send selection back to Go

main.go

@@ -21,23 +21,19 @@ func exit(status int, t string, args ...interface{}) {
 	os.Exit(status)
 }
 
-type failable func() error
-
-func must(fn failable, status int, msg string) {
-	msg = strings.TrimSpace(msg)
-	if err := fn(); err != nil {
-		exit(status, "%s: %s", msg, err)
-	}
-}
-
 func main() {
 	log.Println("Creating new Desktop UI")
-	ui, err := ui.NewDesktop()
-	if err != nil {
-		exit(1, "unable to create desktop ui: %s", err)
-	}
-	log.Println("Initializing Desktop UI")
-	must(ui.Init, 1, "unable to initialize desktop ui")
+	desktop := ui.Desktop()
+
+	c := make(chan ui.Event, 1)
+	go func() {
+		for e := range c {
+			log.Printf("UI Event: %v\n", e)
+		}
+	}()
+
 	log.Println("Running Desktop UI")
-	must(ui.Run, 1, "unable to run desktop ui")
+	if err := desktop.Run(c); err != nil {
+		exit(1, "UI Error: %v", err)
+	}
 }

ui/MainViewController.h

@@ -1,4 +1,4 @@
 #import <Cocoa/Cocoa.h>
 
-@interface MainViewController : NSViewController <NSOpenSavePanelDelegate>
+@interface MainViewController : NSViewController
 @end

ui/MainViewController.m

@@ -1,3 +1,4 @@
+#import "_cgo_export.h"
 #import "MainViewController.h"
 #import "MainView.h"
 
@@ -27,12 +28,11 @@
     self.selectDirectoryPanel = [NSOpenPanel openPanel];
     [self.selectDirectoryPanel setCanChooseFiles:NO];
     [self.selectDirectoryPanel setCanChooseDirectories:YES];
-    [self.selectDirectoryPanel setDelegate:self];
 
     // create select directory button
     self.selectDirectoryButton = [NSButton buttonWithTitle:@"select directory"
-                                                    target:self.selectDirectoryPanel
-                                                    action:@selector(runModal)];
+                                                    target:self
+                                                    action:@selector(selectDirectory)];
     [self.selectDirectoryButton setTranslatesAutoresizingMaskIntoConstraints:NO];
     [self.view addSubview:self.selectDirectoryButton];
 
@@ -45,9 +45,17 @@
                        constant:8.0].active = YES;
 }
 
-- (void) panel:(id)sender didChangeToDirectoryURL:(NSURL *)url {
-    NSLog(@"[MainViewController] panel: %@ didChangeToDirectoryURL: %@", sender, url);
-    return [super viewWillAppear];
+- (void) selectDirectory {
+    NSLog(@"[MainViewController] select directory start");
+    [self.selectDirectoryPanel beginWithCompletionHandler:^(NSInteger result) {
+        if (result != NSFileHandlingPanelOKButton) {
+            NSLog(@"[MainViewController] user canceled select directory window");
+            return;
+        }
+        NSURL *selected = [[self.selectDirectoryPanel URLs] objectAtIndex:0];
+        NSString *path = [selected path];
+        selectDirectory((GoString){path.UTF8String, path.length});
+    }];
 }
 
 - (void) viewWillAppear {

ui/ui.go

@@ -1,6 +1,18 @@
 package ui
 
 type UI interface {
-	Init() error
-	Run() error
+	Run(chan Event) error
+}
+
+type Event interface {
+	isUIEvent()
+}
+
+type event struct{}
+
+func (e event) isUIEvent() {}
+
+type SelectDirectoryEvent struct {
+	Path string
+	event
 }

ui/ui_darwin.go

@@ -12,21 +12,31 @@ import (
 */
 import "C"
 
-func NewDesktop() (UI, error) {
-	runtime.LockOSThread()
+var desktopUI *cocoaUI
+
+func Desktop() UI {
+	if desktopUI != nil {
+		return desktopUI
+	}
+
 	log.Println("Creating new cocoaUI")
-	return new(cocoaUI), nil
+	runtime.LockOSThread()
+	C.Initialize()
+	desktopUI = new(cocoaUI)
+	return desktopUI
 }
 
 type cocoaUI struct {
+	out chan Event
 }
 
-func (ui *cocoaUI) Init() error {
-	C.Initialize()
+func (ui *cocoaUI) Run(out chan Event) error {
+	ui.out = out
+	C.Run()
 	return nil
 }
 
-func (ui *cocoaUI) Run() error {
-	C.Run()
-	return nil
+//export selectDirectory
+func selectDirectory(path string) {
+	desktopUI.out <- SelectDirectoryEvent{Path: path}
 }