The Dilemma of using forRoot() in Angular 2/4+ Shared Modules

After uncovering the treasure that is forRoot() while delving deeper into Angular dependency injection (DI), I find myself pondering on the best practices for its usage.

I came across this method when trying to enable a lazy loaded module to access a service from the root context, allowing data to be shared between two modules, both of which could potentially be lazy loaded. This led me to question whether forRoot() could be used for all dependencies in a shared module, reducing the need for multiple import statements throughout an application. What are the potential drawbacks? Are there specific use cases where forRoot() works well, and others where it might not be appropriate? Is forRoot() primarily meant to address DI context issues when dealing with lazy loaded modules?

angulartypescriptrxjsangular-servicesangular-module

Answer №1

The main objective of utilizing the forRoot() method is to establish singleton services across the entire application.

In essence, by employing the forRoot() function, it ensures that there is only a single instance of the particular service that was exported by the corresponding ModuleWithProviders. Without incorporating the forRoot(), multiple instances of the same service may be created within different sections of the application when using the module in various areas. However, with the inclusion of forRoot(), a new instance of the service will be generated if no previous instance is detected anywhere within the application.

Answer №2

The concept of using a static method like forRoot is commonly seen as a way to set up the providers for a module.

Take, for instance, RouterModule.forRoot: By passing the routes to the forRoot method, you are essentially configuring the app-wide Router service with these routes.

Consider creating a SharedModule that contains components, directives, and pipes used throughout your application.

Keep in mind that the SharedModule should not contain providers for various reasons, as explained here. Additionally, any modules imported or re-exported by the SharedModule should also avoid providing services. It's important to understand why you might deviate from this guideline if you choose to do so.

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