我正在使用@Input和@Output装饰器在Angular 6项目中工作。我将Bookride Component作为父组件,将RideDetails作为子组件。我可以使用@Input装饰器成功地将数据从我的父组件传递到子组件,但是当我尝试将数据从子组件传递到父组件时,我在控制台中收到以下错误
“ERROR TypeError:无法读取未定义的属性'seatavailable'
BookRide组件 - HTML(父组件)
<tr *ngFor = "let book of shrides | filterpipe:filterargs" (click) = "message = book">
<td>{{book.startloc}}</td>
<td>{{book.destination}}</td>
<td>{{book.seatsavailable}}</td>
<td (click)="deleteProduct(book.id)"><a>DELETE</a></td>
<td [routerLink] = "['/update-ride', book.id]" (click) = "update(book.id)"><a>UPDATE</a></td>
<app-ridedetails [cName] = "message" (onRegister)="courseReg($event)"></app-ridedetails>
在控制台中,错误在上面的行中显示为“ERROR TypeError:无法读取属性'seatavailable'的未定义的RestserviceService.push ../ src / app / restservice.service.ts.RestserviceService.updateRide2(restservice.service.ts: 84)”
BookRide组件 - TS
export class RidedetailsComponent implements OnInit {
seatsavailable: number;
courseReg(seatsavailable: number){
console.log("Booking ID", seatsavailable);
this.messages = `Booking Done. Your Booking name is : ${seatsavailable}`;
this.render = !this.render;
}}
RideDetails组件 - HTML(子组件)
<tr>
<td>{{loadData?.id}}</td>
<td>{{loadData?.name}}</td>
<td>{{loadData?.car}}</td>
<td>{{loadData?.seatsavailable}}</td>
<td>{{loadData?.startloc}}</td>
<td>{{loadData?.destination}}</td>
</tr>
<button type="button" (click)="register(loadData.id, loadData.seatsavailable)" [ngClass] = "render ? 'btn-primary' : 'btn-danger'"> {{render == true ? 'Book!' : 'Cancel! Booked ride'}} </button>
RideDetails组件 - TS
export class RidedetailsComponent implements OnInit {
loadData:any;
sendData: any;
messages: any;
render: boolean = true;
seatsavailable: number;
ride: Ride[];
constructor(private restservice : RestserviceService) { }
ngOnInit() {
}
@Input() set cName(sampleObject){
this.loadData=sampleObject;
}
//Child to Parent Communication
//Sending an event to BookrideComponent and hide the table using @Output Decorator
@Output() onRegister = new EventEmitter();
register(bookingID: string, seatsavailable: number, ride: Ride) {
this.render = !this.render;
this.onRegister.emit({seatsavailable} as Ride);
this.messages = `Booking Done(ridedetails). Your Booking id: ${bookingID}`;
console.log("After clicking on Book button, the seats available data in ride details component is", this.loadData.seatsavailable);
// console.log("seats avaiable in ride details component", this.loadData.seatsavailable);
if(this.loadData.seatsavailable === seatsavailable){
console.log("this.loadData.seatsavailable", this.loadData.seatsavailable - 1);
this.restservice.updateRide2(ride, seatsavailable).subscribe( shride => { this.loadData.seatsavailable - 1 });
}
}
}
我从RideDetails组件中理解的是,我创建了一个名为onRegister的属性EventEmitter并附加了@Output装饰器,该属性使属性可以将数据从子组件发送到父组件。稍后在register()内部,它会将seatavailable值发送回父组件。所以一旦它到达父组件,它就会以错误结束。
同样在BookRide组件的courseReg()中,它将您的预订名称呈现为控制台:[object Object]
一切似乎都是正确的,但我的代码有一些变化 - 我不确定它会起作用,但你可以尝试
this.onRegister.emit(seatsavailable);
如果你只是将seatsavailable
从孩子发送到父母只是传递它将作为一个对象传递的值。
最后当你读到你的价值时,你可以这样读 -
courseReg(event: any){
console.log("Booking ID", event.seatsavailable);
this.messages = `Booking Done. Your Booking name is : ${event.seatsavailable}`;
this.render = !this.render;
}}
我相信这可行,请尝试谢谢快乐编码!!
此错误通常是由于在加载路由之前未解析对象。因此,我们使用存在/安全运算符book?
(存在 - 它'存在')。如果错误是由此引起的,那么最佳方法(除非您使用加载微调器)是使用Angular解析器,它在加载路径之前解析组件中的数据。
如果您不熟悉,这里有一篇关于解析器的精彩文章:https://codeburst.io/understanding-resolvers-in-angular-736e9db71267
因此,您的数据将在其解析的路径之前在组件中可用,您不需要使用?
来检查数据是否存在。