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  • RestKit : Not able to perform mapping using coredata

    - by Ashish Beuwria
    I'm using rest kit 0.20.3 and Xcode 5. Without core data I'm able to perform all rest kit operation, but when I've tried it with core data, I'm not even able to perform GET due to some problem. I can't figure it out. I'm new with core data. So pls help. Here is my code: AppDelegate.m @implementation CardGameAppDelegate @synthesize managedObjectContext = _managedObjectContext; @synthesize managedObjectModel = _managedObjectModel; @synthesize persistentStoreCoordinator = _persistentStoreCoordinator; - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { RKLogConfigureByName("RestKit", RKLogLevelWarning); RKLogConfigureByName("RestKit/ObjectMapping", RKLogLevelTrace); RKLogConfigureByName("RestKit/Network", RKLogLevelTrace); RKObjectManager *objectManager = [RKObjectManager managerWithBaseURL:[NSURL URLWithString:@"http://192.168.1.3:3010/"]]; RKManagedObjectStore *objectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:self.managedObjectModel]; objectManager.managedObjectStore = objectStore; RKEntityMapping *playerMapping = [RKEntityMapping mappingForEntityForName:@"Player" inManagedObjectStore:objectStore]; [playerMapping addAttributeMappingsFromDictionary:@{@"id": @"playerId", @"name": @"playerName", @"age" : @"playerAge", @"created_at": @"createdAt", @"updated_at": @"updatedAt"}]; RKResponseDescriptor *responseDesc = [RKResponseDescriptor responseDescriptorWithMapping:playerMapping method:RKRequestMethodGET pathPattern:@"/players.json" keyPath:nil statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)]; [objectManager addResponseDescriptor:responseDesc]; PlayersTableViewController *ptvc = (PlayersTableViewController *)self.window.rootViewController; ptvc.managedObjectContext = self.managedObjectContext; return YES; } and code for playerTableViewController.h #import <UIKit/UIKit.h> @interface PlayersTableViewController : UITableViewController <NSFetchedResultsControllerDelegate> @property (strong, nonatomic) NSFetchedResultsController *fetchedResultsController; @property (strong, nonatomic) NSManagedObjectContext *managedObjectContext; @end and PlayerTableViewController.m get method: -(void)loadPlayers{ [[RKObjectManager sharedManager] getObjectsAtPath:@"/players.json" parameters:nil success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult){ [self.refreshControl endRefreshing]; } failure:^(RKObjectRequestOperation *operation, NSError *error) { [self.refreshControl endRefreshing]; UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"An Error Has Occurred" message:[error localizedDescription] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil]; [alertView show]; }]; } I'm getting the following error : Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Unable to perform mapping: No `managedObjectContext` assigned. (Mapping response.URL = http://192.168.1.3:3010/players.json)'

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  • Java multithreaded server - each connection returns data. Processing on main thread?

    - by oliwr
    I am writing a client with an integrated server that should wait indefinitely for new connections - and handle each on a Thread. I want to process the received byte array in a system wide available message handler on the main thread. However, currently the processing is obviously done on the client thread. I've looked at Futures, submit() of ExecutorService, but as I create my Client-Connections within the Server, the data would be returned to the Server thread. How can I return it from there onto the main thread (in a synchronized packet store maybe?) to process it without blocking the server? My current implementation looks like this: public class Server extends Thread { private int port; private ExecutorService threadPool; public Server(int port) { this.port = port; // 50 simultaneous connections threadPool = Executors.newFixedThreadPool(50); } public void run() { try{ ServerSocket listener = new ServerSocket(this.port); System.out.println("Listening on Port " + this.port); Socket connection; while(true){ try { connection = listener.accept(); System.out.println("Accepted client " + connection.getInetAddress()); connection.setSoTimeout(4000); ClientHandler conn_c= new ClientHandler(connection); threadPool.execute(conn_c); } catch (IOException e) { System.out.println("IOException on connection: " + e); } } } catch (IOException e) { System.out.println("IOException on socket listen: " + e); e.printStackTrace(); threadPool.shutdown(); } } } class ClientHandler implements Runnable { private Socket connection; ClientHandler(Socket connection) { this.connection=connection; } @Override public void run() { try { // Read data from the InputStream, buffered int count; byte[] buffer = new byte[8192]; InputStream is = connection.getInputStream(); ByteArrayOutputStream out = new ByteArrayOutputStream(); // While there is data in the stream, read it while ((count = is.read(buffer)) > 0) { out.write(buffer, 0, count); } is.close(); out.close(); System.out.println("Disconnect client " + connection.getInetAddress()); connection.close(); // handle the received data MessageHandler.handle(out.toByteArray()); } catch (IOException e) { System.out.println("IOException on socket read: " + e); e.printStackTrace(); } return; } }

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  • How to actually use Swing Application Framework?

    - by Joonas Pulakka
    Hello, I'd like to learn how to effectively use Swing Application Framework. Most of the the examples I've found are blog entries that just explain how to great it is to extend SingleFrameApplication and override its startup method, but that's about it. Sun's article is almost two years old, as is the project's own introduction, and there has apparently been some evolution since then. Are there any recent and thorough tutorials/HOWTOs available anywhere? There is JavaDoc of course, but it's hard to get the big picture from there. Any pointers are appreciated. Update: I realized that there's a mailing list archive at the project's site. While somewhat clumsy (compared to StackOverflow ;) it seems to be quite active. Still it's a pity that there are no real tutorials anywhere. The information is scattered here and there. Update 2: Let me clarify - I'm not having trouble using Swing (the widget toolkit) itself, I'm talking about its Application Framework, which is supposed to ease things like application lifecycle (startup, exit and whatever happens between them), action management etc. - that is, things that most Swing applications will need. It's cool to get such framework to be standard part of Java. The only problem is to learn how it's intended to be used. Update 3: For the interested, there was just some discussion at the project's forum regarding the current state and future of JSR 296. Shortly: the current version 1.03 is considered to be quite usable, but the API is not stable and it will change to the final version in Java 7. The package name will also change so Java 7 will not break current applications made on SAF. Update 4: Karsten Lentzsch stated at the above mentioned forum: "I doubt that it can be included in Java 7; and I'll vote against it.". I would rather not question the sincerity of this great guru, and it's certainly wise not to let anything flawed to slip into the core JDK, but frankly it's a strange situation - he is the author of JGoodies Swing Suite which is partly a commercial competitor of JSR 296, and he is sitting in the committee that will decide whether this JSR will be included to standard Java. It was the same thing with JSR 295 Beans Binding which I wrote about earlier. Given the current state of SAF, I think the best solution is to wrap the current implementation into a "homebrew" framework, which can then accommodate possible changes to the existing API.

