Static Type Mess

Question

Static Type cant be used as type arguments

BUT

Extension Method should be in a Static class

I have a class piece so I can create List<piece> in my code

Now when I try to create an extension and ask me to create the class as static. But if I do that can't create List<piece>. So I'm in a recursive dilema here.

As you can see I'm trying to clone my piece.

public class piece
{
    public int height { get; set; }
    public int width { get; set; }
    public int[] shape { get; set; }
    public int quality { get; set; }
    public int x { get; set; }
    public int y { get; set; }

    public static T CloneJson<T>(this T source)
    {
        // Don't serialize a null object, simply return the default for that object
        if (Object.ReferenceEquals(source, null))
        {
            return default(T);
        }

        return JsonConvert.DeserializeObject<T>(JsonConvert.SerializeObject(source));
    }
}

So what is the proper way to handle this scenario?

I have my class working fine. I try to add clone functionality and found that extension method. That is when mess start, yes, I'm not really familiar with extension or instance method. I'm trying to make it work

My guess is create the extension as a method instead, but I don't know how to do that.

Why is that method in the `piece` class to begin with? It has nothing to do with that type. — Servy, May 19 '15 at 16:51
What you're doing makes no sense. If you want a method that acts like the 'extension method' you''re trying to create, add an *instance* method. If you actually want a generic extension method, put it in another static class - it has nothing to do with this one. — Charles Mager, May 19 '15 at 16:54
Create a different class, make it static, put your extension method there. — juharr, May 19 '15 at 16:54
Ok, Looks like I dont have idea what I'm doing here. So I apologize in advance. What im trying to do is have a list of pieces, but also sometime i have create sublist, so I need clone the element on that List. To clone I found this extension and try to include it in my class. I'm not really familiar with `extension` or `instance` method so not really sure what should be the correct aproach. — Juan Carlos Oropeza, May 19 '15 at 17:04
@CharlesMager I have my class working fine. I try to add clone functionality and found that extension method. That is when mess start, yes, im not really familiar with extension or instance method. Im trying to make it work. — Juan Carlos Oropeza, May 19 '15 at 17:08
@JuanCarlosOropeza that clears things up a lot. The answers below should help! — Charles Mager, May 19 '15 at 17:11

Gabriel Rainha · Accepted Answer · 2016-11-04T18:11:00.623

Two things you need to consider:

First: that method have no reason to be on that class. It does not represent any functionality of piece, as it is generic and can return any type.

Second: Extension methods should be on static class, yeah, but not on the same class where the type is defined. It must be defined on a static class and is consumed by other classes by referencing to that static class namespace.

So what you probably want to do is something like this:

namespace MyApp.MyExtensions
{
   public static class CloneExtensions 
   {
       public static T CloneJson<T>(this T source)
       {
           if (Object.ReferenceEquals(source, null))
               return default(T);

           return JsonConvert.DeserializeObject<T>(JsonConvert.SerializeObject(source));
       }
   }
}

Then you could use

namespace MyApp
{
    using MyApp.Extensions;

    public class TestClass
    {
        public TestClass()
        {
            var item = new piece();
            var clone = piece.CloneJson();
        }
    }
}

That method would only make sense to be on the piece class if it was explicitly typed to clone only that piece class. In that case, it shouldn't be an extension method at all, but just an regular non-static method on that class.

Thanks that make sense. I just saw the example and try to copy the extension as part of the class. — Juan Carlos Oropeza, May 19 '15 at 17:11

score 0 · Answer 2 · answered May 19 '15 at 16:57

0

If you need extension methods of the piece class, just throw the extension method into another class - PieceExtensions or such. This is done even in .NET for the IEnumerable Extension Methods.

answered May 19 '15 at 16:57

David

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