Re: [Q] How would you do method extensions (sometimes called class extensions) in Ruby?

Hi Markus,

I think you better ask this question on the ruby-talk ML.

Cheers,

Nicolas

On 8/31/06, Markus Gaelli <[e-mail]> wrote:
> Hi List,
>
> (1) The Problem: Bridge Gap between Tests and Documentation with
> Executable Examples
> May I introduce myself shortly: I am a long-term OOer using mainly
> Smalltalk until now [0] - and I am interested in bridging the gap
> between documentation (static, bound (comments possible for classes
> and methods), often outdated) and unit testing (dynamic, unbound [2],
> up to date) by the metaphor of examples.
>
> (2) The Concept
> I'd like to be able to see exemplified calls for methods ("method
> examples") - and compose new method examples using example instances
> of classes - which in turn are created by "method examples" [3]
>
> (3) The Proof of Concept
> I have some prototypes for "Eg" in Smalltalk [3], but wonder how it
> would be possible to do something like this in Ruby.
>
> (4) My Approach in Smalltalk: Relying on Conventions and Method
> Extensions
>
> (4.1) Exemplifying Classes
> The easiest solution to bind examples at least to their classes
> (where they should give an exemplified instance of) is by making them
> factory methods of them on the class side. At least in Smalltalk you
> can see this pattern a lot (usually these class methods also start
> with "example..."), I am sure Ruby folks do something similar.
>
> (4.2) Exemplifying and Testing Methods
> I just say that the last method called in these class methods is the
> one exemplified by this example. So this is how I can bind the
> methods to their "method examples" in a light-way and very readable
> manner.
>
> If the method under test (yes, the last one called in the factory
> method / example method) has some postconditions I would declare this
> method to be a "checked method example".
> If there are some assertions in the "method example" itself, I take
> the last method called before the assertions as the tested/
> exemplified method. I  call these kind of "commands" "method tests".
> Note that these "method commands" do return an instance of the class
> they are bound to. This is my invariant for storing them and also
> ensures that the instances they create can be reused by higher-level
> examples/ tests. I do not believe tests should be "void" as JUnit,
> one only needed to call the highest level tests, which in turn can
> call lower level ones. And yes - all tests shall be side effect free,
> and everything but the return value should get garbage collected
> after a test is over.
>
> (5) Finally: My Concrete Problem
> As you can see I am heavily relying on conventions to keep the code
> readable, but still machine parsable. But for doing so I need to
> denote these "method commands" (including "method examples", "checked
> method examples" and "method tests") as being of this kind. Besides
> many people do not like the idea to deploy their code together with
> tests, so they needed to be separable.
>
> This is fine in Smalltalk, as we have method extensions, which scope
> allow Smalltalkers to add methods to classes in packages, in which
> these classes have _not_ been originally defined, but how would you
> do this in Ruby?
>
> I am aware of Singleton Methods, but as they can extend instances,
> (how) can I extend classes without changing their original class
> definition in Ruby?
>
> I would be very grateful for some help, or pointers - certainly I
> wouldn't mind if somebody stole this idea, actually I'd love to see
> "Eg" ported to Ruby, but I am lacking a bit time to do it myself: I
> have to finish my PhD soon and then a Smalltalk (Seaside) job to start.
> - But I do would like not to look too Smalltalk-Snobbish and include
> some help in my PhD to any guys of other fine languages, who decided
> some day, that this might be a good idea.
>
> Cheers,
>
> Markus
>
> [1] http://www.iam.unibe.ch/~scg/cgi-bin/scgbib.cgi?query=gaelli
> [2] Markus Gaelli, Michele Lanza and Oscar Nierstrasz, "Towards a
> Taxonomy of SUnit Tests," Proceedings of ESUG 2005 (13th
> International Smalltalk Conference), September 2005.
> http://www.iam.unibe.ch/~scg/Archive/Papers/
> Gael05aTowardsATaxonomyOfUnitTests.pdf
> [3] Markus Gaelli, Oscar Nierstrasz and St駱hane Ducasse, "One-Method
> Commands: Linking Methods and Their Tests," OOPSLA Workshop on
> Revival of Dynamic Languages, October 2004.
> http://www.iam.unibe.ch/~scg/Archive/Papers/
> Gael04cLinkingMethodsAndTests.pdf
>
>


-- 
Nicolas Despr鑚