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  • Yii - Custom GridView with Multiple Tables

    - by savinger
    So, I've extended GridView to include an Advanced Search feature tailored to the needs of my organization. Filter - lets you show/hide columns in the table, and you can also reorder columns by dragging the little drag icon to the left of each item. Sort - Allows for the selection of multiple columns, specify Ascending or Descending. Search - Select your column and insert search parameters. Operators tailored to data type of selected column. Version 1 works, albeit slowly. Basically, I had my hands in the inner workings of CGridView, where I snatch the results from the DataProvider and do the searching and sorting in PHP before rendering the table contents. Now writing Version 2, where I aim to focus on clever CDbCriteria creation, allowing MySQL to do the heavy lifting so it will run quicker. The implementation is trivial when dealing with a single database table. The difficulty arises when I'm dealing with 2 or more tables... For example, if the user intends to search on a field that is a STAT relation, I need that relation to be present in my query. Here's the question. How do I assure that Yii includes all with relations in my query so that I include comparisons? I've included all my relations with my criteria in the model's search function and I've tried CDbCriteria's together ... public function search() { $criteria=new CDbCriteria; $criteria->compare('id', $this->id); $criteria->compare( ... ... $criteria->with = array('relation1','relation2','relation3'); $criteria->together = true; return new CActiveDataProvider( get_class($this), array( 'criteria'=>$criteria, 'pagination' => array('pageSize' => 50) ));} But I still get errors like this... CDbCommand failed to execute the SQL statement: SQLSTATE[42S22]: Column not found: 1054 Unknown column 't.relation3' in 'where clause'. The SQL statement executed was: SELECT COUNT(DISTINCT `t`.`id`) FROM `table` `t` LEFT OUTER JOIN `relation_table` `relation0` ON (`t`.`id`=`relation0`.`id`) LEFT OUTER JOIN `relation_table` `relation1` ON (`t`.`id`=`relation1`.`id`) WHERE (`t`.`relation3` < 1234567890) Where relation0 and relation1 are BELONGS_TO relations, but any STAT relations are missing. Furthermore, why is the query a SELECT COUNT(DISTINCT 't'.'id') ?

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  • Efficiency of data structures in C99 (possibly affected by endianness)

    - by Ninefingers
    Hi All, I have a couple of questions that are all inter-related. Basically, in the algorithm I am implementing a word w is defined as four bytes, so it can be contained whole in a uint32_t. However, during the operation of the algorithm I often need to access the various parts of the word. Now, I can do this in two ways: uint32_t w = 0x11223344; uint8_t a = (w & 0xff000000) >> 24; uint8_t b = (w & 0x00ff0000) >> 16; uint8_t b = (w & 0x0000ff00) >> 8; uint8_t d = (w & 0x000000ff); However, part of me thinks that isn't particularly efficient. I thought a better way would be to use union representation like so: typedef union { struct { uint8_t d; uint8_t c; uint8_t b; uint8_t a; }; uint32_t n; } word32; Using this method I can assign word32 w = 0x11223344; then I can access the various parts as I require (w.a=11 in little endian). However, at this stage I come up against endianness issues, namely, in big endian systems my struct is defined incorrectly so I need to re-order the word prior to it being passed in. This I can do without too much difficulty. My question is, then, is the first part (various bitwise ands and shifts) efficient compared to the implementation using a union? Is there any difference between the two generally? Which way should I go on a modern, x86_64 processor? Is endianness just a red herring here? I could inspect the assembly output of course, but my knowledge of compilers is not brilliant. I would have thought a union would be more efficient as it would essentially convert to memory offsets, like so: mov eax, [r9+8] Would a compiler realise that is what happening in the bit-shift case above? If it matters, I'm using C99, specifically my compiler is clang (llvm). Thanks in advance.

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  • NSTimer as a self-targeting ivar.

    - by Matt Wilding
    I have come across an awkward situation where I would like to have a class with an NSTimer instance variable that repeatedly calls a method of the class as long as the class is alive. For illustration purposes, it might look like this: // .h @interface MyClock : NSObject { NSTimer* _myTimer; } - (void)timerTick; @end - // .m @implementation MyClock - (id)init { self = [super init]; if (self) { _myTimer = [[NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(timerTick) userInfo:nil repeats:NO] retain]; } return self; } - (void)dealloc { [_myTimer invalidate]; [_myTImer release]; [super dealloc]; } - (void)timerTick { // Do something fantastic. } @end That's what I want. I don't want to to have to expose an interface on my class to start and stop the internal timer, I just want it to run while the class exists. Seems simple enough. But the problem is that NSTimer retains its target. That means that as long as that timer is active, it is keeping the class from being dealloc'd by normal memory management methods because the timer has retained it. Manually adjusting the retain count is out of the question. This behavior of NSTimer seems like it would make it difficult to ever have a repeating timer as an ivar, because I can't think of a time when an ivar should retain its owning class. This leaves me with the unpleasant duty of coming up with some method of providing an interface on MyClock that allows users of the class to control when the timer is started and stopped. Besides adding unneeded complexity, this is annoying because having one owner of an instance of the class invalidate the timer could step on the toes of another owner who is counting on it to keep running. I could implement my own pseudo-retain-count-system for keeping the timer running but, ...seriously? This is way to much work for such a simple concept. Any solution I can think of feels hacky. I ended up writing a wrapper for NSTimer that behaves exactly like a normal NSTimer, but doesn't retain its target. I don't like it, and I would appreciate any insight.

