MacRuby and Core Data Tutorial

#
#  AppDelegate.rb
#  MyGreatApp
#
#  Created by Johannes Fahrenkrug on 10/17/08.
#  Copyright __MyCompanyName__ 2008 . All rights reserved.
#


class AppDelegate
attr_writer :window

#    Returns the support folder for the application, used to store the Core Data
#    store file.  This code uses a folder named "MyGreatApp" for
#    the content, either in the NSApplicationSupportDirectory location or (if the
#    former cannot be found), the system's temporary directory.
def applicationSupportFolder
paths = NSSearchPathForDirectoriesInDomains(NSApplicationSupportDirectory, NSUserDomainMask, true)
basePath = (paths.count > 0) ? paths[0] : NSTemporaryDirectory()
return basePath.stringByAppendingPathComponent("MacObjTalks")
end


#
#    Creates and returns the managed object model for the application
#    by merging all of the models found in the application bundle.
#
def managedObjectModel
if @managedObjectModel
 return @managedObjectModel
end

@managedObjectModel = NSManagedObjectModel.mergedModelFromBundles(nil)
return @managedObjectModel
end


#
#    Returns the persistent store coordinator for the application.  This
#    implementation will create and return a coordinator, having added the
#    store for the application to it.  (The folder for the store is created,
#    if necessary.)
#
def persistentStoreCoordinator
if @persistentStoreCoordinator
 return @persistentStoreCoordinator;
end

error = nil

fileManager = NSFileManager.defaultManager
applicationSupportFolder = self.applicationSupportFolder

if !fileManager.fileExistsAtPath(applicationSupportFolder, isDirectory:nil)
 fileManager.createDirectoryAtPath(applicationSupportFolder, attributes:nil)
end

url = NSURL.fileURLWithPath(applicationSupportFolder.stringByAppendingPathComponent("MyData.xml"))
@persistentStoreCoordinator = NSPersistentStoreCoordinator.alloc.initWithManagedObjectModel(self.managedObjectModel)
if !@persistentStoreCoordinator.addPersistentStoreWithType(NSXMLStoreType, configuration:nil, URL:url, options:nil, error:error)
 NSApplication.sharedApplication.presentError(error)
end

return @persistentStoreCoordinator
end


#
#    Returns the managed object context for the application (which is already
#    bound to the persistent store coordinator for the application.)
#
def managedObjectContext
return @managedObjectContext if @managedObjectContext

coordinator = self.persistentStoreCoordinator
if coordinator
 @managedObjectContext = NSManagedObjectContext.alloc.init
 @managedObjectContext.setPersistentStoreCoordinator(coordinator)
end

return @managedObjectContext
end


#
#    Returns the NSUndoManager for the application.  In this case, the manager
#    returned is that of the managed object context for the application.
#
def windowWillReturnUndoManager(window)
return self.managedObjectContext.undoManager
end


#
#    Performs the save action for the application, which is to send the save:
#    message to the application's managed object context.  Any encountered errors
#    are presented to the user.
#
def saveAction(sender)
error = nil;
if !self.managedObjectContext.save(error)
 NSApplication.sharedApplication.presentError(error)
end
end


#
#    Implementation of the applicationShouldTerminate: method, used here to
#    handle the saving of changes in the application managed object context
#    before the application terminates.
#
def applicationShouldTerminate(sender)
error = nil
reply = NSTerminateNow

if self.managedObjectContext
 if (self.managedObjectContext.commitEditing)
  if (self.managedObjectContext.hasChanges and !self.managedObjectContext.save(error))
   # This error handling simply presents error information in a panel with an
   # "Ok" button, which does not include any attempt at error recovery (meaning,
   # attempting to fix the error.)  As a result, this implementation will
   # present the information to the user and then follow up with a panel asking
   # if the user wishes to "Quit Anyway", without saving the changes.

   # Typically, this process should be altered to include application-specific
   # recovery steps.

   errorResult = NSApplication.sharedApplication.presentError(error)
 
   if errorResult
    reply = NSTerminateCancel
   else
    alertReturn = NSRunAlertPanel(nil, "Could not save changes while quitting. Quit anyway?" , "Quit anyway", "Cancel", nil)
    if (alertReturn == NSAlertAlternateReturn)
     reply = NSTerminateCancel
    end
   end
  end
 else
  reply = NSTerminateCancel
 end
end

return reply
end

end