How to call a static method of a type parameter?

When working with TypeScript, you may encounter situations where you need to call a static method of a type parameter. This can be a bit tricky, but there are a few approaches you can take to achieve this. Let’s explore them one by one.

Approach 1: Using a type assertion

One way to call a static method of a type parameter is by using a type assertion. This involves asserting the type of the type parameter to a specific class or interface that contains the static method you want to call. Here’s an example:


class MyClass {
  static myStaticMethod() {
    console.log("Hello, world!");
  }
}

function callStaticMethod() {
  (T as typeof MyClass).myStaticMethod();
}

callStaticMethod(); // Output: Hello, world!

In this example, we define a class MyClass with a static method myStaticMethod. Then, we create a generic function callStaticMethod that takes a type parameter T. Inside the function, we assert the type of T to typeof MyClass and call the static method myStaticMethod.

Approach 2: Using a type constraint

Another approach is to use a type constraint to ensure that the type parameter has a static method with a specific name. Here’s an example:


class MyClass {
  static myStaticMethod() {
    console.log("Hello, world!");
  }
}

function callStaticMethod void }>() {
  T.myStaticMethod();
}

callStaticMethod(); // Output: Hello, world!

In this example, we define a class MyClass with a static method myStaticMethod. Then, we create a generic function callStaticMethod that takes a type parameter T with a type constraint. The type constraint ensures that T has a static method myStaticMethod. Inside the function, we directly call T.myStaticMethod().

Approach 3: Using a factory function

Alternatively, you can use a factory function to create an instance of the type parameter and then call the static method on that instance. Here’s an example:


class MyClass {
  static myStaticMethod() {
    console.log("Hello, world!");
  }
}

function createInstance(): T {
  return new (T as { new (): T })();
}

const instance = createInstance();
instance.constructor.myStaticMethod(); // Output: Hello, world!

In this example, we define a class MyClass with a static method myStaticMethod. Then, we create a generic function createInstance that takes a type parameter T. Inside the function, we create an instance of T using a type assertion. Finally, we call the static method myStaticMethod on the constructor of the instance.

These are three different approaches you can use to call a static method of a type parameter in TypeScript. Choose the one that best suits your needs and the specific requirements of your project.

Happy coding!

How to call a static method of a type parameter?