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  • Deleting items from a ListView using a custom BaseAdapter

    - by HXCaine
    I am using a customised BaseAdapter to display items on a ListView. The items are just strings held in an ArrayList. The list items have a delete button on them (big red X), and I'd like to remove the item from the ArrayList, and notify the ListView to update itself. However, every implementation I've tried gets mysterious position numbers given to it, so for example clicking item 2's delete button will delete item 5's. It seems to be almost entirely random. One thing to note is that elements may be repeated, but must be kept in the same order. For example, I can have "Irish" twice, as elements 3 and 7. My code is below: private static class ViewHolder { TextView lang; int position; } public View getView(final int position, View convertView, ViewGroup parent) { ViewHolder holder; if (convertView == null) { convertView = mInflater.inflate(R.layout.language_link_row, null); holder = new ViewHolder(); holder.lang = (TextView)convertView.findViewById(R.id.language_link_text); holder.position = position; final ImageView deleteButton = (ImageView) convertView.findViewById(R.id.language_link_cross_delete); deleteButton.setOnClickListener(this); convertView.setTag(holder); deleteButton.setTag(holder); } else { holder = (ViewHolder) convertView.getTag(); } holder.lang.setText(mLanguages.get(position)); return convertView; } I later attempt to retrieve the deleted element's position by grabbing the tag, but it's always the wrong position in the list. There is no noticeable pattern to the position given here, it always seems random. // The delete button's listener public void onClick(View v) { ViewHolder deleteHolder = (ViewHolder) v.getTag(); int pos = deleteHolder.position; ... ... ... } I would be quite happy to just delete the item from the ArrayList and have the ListView update itself, but the position I'm getting is incorrect so I can't do that. Please note that I did, at first, have the deleteButton clickListener inside the getView method, and used 'position' to delete the value, but I had the same problem. Any suggestions appreciated, this is really irritating me.

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  • Historical / auditable database

    - by Mark
    Hi all, This question is related to the schema that can be found in one of my other questions here. Basically in my database I store users, locations, sensors amongst other things. All of these things are editable in the system by users, and deletable. However - when an item is edited or deleted I need to store the old data; I need to be able to see what the data was before the change. There are also non-editable items in the database, such as "readings". They are more of a log really. Readings are logged against sensors, because its the reading for a particular sensor. If I generate a report of readings, I need to be able to see what the attributes for a location or sensor was at the time of the reading. Basically I should be able to reconstruct the data for any point in time. Now, I've done this before and got it working well by adding the following columns to each editable table: valid_from valid_to edited_by If valid_to = 9999-12-31 23:59:59 then that's the current record. If valid_to equals valid_from, then the record is deleted. However, I was never happy with the triggers I needed to use to enforce foreign key consistency. I can possibly avoid triggers by using the extension to the "PostgreSQL" database. This provides a column type called "period" which allows you to store a period of time between two dates, and then allows you to do CHECK constraints to prevent overlapping periods. That might be an answer. I am wondering though if there is another way. I've seen people mention using special historical tables, but I don't really like the thought of maintainling 2 tables for almost every 1 table (though it still might be a possibility). Maybe I could cut down my initial implementation to not bother checking the consistency of records that aren't "current" - i.e. only bother to check constraints on records where the valid_to is 9999-12-31 23:59:59. Afterall, the people who use historical tables do not seem to have constraint checks on those tables (for the same reason, you'd need triggers). Does anyone have any thoughts about this? PS - the title also mentions auditable database. In the previous system I mentioned, there is always the edited_by field. This allowed all changes to be tracked so we could always see who changed a record. Not sure how much difference that might make. Thanks.

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  • Hide button on first of two UIViews, but have it visible on second...

    - by Scott
    So I have a UIViewController (main application controller is a TabBarController). On this there is a UINavigationBar, and a UIBarButtonItem. I'm PRETTY sure I hooked up everything correctly in the Interface Builder and that the outlet in the code is connected to the button in the .xib. It should be because the method works correctly. Now I have another button on this view that brings up a second view, a UIWebView. I want this UIBarButtonItem, labeled "Back", to make the UIWebView dissapear, and bring back the first UIView, which it DOES DO correctly. However, when you are on the first UIView, there is no need to see the UIBarButtonItem, so how can I hide it but then bring it up for the UIWebView. By the way, both views use the same UINavigationBar, the UIWebView is brought up inside the tab bar and the nav bar. Here is my code: #import "WebViewController.h" @implementation WebViewController @synthesize webButton; @synthesize item; @synthesize infoView; UIWebView *webView; + (UIColor*)myColor1 { return [UIColor colorWithRed:0.0f/255.0f green:76.0f/255.0f blue:29.0f/255.0f alpha:1.0f]; } // Creates Nav Bar with default Green at top of screen with given String as title + (UINavigationBar*)myNavBar1: (NSString*)input { UIView *test = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]]; UINavigationBar *navBar = [[UINavigationBar alloc] initWithFrame:CGRectMake(0.0, 0.0, test.bounds.size.width, 45)]; navBar.tintColor = [WebViewController myColor1]; UINavigationItem *navItem; navItem = [UINavigationItem alloc]; navItem.title = input; [navBar pushNavigationItem:navItem animated:false]; return navBar; } - (IBAction) pushWebButton { self.navigationItem.rightBarButtonItem = item; CGRect webFrame = CGRectMake(0.0, 45.0, 320.0, 365.0); webView = [[UIWebView alloc] initWithFrame:webFrame]; [webView setBackgroundColor:[UIColor whiteColor]]; NSString *urlAddress = @"http://www.independencenavigator.com"; NSURL *url = [NSURL URLWithString:urlAddress]; NSURLRequest *requestObj = [NSURLRequest requestWithURL:url]; webView.scalesPageToFit = YES; [webView loadRequest:requestObj]; [self.view addSubview:webView]; [webView release]; } - (void) pushBackButton { [webView removeFromSuperview]; } // Implement viewDidLoad to do additional setup after loading the view, typically from a nib. - (void)viewDidLoad { self.navigationItem.rightBarButtonItem = nil; [super viewDidLoad]; } @end Anyone know?

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  • Inherited TShape.Paint does not work after overriding Shape property

    - by DarkWalker
    I'm to code a TExpandedShape class inherited from TShape. TExpandedShape must act like TShape and be able to draw extra shapes: Polygon and Star. Here is my code unit ExpandedShape; interface uses SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls, Forms, Dialogs, ExtCtrls, Windows; type TExpandedShapeType = ( stRectangle, stSquare, stRoundRect, stRoundSquare, stEllipse, stCircle, stPolygon, stStar ); TExpandedShape = class(TShape) private FShape: TExpandedShapeType; FEdgeCount: integer; procedure SetShape(const Value: TExpandedShapeType); procedure SetEdgeCount(const Value: integer); public procedure Paint; override; published property Shape : TExpandedShapeType read FShape write SetShape;// default stPolygon; property EdgeCount : integer read FEdgeCount write SetEdgeCount default 5; end; procedure Register; implementation procedure Register; begin RegisterComponents('Course', [TExpandedShape]); end; // TExpandedShape procedure TExpandedShape.Paint; begin case Shape of stStar : begin {Draw Star} end; stPolygon : begin {Draw Polygon} end; else begin {It is supposed to draw Circle, Rectangle etc, but it does not} inherited; end; end; end; procedure TExpandedShape.SetEdgeCount(const Value: integer); begin FEdgeCount := Value; Repaint; end; procedure TExpandedShape.SetShape(const Value: TExpandedShapeType); begin FShape := Value; Repaint; end; end. So, what is wrong? IMO TShape.Paint checks private value like FShape in case section and then decides what to draw. When inherited Paint method is called in my code it checks FShape value sees default 0 value [stRectangle] in there and draws it. PS: I did solve it with blackmagic way using Shape1 property instead of Shape one and if Shape1 value is not stPolygon or stStar i do like this: begin Shape := TShapeType(Shape1); inherited end; But this option is not really an option. I need a good short nice-looking one.

