Welcome to the tutorial on using the provideIn root
, any
, and platform
options in Angular!
In this tutorial, we will recall quickly the different ways to provide dependencies in Angular, and we will learn how to use the provideIn root
, any
, and platform
options.
We will also discuss when and how to use these options in different scenarios.
Table of Contents
Reminder about dependency injection in Angular
Dependency injection is a design pattern that allows a class to receive its dependencies from external sources rather than creating them itself. In Angular, dependency injection is used to provide the required dependencies for a class when it is created.
There are several ways to provide dependencies in Angular:
Using the
@Injectable
decorator: This is the most common way to provide dependencies in Angular. When you use the@Injectable
decorator to decorate a class, Angular creates a new instance of the class when it is needed and injects it into the component or service that requires it.Using the
@NgModule
decorator: You can use theproviders
property of the@NgModule
decorator to provide dependencies at the module level. This means that the dependency will be available for injection in all components and services within the module.Using the
@Component
decorator: You can use theproviders
property of the@Component
decorator to provide dependencies at the component level. This means that the dependency will be available for injection only in the component and its child components.
What is provideIn option in Angular ?
In Angular, the provideIn
option is a way to specify where a service should be registered for injection.
It is used in conjunction with the @Injectable
decorator to define a service and specify how it should be provided to the rest of the application.
The provideIn
option can take one of three values: 'root'
, 'platform'
, or any
.
Overall, the provideIn
option is a powerful way to specify where a dependency should be provided and can be used to manage dependencies more effectively in large Angular applications.
Using provideIn root option
The provideIn: 'root'
option can be used to specify that a dependency should be provided at the root level in an Angular application.
There are several scenarios where the provideIn: 'root'
option can be useful:
When you wish to register a singleton service at the application level. This allows the service to be injected and utilized throughout the entire application, rather than being limited to a specific module or component.
- If you have multiple Angular applications running on the same page and want to make sure that each application has its own independent instance of a service.
ProvideIn “root” Syntax:
Here is the syntax of how to use the provideIn: 'root'
option to provide a dependency in an Angular application:
import {Injectable } from '@angular/core';
@Injectable({
providedIn: 'root',
})
export class Dependency {
constructor(public value: string) {}
}
Using provideIn "any" option
The provideIn: 'any'
option when you want each lazy-loaded module to receive its own instance of the service.
This can be useful if you need to ensure that each lazy module has its own isolated instance of the service, rather than sharing a single instance across the entire application.
ProvideIn “any” Syntax:
Here is the syntax of how to use the provideIn: 'any'
option to provide a dependency in an Angular application:
import {Injectable } from '@angular/core';
@Injectable({
providedIn: 'any',
})
export class Dependency {
constructor(public value: string) {}
}
Using provideIn "platform" option
The provideIn: 'platform'
option is used to indicate that the dependency should be provided in the platform injector in the Angular application.
By default, the platform injector is shared by all applications on the page.
This means, if you have multiple Angular applications running on the same page, they will all share the same platform injector and any services that are registered with it.
ProvideIn “platform” Syntax:
Here is the syntax of how to use the provideIn: 'platform'
option to provide a dependency in an Angular application:
import {Injectable } from '@angular/core';
@Injectable({
providedIn: 'platform',
})
export class Dependency {
constructor(public value: string) {}
}
The default provideIn option
The default value for the providedIn
option in the @Injectable
decorator is 'root'
, which means that a dependency will be provided at the root level by default.
Here is an example of how to use the default providedIn: 'root'
option to provide a dependency at the root level:
import { Injectable } from '@angular/core';
@Injectable()
export class Dependency {
// ...
}
In this example, we have not specified a value for the providedIn
option, so it will use the default value of 'root'
.
This means that the Dependency
class will be provided at the root level and will be available for injection in any part of the application.
To inject the Dependency
class in a component or service, you can use the @Inject
decorator like this:
import { Component } from '@angular/core';
@Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css']
})
export class AppComponent {
constructor(@Inject(Dependency) public dependency: Dependency) {}
}
In this example, we have injected the Dependency
class using the @Inject
decorator.
The Dependency
class will be provided at the root level, and the component will be able to use it.
Overall, the default value for the providedIn
option is 'root'
, which means that a dependency will be provided at the root level by default.
This can be useful in many scenarios, but you can also use the providedIn
option to specify a different location for the dependency if needed
Using provideIn options effectively in Angular
Here are a few tips for effectively using the provideIn
options in your Angular applications:
Use the
provideIn: 'root'
option unless you have a specific reason to use theprovideIn: 'platform'
orprovideIn: any
options. This will allow you to keep your service registrations centralized in the root injector, which can make it easier to manage your services and avoid potential injection errors.Use the
provideIn: 'platform'
option sparingly and only when you need to create a service that is only available for injection in the root component and its children.Use the
provideIn: any
option sparingly and only when you need to ensure that each lazy-loaded module has its own isolated instance of a service.Avoid using the
provideIn: 'platform'
andprovideIn: any
options for services that will be used and shared beyond the entire application. This can cause confusion and make managing your service dependencies much more difficult.
By following these tips, you can effectively use the provideIn
options to manage the scope and availability of your services in your Angular applications.
References
Here are more related references and links that discuss the same subject:
- The Angular dependency injection documentation
- The Angular documentation on hierarchical dependency injection
- Dependency injection in Angular
- How to use Services in Angular ?
- How to use Providers in Angular ?
- Using Injector , @Injectable & @Inject in Angular
- How to create a singleton service in Angular ?
- Using provideIn root , any & platform in Angular ?
- How to use ViewProviders in Angular ?
- Using @Self , @SkipSelf & Optional Decorators in Angular
- How to use APP_INITIALIZER provider in Angular ?