"Error: In TypeScript, the Child Method is not recognized within the Parent

Question

"Error: In TypeScript, the Child Method is not recognized within the Parent

I'm a newcomer to TypeScript and object-oriented programming. I am attempting to use a method from a child class in the parent class, but for some reason, the method is not being recognized.

Below is my Child class:

import {Ouvrage} from "./Class_Ouvrage";
import {Emprunt} from "./Class_Emprunt";
import {Adherant} from "./Class_Adherant";

export class Volumes extends Ouvrage {

private _NombreExemplaire: number;
private _NombreExemplaireEmpruntes: number;
private _auteur: string;

public get NombreExemplaire(): number {
    return this._NombreExemplaire;
}

set NombreExemplaireEmpruntes(value: number) {
    this._NombreExemplaireEmpruntes = value;

}

get NombreExemplaireEmpruntes(): number {
    return this._NombreExemplaireEmpruntes;
}

get auteur(): string {
    return this._auteur;
}

constructor(Pnombreexemplaire: number, Pnombreexemplairemprunte: number, Pauteur: string, PID: number, PTitre: string, Pdate: Date) {

    super(PID, PTitre, Pdate);
    this._auteur = Pauteur;
    this._NombreExemplaire = Pnombreexemplaire;
    this._NombreExemplaireEmpruntes = Pnombreexemplairemprunte;


}

descriptionVolume(): string {
    return "l'auteur de ce volume s'apelle : " + this.auteur + " , il reste " + this.NombreExemplaire + "disponible(s)" + " Le nombre de volumes déja emprunté, s'éleve a " + this.NombreExemplaireEmpruntes;
}



 public NbExemplaireDispo() : number{
        return this.NombreExemplaire - this.NombreExemplaireEmpruntes;
    }

}

Here is the parent class where I would like to call the method:

import {Volumes} from "./Class_Volume";
import {Adherant} from "./Class_Adherant";    
export class Ouvrage{
    private _id : number;
    private _titre : string;
    private _date : Date;
get id(): number {
    return this._id;
}


get titre(): string {
    return this._titre;
}

get date(): Date {

    return this._date;
}

constructor(PID : number, PTitre : string, Pdate : Date) {


    this._id = PID;
    this._titre = PTitre;
    this._date = Pdate;


}

descriptionOuvrage() : string{

    return "Cet ouvrage s'apelle " + this.titre + " et il est sorti le " + this.date+" ";
}

 this.NbExemplaireDispo();

}

How can I get NbExemplaireDispo() to work?

As mentioned earlier, since I am new to oop, is it considered good practice to make this kind of call?

Thank you!

typescript oop

Answer 1

Answer №1

Having trouble using a child method from the parent class? The method might not be recognized due to some reasons.

...

If you're new to object-oriented programming, it's generally not recommended for parent classes to call methods defined in child classes. This can lead to issues with instances and inheritance.

For example, consider this scenario where a parent class tries to call a method defined in a child class:

class Parent {
    parentMethod() {
        this.childMethod(); // This won't work as intended
    }
}
class Child extends Parent {
    childMethod() {
        // Method implementation
    }
}
const p = new Parent();
p.parentMethod(); // An error would occur because `parentMethod` is calling `childMethod` which belongs to `Child`

This issue becomes even more complex when dealing with multiple child classes that may or may not have the required method defined.

To avoid such pitfalls, it's best practice to define methods in the parent class and override them in child classes if needed. Here's an example:

class Parent {
    parentMethod() {
        this.theMethod();
    }
    theMethod() {
        // Default implementation
    }
}
class Child extends Parent {
    theMethod() {
        // Customized method for child class
    }
}
const p = new Parent();
p.parentMethod(); // Works as expected

Alternatively, you could use an abstract method in the parent class to enforce implementation in child classes:

class Parent {
    parentMethod() {
        this.theMethod();
    }
    abstract theMethod();
}
class Child extends Parent {
    theMethod() {
        // Implementing the abstract method
    }
}
const c = new Child();
c.theMethod(); // Executed successfully
const p = new Parent(); // Compilation error: Cannot instantiate abstract class `Parent`

Answer 2

Having trouble using a child method from the parent class? The method might not be recognized due to some reasons.

...

If you're new to object-oriented programming, it's generally not recommended for parent classes to call methods defined in child classes. This can lead to issues with instances and inheritance.

For example, consider this scenario where a parent class tries to call a method defined in a child class:

class Parent {
    parentMethod() {
        this.childMethod(); // This won't work as intended
    }
}
class Child extends Parent {
    childMethod() {
        // Method implementation
    }
}
const p = new Parent();
p.parentMethod(); // An error would occur because `parentMethod` is calling `childMethod` which belongs to `Child`

This issue becomes even more complex when dealing with multiple child classes that may or may not have the required method defined.

To avoid such pitfalls, it's best practice to define methods in the parent class and override them in child classes if needed. Here's an example:

class Parent {
    parentMethod() {
        this.theMethod();
    }
    theMethod() {
        // Default implementation
    }
}
class Child extends Parent {
    theMethod() {
        // Customized method for child class
    }
}
const p = new Parent();
p.parentMethod(); // Works as expected

Alternatively, you could use an abstract method in the parent class to enforce implementation in child classes:

class Parent {
    parentMethod() {
        this.theMethod();
    }
    abstract theMethod();
}
class Child extends Parent {
    theMethod() {
        // Implementing the abstract method
    }
}
const c = new Child();
c.theMethod(); // Executed successfully
const p = new Parent(); // Compilation error: Cannot instantiate abstract class `Parent`

"Error: In TypeScript, the Child Method is not recognized within the Parent

Answer №1

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