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  • How to fine tune a Membership Provider?

    - by Venemo
    After all the answers to my last question about fine-tuning turned out to be more useful than I expected, I thought that I would ask another similar Question about the MembershipProviders as well. Okay, so firstly, to clarify: I know what a Membership, Role, and Profile provider is, how to implement my own, and how to configure them, and most of the things about them. Implementing a role and profile provider is pretty straightforward, because they only require simple CRUD most of the time. (A single line of LINQ is enough for about half of the RoleProvider's methods.) However, the Membership provider is a differend beast. Many of you may realize that it violates the SR (Single Responsibility) principle, because it has to do EVERYTHING related to user management. While this leaves a lot of room for customizations, it has its downsides as well. There is no information on the Internet about what their EXACT expected behaviour is, such as when should they throw exceptions or simply return null, and stuff like that. I use this sample implementation for reference, but it also contains several contradictions. For example, it uses its own ValidateUser method for checking for credentials in the ChangePassword method. But the ValidateUser also updates the user's LastLoginDate to the current date. So, does the framework expect that I set it in my own provider as well, or is it simply a mistake in the sample? The other is: the ChangePassword method throws an exception every time when validating the new password, but CreateUser doesn't ever throw an exception, it simply returns false. And last, but not least: it counts the invalid password attempts of the user and locks them if it passes a threshold. While this is good, but it requires manual action to unlock the users. Is it a problem if my provider automatically unlocks the user after a certain amount of time? (EDIT) I almost forgot: the CreateUser method in the sample inserts the ID from the method parameter. I actually think this is bad practice, because I use inters with auto incement as IDs, so inserting them from some method parameter is not an option. Should I just ignore the parameter, or require that its value is null and throw an exception if it isn't? All in all, does ASP.NET have any assumptions about the behaviour of a MembershipProvider? Is there any documentation which describes when should I throw an exception or just return null? I also tried to find a set of generic unit tests which would provide some guidance about the expected behaviour, but no luck, I found plenty of articles about "Unit testing is good", and "How to unit test a MembershipProvider", but not one where there would be any actual tests. Thanks in advance for everyone!

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  • Issues with mx:method, mx.rpc.remoting.mxml.RemoteObject, and sub-classing mx.rpc.remoting.mxml.Remo

    - by Ryan Wilson
    I am looking to subclass RemoteObject. Instead of: <mx:RemoteObject ... > <mx:method ... /> <mx:method ... /> </mx:RemoteObject> I want to do something like: <remoting:CustomRemoteObject ...> <mx:method ... /> <mx:method ... /> </remoting:CustomRemoteObject> where CustomRemoteObject extends mx.rpc.remoting.mxml.RemoteObject like so: package remoting { import mx.rpc.remoting.mxml.RemoteObject; public class CustomRemoteObject extends RemoteObject { public function CustomRemoteObject(destination:String=null) { super(destination); } } } However, when doing so and declaring a CustomRemoteObject in MXML as above, the flex compiler shows the error: Could not resolve <mx:method> to a component implementation At first I thought it had something to do with CustomRemoteObject failing to do something, despite that (or since) it had no change except as to the name. So, I copied the source from mx.rpc.remoting.mxml.RemoteObject into CustomRemoteObject and modified it so the only difference was a refactoring of the class and package name. But still, the same error. Unlike many MXML components, I cannot cmd+click <mx:method> in FlashBuilder to open the source. Likewise, I have not found a reference in mx.rpc.remoting.mxml.RemoteObject, mx.rpc.remoting.RemoteObject, or mx.rpc.remoting.AbstractService, and have been unsuccessful in find its source online. Which leads me to the questions in the title: What exactly is <mx:method>? (yes, I know it's a declaration of a RemoteObject method, and I know how to use it, but it's peculiar in regard to other components) Why did my attempt at subclassing RemoteObject fail, despite it effectually being a rename? Perhaps the root, why can mx.rpc.remoting.mxml.RemoteObject as an MXML declaration accept <mx:method> child tags, yet the source of said class cannot when refactored in name only?

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  • Data aggregation mongodb vs mysql

    - by Dimitris Stefanidis
    I am currently researching on a backend to use for a project with demanding data aggregation requirements. The main project requirements are the following. Store millions of records for each user. Users might have more than 1 million entries per year so even with 100 users we are talking about 100 million entries per year. Data aggregation on those entries must be performed on the fly. The users need to be able to filter on the entries by a ton of available filters and then present summaries (totals , averages e.t.c) and graphs on the results. Obviously I cannot precalculate any of the aggregation results because the filter combinations (and thus the result sets) are huge. Users are going to have access on their own data only but it would be nice if anonymous stats could be calculated for all the data. The data is going to be most of the time in batch. e.g the user will upload the data every day and it could like 3000 records. In some later version there could be automated programs that upload every few minutes in smaller batches of 100 items for example. I made a simple test of creating a table with 1 million rows and performing a simple sum of 1 column both in mongodb and in mysql and the performance difference was huge. I do not remember the exact numbers but it was something like mysql = 200ms , mongodb = 20 sec. I have also made the test with couchdb and had much worse results. What seems promising speed wise is cassandra which I was very enthusiastic about when I first discovered it. However the documentation is scarce and I haven't found any solid examples on how to perform sums and other aggregate functions on the data. Is that possible ? As it seems from my test (Maybe I have done something wrong) with the current performance its impossible to use mongodb for such a project although the automated sharding functionality seems like a perfect fit for it. Does anybody have experience with data aggregation in mongodb or have any insights that might be of help for the implementation of the project ? Thanks, Dimitris

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  • indentationLevelForRowAtIndexPath not indenting custom cell

