在router.navigate之后没有调用Angular 4 ngOnInit

Question

我有3个选项卡,其中一个选项卡显示一个包含员工列表的表.第一次加载时工作正常.ngOnInit使用http get从服务器获取数据.之后,当我点击添加新员工打开一个表单,该表单从用户那里获取输入,当点击该提交时,我调用一个调用http post服务的函数将该数据发布到我的服务器,在那里它插入记录然后在那之后它被重定向回员工组件,但是现在已经加载了该员工组件,除非我重新编译我的代码,否则我看不到我在表中插入的新记录.

employee.component.ts(加载员工表)

import { Component, OnInit, OnDestroy } from '@angular/core';
import { EmployeeService } from '../employee.service';
@Component({
  selector: 'app-employees',
  templateUrl: './employees.component.html',
  styleUrls: ['./employees.component.css']
})
export class EmployeesComponent implements OnInit {

public employeeObj:any[] = [{emp_id:'',empname:'',joindate:'',salary:''}] ;
constructor(private employeService:EmployeeService) { }

ngOnInit() {    
this.employeService.getEmployees().subscribe(res => this.employeeObj = res);
}

}

form.component.ts

import { Component, OnInit, OnDestroy } from '@angular/core';
import { FormGroup, FormControl } from '@angular/forms';
import { EmployeeService } from '../../employee.service';
import { Router } from '@angular/router';

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

})
export class FormComponent implements OnInit {
empform;

ngOnInit() { 
this.empform = new FormGroup({
    empname: new FormControl(""),
    joindate: new FormControl(""),
    salary: new FormControl("")
})
} 
constructor(private employeeService: EmployeeService, private router:Router) 
{ }

 onSubmit = function(user){
    this.employeeService.addEmployee(user)
    .subscribe(
        (response) => { this.router.navigate(['/employees']); }  
    );

}
}

employee.service.ts

import { Injectable } from '@angular/core';
import { Http, Response } from '@angular/http';
import 'rxjs/add/operator/map';
import 'rxjs/Rx';
@Injectable()
export class EmployeeService{
constructor(private http:Http){}
addEmployee(empform: any[]){
    return this.http.post('MY_API',empform);
}

getEmployees(){
    return 
this.http.get('MY_API').map((response:Response)=>response.json());
}
}

AppModule.ts

    import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';
import { ReactiveFormsModule } from '@angular/forms';

import { HttpModule } from '@angular/http';
import { RouterModule } from '@angular/router';
import { EmployeeService } from './employee.service';
import { AppComponent } from './app.component';
import { HeaderComponent } from './header/header.component';
import { NavComponent } from './nav/nav.component';
import { ContainerComponent } from './container/container.component';
import { DashboardComponent } from './dashboard/dashboard.component';
import { EmployeesComponent } from './employees/employees.component';
import { CompaniesComponent } from './companies/companies.component';
import { InternsComponent } from './interns/interns.component';
import { FormComponent } from './employees/form/form.component';
import { ComformComponent } from './companies/comform/comform.component';
import { InternformComponent } from './interns/internform/internform.component';

@NgModule({
  declarations: [
    AppComponent,
    HeaderComponent,
    NavComponent,
    ContainerComponent,
    DashboardComponent,
    EmployeesComponent,
    CompaniesComponent,
    InternsComponent,
    FormComponent,
    ComformComponent,
    InternformComponent
  ],
  imports: [    
    BrowserModule,
    FormsModule,
    ReactiveFormsModule,
    HttpModule,
    RouterModule.forRoot([
            {
                path:'dashboard',
                component:DashboardComponent
            },
            {
                path:'employees',
                component:EmployeesComponent
            },
            {
                path:'companies',
                component:CompaniesComponent
            },
            {
                path:'interns',
                component:InternsComponent
            },
            {
                path:'addemployee',
                component:FormComponent
            },
            {
                path:'comform',
                component:ComformComponent
            },
            {
                path:'internform',
                component:InternformComponent
            }       
      ])
  ],
  providers: [EmployeeService],
  bootstrap: [AppComponent]
})
export class AppModule { }

问题是我从ngOnInit调用我的API,它在第一次加载组件时完全加载.当我提交表单时,它会转到我的API,然后重定向回员工组件,但数据不会更新.

