Angular Lifecycle & ngrx Store: A Deep Dive into Architecture

Introduction:

Angular, one of the most popular front-end frameworks, provides a powerful mechanism for managing applications in a clean and structured way. In this article, we will break down the Angular lifecycle, its architecture, and best practices using the latest version of Angular. We will explain how the view model, components, lifecycle hooks, and the ngrx store work together to manage state and facilitate seamless user interaction.

Section 1: Understanding the Angular Architecture

Angular's architecture is designed to promote modularity, scalability, and maintainability. The architecture revolves around several key components:

• View (HTML): This is the UI part of the application, where the user interacts with the app.
• ViewModel: The view model is responsible for binding the data to the view and handling the business logic. It is connected to the component class, which has properties and methods for the application logic.
• Component Lifecycle: Each component in Angular follows a well-defined lifecycle with hooks that control its initialization, updates, and destruction.
• ngrx Store: The ngrx store is a state management solution for Angular applications. It enables a predictable state container for managing application state in a reactive way.

Section 2: Lifecycle Hooks in Angular

Angular provides several lifecycle hooks that allow developers to run specific code at different stages in a component’s lifecycle. These hooks allow you to respond to changes in the component, its inputs, and its view. Here are the most common lifecycle hooks:

1. ngOnInit: Called once, right after the component’s inputs are initialized. It's a great place for initialization logic.
2. ngOnChanges: Called whenever any of the input properties change. This is useful for responding to changes in bound input properties.
3. ngDoCheck: Called during every change detection cycle. This allows for custom change detection.
4. ngAfterViewInit: Called after the component’s view is initialized. Ideal for logic that requires a fully rendered view.
5. ngAfterViewChecked: Called after the view has been checked by Angular’s change detection.
6. ngOnDestroy: Called just before Angular destroys the component. Perfect for cleanup logic, such as unsubscribing from observables.

Section 3: How the ngrx Store Fits Into the Architecture

ngrx is a powerful state management library for Angular applications, built on the principles of Redux. It works by using a single state container that can be accessed and updated through actions, reducers, and effects. This process involves:

• Actions: Actions represent the intention to change the state.
• Reducers: Reducers define how the state should change based on actions.
• Effects: Effects handle side-effects, such as API calls, and dispatch actions to update the state.

The ngrx store works by dispatching actions, which are handled by reducers to update the state. Components then subscribe to the store and automatically update the view whenever the state changes.

Section 4: Best Practices for Angular and ngrx

• Use Lazy Loading: In large Angular applications, lazy loading helps to load modules only when needed, improving the performance.
• Keep State Immutable: Always treat the state as immutable. This helps in tracking changes and ensures that the state doesn’t accidentally change outside the store.
• Use Selectors: Use selectors to query the state from the store. This helps to keep the components clean and free from direct logic that interacts with the state.
• Avoid Direct Service Injection in Components: If you are using ngrx, you don’t need to inject services directly into components. Instead, use the store to manage state, and the component will automatically subscribe to changes.

Section 5: Event Binding and Property Binding in Angular

Event binding and property binding are two essential features in Angular for handling user interactions and updating the view:

• Event Binding: This allows you to bind user events, such as clicks or input changes, to component methods. For example, when a user clicks a button, an event binding triggers the corresponding method in the component.
• Property Binding: This allows you to bind a property of an element (like an image source or class) to a component property. Whenever the component property changes, the view is updated.

When you use ngrx, the state of the application is managed globally and changes in the state can automatically trigger updates in the view. This is an advantage over direct service injection in components, as the state management becomes predictable and decoupled from individual components.

Section 6: Injecting Services vs. Using ngrx Store

In Angular, there are two primary ways to handle data in a component: using services or using the ngrx store. If you’re not using ngrx, you typically inject services directly into components to manage state and perform API calls. For example:

constructor(private userService: UserService) { }        

However, when you adopt ngrx for state management, you no longer need to inject the service directly into the component. Instead, you interact with the store, which encapsulates the state and dispatches actions. The component subscribes to the store and automatically updates when the state changes.

Conclusion

Angular’s lifecycle, components, and state management with ngrx provide a robust architecture for building modern, reactive applications. By using lifecycle hooks, event binding, and the ngrx store, you can ensure that your Angular applications are clean, maintainable, and efficient.