    - by Xetius
    I have overridden the tableView:indentationLevelForRowAtIndexPath method in my UITableViewController derived class as follows: - (NSInteger)tableView:(UITableView *)tableView indentationLevelForRowAtIndexPath:(NSIndexPath *)indexPath { NSDictionary* item = [self.projects objectAtIndex:indexPath.row]; int indentationLevel = [[item objectForKey:@"indent"] intValue]; DLog (@"Indentation Level for Row %d : %d", indexPath.row, indentationLevel); return indentationLevel; } I initially thought that this was not being called but that was operator error (err, mine) and I hadn't defined the symbol DEBUG=1. However, it is being called (duh me!) and this is the log output: -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 0 : 1 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 1 : 1 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 2 : 2 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 3 : 2 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 4 : 2 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 5 : 1 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 6 : 2 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 7 : 2 -[RootViewController tableView:indentationLevelForRowAtIndexPath:] [Line 129] Indentation Level for Row 8 : 1 But, this is not affecting the layout of the cells. No indentation. This is my itemCellForRowAtIndexPath implementation, if that makes any difference: -(UITableViewCell*)tableView:(UITableView *)tableView itemCellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString* cellIdentifier = @"projectItemCell"; ProjectItemTableViewCell* cell = (ProjectItemTableViewCell*)[tableView dequeueReusableCellWithIdentifier:cellIdentifier]; if (cell == nil) { NSArray* nib = [[NSBundle mainBundle] loadNibNamed:@"ProjectItemTableViewCell" owner:self options:nil]; for (id oneObject in nib) { if ([oneObject isKindOfClass:[ProjectItemTableViewCell class]]) { cell = (ProjectItemTableViewCell*)oneObject; } } } NSDictionary* item = [self.projects objectAtIndex:indexPath.row]; cell.projectDescLabel.text = [item objectForKey:@"name"]; cell.itemCountlabel.text = [NSString stringWithFormat:@"%d", [[item objectForKey:@"cache_count"] intValue]]; cell.itemCountlabel.backgroundColor = [UIColor colorForHex:[item objectForKey:@"color"]]; cell.indentationWidth = 20; return cell; } How do I indent a custom UITableViewCell which I have defined in Interface Builder? If I change the itemCellForRowAtIndexPath to use a default UITableViewCell with the code below, then it indents fine. static NSString* cellIdentifier = @"projectItemCell"; UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier] autorelease]; } NSDictionary* item = [self.projects objectAtIndex:indexPath.row]; cell.textLabel.text = [item objectForKey:@"name"]; cell.indentationWidth = 40; return cell;

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  • ASP.NET Client to Server communication

    - by Nelson
    Can you help me make sense of all the different ways to communicate from browser to client in ASP.NET? I have made this a community wiki so feel free to edit my post to improve it. Specifically, I'm trying to understand in which scenario to use each one by listing how each works. I'm a little fuzzy on UpdatePanel vs CallBack (with ViewState): I know UpdatePanel always returns HTML while CallBack can return JSON. Any other major differences? ...and CallBack (without ViewState) vs WebMethod. CallBack goes through most of the Page lifecycle, WebMethod doesn't. Any other major differences? IHttpHandler Custom handler for anything (page, image, etc.) Only does what you tell it to do (light server processing) Page is an implementation of IHttpHandler If you don't need what Page provides, create a custom IHttpHandler If you are using Page but overriding Render() and not generating HTML, you probably can do it with a custom IHttpHandler (e.g. writing binary data such as images) By default can use the .axd or .ashx file extensions -- both are functionally similar .ashx doesn't have any built-in endpoints, so it's preferred by convention Regular PostBack (System.Web.UI.Page : IHttpHandler) Inherits Page Full PostBack, including ViewState and HTML control values (heavy traffic) Full Page lifecycle (heavy server processing) No JavaScript required Webpage flickers/scrolls since everything is reloaded in browser Returns full page HTML (heavy traffic) UpdatePanel (Control) Control inside Page Full PostBack, including ViewState and HTML control values (heavy traffic) Full Page lifecycle (heavy server processing) Controls outside the UpdatePanel do Render(NullTextWriter) Must use ScriptManager If no client-side JavaScript, it can fall back to regular PostBack with no JavaScript (?) No flicker/scroll since it's an async call, unless it falls back to regular postback. Can be used with master pages and user controls Has built-in support for progress bar Returns HTML for controls inside UpdatePanel (medium traffic) Client CallBack (Page, System.Web.UI.ICallbackEventHandler) Inherits Page Most of Page lifecycle (heavy server processing) Takes only data you specify (light traffic) and optionally ViewState (?) (medium traffic) Client must support JavaScript and use ScriptManager No flicker/scroll since it's an async call Can be used with master pages and user controls Returns only data you specify in format you specify (e.g. JSON, XML...) (?) (light traffic) WebMethod Class implements System.Web.Service.WebService HttpContext available through this.Context Takes only data you specify (light traffic) Server only runs the called method (light server processing) Client must support JavaScript No flicker/scroll since it's an async call Can be used with master pages and user controls Returns only data you specify, typically JSON (light traffic) Can create instance of server control to render HTML and sent back as string, but events, paging in GridView, etc. won't work PageMethods Essentially a WebMethod contained in the Page class, so most of WebMethod's bullet's apply Method must be public static, therefore no Page instance accessible HttpContext available through HttpContext.Current Accessed directly by URL Page.aspx/MethodName (e.g. with XMLHttpRequest directly or with library such as jQuery) Setting ScriptManager property EnablePageMethods="True" generates a JavaScript proxy for each WebMethod Cannot be used directly in user controls with master pages and user controls Any others?

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  • Spring AOP pointcut that matches annotation on interface

