga gaida da ke nema kuma yana kumfe zuwa wajen gida. **na farko** provider da aka samu yana lashe. ## Inda ka ba da mulkin ikon kadarori ```ts // 1. App-wide singleton — ONE instance shared everywhere @Injectable({ providedIn: "root" }) export class AuthService {} // 2. Component-scoped — a NEW instance per component (and its children) @Component({ selector: "app-widget", providers: [DataService], // each gets its OWN DataService }) export class WidgetComponent {} ``` Dan nan shine babbar domin: `providedIn: 'root'` yana ba da gida daya da aka raba; lissafin provider a jerin `providers` na gaida yana yin sabuwar asali da aka ɗora gaida (mai amfani don katanya jiya ɓaugwari gida). ## Injection modifiers ```ts constructor( @Optional() private logger: Logger, // null instead of error if not provided @Self() private local: LocalService, // only look in THIS injector @SkipSelf() private parent: ParentService, // skip self, start at the parent @Host() private host: HostService, // stop at the host component ) {} ``` Waɗannan masu sune suna lanawa *nesa* Angular yana neman bishiyar injector — misali `@Optional` yana kauce wa kariya lokacin da dogaro ba shi ciki, `@SkipSelf` yana tilasta amfani da uwarsa. ## Injection tokens don dogaro maras-jama'a ```ts export const API_URL = new InjectionToken("apiUrl"); // provide: { provide: API_URL, useValue: "https://api.example.com" } constructor(@Inject(API_URL) private apiUrl: string) {} ``` Tokens suna ba da damar ka chev ƙimasosu / tsare (ba kawai azuzuwan ba) da sauya aiwatarwa (`useClass`, `useValue`, `useFactory`). ## Me yasa ya zama mahimmanci Ganin injector hierarchical yana bayyanar *me yasa* aiki yana ba jama'a app-wide kasua aikin gida per gaida — tushen yada "me yasa waɗannan gida raba / bai raba jiya?" rudani. Lanawa kadarori kadarori (`root` kasua gaida `providers`), amfani modifiers (`@Optional`, `@SkipSelf`), da injection tokens don tsare / swappable aiwatarwa shine abin ya ba Angular's DI karfi don gida da tsari.