Michel Fortin wrote:
On 2010-11-03 13:55:35 -0400, Walter Bright <[email protected]>
said:
Thanks for doing this!
You're welcome.
"To make Objective-C methods accessible to D programs, we need to map
them to a D function name. This is acomplished by declaring a member
function and giving it a selector:"
Why not just make the D member function the selector name?
The primary reason is that selectors have a different syntax than D
identifiers (they often contain colons). We could add some sort of
mapping, converting colons to underscores for instance, but that's not
very clean and would be a little ugly. Let me show you why.
Because in Objective-C arguments are interleaved inside the multi-part
method name (the selector), it's deemed good there to have very
expressive names. For instance, key-value-observing in Cocoa use this
method selector:
addObserver:forKeyPath:options:context:
When you call this method in Objective-C, it's done like this:
[o addObserver:self forKeyPath:@"window.frame" option:0 context:nil];
Let's convert this in a D-compatible syntax by replacing colons by
underscores:
o.addObserver_forKeyPath_options_context_(this, "window.frame", 0,
nil);
Now imagine a whole program with functions like this one. Would you want
to write a program like that? I'd surely like to hear other's opinions
on that subject, but to me it seems to be a better idea to provide
adapted function names.
How about a way to use . instead?
o.addObserver.forKeyPath.options.context(this, "window.frame", 0, nil);
That would fit right in with, say, forKeyPath being a "member" of addObserver.
Another reason is that it allows Objective-C objects to behave more like
normal D objects. Objective-C doesn't have overloading -- you can't have
two methods with the same selector -- so overloading requires some kind
of mapping between the selector and the D function name. And some
algorithms might expect overloading, so having this capability improves
interoperability. But this is more like a secondary benefit.
I would say, for extern(Objective-C) functions, simply disallow overloading.
