Weird Language Features

Steven D. Majewski sdm7g at Virginia.EDU
Mon Feb 19 13:30:52 EST 2001

In objective-c, the functional/procedural part of the language is
just ANSI C, so, with respect to undefined functions, the answer
would be the same as C: no. 

The object-oriented feature of objective-C are based on smalltalk,
so with respect to methods, it's like smalltalk. Any class can
implement forwardInvocation: (as well as some other introspective
methods) to pass methods it doesn't understand to a proxy or delegate.

(I believe you can even redefine this method for NSObject itself, so
 that all subclasses will inherit this new implementation. )

The python<->objective-c bridge in PyObjC uses this in it's
implementation. There are proxy objects sitting between python
classes and their objective-c equivalents. Some common transformations
are built in, so NSStrings and NSArrays can be treated as python
sequences, but in general, python methods are name-mangled into
objective-c method names by translating colons to/from underscores,
and the proxies forward them (depending on which direction you're
going -- objective-C calling Python or Python calling objective-c.) 

-- Steve Majewski <sdm7g at Virginia.EDU>

On Sun, 18 Feb 2001, Eric Clayberg wrote:

> "Dave Cross" <dave at> wrote in message
> news:nnhv8t4obq30ljfgseplp7pi4khhsf9g9n at
> >
> > [Please watch the replies on this message as it's heavily
> > cross-posted]
> >
> > I'm doing some comparisons on programming language features and I'd be
> > very interested to know how you would handle the following scenarios
> > in your programming language of choice.
> >
> > 1/ The programmer calls a function that doesn't actually exist within
> > the application (or libraries). Is the a feature whereby the
> > programmer can create a "catch-all" function which is called in cases
> > like these? Can this function examine the list of existing functions
> > and call the most appropriate one? Or create a new function on the fly
> > and install it into the application?
> Smalltalk can do all of the above very easily. This general technique is
> used to create generic proxies, for example. I have also played around with
> "fault tolerant" apps that could automatically detect and correct spelling
> errors in function calls (as a lark; never in production code).

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