PS:我很抱歉这么小的帖子.我是这个网站的新手.

更新:

自从我发布这个帖子以来已经有一年多了,我看到很多人都从中受益或者可能没有受益.但是我想指出我已经理解了导致错误的原因,现在我将尝试让您理解解决方案.

这里适应的最重要的概念是角度生命周期钩.发生的是,我们在第一次加载组件时调用ngOnInit,这只会在角度应用程序被引导时触发一次.这类似于类构造函数,但它只触发一次.所以你不应该在这里进行任何与DOM相关的修改.你应该了解Angular Life Cycle Hook来解决这个问题.自从我过去8个月搬到Vuejs后,我没有工作的解决方案,但在一些空闲时间我会在这里发布更新.

Answer 1

请尝试router在employee组件中添加事件。这样，每当/employee路由url状态时，它将获取员工详细信息。

employee.ts组件

constructor(private employeeService: EmployeeService, private router:Router) 
{ }

ngOnInit() {    
  this.router.events.subscribe(
    (event: Event) => {
           if (event instanceof NavigationEnd) {
                this.employeService.getEmployees().subscribe(res => this.employeeObj = res);
           }
    });
}

Answer 2

作为一般规则，在路由时，角度路由器将尽可能重用组件的相同实例。

因此，例如，从/component/1to导航到/component/2url 映射到相同的组件（但具有不同的参数）将导致路由器在导航到 时实例化 Component 的实例/component/1，然后在导航时重新使用相同的实例到/component/2。根据您所描述的内容（ wherengOnInit只被调用一次），似乎这就是您遇到的情况。如果没有看到您的模板和路线配置，就很难确定。我知道您说您的 URL 正在从 更改/employees为/form，但这可能无关紧要，具体取决于您的模板和路由配置的设置方式。如果您愿意，您可以在此处发布该代码（您的模板和路由器配置）以供检查。

除此之外，另一种选择是路由器将其所有事件作为流公开。因此，您可以订阅该流并对其采取行动，而不仅仅是依赖ngOnInit.

在您的 employee.component.ts 中

.....
export class EmployeesComponent implements OnInit {

.....

ngOnInit() {


   this.router.events
              // every navigation is composed of several events,
              // NavigationStart, checks for guards etc
              // we don't want to act on all these intermediate events,
              // we just care about the navigation as a whole,
              // so only focus on the NavigationEnd event
              // which is only fired once per router navigation
              .filter(e => e instanceof NavigationEnd)
              // after each navigation, we want to convert that event to a call to our API
              // which is also an Observable
              // use switchMap (or mergeMap) when you want to take events from one observable
              // and map each event to another observable 
              .switchMap(e => this.employeeService.getEmployees())
              .subscribe(res => this.employeeObj = res);    
}

编辑

我看到一段奇怪的代码：

import { Component, OnInit, OnDestroy } from '@angular/core';
import { FormGroup, FormControl } from '@angular/forms';
import { EmployeeService } from '../../employee.service';
import { Router } from '@angular/router';

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

})
export class FormComponent implements OnInit {
  empform;

  ngOnInit() { 
    this.empform = new FormGroup({
      empname: new FormControl(""),
      joindate: new FormControl(""),
      salary: new FormControl("")
    })
  } 

  constructor(private employeeService: EmployeeService, private router:Router) { }

 onSubmit(user){   // <--  change this line
    this.employeeService.addEmployee(user)
    .subscribe(
        (response) => { this.router.navigate(['/employees']); }  
    );

  }
}

但总的来说，您是说如果您导航到您的员工组件，然后导航到您的表单组件，然后返回您的员工组件，当您第二次点击员工组件时，您的员工列表不会刷新。

您可以使用console.log语句来确保ngOnInit在上面的屏幕流中多次调用吗？因为，根据您的路由器配置，当您导航到员工列表以形成并返回时，您的员工组件应该重新初始化（通过ngOnInit再次调用）