Injectiontoken

Angular's dependency injection DI system manages dependencies in a modular, scalable manner, injectiontoken.

Zahra Namini. March 15, in. Injection tokens are a popular way of providing dependencies in Angular. They are used to provide a value, such as a service instance or a configuration setting, to a component or other part of the application. Below is a simple example of setting up an injection token and using it. Suppose you have a constant value that is needed in several components.

Injectiontoken

As you might have already understood the Angular dependency injection layer keeps a map of providers that are being identified by "keys", also known as "injection tokens", and uses this map to resolve, create and inject instances at runtime. The injection tokens can be of different types. We have already tried Types and Strings in action in previous sections. Type-based injection tokens are the most commonly used way to register providers. Typically you import the service type from the corresponding file and put it into the providers section of the module. Another way to register a provider involves the string-based injection tokens. Typically you are going to use strings when there is no Type reference available, for example when registering plain values or objects:. That enables static type checks and prevents many type-related errors at early stages. Let's create separate file tokens. Now we can use this token within the main application module to register a URL value that all components and services can use when needed:. From this moment we can use the same token to import registered value in the service or a component like in the example below:. That does not affect the process of dependency injection but gives you an opportunity for static compile-time checks and auto completion if your code editor supports TypeScript. Let's create a token for the LoggerConfig interface we set up in this chapter earlier:. You can now define a type-safe configuration object and register it with the dependency injection system using main application module:.

You can now define a type-safe configuration object and register it with the dependency injectiontoken system using main application module:, injectiontoken.

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Today, I'm thrilled to dive into the fascinating world of InjectionTokens in Angular. If you're not already familiar with them, InjectionTokens are superheroes in the Angular universe, allowing us to leverage the full potential of dependency injection with a hint of TypeScript magic. In this blog post, we'll explore how these powerful tokens will be used to handle small values and tackle complex data structures, unlocking a plethora of possibilities for your app. In Angular, dependency injection is the backbone of building scalable and maintainable applications. It enables us to provide the necessary dependencies to our components and services without hardcoding them, promoting flexibility and testability. Enter InjectionTokens, an elegant way to inject dependencies that don't fit the traditional mold of classes or interfaces. These tokens are unique markers used to identify and retrieve specific instances from the Angular injector. Next, we must provide the theme configuration using the InjectionToken in the app's module or a feature module. Now, we can inject the theme configuration using the InjectionToken in our components and services.

Injectiontoken

At first, I would like to thank Omer Incirkus , who helped me write this article and was with me while I was learning, for his contributions. Dependency injection is a crucial concept in Angular that enables you to create loosely coupled components, services, and modules. With dependency injection, you can declare a service or component once and reuse it throughout your application, which makes your code more modular, testable, and maintainable. Angular provides different ways to inject dependencies into your components, such as constructor injection. However, sometimes you may want to inject a value that is not a class or a service instance but rather a simple configuration value, such as a string, number, or boolean. In this case, you can use the InjectionToken class to define a token that represents the value you want to inject. An InjectionToken is a class in Angular that represents a unique identifier for a dependency. It provides a way to decouple the provider and the consumer of a dependency by allowing you to register a token with a provider and then inject the token into a consumer. The consumer can then use the token to retrieve the value of the dependency from the provider. The InjectionToken class has a generic type parameter that specifies the type of the value that the token represents.

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Suppose you have a constant value that is needed in several components. Building the Packages Template Literals 2. Rather than hard-coding these settings within the service, we can create an Injection Token and use it to provide the configuration values. Output Events 5. Use Cases of Injection Tokens 1. Visual Studio Code 2. For example, consider a service that requires some application-specific settings. Creating Translate Pipe Components 5. Injection Tokens are unique identifiers used by the system to resolve dependencies flexibly. Custom Pipes 9. You can do this in your module as follows:.

As you might have already understood the Angular dependency injection layer keeps a map of providers that are being identified by "keys", also known as "injection tokens", and uses this map to resolve, create and inject instances at runtime.

Using Configuration Settings Generating Standalone Scripts 5. Running Application 4. Preparing the Configuration File Reusable Component Libraries Type Tokens Type-based injection tokens are the most commonly used way to register providers. Creating Component Libraries Angular CLI 4. Prerequisites 1. Plugins You can define it as a static value and provide it to the components or services requiring it:. Another way to register a provider involves the string-based injection tokens. Angular will automatically resolve the Dependency and inject an instance of MyDependency into the myDependency parameter. See Also In Angular, the dependency injection system is responsible for creating and managing instances of services, components, and other objects throughout the application.