D言語からObjective-CとCocoaAPIを使いたい

{
    "authors": ["hidhok"],
    "description": "A D/Objective-C Cocoa application.",
    "name": "star",
    "dflags": ["-L-framework", "-LCocoa"],
    "sourceFiles": ["../cocoa/window",
                    "../cocoa/control",
                    "../cocoa/menus"]
}               

/**
 *	  star/source/app.d       Version 0.0.5
 */
module star.main;
import core.attribute : optional, selector;
import std.conv : to;
import std.math;
import std.stdio;
import cocoa.window;
import cocoa.menus;

string appName;
string versionNo = "0.0.5";
string helpMessage =  "CocoaAPIを使用して、NSBezierPath を\nD言語で表示してみました。";

void main() {
    auto delegate_ = AppDelegate.alloc.init;
    NSApp.delegate_ = cast(void*) delegate_;
    NSApp.activationPolicy = NSAppActivationPolicy.regular;
    NSApp.run;
}

extern (Objective-C)
class DrawView : NSView {
    override static DrawView alloc() @selector("alloc");
    override DrawView init() @selector("init");
    override DrawView init(NSRect) @selector("initWithFrame:");
    override void drawRect(NSRect r) @selector("drawRect:") {
        double X(ref double t) { return (sin(t) + 1) * r.size.width * 0.5; }
        double Y(ref double t) { return (cos(t) + 1) * r.size.height * 0.5; }
        double f, g;
        double pi = PI;  // 2 * acos(0.0);
        int n = 12;

        NSColor.white.setFill;
        NSRectFill(r);
        NSBezierPath.bezierPath;
        NSBezierPath.lineWidth(0.3);
        NSColor.black.stroke; 

        for (f = 0; f < 2 * pi; f += 2 * pi / n) {
            for (g = 0; g < 2 * pi; g += 2 * pi / n) {
                NSPoint p1 = NSMakePoint(X(f), Y(f));
                NSPoint p2 = NSMakePoint(X(g), Y(g));
                NSBezierPath.strokeLine(p1, p2);
            }
        }
    }
}

extern (Objective-C)
class AppDelegate : NSObject {
    override static AppDelegate alloc() @selector("alloc");
    override typeof(this) init() @selector("init");
    bool applicationShouldTerminateAfterLastWindowClosed(
            NSNotification notification) @selector(
            "applicationShouldTerminateAfterLastWindowClosed:") {
        return true;
    }
    void applicationDidFinishLaunching(NSNotification notification) 
                @selector("applicationDidFinishLaunching:") {
        buildWindow;
    }
    void aboutPanel() @selector("aboutPanel") {
        dialog(appName, "Version " ~ versionNo);
    }
    void showHelp() @selector("showHelp") {
        dialog("Help", helpMessage);
    }
} 

void buildWindow() {
    NSWindow win;
    NSRect w_rect = NSMakeRect(100, 550, 400, 400);
    appName = NSProcessInfo.processInfo.processName.toDs;
    NSApp.menu = miniMenu(appName);
    immutable w_style = NSWindowStyleMask.titled |
                        NSWindowStyleMask.closable |
                        NSWindowStyleMask.resizable |
                        NSWindowStyleMask.miniaturizable;
    win = NSWindow.alloc.init(w_rect, w_style, backing.buffered, false);
    win.title = (appName ~ " (D言語テスト)").toNs;
    DrawView dView = DrawView.alloc.init;
    win.contentView = dView;
    // dView.bgColor = NSColor.white;
    ViewController vCtrler = ViewController.alloc.init;
    vCtrler.view.subview = dView;
    win.makeKeyAndOrderFront = null ;
    NSApp.activateIgnoringOtherApps = true;
}


extern (Objective-C) 
class ViewController : NSViewController {
    override static ViewController alloc() @selector("alloc");
    override ViewController init() @selector("init");
    override void loadView() @selector("loadView") {
        printf("loadView\n");
    }
    override void viewDidLoad() @selector("viewDidLoad") {
        printf("viewDidLoad\n");
    }
}