类使用 Angular 特性但没有修饰。 请添加一个显式的 Angular 装饰器

Question

I have some components like CricketComponent , FootballComponent , TennisComponent etc. All These Classes have some common properties:- TeamName, teamSize, players etc which are @Input() .

Now I created a BaseComponent class, defined all these properties in there and this baseComponent class will be extended by cricket/football/tennis/etcComponents.

baseComponent.ts

export class BaseComponent {

    @Input() TeamName: string;
    @Input() teamSize: number;
    @Input() players: any;

}

CricketComponent.ts

@Component({
  selector: 'app-cricket',
  templateUrl: './cricket.component.html',
  styleUrls: ['./cricket.component.scss']
})
export class cricketComponent extends BaseComponent implements OnInit {

  constructor() {
    super();
  }

  ngOnInit(): void {
  }

}

I am getting this error:

ERROR in src/app/base-screen.ts:4:14 - error NG2007:

Class is using Angular features but is not decorated. Please add an explicit Angular decorator.

Answer 1

You'll need to add a @Component decorator to that base class (which should probably also be declared abstract ).

This is the bare minimum you can get away with in Angular 9:

@Component({
  template: ''
})
export abstract class BaseComponent {

    @Input() teamName: string;
    @Input() teamSize: number;
    @Input() players: any;
}

For Angular 10+, see this answer .

Answer 2

From Angular 10, you can fix this issue by adding the decorator @Injectable() to your abstract base class like this:

@Injectable()
export abstract class BaseComponent {    
    @Input() teamName: string;
    @Input() teamSize: number;
    @Input() players: any;
}

Answer 3

While the accepted answer is correct in using @Component , one minor downside is that it requires all constructor argument types to be resolvable by DI. So if your base class constructor takes a constant/literal - say, an enum - as a flag, you're going to have to set up a corresponding DI provider/token just to get it to compile.

You can however also resolve NG2007 using the @Directive decorator instead, which doesn't require DI compatibility

Answer 4

Look it: Missing @Directive()/@Component() decorator migration

Before:

export class BaseComponent {
    @Input() TeamName: string;
    @Input() teamSize: number;
    @Input() players: any;
}

Afert:

@Directive()
export class BaseComponent {
    @Input() TeamName: string;
    @Input() teamSize: number;
    @Input() players: any;
}

Answer 5

If you are experiencing this in Angular 15, use an exact version of TypeScript. 4.8.2 worked for me.

npm i typescript@4.8.2 -D --save-exact

Answer 6

I had a similar situation when running ng serve . I was getting that error for 3rd party libraries and for all my Angular components even though they were decorated.

If you're having this problem, see this answer for Angular 11 'error NG2007: Class is using Angular features but is not decorated.' But the class is Decorated

Answer 7

For These errors: NG6001: The class 'XComponent' is listed in the declarations of the NgModule 'AppModule', but is not a directive, a component, or a pipe. Either remove it from the NgModule's declarations, or add an appropriate Angular decorator.

NG2003: No suitable injection token for parameter 'A' of class 'Y'.

NG2007: Class is using Angular features but is not decorated. Please add an explicit Angular decorator.

You may be writing the new class between @Component declaration and Component class.

ex.

// export class Y{ // }

@Component({
  selector: 'app-X',
  templateUrl: './X.component.html',
  styleUrls: ['./X.component.css']
})



export class XComponent implements OnInit {

todos : Y[]  = [
  new Y(1 ),
  new Y(2 ),
  new Y(3 )
]
  
  constructor() { }

  ngOnInit(): void {
  }

}

//export class Y{ //}

ie if you have more than one class. let say class XComponent and Class Y, where class Y is being used in class XComponent, then write code for class Y either above @Component({}) or below class XComponent