我有一个组件员工,我正在尝试创建一个表单,为此我创建了“员工组件”,“员工服务”和“员工模型”
在employee.component.html我有下面的表格
<form #employeeform="ngForm" (ngSubmit)="onSubmit(employeeform)">
<input type="hidden" name="_id" [(ngModel)]="employeeservice.selectedEmployee._id" #_id="ngModel"/>
</form>
在employee.component.ts中,我有以下代码
import { Component, OnInit } from '@angular/core';
import { EmployeeService } from '../shared/employee.service';
@Component({
selector: 'app-employee',
templateUrl: './employee.component.html',
styleUrls: ['./employee.component.css'],
providers : [EmployeeService]
});
export class EmployeeComponent implements OnInit {
constructor(private employeeservice : EmployeeService) { }
ngOnInit() {
}
}
这是我在employee组件中导入的employee.service.ts文件
import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';
import { Employee } from './employee.model';
@Injectable({
providedIn: 'root'
})
export class EmployeeService {
selectedEmployee : Employee;
employees: Employee[];
constructor() { }
}
这是我在员工服务中导入的employee.model.ts
export class Employee {
_id: string;
name: string;
position : string;
office : string;
salary : number;
}
当我运行命令“ng serve”时,我在浏览器控制台中收到以下错误
EmployeeComponent.html:9 ERROR TypeError: Cannot read property '_id' of undefined
at Object.eval [as updateDirectives] (EmployeeComponent.html:9)
at Object.debugUpdateDirectives [as updateDirectives] (core.js:23911)
at checkAndUpdateView (core.js:23307)
at callViewAction (core.js:23548)
at execComponentViewsAction (core.js:23490)
at checkAndUpdateView (core.js:23313)
at callViewAction (core.js:23548)
at execComponentViewsAction (core.js:23490)
at checkAndUpdateView (core.js:23313)
我错过了表单需要的任何导入或错误。我是一个初学者,并试图学习角度。我已经google了解决方案,但我找不到任何相关的解决方案。请帮帮我
正如错误所说:你想要访问_id,但selectedEmployee
实际上从未被定义过。
你可以只在你的html元素上使用*ngIf
定义元素时显示元素,或者给它一个默认值,如selectedEmployee : Employee = {}
(相应地设置所需的任何变量)
我建议您在EmployeeComponent内部创建一个员工实例,每次打开组件时 - 从服务中检索它并以html代码为目标。就像是:
export class EmployeeComponent implements OnInit {
employee: Employee;
constructor(private employeeservice : EmployeeService) {
this.employee = employeeservice.getSelectedEmployee();
}
ngOnInit() {
}
}
后来在html:
<form #employeeform="ngForm" (ngSubmit)="onSubmit(employeeform)">
<input type="hidden" name="_id" [(ngModel)]="employee._id" #_id="ngModel"/>
</form>
或者用注射再次传递它。目前,问题是你的EmployeeComponent不能像你想要的那样(从html传递到服务变量),所以你得到了 - 未定义的错误。
最初,当加载组件时,employee.service
没有为selectedEmployee
设置值。 html被渲染,[(ngModel)]="employeeservice.selectedEmployee._id"
期望值为employeeservice.selectedEmployee._id
。但employeeservice.selectedEmployee
尚未初始化,因此错误。
如果你没有设置employeeservice.selectedEmployee._id
,我建议你使用默认的_id。
为此使用[(ngModel)]="employeeservice.selectedEmployee ? employeeservice.selectedEmployee._id : 0"