    - by seanizer
    Hello, this is my first post here, so I apologize in advance for any stupidity on my side. I have a service class implemented in Java 6 / Spring 3 that needs an annotation to restrict access by role. I have defined an annotation called RequiredPermission that has as its value attribute one or more values from an enum called OperationType: public @interface RequiredPermission { /** * One or more {@link OperationType}s that map to the permissions required * to execute this method. * * @return */ OperationType[] value();} public enum OperationType { TYPE1, TYPE2; } package com.mycompany.myservice; public interface MyService{ @RequiredPermission(OperationType.TYPE1) void myMethod( MyParameterObject obj ); } package com.mycompany.myserviceimpl; public class MyServiceImpl implements MyService{ public myMethod( MyParameterObject obj ){ // do stuff here } } I also have the following aspect definition: /** * Security advice around methods that are annotated with * {@link RequiredPermission}. * * @param pjp * @param param * @param requiredPermission * @return * @throws Throwable */ @Around(value = "execution(public *" + " com.mycompany.myserviceimpl.*(..))" + " && args(param)" + // parameter object " && @annotation( requiredPermission )" // permission annotation , argNames = "param,requiredPermission") public Object processRequest(final ProceedingJoinPoint pjp, final MyParameterObject param, final RequiredPermission requiredPermission) throws Throwable { if(userService.userHasRoles(param.getUsername(),requiredPermission.values()){ return pjp.proceed(); }else{ throw new SorryButYouAreNotAllowedToDoThatException( param.getUsername(),requiredPermission.value()); } } The parameter object contains a user name and I want to look up the required role for the user before allowing access to the method. When I put the annotation on the method in MyServiceImpl, everything works just fine, the pointcut is matched and the aspect kicks in. However, I believe the annotation is part of the service contract and should be published with the interface in a separate API package. And obviously, I would not like to put the annotation on both service definition and implementation (DRY). I know there are cases in Spring AOP where aspects are triggered by annotations one interface methods (e.g. Transactional). Is there a special syntax here or is it just plain impossible out of the box. PS: I have not posted my spring config, as it seems to be working just fine. And no, those are neither my original class nor method names. Thanks in advance, Sean PPS: Actually, here is the relevant part of my spring config: <aop:aspectj-autoproxy proxy-target-class="false" /> <bean class="com.mycompany.aspect.MyAspect"> <property name="userService" ref="userService" /> </bean>

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  • handling NSStream events when using EASession in MonoTouch

    - by scotru
    Does anyone have an example of how to handle read and write NSStream events in Monotouch when working with accessories via EASession? It looks like there isn't a strongly typed delegate for this and I'm having trouble figuring out what selectors I need to handle on the delegates of my InputStream and OutputStream and what I actually need to do with each selector in order to properly fill and empty the buffers belonging to the EASession object. Basically, I'm trying to port Apple's EADemo app to Monotouch right now. Here's the Objective-C source that I think is relevant to this problem: / / asynchronous NSStream handleEvent method - (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode { switch (eventCode) { case NSStreamEventNone: break; case NSStreamEventOpenCompleted: break; case NSStreamEventHasBytesAvailable: [self _readData]; break; case NSStreamEventHasSpaceAvailable: [self _writeData]; break; case NSStreamEventErrorOccurred: break; case NSStreamEventEndEncountered: break; default: break; } } / low level write method - write data to the accessory while there is space available and data to write - (void)_writeData { while (([[_session outputStream] hasSpaceAvailable]) && ([_writeData length] > 0)) { NSInteger bytesWritten = [[_session outputStream] write:[_writeData bytes] maxLength:[_writeData length]]; if (bytesWritten == -1) { NSLog(@"write error"); break; } else if (bytesWritten > 0) { [_writeData replaceBytesInRange:NSMakeRange(0, bytesWritten) withBytes:NULL length:0]; } } } // low level read method - read data while there is data and space available in the input buffer - (void)_readData { #define EAD_INPUT_BUFFER_SIZE 128 uint8_t buf[EAD_INPUT_BUFFER_SIZE]; while ([[_session inputStream] hasBytesAvailable]) { NSInteger bytesRead = [[_session inputStream] read:buf maxLength:EAD_INPUT_BUFFER_SIZE]; if (_readData == nil) { _readData = [[NSMutableData alloc] init]; } [_readData appendBytes:(void *)buf length:bytesRead]; //NSLog(@"read %d bytes from input stream", bytesRead); } [[NSNotificationCenter defaultCenter] postNotificationName:EADSessionDataReceivedNotification object:self userInfo:nil]; } I'd also appreciate any architectural recommendations on how to best implement this in monotouch. For example, in the Objective C implementation these functions are not contained in any class--but in Monotouch would it make sense to make them members of my

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  • Using a type parameter and a pointer to the same type parameter in a function template

    - by Darel
    Hello, I've written a template function to determine the median of any vector or array of any type that can be sorted with sort. The function and a small test program are below: #include <algorithm> #include <vector> #include <iostream> using namespace::std; template <class T, class X> void median(T vec, size_t size, X& ret) { sort(vec, vec + size); size_t mid = size/2; ret = size % 2 == 0 ? (vec[mid] + vec[mid-1]) / 2 : vec[mid]; } int main() { vector<double> v; v.push_back(2); v.push_back(8); v.push_back(7); v.push_back(4); v.push_back(9); double a[5] = {2, 8, 7, 4, 9}; double r; median(v.begin(), v.size(), r); cout << r << endl; median(a, 5, r); cout << r << endl; return 0; } As you can see, the median function takes a pointer as an argument, T vec. Also in the argument list is a reference variable X ret, which is modified by the function to store the computed median value. However I don't find this a very elegant solution. T vec will always be a pointer to the same type as X ret. My initial attempts to write median had a header like this: template<class T> T median(T *vec, size_t size) { sort(vec, vec + size); size_t mid = size/2; return size % 2 == 0 ? (vec[mid] + vec[mid-1]) / 2 : vec[mid]; } I also tried: template<class T, class X> X median(T vec, size_t size) { sort(vec, vec + size); size_t mid = size/2; return size % 2 == 0 ? (vec[mid] + vec[mid-1]) / 2 : vec[mid]; } I couldn't get either of these to work. My question is, can anyone show me a working implementation of either of my alternatives? Thanks for looking!

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  • agent-based simulation: performance issue: Python vs NetLogo & Repast

