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Thypari
Thypari

Reputation: 861

c# .net: Extend existing class with method that should be overriden when initialized

Is something like that possible?

Let's say I have the String Class. And I want to add a Method DoStringCalc(). Now I want one Class which holds all these special strings and calls DoStringCalc() on all of them. But every String can have a different logic in DoStringCalc() and there can be thousands of them.

Most logical for me (coming from java) would be to override the Method DoStringCalc() when initializing a new String. e.g:

String hello = new String() {
    public override DoStringCalc() {
        //do something here
    }
}

How is this solved in C#?

Upvotes: 0

Views: 117

Answers (4)

kessmahat
kessmahat

Reputation: 1

as far as I know it is not possible to change classes you do not own the sourcecode. E.g. .Net Classes.

You can extend existing classs with Extensionmethods:

public static classe StringExtension
{
    public static void DoStingCalc(this string str)
    {
         //Do your Stuff here
    }
}

If you want to Force a specific Method. You have to derive from your class an decorate it with the interface you want to ensure. Or make an abstact method declaration.

Upvotes: 0

Michał Żołnieruk
Michał Żołnieruk

Reputation: 2105

If you have many different calculations logic, consider passing the transformation function to the class. Wrap the value which you will work with by a class and also store an appropriate tranformation in the same class:

public class Foo
{
    public string Value;
    private Func<string, string> doStringCalc;

    public Foo(string value, Func<string, string> doStringCalc)
    {
        this.Value = value;
        this.doStringCalc = doStringCalc;
    }

    public void ExecuteTransform()
    {
        this.Value = this.doStringCalc(this.Value);
    }
}

Then add different transforms as follows:

var foo1 = new Foo("A", (initialValue) => initialValue + initialValue);
var foo2 = new Foo("B", (initialValue) => initialValue + "bar");
var foo3 = new Foo("C", (initialValue) => " ");

foo1.ExecuteTransform();
foo2.ExecuteTransform();
foo3.ExecuteTransform();

Debug.WriteLine(foo1.Value); // prints "AA"
Debug.WriteLine(foo2.Value); // prints "Bbar"
Debug.WriteLine(foo3.Value); // prints " "

Upvotes: 3

DavidG
DavidG

Reputation: 118937

One option is to pass in an Action as part of the class constructor (or a Func if you want to return a value). For example:

public class MyThing
{
    private Action<MyThing> _doCalc { get; set; }

    public MyThing(Action<MyThing> doCalc)
    {
        _doCalc = doCalc;

    }

    public void DoCalc()
    {
        _doCalc(this);
    }

    public string SomeString { get; set; }
}

And call it like this:

var thing = new MyThing(t => Console.WriteLine(t.SomeString));
thing.SomeString = "Hello world";
thing.DoCalc();

Another variation of this would be to create a generic wrapper class, for example:

public class Wrapper<T>
{
    private Action<T> _doCalc { get; set; }

    public Wrapper(Action<T> doCalc)
    {
        _doCalc = doCalc;
    }

    public T Value { get; set; }

    public void DoCalc()
    {
        _doCalc(this.Value);
    }
}

And now you can do this:

var stringWrapper = new Wrapper<string>(t => Console.WriteLine("string wrapper"));
var intWrapper = new Wrapper<int>(t => Console.WriteLine("int wrapper"));

stringWrapper.DoCalc();
intWrapper.DoCalc();

Upvotes: 1

NotFound
NotFound

Reputation: 6102

If I understand correctly interface is what you are looking for.

Create an interface that requires a method DoStringCalc(). Then have all the string classes inherit the interface and implement their DoStringCalc() method. After that you can e.g. use a strongly typed List List<IExampleInterface> that allows instances of any of the string classes and call their respective DoStringCalc() from it.

Upvotes: 1

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