D on the Objective-C runtime?

[Jacob Carlborg]

On 9/6/09 12:51, Michel Fortin wrote:
> On 2009-09-06 06:10:03 -0400, Jacob Carlborg <doob at me.com> said:
>
>> I've been thinking for a while what it would take to get D running on
>> the Objective-C runtime, in other words a D object will actually be an
>> objc object, kind of like MacRuby but for D. How difficult it would
>> be, how much work, what needs to change, both the runtime and the
>> compiler? And if it would be worth the trouble.
>>
>> The reason for this is to make it easier to interface with Mac OS X
>> system libraries like Cocoa.
>
> It certainly could be done, but first you'd need a way to handle the
> differences between Objective-C and D methods:
>
> - Objective-C methods are of the form "setObject:forKey:", which is
> difficult to map to D.

I was thinking you sill have to create bindings and use objc_msgSend and 
friends. Or something like "extern (Objc) void foo (int arg1, int 
arg2);" would automatically be converted to "objc_msgSend(this, 
sel_registerName("foo:arg2"), arg1, arg2);".

> - Objective-C methods do not support overloading.

"void foo (int arg1, int arg2)" could be transformed to "foo:arg2" or 
similar.

> - Objective-C class methods (equivalent to D static member functions)
> are "virtual", this is used within Cocoa

This would be a problem.

> - Objective-C 2.0 allows a default method implementation in protocols
> (equivalent to D interfaces).
> - Templates, exceptions?

D would use the the objc exceptions and add new exception classes where 
necessary. Templates would probably be disallowed.

> If all you wanted was to make D work using the Objective-C runtime (with
> overloading), you could apply some special name mangling rules, but that
> would make it pretty incompatible with anything really in Objective-C.
>
> On the other side, you could change the D method syntax to disallow
> overloading, use that colon-separated-multiple-part syntax, depend on
> static methods being "virtual" (this pattern is used at some places in
> Cocoa) and add the capability to interfaces to have default
> implementations. but then it wouldn't really be D.

I do not want the colon-separated-multiple-part syntax. I don't want to 
modify the compiler too much, I sill want it to be D but virtual static 
methods could be an acceptable modification for example.

> Another approach is my D/Objective-C bridge:
> <http://michelf.com/projects/d-objc-bridge/>, which allows you to write
> a bridged class like below. It needs D1 and is not multithreaded, only
> can do classes (no protocols, no categories for now), but it works quite
> well for what it does.

Yes I know about your D/objc bridge.

> class AppController : NSObject {
>
> /** Counter for window title in openWindow. */
> uint windowCount;
>
> this() {
> super();
> }
>
> /** Open this application's website. */
> void openWebsite(Object sender) {
> auto a = NSAlert.alert("Cannot open web site.", "OK", null, null,
> "The D/Objective-C bridge doesn’t have access to NSWorkspace yet, "
> "so we cannot open a website. Displaying an alert works though. ;-)");
> a.runModal;
> }
>
> /** Open a new window and put it on the center of the screen. */
> void openWindow(Object sender) {
> auto window = new NSWindow(NSMakeRect(20, 20, 300, 200),
> NSTitledWindowMask + NSClosableWindowMask + NSMiniaturizableWindowMask +
> NSResizableWindowMask,
> NSBackingStoreType.BUFFERED, false);
> window.title = "untitled "~ std.string.toString(++windowCount);
> window.center();
> window.makeKeyAndOrderFront(this);
> }
>
> // Objective-C binding for IB actions.
> mixin IBAction!(openWindow);
> mixin IBAction!(openWebsite);
>
>
> // Overrides from NSApplication delegate.
>
> bool openUntitledFile(NSApplication sender) {
> openWindow(sender);
> return true;
> }
>
> bool shouldTerminateAfterLastWindowClosed(NSApplication sender) {
> return true;
> }
>
> // Objective-C bindings for the above delegate methods.
> mixin ObjcBindMethod!(openUntitledFile, bool,
> "applicationOpenUntitledFile:", NSApplication);
> mixin ObjcBindMethod!(shouldTerminateAfterLastWindowClosed, bool,
> "applicationShouldTerminateAfterLastWindowClosed:", NSApplication);
>
> }
>