I'm looking for some information on Typescript static functions - can anyone help me

Question

I'm looking for some information on Typescript static functions - can anyone help me

Below is the code I am currently working with:

class BaseClass {
   // includes a static method
   static someMethod() {
   }
}

class ChildClass extends BaseClass{

}

class AnotherClass {
   protected variable: BaseClass; // Works fine with type 'any'

   protected someFunction() {
      return this.variable.someMethod(); // Shows an error that there's no someMethod in the BaseClass
   }
}

The issue at hand is that I need the protected variable in AnotherClass to store the class function rather than the class instance.

Is it feasible to achieve this?

Thank you for your assistance.

Please excuse any errors in my English.

typescript

Answer 1

Answer №1

When looking at your scenario, it is important to note that the variable property represents an instance of the BaseClass, rather than the class itself.

To ensure that the type of variable aligns with the type of BaseClass, you should define it as typeof BaseClass:

class AnotherClass {
  protected variable: typeof BaseClass;

  public constructor(v: typeof BaseClass) {
    this.variable = v;
  }

  protected someFunction() {
    return this.variable.someMethod();
  }
}

const a: AnotherClass = new AnotherClass(BaseClass);

Answer 2

When looking at your scenario, it is important to note that the variable property represents an instance of the BaseClass, rather than the class itself.

To ensure that the type of variable aligns with the type of BaseClass, you should define it as typeof BaseClass:

class AnotherClass {
  protected variable: typeof BaseClass;

  public constructor(v: typeof BaseClass) {
    this.variable = v;
  }

  protected someFunction() {
    return this.variable.someMethod();
  }
}

const a: AnotherClass = new AnotherClass(BaseClass);

Answer 3

Answer №2

The cause of this error can be attributed to tsc rather than the editor.

Identify some issues within your code.

class AnotherClass {
    protected variable: BaseClass; // This signifies that the variable is an instance of BaseClass
    protected someFunction() {
        return this.variable.someMethod(); // Therefore, you cannot access a static method from an instance
    }
}

If you need to access a static method of a class, you should call it from the class object and not the instance of the class. Thus, you need to adjust the type of the variable member from BaseClass to typeof BaseClass.
The following example demonstrates this concept. To simplify the explanation, I have adjusted the access levels of members.

class BaseClass {
  static someMethod(): void {}
}

class DeriveClass extends BaseClass {
}

class AnotherClass {
    public variable: typeof BaseClass = BaseClass;
    public someFunction() {
        return this.variable.someMethod();
    }
}

let instance = new AnotherClass();
instance.variable = DeriveClass; // This works because DeriveClass extends from BaseClass
instance.someFunction();

Answer 4

The cause of this error can be attributed to tsc rather than the editor.

Identify some issues within your code.

class AnotherClass {
    protected variable: BaseClass; // This signifies that the variable is an instance of BaseClass
    protected someFunction() {
        return this.variable.someMethod(); // Therefore, you cannot access a static method from an instance
    }
}

If you need to access a static method of a class, you should call it from the class object and not the instance of the class. Thus, you need to adjust the type of the variable member from BaseClass to typeof BaseClass.
The following example demonstrates this concept. To simplify the explanation, I have adjusted the access levels of members.

class BaseClass {
  static someMethod(): void {}
}

class DeriveClass extends BaseClass {
}

class AnotherClass {
    public variable: typeof BaseClass = BaseClass;
    public someFunction() {
        return this.variable.someMethod();
    }
}

let instance = new AnotherClass();
instance.variable = DeriveClass; // This works because DeriveClass extends from BaseClass
instance.someFunction();

I'm looking for some information on Typescript static functions - can anyone help me

Answer №1

Answer №2

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