Class and static variable

Question

OutputFormatsBase is base class for managing Output Formats. OutputFormats1 and OutputFormats2 classes are inherited from OutputFormatsBase class.

I have the problem with static variable _listOfObjects which is in OutputFormatsBase class and can't find a way to solve it.

If I make _listOfObjects static everything works fine except that OutputFormats1 and OutputFormats2 classes static instances are shared, not good.

Could anyone suggest how to solve this? I completely lost.

public class OutputFormats1 : OutputFormatsBase
{
    public static readonly OutputFormats1 Bmp = new OutputFormats1 { Value = "BMP", FileExtension = "bmp", Id = 1 };
    public static readonly OutputFormats1 Jpg = new OutputFormats1 { Value = "JPG", FileExtension = "jpg", Id = 2 };
    public static readonly OutputFormats1 Png = new OutputFormats1 { Value = "PNG", FileExtension = "png", Id = 3 };
    public static readonly OutputFormats1 Tiff = new OutputFormats1 { Value = "TIFF", FileExtension = "tif", Id = 4 };
    public override OutputFormatsBase Selected { get; set; }
    public override OutputFormatsBase Default
    {
        get { return Png; }
    }
}

public class OutputFormats2 : OutputFormatsBase
{
    public static readonly OutputFormats2 Pdf = new OutputFormats2 { Value = "PDF", FileExtension = "pdf", Id = 1 };
    public override OutputFormatsBase Selected { get; set; }
    public override OutputFormatsBase Default
    {
        get { return Pdf; }
    }
}

public abstract class OutputFormatsBase
{
     private static readonly List<OutputFormatsBase> _listOfObjects = new List<OutputFormatsBase>();
     public string Value { get; protected internal set; }
     public string FileExtension { get; protected internal set; }
     public int Id { get; protected internal set; }

     public abstract OutputFormatsBase Selected { get; set; }
     public abstract OutputFormatsBase Default { get; }


     protected OutputFormatsBase()
     {
         _listOfObjects.Add(this);
     }


     public bool Validate(string format)
     {
         for (var i = 0; i < _listOfObjects.Count - 1; i++)
         {
             var outputFormats = _listOfObjects[i];
             if (format.ToLower() == outputFormats.Value.ToLower())
             {
                 Selected = outputFormats;
                 return true;
             }
         }
         return false;
     }
 }

what do you mean by "except that OutputFormats1 and OutputFormats2 classes static instances are shared"? — thumbmunkeys
– thumbmunkeys, Commented Sep 7, 2011 at 9:00
What is that you want to do? You want a new list for each derived or what? — Tony The Lion
– Tony The Lion, Commented Sep 7, 2011 at 9:01
what is your problem and what is the behavior you want and what is what you get? — Kolja
– Kolja, Commented Sep 7, 2011 at 9:05
I want to collect the list of Static Derived class instances to _listOfObjects variable. I use it in Validate method. But _listOfObjects must be unique for every OutputFormats1 and OutputFormats2 class. — Tomas
– Tomas, Commented Sep 7, 2011 at 9:06
@Tony I want a list of Derived Static Classes in Base class and it should unique for every non static derived class. For example OutputFormatEnum1 = new OutputFormats1(); OutputFormatEnum2 = new OutputFormats2(); OutputFormatEnum2.Validate If you call code above, the Validate method will not work because _listOfObjects object is shared among OutputFormatEnum1 classes and OutputFormatEnum2 classes. — Tomas
– Tomas, Commented Sep 7, 2011 at 9:12

Seb · Accepted Answer · 2011-09-07 09:17:19Z

2

You could try something like that :

public abstract class OutputFormatsBase<T> where T : OutputFormatsBase
{
 private static readonly List<T> _listOfObjects = new List<T>();

 protected OutputFormatsBase()
 {
  _listOfObjects.Add((T)this);
 }
}

You'll have one instance of _listOfObjects per template instanciation.

answered Sep 7, 2011 at 9:17

Seb

2,7151 gold badge17 silver badges19 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Bob Vale · Accepted Answer · 2011-09-07 09:22:15Z

If you use generics then the static values will be unique to each generic type

public class OutputFormats1 : OutputFormatsBase<OutputFormats1> 
{ 
    public static readonly OutputFormats1 Bmp = new OutputFormats1 { Value = "BMP", FileExtension = "bmp", Id = 1 }; 
    public static readonly OutputFormats1 Jpg = new OutputFormats1 { Value = "JPG", FileExtension = "jpg", Id = 2 }; 
    public static readonly OutputFormats1 Png = new OutputFormats1 { Value = "PNG", FileExtension = "png", Id = 3 }; 
    public static readonly OutputFormats1 Tiff = new OutputFormats1 { Value = "TIFF", FileExtension = "tif", Id = 4 }; 
    public override OutputFormatsBase Selected { get; set; } 
    public override OutputFormatsBase Default 
    { 
        get { return Png; } 
    } 
} 

public class OutputFormats2 : OutputFormatsBase<OutputFormats2> 
{ 
    public static readonly OutputFormats2 Pdf = new OutputFormats2 { Value = "PDF", FileExtension = "pdf", Id = 1 }; 
    public override OutputFormatsBase Selected { get; set; } 
    public override OutputFormatsBase Default 
    { 
        get { return Pdf; } 
    } 
} 

public abstract class OutputFormatsBase<T> where T:OutputFormatsBase 
{ 
     private static readonly List<T> _listOfObjects = new List<T>(); 
     public string Value { get; protected internal set; } 
     public string FileExtension { get; protected internal set; } 
     public int Id { get; protected internal set; } 

     public abstract OutputFormatsBase Selected { get; set; } 
     public abstract OutputFormatsBase Default { get; } 


     protected OutputFormatsBase() 
     { 
         _listOfObjects.Add((T)this); 
     } 


     public bool Validate(string format) 
     { 
         for (var i = 0; i < _listOfObjects.Count - 1; i++) 
         { 
             var outputFormats = _listOfObjects[i]; 
             if (format.ToLower() == outputFormats.Value.ToLower()) 
             { 
                 Selected = outputFormats; 
                 return true; 
             } 
         } 
         return false; 
     } 
 }

Collectives™ on Stack Overflow

Class and static variable

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related