Angular 4 Can't bind to <property> since it isn't a known property of <component>

Question

I'm trying to create my own directive in Angular 4. But, I got this error when bind the property of class into component template.

Console error:

Unhandled Promise rejection: Template parse errors: Can't bind to
'data' since it isn't a known property of 'tree'. ("<tree [ERROR
->][data]="data"></tree>"):

My tree-view-component.ts:

@Component({
    selector: 'app-tree-view',
    template: '<tree [data]="data"></tree>'
})
export class TreeViewComponent implements OnInit {

    @Input() data: any[];

    constructor() {
        this.data = [
        {
            label: 'a1',
            subs: [
                {
                    label: 'a11',
                    subs: [
                        {
                            label: 'a111',
                            subs: [
                                {
                                    label: 'a1111'
                                },
                                {
                                    label: 'a1112'
                                }
                            ]
                        },
                        {
                            label: 'a112'
                        }
                    ]
                },
                {
                    label: 'a12',
                }
            ]
         }
     ];
  }

  ngOnInit() { }

}

Here is my complete script file: https://pastebin.com/hDyX2Kjj

Is there anyone know about this? TiA

Answer 1

Every component, directive, and pipe needs to be registered in @NgModule()

@NgModule({
  declarations: [TreeViewComponent]
})
export class AppModule {}

For more details see

• https://angular.io/api/core/NgModule
• https://angular.io/guide/ngmodules
• https://angular.io/guide/ngmodule-api

Answer 2

I've the same error, when run test for ParentComponent. Inside was ChildComponent component with @Input property: string;. Both components were also declared inside app.module.ts.

I've fixed this like that (parent component test file):

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [ParentComponent, ChildComponent]// added child component declaration here
    })
      .compileComponents();
  }));

Answer 3

As The Aelfinn pointed out if you are using your Component across Modules you need to export it. BUT you should not import, export and declare it in the Module you want to use it, since its not part of this Module !!!
So suppose you have a TreeViewStuffModule which declares the TreeViewComponent and a DoSomethingWithTreeViewModule where the TreeViewComponent is used in, your declarations would be as follows:

@NgModule({
  declarations: [
    TreeViewComponent
  ],
  exports: [
    TreeViewComponent
  ]
})
export class TreeViewStuffModule { }

@NgModule({
  imports: [
    TreeViewStuffModule
  ]
})
export class DoSomethingWithTreeViewModule

Answer 4

If you are using TreeViewComponent in another module, you will need to import the component into the @NgModule as follows:

@NgModule({
    imports: [TreeViewComponent],
    // This says that all components in this module can import TreeViewComponent
    exports: [ThisModulesComponents],
    declarations: [ThisModulesComponents]
})
export class ModuleDependentOnTreeViewComponent