Sharpening Your Angular Skills: Effective Component Sharing Between Modules

• Angular applications are organized into modules (NgModules) for better code management and reusability.
• An NgModule encapsulates components, directives, pipes, and services that work together for a specific feature or functionality.
• To use a component from one module in another, you need to establish a dependency between the modules.

Steps:

1. Export the Component:

   • In the module where the component is declared (source module), modify its @NgModule decorator to include the component in the exports array.
   • This makes the component publicly available for other modules to import and use.

   // source.module.ts
   import { NgModule } from '@angular/core';
   import { MyComponent } from './my.component'; // Import the component
   
   @NgModule({
     declarations: [MyComponent], // Declare the component in the module
     exports: [MyComponent] // Export the component to make it available to other modules
   })
   export class SourceModule {}
   

2. Import the Module:

   • In the module where you want to use the component (target module), import the source module using the imports array in the @NgModule decorator.
   • This gives the target module access to the exported components, directives, pipes, and services from the source module.

   // target.module.ts
   import { NgModule } from '@angular/core';
   import { MyComponent } from './my.component'; // Incorrect (don't import component directly)
   import { SourceModule } from './source.module'; // Import the source module
   
   @NgModule({
     imports: [SourceModule] // Import the source module
   })
   export class TargetModule {}
   

3. Use the Component in Templates:

   • Now you can use the exported component from the source module in the templates of the target module's components.
   • Simply reference the component's selector tag in the target component's template, just like you would use any built-in Angular component.

   // target.component.ts
   import { Component } from '@angular/core';
   
   @Component({
     selector: 'app-target',
     template: `
       <app-my></app-my> `
   })
   export class TargetComponent {}
   

Key Points:

• This approach promotes code organization, reusability, and separation of concerns.
• You can export multiple components from a single source module.
• For larger applications, consider creating a dedicated shared module to hold commonly used components, directives, and pipes, and import it into modules that need them.

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common'; // Import for common directives like NgIf

// Import the component you want to share
import { UserCardComponent } from './user-card.component';

@NgModule({
  declarations: [UserCardComponent],
  exports: [UserCardComponent, CommonModule], // Export the component and CommonModule
  imports: [CommonModule] // Import CommonModule for directives used in UserCardComponent
})
export class SourceModule { }

Explanation:

• We import CommonModule from @angular/common because it provides common directives that our UserCardComponent might use (like NgIf).
• We declare UserCardComponent in the declarations array.
• We crucially export UserCardComponent and CommonModule in the exports array. Exporting CommonModule ensures that any module importing SourceModule has access to common directives without needing a separate import.

Target Module (target.module.ts):

import { NgModule } from '@angular/core';
import { AppComponent } from './app.component';

// Import the source module
import { SourceModule } from './source.module';

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

• We import SourceModule in the imports array. This gives our AppModule access to the exported components, directives, and pipes from SourceModule.

Target Component Template (app.component.html):

<div>
  <app-user-card (userClicked)="onUserClicked($event)"></app-user-card>
</div>

• We use the selector tag <app-user-card> in the target component's template to reference the UserCardComponent from the source module.
• We can even bind to events and properties of the component as usual (e.g., (userClicked)='onUserClicked($event)').

• In the target module, directly import the component from the source module in the declarations array of the @NgModule decorator.

// target.module.ts (Not recommended)
import { NgModule } from '@angular/core';
import { MyComponent } from '../source.module'; // Incorrect import

@NgModule({
  declarations: [MyComponent],
  imports: [] // No need to import SourceModule here (incorrect)
  // ...
})
export class TargetModule {}

Caveats:

• This approach tightly couples the target module to the source module, making the code less modular and reusable.
• It can lead to circular dependencies if both modules try to import from each other.
• The component won't have access to any directives, pipes, or services from the source module unless they are explicitly imported in the target module as well.

Lazy Loading with Remote Entry (Advanced):

• This technique involves splitting your application into smaller, independent modules that can be loaded on demand.
• Remote Entry allows you to load components from a separate Angular application.

• This approach is more complex to set up and requires a deeper understanding of Angular's build system and lazy loading mechanisms.
• It's generally used for micro-frontends or large applications with many features that don't need to be loaded all at once.

Recommendation:

• In most cases, creating a shared module is the preferred approach for sharing components across modules in Angular. It promotes code organization, reusability, and separation of concerns.
• Use direct component import only if you have a very specific reason for doing so, and be aware of the potential downsides.
• Consider lazy loading with remote entry for advanced scenarios where micro-frontends or on-demand loading are necessary.