AngularJS Modules
In Angular, an AngularJS Modules is a mechanism for organizing and structuring an application into cohesive blocks of functionality. Angular applications are typically organized into a tree of modules, where each module corresponds to a different feature or aspect of the application.
Angular modules are defined using the @NgModule decorator. The @NgModule decorator takes a metadata object that specifies various details about the module, such as its declarations, imports, providers, and bootstrap components. Here’s a basic example of an Angular module:
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import { NgModule } from ‘@angular/core’;
import { BrowserModule } from ‘@angular/platform-browser’;
import { AppComponent } from ‘./app.component’;
@NgModule({
declarations: [
AppComponent
// Other components, directives, or pipes used in this module
],
imports: [
BrowserModule
// Other modules that this module depends on
],
providers: [
// Services or other providers that this module provides
],
bootstrap: [AppComponent]
// The main component(s) that should be bootstrapped when this module is loaded })
export class AppModule { }
Let’s break down the key properties of the @NgModule decorator:
declarations: This property is an array of the components, directives, and pipes that belong to this module.
imports: This property is an array of other modules that this module depends on. In the example, BrowserModule is imported, which is required for browser-specific features.
providers: This property is an array of services or other providers that this module makes available to other parts of the application.
bootstrap: This property specifies the main component(s) that should be bootstrapped when this module is loaded. The AppComponent is often specified here, and it represents the root component of the application.
Once you have defined a module, you can use it in other parts of your application by importing it into the modules that depend on it. Modules help to organize and modularize your Angular application, making it easier to manage and scale.
Feature Modules: Angular applications are often organized into feature modules, where each module corresponds to a specific feature or a set of related features. This helps in modularizing the application and managing its complexity.
Shared Modules: You can create shared modules to encapsulate common components, directives, and services that can be reused across multiple feature modules. This promotes code reusability and maintainability.
Lazy Loading: Angular allows for lazy loading of modules, which means that modules are loaded on demand as the user navigates through the application. This can significantly improve the initial loading time of the application.
RouterModule: The RouterModule is a special module provided by Angular for handling routing in applications. It provides directives and services for configuring navigation between different views or components.
NgModule Lifecycle Hooks: Modules have a lifecycle, and Angular provides lifecycle hooks that allow you to execute logic at specific points in the module’s lifecycle. For example, you can use ngOnInit to perform initialization logic when the module is created.
Entry Components: In addition to the components specified in the bootstrap property, a module can have entry components. Entry components are components that are not referenced in the template of other components but are created dynamically using the ComponentFactoryResolver.
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Providers and Dependency Injection: Modules are also used to configure the dependency injection system in Angular. The provider’s array in the @NgModule decorator is used to register services and other providers at the module level.
NgModule Metadata: The metadata provided in the @NgModule decorator is crucial for configuring various aspects of the module. This includes setting up the components, importing other modules, providing services, and specifying bootstrap components.
NgModule Best Practices: It’s recommended to keep modules small, focused, and cohesive. Avoid putting everything into a single module. Consider the separation of concerns and create modules that encapsulate specific functionalities.
NgModule for Testing: Angular modules can be configured differently for testing purposes. You can create separate testing modules or override providers during the testing setup to isolate and control dependencies.
.
Feature Modules and Core Module: It’s a common practice to have a Core Module in addition to feature modules. The Core Module contains services, components, and other artifacts that are shared throughout the application. Feature modules then import the Core Module to access these shared resources.
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Module forRoot() Method: When creating a feature module that provides a service that needs configuration, you might use a static method conventionally named forRoot() to allow configuration of the module. This is often seen in modules related to routing and services.
@NgModule({
imports: [RouterModule.forRoot(routes)],
exports: [RouterModule],
})
export class AppRoutingModule { }
NgModules and NgModules with NgModules: Angular libraries are often distributed as NgModules. These NgModules can have their own components, directives, and services encapsulated within them. When you import a library module, you can use its exported components and services in your application
Module Imports Order: The order of imports in the imports array can be important. Modules are executed in the order they are listed. This can impact the availability of services and other resources.
Module Entry Components: While entryComponents used to be required for components created dynamically (like in a modal), as of Angular 9, this property is mostly deprecated, and Angular can usually detect entry components automatically.
Do watch our Components Of Angular video on YouTube.
NgModule and Angular CLI: When generating components, services, or other artifacts using Angular CLI, the CLI automatically adds the necessary import statements to the module files.
Author:-
Pooja Ghodekar
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