Take your Angular components to the next level with Dynamic Injection: A hands-on Tutorial

Angular Dynamic Injection is a technique that enables a component to dynamically inject services or other components at runtime, based on certain conditions. This technique is useful when we don't know the exact dependencies of a component at the time of its creation, or when we need to swap out dependencies at runtime based on user input or other factors. In this tutorial, we'll explore how to use dynamic injection in an Angular application.

Advantages:

The advantages of dynamic injection in Angular are:

1. It allows for more flexibility in component creation and reuse.
2. It reduces the amount of code needed to create components with complex dependencies.
3. It enables conditional dependency injection based on runtime factors, such as user input or data from an API.
4. It allows for easier testing of components, as dependencies can be easily swapped out with mock objects.

Example:

Let's create an example where we use dynamic injection to create a component that displays a list of items. The items could be retrieved from an API, but we want to provide the option to display a default list if the API is unavailable.

To start, we'll create a new Angular project using the Angular CLI:

Next, we'll create a service that retrieves the list of items from an API:

In the item.service.ts file, we'll create a method that retrieves the list of items:

Now, let's create a component that displays the list of items:

In the item-list.component.ts file, we'll inject the ItemService and retrieve the list of items:

We can now use this component in our application, and it will retrieve the list of items from the API and display them. However, if the API is unavailable, the component will fail to load.

To provide a default list of items, we can create another component that generates a list of items at runtime:

In the default-item-list.component.ts file, we'll create a method that generates a list of items:

We can now modify the ItemListComponent to use dynamic injection, and inject either the ItemService or the DefaultItemListComponent at runtime, based on whether the API is available.

In the item-list.component.ts file, we'll modify the ngOnInit method to check whether the API is available:

In this modified version of ItemListComponent, we inject the ComponentFactoryResolver and ViewContainerRef, which allow us to dynamically create and insert a component at runtime.

In the ngOnInit method, we first attempt to retrieve the list of items from the API using the ItemService. If the API call is successful, we create a new instance of the ItemListComponent and pass in the retrieved list of items.

If the API call fails, we create a new instance of the DefaultItemListComponent, which displays a default list of items.

We can now use the ItemListComponent in our application, and it will display either the list of items retrieved from the API or a default list of items, depending on whether the API is available.

Conclusion:

In this tutorial, we learned how to use dynamic injection in an Angular application. We explored the advantages of dynamic injection and created an example that demonstrates how to use dynamic injection to create a component that displays a list of items. We used the ComponentFactoryResolver and ViewContainerRef to dynamically create and insert a component at runtime, based on whether the API is available. Dynamic injection is a powerful technique that allows for more flexibility in component creation and reuse, and can greatly simplify the code required to create components with complex dependencies.