How to dynamically pass parameters in dependency constructors when using DI in typescript

How to Dynamically Pass Parameters in Dependency Constructors When Using DI in TypeScript

Dependency Injection (DI) is a powerful design pattern that allows for loose coupling between components in an application. In TypeScript, DI is commonly used to manage dependencies and improve the testability and maintainability of code. However, there may be situations where you need to dynamically pass parameters to dependency constructors. In this blog post, we will explore different solutions to achieve this in TypeScript.

Solution 1: Using a Factory Function

One way to dynamically pass parameters in dependency constructors is by using a factory function. The factory function acts as a wrapper around the dependency and allows you to provide the necessary parameters at runtime.

Here’s an example:

class Dependency {
  constructor(private readonly param1: string, private readonly param2: number) {
    // constructor logic
  }
}

function createDependency(param1: string, param2: number): Dependency {
  return new Dependency(param1, param2);
}

// Usage
const param1 = "Hello";
const param2 = 42;
const dependency = createDependency(param1, param2);

In this example, the createDependency function acts as a factory function that creates an instance of the Dependency class with the provided parameters.

Solution 2: Using a DI Container

Another approach to dynamically pass parameters in dependency constructors is by using a DI container. A DI container manages the creation and resolution of dependencies, allowing you to specify the parameters at runtime.

Here’s an example using the popular InversifyJS DI container:

import { injectable, inject, Container } from "inversify";

@injectable()
class Dependency {
  constructor(@inject("Param1") private readonly param1: string, @inject("Param2") private readonly param2: number) {
    // constructor logic
  }
}

// Usage
const container = new Container();
container.bind("Param1").toConstantValue("Hello");
container.bind("Param2").toConstantValue(42);

const dependency = container.resolve(Dependency);

In this example, the Dependency class is decorated with the @injectable decorator to indicate that it is a dependency managed by the DI container. The parameters are decorated with the @inject decorator, specifying the corresponding keys used for resolution.

The container.bind method is used to bind the parameter values to their respective keys. Finally, the container.resolve method is called to resolve the dependency with the dynamically passed parameters.

Conclusion

Dynamic parameter passing in dependency constructors can be achieved using a factory function or a DI container. Both approaches provide flexibility and allow for runtime customization of dependencies. Choose the approach that best suits your application’s needs and coding style.

By leveraging these techniques, you can enhance the flexibility and maintainability of your TypeScript code when working with DI and dynamically passing parameters in dependency constructors.

That’s it for this blog post! We hope you found it helpful in solving your problem. If you have any further questions or suggestions, feel free to leave a comment below. Happy coding!