re: Write a function that shows off something unique or interesting about the language you're using VIEW POST

FULL DISCUSSION
 

In Ruby we can monkeypatch to easily add functionality to any class.

For example:


class String

  def yell!
    self.upcase + "!!!"
  end

end

I'm extending the string class so that "hello".yell! outputs "HELLO!!!"

And now all strings in the program have access to the yell! method. ❤️

I'll add that this is sort of bonkers and an easy way to add some really hard-to-debug code to an app. Use with great fear and caution.

 

Lots of languages support that, including most obviously Javascript.

 

Interesting. Is that possible via class definitions (class syntax I mean) or only via the prototype syntax?

 

In F# it is also easy to add functionality to existing classes.

type String with

    member me.yell () =
        me.ToUpper() + "!!!"

You can also add functions to existing static classes (modules) too.

module Array =
    let shuffle arr =
        ...

[| for i in 0 .. 23 do yield i * i |]
    |> Array.filter isOdd   // filter is built-in
    |> Array.shuffle        // i added
 

That's amazing that Ruby and other languages can extend built-in classes as well.

Anyways, to show off C#, here you go.

C# can extend any classes using extension method syntax.

using System;

namespace extensionmethod
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!".Yell());
        }
    }

    public static class StringExtensions
    {
        public static string Yell(this string message)
        {
            return $"{message.ToUpper()}!!!";
        }
    }
}

Outputs

c:\misc\Sources\throwaway\extensionmethod>
$ dotnet run
HELLO WORLD!!!!

Note that you should mark the parameter with this

Yell(this string message)...
 

Here's how this would look in Kotlin:

fun String.yell() = this.toUpperCase()

Another interesting use is to create an Extension Property so you can print any type to the console, like this:

// Define the extension property
val Any.sout
    get() = println(this)

Which can be used like:

fun main(args: Array<String>) {
    "hi".sout // prints hi
    123.sout  // prints 123
    true.sout // prints true
}

Since this is also available on any other class, any object you create will also have this property and it will call their toString().

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