Calling constructor when static .New() method is defined

Ruby IronRuby
1

Shay F. suggested I’d post this to the mailing list, as it may be
a bug in IronRuby:

It seems impossible to call a constructor when there is a static .New()
method defined on a class.

This is a minimal test case demonstrating the problem:

.NET (C#) class:

public class Tester
{
    public static void New()
    {
        Console.WriteLine("In Tester.New()");
    }

    public Tester()
    {
        Console.WriteLine("In constructor");
    }
}

IronRuby code:

Tester.new
Tester.New

The ruby code above calls Tester.New() in both cases. There seems to be
no way to call the regular constructor of this class.

2

You can call CLR constructor using “clr_new” method:

Tester.clr_new

Tomas

3

Thanks, that does seem to work.

But I personally think this behavior is completely wrong. Calling .new
from IronRuby should always call the constructor, not a static method
named .New() that happens to exist somewhere in the class hierarchy. (if
the .New() method is defined in a base class, you get the same problem).

Philippe

4

Philippe Leybaert wrote:

But I personally think this behavior is completely wrong. Calling .new from
IronRuby should always call the constructor, not a static method named
.New() that happens to exist somewhere in the class hierarchy. (if the
.New() method is defined in a base class, you get the same problem).

“new” is just a Ruby method on the Class object, which Ruby happens to
call to construct an object. Because it’s just a method, it can be
overridden. For example, a Ruby class’s #new can be overridden to return
ANY object.

class Foo
… def self.new
… 42
… end
… end
=> nil

Foo.new
=> 42

Foo.new.class
=> Fixnum

So, anywhere in the class hierarchy, #new can be overridden. For
example, if a base class overrides new, it does so for all its
subclasses also, just as normal inheritance tells it do:

class Bar < Foo
… end
=> nil

Bar.new
=> 42

At a high-level, the way IronRuby’s .NET interop works is by treating
any .NET-based code as if it were Ruby code, so a CLR Type will be shown
as a Ruby Class. Therefore, defining a “New” method in C# is the moral
equivalent of defining “new” on any Ruby class, which will override
Class#new, which in turn overrides the CLR .ctor. Which is why “clr_new”
is provided.

~js

5

I said “#new” in some places where I shouldn’t have … so corrected
below in case there was some confusion …