Learn more about routing in Angular and how to get started quickly?

This article will give you an in-depth understanding of routing in Angular, look at how to get started quickly, and introduce matching rules, routing parameters, routing nesting, routing guards, etc. I hope it will be useful to everyone. Helped!

In Angular, routing is based on modules, and each module can have its own route. [Related tutorial recommendations: "angular tutorial"]

Get started quickly

Create page components, Layout components andNavigation Component, used for routing

• CreateHomepagePage componentng g c pages/home

• CreateAbout usPage componentsng g c pages/about

• ##Create

  LayoutComponentng g c pages/layout

• Create

  NavigationComponentng g c pages/navigation

Create routing rules

// app.module.ts
import { Routes } from "@angular/router"

const routes: Routes = [
  {
    path: "home",
    component: HomeComponent
  },
  {
    path: "about",
    component: AboutComponent
  }
]

Introduce the routing module and start it

// app.module.ts
import { RouterModule, Routes } from "@angular/router"

@NgModule({
  imports: [RouterModule.forRoot(routes, { useHash: true })],
})
export class AppModule {}

Add routing socket

<!-- 路由插座即占位组件 匹配到的路由组件将会显示在这个地方 -->
<router-outlet></router-outlet>

Define links in the navigation component

<a routerLink="/home">首页</a>
<a routerLink="/about">关于我们</a>

Match Rule

1, Redirect

const routes: Routes = [
  {
    path: "home",
    component: HomeComponent
  },
  {
    path: "about",
    component: AboutComponent
  },
  {
    path: "",
    // 重定向
    redirectTo: "home",
    // 完全匹配
    pathMatch: "full"
  }
]

2,404<span style="font-size: 16px;"></span> Page

const routes: Routes = [
  {
    path: "home",
    component: HomeComponent
  },
  {
    path: "**",
    component: NotFoundComponent
  }
]

Route parameters

1. Query parameters

<a routerLink="/about" [queryParams]="{ name: &#39;kitty&#39; }">关于我们</a>

import { ActivatedRoute } from "@angular/router"

export class AboutComponent implements OnInit {
  constructor(private route: ActivatedRoute) {}

  ngOnInit(): void {
    this.route.queryParamMap.subscribe(query => {
      query.get("name")
    })
  }
}

2. Dynamic parameters

const routes: Routes = [
  {
    path: "home",
    component: HomeComponent
  },
  {
    path: "about/:name",
    component: AboutComponent
  }
]

<a [routerLink]="[&#39;/about&#39;, &#39;zhangsan&#39;]">关于我们</a>

import { ActivatedRoute } from "@angular/router"

export class AboutComponent implements OnInit {
  constructor(private route: ActivatedRoute) {}

  ngOnInit(): void {
    this.route.paramMap.subscribe(params => {
      params.get("name")
    })
  }
}

Routing nesting

Routing nesting refers to how to define sub- Level routing

const routes: Routes = [
  {
    path: "about",
    component: AboutComponent,
    children: [
      {
        path: "introduce",
        component: IntroduceComponent
      },
      {
        path: "history",
        component: HistoryComponent
      }
    ]
  }
]

<!-- about.component.html -->
<app-layout>
  <p>about works!</p>
  <a routerLink="/about/introduce">公司简介</a>
  <a routerLink="/about/history">发展历史</a>
  <div>
    <router-outlet></router-outlet>
  </div>
</app-layout>

Named outlets

Display child routing components into different routing outlets

{
  path: "about",
  component: AboutComponent,
  children: [
    {
      path: "introduce",
      component: IntroduceComponent,
      outlet: "left"
    },
    {
      path: "history",
      component: HistoryComponent,
      outlet: "right"
    }
  ]
}

<!-- about.component.html -->
<app-layout>
  <p>about works!</p>
  <router-outlet name="left"></router-outlet>
  <router-outlet name="right"></router-outlet>
</app-layout>

<a
    [routerLink]="[
      &#39;/about&#39;,
      {
        outlets: {
          left: [&#39;introduce&#39;],
          right: [&#39;history&#39;]
        }
      }
    ]"
>关于我们</a>

Navigation routing

<!-- app.component.html -->
<button (click)="jump()">跳转到发展历史</button>

// app.component.ts
import { Router } from "@angular/router"

export class HomeComponent {
  constructor(private router: Router) {}
  jump() {
    this.router.navigate(["/about/history"], {
      queryParams: {
        name: "Kitty"
      }
    })
  }
}

Routing module

Abstract the routing configuration in the root module into a separate routing module, called the root routing module, and then introduce the root routing module into the root module

import { NgModule } from "@angular/core"

import { HomeComponent } from "./pages/home/home.component"
import { NotFoundComponent } from "./pages/not-found/not-found.component"

const routes: Routes = [
  {
    path: "",
    component: HomeComponent
  },
  {
    path: "**",
    component: NotFoundComponent
  }
]

@NgModule({
  declarations: [],
  imports: [RouterModule.forRoot(routes, { useHash: true })],
  // 导出 Angular 路由功能模块，因为在根模块的根组件中使用了 RouterModule 模块中提供的路由插座组件
  exports: [RouterModule]
})
export class AppRoutingModule {}

import { BrowserModule } from "@angular/platform-browser"
import { NgModule } from "@angular/core"
import { AppComponent } from "./app.component"
import { AppRoutingModule } from "./app-routing.module"

@NgModule({
  declarations: [AppComponent],
  imports: [BrowserModule, AppRoutingModule],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule {}

Routing lazy loading

Routing lazy loading is based on modules.

