Uncovering TypeScript's Type Inference Power Through the keyof Keyword

Recently, I encountered a situation where I needed to utilize an abstract class.

export abstract class ABaseModel {
  public static isKeyOf<T>(propName: (keyof T)): string {
    return propName;
  }
}

Following that, I also created another class which extends the abstract class:

export class Model extends ABaseModel {

  public id: number;
  public uid: string;
  public createdByUid: string;
}

In order to verify if a given string is a valid property of the Model class, one would typically do this:

Model.isKeyOf<Model>('id');

However, my goal was to simplify this and be able to write:

Model.isKeyOf('id');

I wondered if Type Inference could make this possible without the need for explicit type definitions.

Answer №1

Here's a solution that appears to be effective:

abstract class ABaseModel {
    public static isKeyOf<T>(this: { new(): T }, propName: (keyof T)): string {
        return propName;
    }
}

Model.isKeyOf("id"); // works fine
Model.isKeyOf("name"); // issue: Argument of type '"name"' is not compatible with parameter of type '"id" | "uid" | "createdByUid"'

(code in playground)

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