    - by max
    I'm replicating a small piece of Sugarscape agent simulation model in Python 3. I found the performance of my code is ~3 times slower than that of NetLogo. Is it likely the problem with my code, or can it be the inherent limitation of Python? Obviously, this is just a fragment of the code, but that's where Python spends two-thirds of the run-time. I hope if I wrote something really inefficient it might show up in this fragment: UP = (0, -1) RIGHT = (1, 0) DOWN = (0, 1) LEFT = (-1, 0) all_directions = [UP, DOWN, RIGHT, LEFT] # point is just a tuple (x, y) def look_around(self): max_sugar_point = self.point max_sugar = self.world.sugar_map[self.point].level min_range = 0 random.shuffle(self.all_directions) for r in range(1, self.vision+1): for d in self.all_directions: p = ((self.point[0] + r * d[0]) % self.world.surface.length, (self.point[1] + r * d[1]) % self.world.surface.height) if self.world.occupied(p): # checks if p is in a lookup table (dict) continue if self.world.sugar_map[p].level > max_sugar: max_sugar = self.world.sugar_map[p].level max_sugar_point = p if max_sugar_point is not self.point: self.move(max_sugar_point) Roughly equivalent code in NetLogo (this fragment does a bit more than the Python function above): ; -- The SugarScape growth and motion procedures. -- to M ; Motion rule (page 25) locals [ps p v d] set ps (patches at-points neighborhood) with [count turtles-here = 0] if (count ps > 0) [ set v psugar-of max-one-of ps [psugar] ; v is max sugar w/in vision set ps ps with [psugar = v] ; ps is legal sites w/ v sugar set d distance min-one-of ps [distance myself] ; d is min dist from me to ps agents set p random-one-of ps with [distance myself = d] ; p is one of the min dist patches if (psugar >= v and includeMyPatch?) [set p patch-here] setxy pxcor-of p pycor-of p ; jump to p set sugar sugar + psugar-of p ; consume its sugar ask p [setpsugar 0] ; .. setting its sugar to 0 ] set sugar sugar - metabolism ; eat sugar (metabolism) set age age + 1 end On my computer, the Python code takes 15.5 sec to run 1000 steps; on the same laptop, the NetLogo simulation running in Java inside the browser finishes 1000 steps in less than 6 sec. EDIT: Just checked Repast, using Java implementation. And it's also about the same as NetLogo at 5.4 sec. Recent comparisons between Java and Python suggest no advantage to Java, so I guess it's just my code that's to blame? EDIT: I understand MASON is supposed to be even faster than Repast, and yet it still runs Java in the end.

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  • access exception when invoking method of an anonymous class using java reflection

    - by Asaf David
    Hello I'm trying to use an event dispatcher to allow a model to notify subscribed listeners when it changes. the event dispatcher receives a handler class and a method name to call during dispatch. the presenter subscribes to the model changes and provide a Handler implementation to be called on changes. Here's the code (I'm sorry it's a bit long). EventDispacther: package utils; public class EventDispatcher<T> { List<T> listeners; private String methodName; public EventDispatcher(String methodName) { listeners = new ArrayList<T>(); this.methodName = methodName; } public void add(T listener) { listeners.add(listener); } public void dispatch() { for (T listener : listeners) { try { Method method = listener.getClass().getMethod(methodName); method.invoke(listener); } catch (Exception e) { System.out.println(e.getMessage()); } } } } Model: package model; public class Model { private EventDispatcher<ModelChangedHandler> dispatcher; public Model() { dispatcher = new EventDispatcher<ModelChangedHandler>("modelChanged"); } public void whenModelChange(ModelChangedHandler handler) { dispatcher.add(handler); } public void change() { dispatcher.dispatch(); } } ModelChangedHandler: package model; public interface ModelChangedHandler { void modelChanged(); } Presenter: package presenter; public class Presenter { private final Model model; public Presenter(Model model) { this.model = model; this.model.whenModelChange(new ModelChangedHandler() { @Override public void modelChanged() { System.out.println("model changed"); } }); } } Main: package main; public class Main { public static void main(String[] args) { Model model = new Model(); Presenter presenter = new Presenter(model); model.change(); } } Now, I except to get the "model changed" message. However, I'm getting an java.lang.IllegalAccessException: Class utils.EventDispatcher can not access a member of class presenter.Presenter$1 with modifiers "public". I understand that the class to blame is the anonymous class i created inside the presenter, however I don't know how to make it any more 'public' than it currently is. If i replace it with a named nested class it seem to work. It also works if the Presenter and the EventDispatcher are in the same package, but I can't allow that (several presenters in different packages should use the EventDispatcher) any ideas?

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  • Uses of a C++ Arithmetic Promotion Header

    - by OlduvaiHand
    I've been playing around with a set of templates for determining the correct promotion type given two primitive types in C++. The idea is that if you define a custom numeric template, you could use these to determine the return type of, say, the operator+ function based on the class passed to the templates. For example: // Custom numeric class template <class T> struct Complex { Complex(T real, T imag) : r(real), i(imag) {} T r, i; // Other implementation stuff }; // Generic arithmetic promotion template template <class T, class U> struct ArithmeticPromotion { typedef typename X type; // I realize this is incorrect, but the point is it would // figure out what X would be via trait testing, etc }; // Specialization of arithmetic promotion template template <> class ArithmeticPromotion<long long, unsigned long> { typedef typename unsigned long long type; } // Arithmetic promotion template actually being used template <class T, class U> Complex<typename ArithmeticPromotion<T, U>::type> operator+ (Complex<T>& lhs, Complex<U>& rhs) { return Complex<typename ArithmeticPromotion<T, U>::type>(lhs.r + rhs.r, lhs.i + rhs.i); } If you use these promotion templates, you can more or less treat your user defined types as if they're primitives with the same promotion rules being applied to them. So, I guess the question I have is would this be something that could be useful? And if so, what sorts of common tasks would you want templated out for ease of use? I'm working on the assumption that just having the promotion templates alone would be insufficient for practical adoption. Incidentally, Boost has something similar in its math/tools/promotion header, but it's really more for getting values ready to be passed to the standard C math functions (that expect either 2 ints or 2 doubles) and bypasses all of the integral types. Is something that simple preferable to having complete control over how your objects are being converted? TL;DR: What sorts of helper templates would you expect to find in an arithmetic promotion header beyond the machinery that does the promotion itself?

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  • LINQ to SQL Could not find key member. Only fails on server.

    - by Adam Carr
    I have a scenario where I am inheriting from an abstract class in my partial linq to sql auto generated class implementation. My base abstract class has an abstract property called ID which I have flagged inside my LINQ to SQL model with the instance modifier override. This works fine locally without any issues. I have also done some development on another machine and it works fine there too (both in VS2008 and using Subversion). I am running CI with TeamCity and the build succeeds and deploys as desired. The problem is when the server tries to hit the database for the first time via the LINQ to SQL data context, it generates the following error. "Could not find key member 'Id' of key 'Id' on type 'CustomType'. The key may be wrong or the field or property on 'CustomType' has changed names." I have tried changing my configuration by not implementing the Id field in my base class but this still fails. Why does it work on both of my DEV machines but not on the server? I am using LINQ to SQL in another project that runs on this server just fine. FYI: LINQ to SQL, SQL 2008, .NET 3.5, SERVER 2008, IIS 7.0 UPDATE I have gone back and added the same table a second time in the same data model but without a base class and have then displayed the results from that table and got no errors. This tells me it has something to do with my base abstract class and the need to flag a property on one of my linq to sql model classes (that belongs to a key relationship) with the instance modifier of override. No answer to this yet but am getting closer. UPDATE I have fixed my issue by simply changing my approach to my problem but I am still interested in why this doesn't work. I created a new WinSrv2008 VPC and patched it, deployed a pre-built version of my site to it and still got the same error. I now assume the issue is like what the person said here, a dependency issue with VS2008. My question is what or what? Will install VS2008 on the VPC to see if it works after that.