• Create user module

  ng g m user --routing=true and create the routing module of this module

• Create login Page component

  ng g c user/pages/login

• Create registration page component

  ng g c user/pages/register

• Configure the routing rules of the user module

import { NgModule } from "@angular/core"
import { Routes, RouterModule } from "@angular/router"
import { LoginComponent } from "./pages/login/login.component"
import { RegisterComponent } from "./pages/register/register.component"

const routes: Routes = [
  {
    path: "login",
    component: LoginComponent
  },
  {
    path: "register",
    component: RegisterComponent
  }
]

@NgModule({
  imports: [RouterModule.forChild(routes)],
  exports: [RouterModule]
})
export class UserRoutingModule {}

• Associate the user routing module to the main routing module

  // app-routing.module.ts
  const routes: Routes = [
    {
      path: "user",
      loadChildren: () => import("./user/user.module").then(m => m.UserModule)
    }
  ]

• Add an access link in the navigation component

  <a routerLink="/user/login">登录</a>
  <a routerLink="/user/register">注册</a>

Route guard

The route guard will tell the route whether navigation to the requested route is allowed.

The route guard method can return

boolean or Observable \ or Promise \, they At some point in the future resolves to a Boolean value

1, CanActivate<span style="font-size: 16px;"></span>

Check whether the user can access a certain route.

CanActivate is an interface, and the route guard class must implement this interface. This interface stipulates that the class needs to have a canActivate method, which determines whether to allow access to the target route.

Routes can apply multiple guards. Only if all guard methods are allowed, the route is allowed to be accessed. If one guard method is not allowed, the route is not allowed to be accessed.

Create routing guards:

ng guard guards/auth

import { Injectable } from "@angular/core"
import { CanActivate, ActivatedRouteSnapshot, RouterStateSnapshot, UrlTree, Router } from "@angular/router"
import { Observable } from "rxjs"

@Injectable({
  providedIn: "root"
})
export class AuthGuard implements CanActivate {
  constructor(private router: Router) {}
  canActivate(): boolean | UrlTree {
    // 用于实现跳转
    return this.router.createUrlTree(["/user/login"])
    // 禁止访问目标路由
    return false
    // 允许访问目标路由
    return true
  }
}

{
  path: "about",
  component: AboutComponent,
  canActivate: [AuthGuard]
}

2、CanActivateChild<span style="font-size: 16px;"> </span>

Check whether the user can access a certain sub-route.

Create routing guards:

ng g guard guards/admin

Note: To select

CanActivateChild, you need to move the arrow to this option and Hit space to confirm selection

import { Injectable } from "@angular/core"
import { CanActivateChild, ActivatedRouteSnapshot, RouterStateSnapshot, UrlTree } from "@angular/router"
import { Observable } from "rxjs"

@Injectable({
  providedIn: "root"
})
export class AdminGuard implements CanActivateChild {
  canActivateChild(): boolean | UrlTree {
    return true
  }
}

{
  path: "about",
  component: AboutComponent,
  canActivateChild: [AdminGuard],
  children: [
    {
      path: "introduce",
      component: IntroduceComponent
    }
  ]
}

3,CanDeactivate<span style="font-size: 16px;"></span>

Check User Whether it is possible to exit routing. For example, the content entered by the user in the form is not saved, and the user wants to leave the route. At this time, the guard can be called to prompt the user

import { Injectable } from "@angular/core"
import {
  CanDeactivate,
  ActivatedRouteSnapshot,
  RouterStateSnapshot,
  UrlTree
} from "@angular/router"
import { Observable } from "rxjs"

export interface CanComponentLeave {
  canLeave: () => boolean
}

@Injectable({
  providedIn: "root"
})
export class UnsaveGuard implements CanDeactivate<CanComponentLeave> {
  canDeactivate(component: CanComponentLeave): boolean {
    if (component.canLeave()) {
      return true
    }
    return false
  }
}

{
  path: "",
  component: HomeComponent,
  canDeactivate: [UnsaveGuard]
}

import { CanComponentLeave } from "src/app/guards/unsave.guard"

export class HomeComponent implements CanComponentLeave {
  myForm: FormGroup = new FormGroup({
    username: new FormControl()
  })
  canLeave(): boolean {
    if (this.myForm.dirty) {
      if (window.confirm("有数据未保存, 确定要离开吗")) {
        return true
      } else {
        return false
      }
    }
    return true
  }

4, Resolve <span style="font-size: 16px;"></span>

Allow data to be obtained before entering routing, and then enter routing after data acquisition is completed

$ ng g resolver <name>

import { Injectable } from "@angular/core"
import { Resolve } from "@angular/router"

type returnType = Promise<{ name: string }>

@Injectable({
  providedIn: "root"
})
export class ResolveGuard implements Resolve<returnType> {
  resolve(): returnType {
    return new Promise(function (resolve) {
      setTimeout(() => {
        resolve({ name: "张三" })
      }, 2000)
    })
  }
}

{
   path: "",
   component: HomeComponent,
   resolve: {
     user: ResolveGuard
   }
}

export class HomeComponent {
  constructor(private route: ActivatedRoute) {}
  ngOnInit(): void {
    console.log(this.route.snapshot.data.user)
  }
}

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