Guide on sending a value to index.html from a component in Angular 2

Question

Guide on sending a value to index.html from a component in Angular 2

In my angular2 project, the index.html file contains a header bar. The responsibility of logging in and displaying other content is handled by different components.

I need to display a logo in the header bar only when a user is logged in. To achieve this, I am setting a flag in app.component.ts to track the login status. How can I reference this flag in the index.html file?

<body>
    <div class="content-body">
        <header class="header">
            <div class="header-bar container">
                <div class="header-bar__main">
                    <div class="header-heading">
                        <h1 class="page-title">noHold Application</h1>
                    </div>
                </div>
                <a class="btn btn--small btn--icon ng-scope" title="Logout"><span class="icon-sign-out"></span></a> // this line should be displayed only if user logs in.
            </div>
        </header>
        <div class="content">
            <div class="content__main">
                <div class="container">
                    <app-root>Loading... </app-root>        
                </div>
            </div>
        </div>
    </div>

</body>

app.component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {

  static loggedIn = false;

  getLoggedIn() {
    return AppComponent.loggedIn;
  }

}

angular typescript

Answer 1

Answer №1

When working with Angular, it is considered a recommended practice to have a single bootstrap component (often the AppComponent, as in your particular case), while defining other components for different parts of your application (such as header, menus, page content, login status, etc.).

To implement this structure, you can update your app.component.html file by including child components using their respective selectors. For example:

app.component.html

<header></header>
<router-outlet></router-outlet>

The content of HeaderComponent will be displayed within the header tag/selector, while the content of other navigated components (e.g., AboutComponent) will be rendered using the router-outlet tag/selector.

header.component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'header',
  templateUrl: './header.component.html',
  styleUrls: ['./header.component.css']
})
export class HeaderComponent {
  public loggedIn = false;

  ...
}

header.component.html

<header class="header">
  <div class="header-bar container">
    <div class="header-bar__main">
      <div class="header-heading">
        <h1 class="page-title">noHold Application</h1>
      </div>
    </div>
    <div *ngIf="loggedIn">
      <a class="btn btn--small btn--icon ng-scope" title="Logout"><span class="icon-sign-out"></span></a>
    </div>
  </div>
</header>

I hope this information is beneficial for your project.

Answer 2

When working with Angular, it is considered a recommended practice to have a single bootstrap component (often the AppComponent, as in your particular case), while defining other components for different parts of your application (such as header, menus, page content, login status, etc.).

To implement this structure, you can update your app.component.html file by including child components using their respective selectors. For example:

app.component.html

<header></header>
<router-outlet></router-outlet>

The content of HeaderComponent will be displayed within the header tag/selector, while the content of other navigated components (e.g., AboutComponent) will be rendered using the router-outlet tag/selector.

header.component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'header',
  templateUrl: './header.component.html',
  styleUrls: ['./header.component.css']
})
export class HeaderComponent {
  public loggedIn = false;

  ...
}

header.component.html

<header class="header">
  <div class="header-bar container">
    <div class="header-bar__main">
      <div class="header-heading">
        <h1 class="page-title">noHold Application</h1>
      </div>
    </div>
    <div *ngIf="loggedIn">
      <a class="btn btn--small btn--icon ng-scope" title="Logout"><span class="icon-sign-out"></span></a>
    </div>
  </div>
</header>

I hope this information is beneficial for your project.

Answer 3

Answer №2

Ensure that your components are not tightly coupled. It is important for a component to not directly access properties of another component. There are various methods available to decouple components. One effective approach in your scenario could be to share common data between components.

Let's consider a simple implementation example. First, create a class representing the user:

class User {
  firstName: string;
  lastName: string;
  ...
}

Create another class that holds the session state of the user:

class Session {
  user: User;
  isLogged: boolean;

  login(user: User) {
    this.user = user;
    this.isLogged = true;
  }
}

Next, configure your application module to provide an instance of the Session class as a singleton:

@NgModule({
  ...
  providers: [
    ...
    { provide: 'session', useValue: new Session() },
    ...
  ],
  ...
})

Now, you can inject the session into all your components. For instance, in the login component, you can set the user when authentication occurs:

@Component({
  ...
})
class LoginComponent {
  constructor(private session: Session) {
  }

  private login() {
    let user = ....;  // Retrieve user from backend service...
    this.session.login(user);
  }
}

Additionally, you can utilize the session in your templates as well:

<div *ngIf="session.isLogged">
  <a class="btn btn--small btn--icon ng-scope" title="Logout"><span class="icon-sign-out"></span></a>
</div>

Answer 4

Ensure that your components are not tightly coupled. It is important for a component to not directly access properties of another component. There are various methods available to decouple components. One effective approach in your scenario could be to share common data between components.

Let's consider a simple implementation example. First, create a class representing the user:

class User {
  firstName: string;
  lastName: string;
  ...
}

Create another class that holds the session state of the user:

class Session {
  user: User;
  isLogged: boolean;

  login(user: User) {
    this.user = user;
    this.isLogged = true;
  }
}

Next, configure your application module to provide an instance of the Session class as a singleton:

@NgModule({
  ...
  providers: [
    ...
    { provide: 'session', useValue: new Session() },
    ...
  ],
  ...
})

Now, you can inject the session into all your components. For instance, in the login component, you can set the user when authentication occurs:

@Component({
  ...
})
class LoginComponent {
  constructor(private session: Session) {
  }

  private login() {
    let user = ....;  // Retrieve user from backend service...
    this.session.login(user);
  }
}

Additionally, you can utilize the session in your templates as well:

<div *ngIf="session.isLogged">
  <a class="btn btn--small btn--icon ng-scope" title="Logout"><span class="icon-sign-out"></span></a>
</div>

Guide on sending a value to index.html from a component in Angular 2

Answer №1

Answer №2

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