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  • Objective-C: properties not being saved or passed

    - by Gerald Yeo
    Hi, i'm a newbie to iphone development. I'm doing a navigation-based app, and I'm having trouble passing values to a new view. @interface RootViewController : UITableViewController { NSString *imgurl; NSMutableArray *galleryArray; } @property (nonatomic, retain) NSString *imgurl; @property (nonatomic, retain) NSMutableArray *galleryArray; - (void)showAll; @end #import "RootViewController.h" #import "ScrollView.h" #import "Model.h" #import "JSON/JSON.h" @implementation RootViewController @synthesize galleryArray, imgurl; - (void)viewDidLoad { UIBarButtonItem *showButton = [[[UIBarButtonItem alloc] initWithTitle:NSLocalizedString(@"Show All", @"") style:UIBarButtonItemStyleBordered target:self action:@selector(showAll)] autorelease]; self.navigationItem.rightBarButtonItem = showButton; NSString *jsonString = [[Model sharedInstance] jsonFromURLString:@"http://www.ddbstaging.com/gerald/gallery.php"]; NSDictionary *resultDictionary = [jsonString JSONValue]; if (resultDictionary == nil) { UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Webservice Down" message:@"The webservice you are accessing is currently down. Please try again later." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil]; [alert show]; [alert release]; } else { galleryArray = [[NSMutableArray alloc] init]; galleryArray = [resultDictionary valueForKey:@"gallery"]; imgurl = (NSString *)[galleryArray objectAtIndex:0]; NSLog(@" -> %@", galleryArray); NSLog(imgurl); } } - (void)showAll { NSLog(@" -> %@", galleryArray); NSLog(imgurl); ScrollView *controller = [[ScrollView alloc] initWithJSON:galleryArray]; [self.navigationController pushViewController:controller animated:YES]; } The RootViewController startup and the json data loads up fine. I can see it from the first console trace. However, once I click on the Show All button, the app crashes. It doesn't even trace the galleryArray and imgurl properyly. Maybe additional pairs of eyes can spot my mistakes. Any help is greatly appreciated! [Session started at 2010-05-08 16:16:07 +0800.] 2010-05-08 16:16:07.242 Photos[5892:20b] -> ( ) GNU gdb 6.3.50-20050815 (Apple version gdb-967) (Tue Jul 14 02:11:58 UTC 2009) Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i386-apple-darwin".sharedlibrary apply-load-rules all Attaching to process 5892. (gdb)

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  • How is IObservable<double>.Average supposed to work?

    - by Dan Tao
    Update Looks like Jon Skeet was right (big surprise!) and the issue was with my assumption about the Average extension providing a continuous average (it doesn't). For the behavior I'm after, I wrote a simple ContinuousAverage extension method, the implementation of which I am including here for the benefit of others who may want something similar: public static class ObservableExtensions { private class ContinuousAverager { private double _mean; private long _count; public ContinuousAverager() { _mean = 0.0; _count = 0L; } // undecided whether this method needs to be made thread-safe or not // seems that ought to be the responsibility of the IObservable (?) public double Add(double value) { double delta = value - _mean; _mean += (delta / (double)(++_count)); return _mean; } } public static IObservable<double> ContinousAverage(this IObservable<double> source) { var averager = new ContinuousAverager(); return source.Select(x => averager.Add(x)); } } I'm thinking of going ahead and doing something like the above for the other obvious candidates as well -- so, ContinuousCount, ContinuousSum, ContinuousMin, ContinuousMax ... perhaps ContinuousVariance and ContinuousStandardDeviation as well? Any thoughts on that? Original Question I use Rx Extensions a little bit here and there, and feel I've got the basic ideas down. Now here's something odd: I was under the impression that if I wrote this: var ticks = Observable.FromEvent<QuoteEventArgs>(MarketDataProvider, "MarketTick"); var bids = ticks .Where(e => e.EventArgs.Quote.HasBid) .Select(e => e.EventArgs.Quote.Bid); var bidsSubscription = bids.Subscribe( b => Console.WriteLine("Bid: {0}", b) ); var avgOfBids = bids.Average(); var avgOfBidsSubscription = avgOfBids.Subscribe( b => Console.WriteLine("Avg Bid: {0}", b) ); I would get two IObservable<double> objects (bids and avgOfBids); one would basically be a stream of all the market bids from my MarketDataProvider, the other would be a stream of the average of these bids. So something like this: Bid Avg Bid 1 1 2 1.5 1 1.33 2 1.5 It seems that my avgOfBids object isn't doing anything. What am I missing? I think I've probably misunderstood what Average is actually supposed to do. (This also seems to be the case for all of the aggregate-like extension methods on IObservable<T> -- e.g., Max, Count, etc.)

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  • WCF Duplex Interaction with Web Server

    - by Mark Struzinski
    Here is my scenario, and it is causing us a considerable amount of grief at the moment: We have a vendor web service which provides base level telephony functionality. This service has a SOAP api, which we are leveraging to build up a custom UI that is integrated into our in house web apps. The api functions on 2 levels. You make standard client calls into the service to initiate actions, such as Login, Place Call, Hang Up, etc. On a different thread, the service sends events back to the client to alert the user of things that are occurring on the system (agent successfully logged in, call was disconnected, etc). I implemented a WCF service to sit between the web server and the vendor service. This WCF service operates in duplex mode, establishing a 2 way connection with the web server. The web server makes outbound calls to the WCF service, which routes them to the vendor's web service. Events are received back to the WCF service, which passes them onto the web server via a callback channel on the WCF client. As events are received on the web server, they are placed into a hash table with the user's name as the key, and a .NET queue as the value to hold the event. Each event is enqueued to the agent who owns it. On a 2 second interval, the web page polls the web server via an ajax request to get new events for the logged in user. It hits the hash table for the user key, dequeues any events that are present, and serializes them back up to the web page. From there, they are processed in order and appropriate messages are displayed to the user. This implementation performs well in a single user scenario. The second I put more than 1 user on the system, I start getting frequent timeouts with the following CommunicationException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond We are running Windows Server 2008 R2 both servers. Both the web app and WCF service are running on .NET 3.5. The WCF service is running under the net.tcp protocol in duplex mode. The web app is ASP.NET MVC 2. Has anyone dealt with anything like this scenario? Is there a more efficient way (or a widely accepted pattern) to implement this?

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