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Hierarchical Inheritance in X++ language - D365 Finance and Operation

Hierarchical inheritance in the X++ programming language, as utilized in D365 Finance and Operations, refers to a structure where classes are organized in a hierarchy, with each class inheriting attributes and behaviors from a single parent class. This type of inheritance fosters a clear and well-defined relationship between classes, allowing for the creation of specialized subclasses that build upon the functionality of their parent classes. Hierarchical inheritance offers several advantages for software development:

1. Structured Code Organization: Hierarchical inheritance provides a structured way to organize classes within a system. Classes are grouped based on their hierarchical relationships, making the codebase more manageable and understandable.

2. Code Reusability: By inheriting attributes and behaviors from a parent class, subclasses can reuse existing code. Common functionality is defined in higher-level classes, reducing redundancy and promoting efficient development.

3. Specialization and Customization: Subclasses in a hierarchical inheritance model can specialize and customize the behavior of their parent classes. They can override or extend methods, add new attributes, and introduce unique functionality tailored to specific requirements.

4. Maintenance and Updates: Changes made to a parent class automatically propagate to its subclasses. This streamlines maintenance tasks, as updates need only be applied to the parent class, and the changes are inherited by all relevant subclasses.

5. Consistency and Standards: Hierarchical inheritance enforces consistent behavior and coding standards across related classes. Common methods and attributes are inherited uniformly by subclasses, ensuring a cohesive design and reducing the likelihood of errors.

6. Encapsulation and Modularity: Hierarchical inheritance supports encapsulation by controlling access to methods and attributes through visibility modifiers. This promotes modularity and data hiding, preventing unauthorized access and ensuring data integrity.

7. Efficient Testing and Debugging: The hierarchical structure allows for easier isolation and testing of individual components. Debugging efforts can be focused on specific sections of the code, speeding up the troubleshooting process.

8. Scalability and Future Expansion: Hierarchical inheritance accommodates scalability by allowing new subclasses to be added as the application evolves. This enables the introduction of new features without disrupting existing code.

9. Clear Hierarchical Relationship: The hierarchical structure provides a visual representation of class relationships. This aids developers in understanding the inheritance hierarchy and the flow of data and functionality.

Practical Coding Example

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VehicleClass

class VehicleClass
{
    real height;
    real width;
    
    public void new(real _height, real _width)
    {
        height = _height;
        width = _width;
    }
    
    public void info()
    {
        Info(strFmt("Vehicle: Height = %1 Width = %2", height, width));
    }
    
    public void run()
    {
        Info("Vehicle class is running");
    }
}
 

CarClass

class CarClass extends VehicleClass
{
    int numberOfPassengers;
    
    public void new(real _height, real _width, int _numberOfPassengers)
    {
        super(_height, _width);
        numberOfPassengers = _numberOfPassengers;
        
        Info(strFmt("Car: Height = %1 Width = %2 No of Passengers = %3", height, width, numberOfPassengers));
    }
    
    public void run()
    {
        super();
        Info("Car class is running");
    }
}

BusClass

class BusClass extends VehicleClass
{
    int seatingCapacity;
    
    public void new(real _height, real _width, int _seatingCapacity)
    {
        super(_height, _width);
        seatingCapacity = _seatingCapacity;
        
        Info(strFmt("Bus: Height = %1 Width = %2 Seating Capacity = %3", height, width, seatingCapacity));
    }
    
    public void run()
    {
        super();
        Info("Bus class is running");
    }
}

Create object and Run above code

class InheritanceExample
{
    public static void main(Args _args)
    {
        // Create an instance of CarClass
        CarClass car = new CarClass(1.5, 2.0, 4);
        car.info();
        car.run();
        
        // Create an instance of BusClass
        BusClass bus = new BusClass(3.5, 2.5, 30);
        bus.info();
        bus.run();
    }
}

In summary, hierarchical inheritance in the X++ programming language, as applied in D365 Finance and Operations, promotes a well-organized, modular, and efficient approach to software development. It empowers developers to create classes that build upon existing functionality, leading to more maintainable, extensible, and adaptable applications.

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