inject
从当前活动的注入器中注入令牌。
Injects a token from the currently active injector.
const inject: { <T>(token: ProviderToken<T>): T; <T>(token: ProviderToken<T>, flags?: InjectFlags): T; };
说明
必须在工厂函数的上下文中使用，比如为 InjectionToken 定义的函数。如果未从这样的上下文中调用，则会引发错误。
Must be used in the context of a factory function such as one defined for an InjectionToken. Throws an error if not called from such a context.
在这样的工厂函数中，使用此函数来请求注入依赖项比提供额外的依赖项数组（在 useFactory 提供者中这很常见）要更快且类型安全性更高。
Within such a factory function, using this function to request injection of a dependency is faster and more type-safe than providing an additional array of dependencies (as has been common with useFactory providers).
Further information available in the Usage Notes...
使用说明
例子
Example
class MyService {
constructor(readonly myDep: MyDep) {}
}
const MY_SERVICE_TOKEN = new InjectionToken<MyService>('Manually constructed MyService', {
providedIn: 'root',
factory: () => new MyService(inject(MyDep)),
});
const instance = injector.get(MY_SERVICE_TOKEN);
expect(instance instanceof MyService).toBeTruthy();
expect(instance.myDep instanceof MyDep).toBeTruthy();
