Injectable Decorator

The @Injectable decorator is a key feature of Depinjionary. It is used to mark a class as a dependency that the container can register and manage.

Features

• Automatic Registration: Marks a class as a dependency for the container.
• Singleton by Default: Dependencies are registered as singletons by default, ensuring one shared instance across the application.
• Transient Option: Optionally specify a dependency as transient to create a new instance each time it is resolved.

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Usage

Default Singleton Dependency

By default, the @Injectable decorator registers the class as a singleton:

import { Injectable } from "depinjionary";

@Injectable()
export class CalculatorService {
  calculate(a: number, b: number): number {
    return a + b;
  }
}

Transient Dependency

To resolve a dependency as transient, specify the type option with Type.TRANSIENT:

import { Injectable, Type } from "depinjionary";

@Injectable({ type: Type.TRANSIENT })
export class CalculatorService {
  calculate(a: number, b: number): number {
    return a + b;
  }
}

Options

The @Injectable decorator accepts the following configuration options:

Option	Type	Default	Description
type	Type	Type.SINGLETON	Defines the lifecycle of the dependency. Use Type.TRANSIENT for a transient lifecycle.

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Requirements

To use the @Injectable decorator, experimental decorator support must be enabled in your TypeScript configuration. Add the following to your tsconfig.json:

{
  "compilerOptions": {
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true
  }
}

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Example

Here's an example that combines the @Injectable decorator with ContainerResolver to register and resolve dependencies:

import { Injectable, ContainerResolver, ContainerInterface } from "depinjionary";

@Injectable()
export class CalculatorService {
  calculate(a: number, b: number): number {
    return a + b;
  }
}

const providers = [{ provide: CalculatorService }];

const container: ContainerInterface = ContainerResolver.init(providers);
const calculator = await container.resolve<CalculatorService>(CalculatorService);
console.log(calculator.calculate(5, 10)); // Outputs: 15

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Notes

• Ensure experimentalDecorators and emitDecoratorMetadata are enabled in your tsconfig.json file.
• The singleton type is suitable for shared services, while transient is ideal for stateless or short-lived dependencies.