Add nullability attributes in headers

Framework/MASPreferencesViewController.h

@@ -2,23 +2,61 @@
 // Any controller providing preference pane view must support this protocol
 //
 
-#import <Cocoa/Cocoa.h>
+#import <AppKit/AppKit.h>
 
+NS_ASSUME_NONNULL_BEGIN
+
+/*!
+ * Requirements for the Preferences panel
+ */
 @protocol MASPreferencesViewController <NSObject>
 
+/*!
+ * Unique identifier of the Panel represented by the view controller.
+ */
+@property (nonatomic, readonly, nullable) NSString *identifier;
+
+/*!
+ * Toolbar icon for the Panel represented by the view controller.
+ */
+@property (nonatomic, readonly, nullable) NSImage *toolbarItemImage;
+
+/*!
+ * Toolbar item label for the Panel represented by the view controller.
+ *
+ * This label may be used as a Preferences window title.
+ */
+@property (nonatomic, readonly, nullable) NSString *toolbarItemLabel;
+
 @optional
 
+/*!
+ * Called when selection goes to the Panel represented by the view controller.
+ */
 - (void)viewWillAppear;
+
+/*!
+ * Called when selection goes to another Panel.
+ */
 - (void)viewDidDisappear;
-- (NSView *)initialKeyView;
 
-@property (nonatomic, readonly) BOOL hasResizableWidth;
-@property (nonatomic, readonly) BOOL hasResizableHeight;
+/*!
+ * Returns initial control in the key view loop.
+ *
+ * @return The view to focus on automatically when the panel is open.
+ */
+- (__kindof NSView *)initialKeyView;
 
-@required
+/*!
+ * The flag used to detect if the Prerences window can be resized horizontally.
+ */
+@property (nonatomic, readonly) BOOL hasResizableWidth;
 
-@property (nonatomic, readonly) NSString *identifier;
-@property (nonatomic, readonly) NSImage *toolbarItemImage;
-@property (nonatomic, readonly) NSString *toolbarItemLabel;
+/*!
+ * The flag used to detect if the Prerences window can be resized vertically.
+ */
+@property (nonatomic, readonly) BOOL hasResizableHeight;
 
 @end
+
+NS_ASSUME_NONNULL_END

Framework/MASPreferencesWindowController.h

@@ -1,16 +1,25 @@
 //
 // You create an application Preferences window using code like this:
-//     _preferencesWindowController = [[MASPreferencesWindowController alloc] initWithViewControllers:controllers
-//                                                                                              title:title]
+//     _preferencesWindowController = [[MASPreferencesWindowController alloc] initWithViewControllers:controllers title:title]
 //
 // To open the Preferences window:
 //     [_preferencesWindowController showWindow:sender]
 //
 
-#import "MASPreferencesViewController.h"
+#import <AppKit/AppKit.h>
 
-extern NSString *const kMASPreferencesWindowControllerDidChangeViewNotification;
+@protocol MASPreferencesViewController;
 
+NS_ASSUME_NONNULL_BEGIN
+
+/*!
+ * Notification posted when you switch selected panel in Preferences.
+ */
+extern NSString * const kMASPreferencesWindowControllerDidChangeViewNotification;
+
+/*!
+ * Window controller for managing Preference view controllers.
+ */
 __attribute__((__visibility__("default")))
 #if MAC_OS_X_VERSION_MAX_ALLOWED > MAC_OS_X_VERSION_10_5
 @interface MASPreferencesWindowController : NSWindowController <NSToolbarDelegate, NSWindowDelegate>
@@ -26,20 +35,90 @@ __attribute__((__visibility__("default")))
     NSToolbar * __unsafe_unretained _toolbar;
 }
 
+/*!
+ * Child view controllers in the Preferences window.
+ */
 @property (nonatomic, readonly) NSMutableArray *viewControllers;
+
+/*!
+ * Index of selected panel in the Preferences window.
+ */
 @property (nonatomic, readonly) NSUInteger indexOfSelectedController;
-@property (nonatomic, readonly, retain) NSViewController <MASPreferencesViewController> *selectedViewController;
-@property (nonatomic, readonly) NSString *title;
-@property (nonatomic, assign) IBOutlet NSToolbar *toolbar;
 
-- (id)initWithViewControllers:(NSArray *)viewControllers;
-- (id)initWithViewControllers:(NSArray *)viewControllers title:(NSString *)title;
-- (void)addViewController:(NSViewController <MASPreferencesViewController> *) viewController;
+/*!
+ * View controller representing selected panel in the Preferences window.
+ */
+@property (nonatomic, readonly) NSViewController <MASPreferencesViewController> *selectedViewController;
+
+/*!
+ * Optional window title provided in the initializer.
+ */
+@property (nonatomic, copy, readonly, nullable) NSString *title;
+
+/*!
+ * The toolbar managed by the Preferences window.
+ */
+@property (nonatomic, unsafe_unretained) IBOutlet NSToolbar *toolbar;
+
+/*!
+ * Creates new a window controller for Preferences with custom title.
+ *
+ * @param viewControllers Non-empty list of view controllers representing Preference panels.
+ * @param title Optional title for the Preferneces window. Pass `nil` to show the title provided by selected view controller.
+ *
+ * @return A new controller with the given title.
+ */
+- (instancetype)initWithViewControllers:(NSArray *)viewControllers title:(NSString * _Nullable)title;
+- (instancetype)init __attribute((unavailable("Please use initWithViewControllers:title:")));
 
