@Input和其他装饰器和继承

Question

我真的不明白对象绑定是如何工作的,所以如果有人能解释我是否可以在基类中使用@Input(),或者更好:装饰器和继承.例如,如果每个表单都应该接收一个客户,我有一个基类:

export class AbstractCustomerForm{

@Input() customer;
...
}

然后我在实际组件中扩展此类:

export AwesomeCustomerForm extends AbstractCustomerForm implements OnInit{
    ngOnInit(){

        if(this.customer)
            doSomething();

    }
}

但这不起作用,客户永远不会被设置:(

Answer 1

更新

自2.3.0-rc.0起,正确支持继承

原版的

装饰器不是继承的.它们需要直接应用于用作组件的类.子类上的装饰器将被忽略.我已经看到它提到@Input()或者@Output()正在工作,如果只有超类有它们而子类没有.

• https://github.com/angular/angular/issues/5794
• https://github.com/angular/angular/issues/5415
• https://github.com/angular/angular/issues/7191

Answer 2

我遵循的一个策略是这样的:

@Component({
    selector: 'my-component',
    template: `......`,
    inputs: MyAbstractComponent.genericInputs
})
export class MyComponent extends MyAbstractComponent {

    @Input() width: number = 200;
    ........
}

哪里:

export abstract class MyAbstractComponent {
    public static genericInputs : string[] = ['base'];
    public base: String;
}

因此,为MyComponent会得到base以及width绑定.事实上,我认为使用反思仍有改进的空间.

Answer 3

即使在 Angular 4.2.4 中，它在开发模式下也能正常工作。但是在进行 prod build ( ng build -prod) 时它失败了：

ERROR in Template parse errors:
Can't bind to 'step' since it isn't a known property of 'app-textarea-step'.
1. If 'app-textarea-step' is an Angular component and it has 'step' input, 
then verify that it is part of this module.
2. If 'app-textarea-step' is a Web Component then add 
'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to 
suppress this message.

我的组件看起来像：

abstract class StepComponent {
  @Input() step: BaseStep;
  @Output() next = new EventEmitter<string>();
  @Output() answer = new EventEmitter<Answer>();
}

abstract class SingleNextStepComponent extends StepComponent {

  onSubmit(answer: string) {
    // ConfirmStep heeft geen answer.
    if (answer) {
      this.answer.emit({ question: this.step.key, value: answer });
    }
    const step = this.step as SingleNextStep;
    this.next.emit(step.next);
  }
}

// Decorator inheritance works in standard build (ng build) but fails in production build (ng build -prod)
// Workaround: inputs element on @Component that contains the inputs.....
@Component({
  selector: 'app-textbox-step',
  templateUrl: './textbox-step.component.html',
  inputs: ['step']
})
export class TextboxStepComponent extends SingleNextStepComponent { }

@Component({
  selector: 'app-textarea-step',
  templateUrl: './textarea-step.component.html',
})
export class TextareaStepComponent extends SingleNextStepComponent { }

幸运的是，该解决方法有效。添加到 TextBoxStepComponent 的输入防止了这个失败，进入下一个，尚未提供“输入”。

但是“ng build”无需在@Component 装饰器上输入即可正常工作...