Tag: visitor

I have the structure Corporation / Company / Facility / Storage and only Storage could be part of Facility and Facility could be part of Company and Company part of Corporation. My main problem is that the code I need to add the corporation to itself works.

public class BusinessEntityData
{
    public Guid ID { get; set; }

    public Guid ParentID { get; set; }

    public string Title { get; set; }
    public string Number { get; set; }

    public int Type { get; set; }
}

public static class Context
{
    public static List BusinessEntityList { get; set; } = new List();
}

This is what the data entity looks like and the context is for the static list that I use for testing.

public interface IBusinessEntity
{
    string Title { get; set; }
    string Number { get; set; }

    int Type { get; set; }

    List GetChildren(string number);
    void AddBusinessEntity(IBusinessEntity entity);
    void Remove(IBusinessEntity entity);

    void Validate(IParentValidationVisitor visitor, BusinessEntityData data);
}

public interface IValidationVisitor
{
    void VisitCompany(BusinessEntityData data);
    void VisitFacility(BusinessEntityData data);
    void VisitCorporation(BusinessEntityData data);
    void VisitStorage(BusinessEntityData data);

}

These are both interfaces that I use for the VisitorPattern and Composite.

Here I implement the interface. Suppose that the numbers between all objects are unique.

public abstract class AbstractBusinessEntity : IBusinessEntity
{

    public string Title { get; set; }
    public string Number { get; set; }

    public int Type { get; set; }

    public AbstractBusinessEntity(string number, string title)
    {
        Title = title;
        Number = number;
    }

    public void AddBusinessEntity(IBusinessEntity entity)
    {
        var currentElement = Context.BusinessEntityList.FirstOrDefault(x => x.Number == this.Number);

        var visitor = new ParentValidationVisitor();
        var data = new BusinessEntityData()
        {
            ID = Guid.NewGuid(),
            Title = entity.Title,
            Number = entity.Number,
            Type = entity.Type,
            ParentID = currentElement == null ? Guid.Empty : currentElement.ID
        };

        Validate(visitor, data);
        Context.BusinessEntityList.Add(data);
    }

    public List GetChildren(string number = null)
    {
        if (number == null)
            number = this.Number;

        List list = new List();
        var currentElement = Context.BusinessEntityList.FirstOrDefault(x => x.Number == number);

        if (currentElement == null)
            return new List();

        var children = Context.BusinessEntityList.Where(x => x.ParentID == currentElement.ID);

        foreach(var item in children)
        {
            list.Add(item);
            list.AddRange(GetChildren(item.Number));
        }

        return list;
    }

    public void Remove(IBusinessEntity entity)
    {
        var result = Context.BusinessEntityList.FirstOrDefault(x => x.Number == entity.Number);

        if (result == null)
            return;

        Context.BusinessEntityList.Remove(result);
    }

    public abstract void Validate(IValidationVisitor visitor, BusinessEntityData data);
}

My classes Facility. Corporation. Company and Storage inherit this AbstractBusinessEntity and implement only the Validate method, where I call a separate visitor method.

This is what the visitor looks like:

public class ValidationVisitor : IValidationVisitor
{
    public void VisitCorporation(BusinessEntityData data)
    {
        if (data.Type == (int)Helper.BusinessEntityType.Corporation)
            return;

        if (data.Type == (int)Helper.BusinessEntityType.Company)
            return;

        throw new BusinessEntityValidationException("You can add only Companies to Corporation");

    }
    public void VisitCompany(BusinessEntityData data)
    {
        if (data.Type == (int)Helper.BusinessEntityType.Facility)
            return;

        throw new BusinessEntityValidationException("You can add only Facility to Companies");
    }

    public void VisitFacility(BusinessEntityData data)
    {
        if (data.Type == (int)Helper.BusinessEntityType.Storage)
            return;

        throw new BusinessEntityValidationException("You can add only Storage to Facility");
    }

    public void VisitStorage(BusinessEntityData data)
    {
        throw new BusinessEntityValidationException("You can't add any business entity to Storage");
    }
}

Should the confirmation be in the visitor's pattern?

What's really strange to me is that when I start the program for this code to work properly, I need to add corporation to itself to add the first element in the collection.

        Corporation corporation = new Corporation("Corporation", "Corporation TEst");
        corporation.AddBusinessEntity(corporation);

        var company1 = new Company("Company1", "Company1");
        var company2 = new Company("Company2", "Company2");
        var company3 = new Company("Company3", "Company3");
        corporation.AddBusinessEntity(company1);
        corporation.AddBusinessEntity(company2);
        corporation.AddBusinessEntity(company3);

I am not sure if this is the right way. Another possibility is that the company is out of the tree, but I am not sure if this is correct as business logic. What could be a better approach?

Here's github demo for the full code of the example.

Here's DotNetFiddle for the full example. (not really readable)