+/*!
+ * Creates new a window controller for Preferences with a flexible title.
+ *
+ * @param viewControllers Non-empty list of view controllers representing Preference panels.
+ *
+ * @return A new controller with title depending on selected view controller.
+ */
+- (instancetype)initWithViewControllers:(NSArray *)viewControllers;
+
+/*!
+ * Appends new panel to the Preferences window.
+ *
+ * @param viewController View controller representing new panel.
+ */
+- (void)addViewController:(NSViewController <MASPreferencesViewController> *)viewController;
+
+/*!
+ * Changes selection in the Preferences toolbar.
+ *
+ * @param controllerIndex Position of the new panel to select in the toolbar.
+ */
 - (void)selectControllerAtIndex:(NSUInteger)controllerIndex;
+
+/*!
+ * Changes selection in the Preferences toolbar using panel identifier.
+ *
+ * @param identifier String identifier of the view controller to select.
+ */
 - (void)selectControllerWithIdentifier:(NSString *)identifier;
 
-- (IBAction)goNextTab:(id)sender;
-- (IBAction)goPreviousTab:(id)sender;
+/*!
+ * Useful action for switching to the next panel.
+ *
+ * For example, you may connect it to the main menu.
+ *
+ * @param sender Menu or toolbar item.
+ */
+- (IBAction)goNextTab:(id _Nullable)sender;
+
+/*!
+ * Useful action for switching to the previous panel.
+ *
+ * For example, you may connect it to the main menu.
+ *
+ * @param sender Menu or toolbar item.
+ */
+- (IBAction)goPreviousTab:(id _Nullable)sender;
 
 @end
+
+NS_ASSUME_NONNULL_END

Framework/MASPreferencesWindowController.m

@@ -1,4 +1,5 @@
 #import "MASPreferencesWindowController.h"
+#import "MASPreferencesViewController.h"
 
 NSString *const kMASPreferencesWindowControllerDidChangeViewNotification = @"MASPreferencesWindowControllerDidChangeViewNotification";
 
@@ -30,13 +31,14 @@ @implementation MASPreferencesWindowController
 
 #pragma mark -
 
-- (id)initWithViewControllers:(NSArray *)viewControllers
+- (instancetype)initWithViewControllers:(NSArray *)viewControllers
 {
     return [self initWithViewControllers:viewControllers title:nil];
 }
 
-- (id)initWithViewControllers:(NSArray *)viewControllers title:(NSString *)title
+- (instancetype)initWithViewControllers:(NSArray *)viewControllers title:(NSString *)title
 {
+	NSParameterAssert(viewControllers.count > 0);
     NSString *nibPath = [[NSBundle bundleForClass:MASPreferencesWindowController.class] pathForResource:@"MASPreferencesWindow" ofType:@"nib"];
     if ((self = [super initWithWindowNibPath:nibPath owner:self]))
     {
@@ -58,8 +60,9 @@ - (void)dealloc
     self.toolbar.delegate = nil;
 }
 
-- (void)addViewController: (NSViewController <MASPreferencesViewController> *) viewController
+- (void)addViewController:(NSViewController <MASPreferencesViewController> *)viewController
 {
+	NSParameterAssert(viewController);
 	[_viewControllers addObject: viewController];
 	[_toolbar insertItemWithItemIdentifier: [viewController identifier] atIndex: ([_viewControllers count] - 1)];
 	[_toolbar validateVisibleItems];
@@ -258,7 +261,7 @@ - (void)setSelectedViewController:(NSViewController <MASPreferencesViewControlle
     [self.window setFrame:newFrame display:YES animate:[self.window isVisible]];
 
     _selectedViewController = controller;
-	
+
     // In OSX 10.10, setContentView below calls viewWillAppear.  We still want to call viewWillAppear on < 10.10,
     // so the check below avoids calling viewWillAppear twice on 10.10.
     // See https://github.com/shpakovski/MASPreferences/issues/32 for more info.
@@ -301,6 +304,7 @@ - (void)selectControllerAtIndex:(NSUInteger)controllerIndex
 
 - (void)selectControllerWithIdentifier:(NSString *)identifier 
 {
+	NSParameterAssert(identifier.length > 0);
     self.selectedViewController = [self viewControllerForIdentifier:identifier];
 }