Cannot setup TypeScript to use `using` keyword

Cannot setup TypeScript to use `using` keyword

As a TypeScript developer, you may have come across the situation where you want to use the using keyword, similar to how it is used in C#. However, TypeScript does not have a built-in using keyword like C#. In this blog post, we will explore a couple of solutions to achieve similar functionality in TypeScript.

Solution 1: Using a Function

One way to mimic the behavior of the using keyword is by using a function that takes a resource as a parameter and executes a callback function. This function will ensure that the resource is properly disposed of after the callback execution, similar to how the using keyword works in C#.

Here’s an example of how you can implement this solution:

function using void }>(resource: T, callback: (resource: T) => void) {
  try {
    callback(resource);
  } finally {
    resource.dispose();
  }
}

// Usage example
class MyResource {
  dispose() {
    console.log("Disposing MyResource");
  }
}

using(new MyResource(), (resource) => {
  console.log("Using MyResource");
});

The above code defines a generic function using that takes a resource and a callback function. Inside the using function, the callback is executed, and then the dispose method of the resource is called in a finally block to ensure proper cleanup.

The output of the above code will be:

Using MyResource
Disposing MyResource

Solution 2: Using a Decorator

Another approach to achieve a similar effect to the using keyword is by using a decorator. Decorators are a feature introduced in TypeScript that allows you to modify the behavior of a class or its members.

Here’s an example of how you can use a decorator to automatically dispose of a resource:

function using void }>() {
  return function (target: any, propertyKey: string, descriptor: PropertyDescriptor) {
    const originalMethod = descriptor.value;
    descriptor.value = function (...args: any[]) {
      const resource = originalMethod.apply(this, args);
      try {
        return resource;
      } finally {
        resource.dispose();
      }
    };
  };
}

// Usage example
class MyClass {
  @using()
  getResource() {
    const resource = new MyResource();
    console.log("Using MyResource");
    return resource;
  }
}

const instance = new MyClass();
instance.getResource();

In the above code, the using decorator is applied to the getResource method of the MyClass class. Inside the decorator, the original method is replaced with a new method that wraps the original method’s execution. After the method is executed, the resource is disposed of in a finally block.

The output of the above code will be:

Using MyResource
Disposing MyResource

These are two possible solutions to mimic the behavior of the using keyword in TypeScript. Depending on your specific use case, you can choose the solution that best fits your needs.

Remember, TypeScript does not have a built-in using keyword, so these solutions provide alternative ways to achieve similar functionality.