InjectionToken dùng khi nào?

InjectionToken dùng khi dependency không phải class concrete, ví dụ config object, primitive value, feature flag, API URL hoặc interface không tồn tại ở runtime.

Ví dụ:

export const API_URL = new InjectionToken<string>("API_URL")

bootstrapApplication(AppComponent, {
  providers: [{ provide: API_URL, useValue: "/api" }],
})

const apiUrl = inject(API_URL)

Với config cần lazy hoặc phụ thuộc dependency khác, provider có thể dùng useFactory.

InjectionToken is used when a dependency is not a concrete class, such as a config object, primitive value, feature flag, API URL or an interface that does not exist at runtime.

Example:

export const API_URL = new InjectionToken<string>("API_URL")

bootstrapApplication(AppComponent, {
  providers: [{ provide: API_URL, useValue: "/api" }],
})

const apiUrl = inject(API_URL)

For lazy config or config depending on another dependency, use a useFactory provider.