Customizing Array.of() in Typescript for a specialized 2D array class that inherits from Array

Question

Customizing Array.of() in Typescript for a specialized 2D array class that inherits from Array

I am working on creating a custom Array2D class by extending the Array class in JavaScript. My goal is for the constructor to accept any number of arguments, each representing an array of type T. Here is the current implementation:

class Array2D<T> extends Array<T[]> {
  constructor(...args: T[][]) {
    super(...args)
  }

  static of(...args: T[][]) {
    return new Array2D(...args)
  }
}

However, I am encountering an error in TypeScript:

Types of property 'of' are incompatible.
    Type '<T>(...args: T[][]) => Array2D<T>' is not assignable to type '<T>(...items: T[]) => T[]'.
      Types of parameters 'args' and 'items' are incompatible.
        Type 'T' is not assignable to type 'T[]'.

Could someone please help me understand what this TypeScript error means and suggest a solution?

arrays typescript inheritance multidimensional-array types

Answer 1

Answer №1

Here is an alternative approach to typing when working with arrays in TypeScript. Instead of directly using the Array constructor, consider widening the type of the constructor:

const VanillaArrayConstructor: new <T>(...args: T[]) => Array<T>
    = Array;

By defining VanillaArrayConstructor, you restrict access to static methods like .from() or .of() which can be helpful in certain scenarios. To further extend this concept, create a custom array class that utilizes this widened constructor:

class Array2D<T> extends VanillaArrayConstructor<T[]> {
    constructor(...args: T[][]) {
        super(...args)
    }

    static of<T>(...args: T[][]) {
        return new Array2D(...args)
    }
}

While this may not change the actual behavior of Array2D during runtime, it provides flexibility in typing where the compiler does not expect Array2D to strictly follow the Array constructor's type.

Feel free to explore this method and good luck coding!

Link to code

Answer 2

Here is an alternative approach to typing when working with arrays in TypeScript. Instead of directly using the Array constructor, consider widening the type of the constructor:

const VanillaArrayConstructor: new <T>(...args: T[]) => Array<T>
    = Array;

By defining VanillaArrayConstructor, you restrict access to static methods like .from() or .of() which can be helpful in certain scenarios. To further extend this concept, create a custom array class that utilizes this widened constructor:

class Array2D<T> extends VanillaArrayConstructor<T[]> {
    constructor(...args: T[][]) {
        super(...args)
    }

    static of<T>(...args: T[][]) {
        return new Array2D(...args)
    }
}

While this may not change the actual behavior of Array2D during runtime, it provides flexibility in typing where the compiler does not expect Array2D to strictly follow the Array constructor's type.

Feel free to explore this method and good luck coding!

Link to code

Customizing Array.of() in Typescript for a specialized 2D array class that inherits from Array

Answer №1

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