Sometimes you can get this error while running tests or in the browser console.
Also, you can face this error after updating the Angular version:
Can't resolve all parameters for AppComponent: (?)
Most сases can be resolved by adding following line in the tsconfig.json:
"compilerOptions": {
"emitDecoratorMetadata": true,
"outDir": "./out-tsc/spec",
With this parameter, you can forget about adding @Inject() to your function parameters. For some versions of Angular, it should be enabled by default.
If you are using decorators and got this error, please check the following: - have you added decorators in all necessary places? - have you typed correctly the decorator’s name with all symbols?
It should look like this:
@Injectable()
export class Service { ... }