static import - Page 247

What are the downsides of implementing a singleton with Java's enum?

- by irreputable

Traditionally, a singleton is usually implemented as public class Foo1 { private static final Foo1 INSTANCE = new Foo1(); public static Foo1 getInstance(){ return INSTANCE; } private Foo1(){} public void doo(){ ... } } With Java's enum, we can implement a singleton as public enum Foo2 { INSTANCE; public void doo(){ ... } } As awesome as the 2nd version is, are there any downsides to it? (I gave it some thoughts and I'll answer my own question; hopefully you have better answers)

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WCF Operations and Multidimensional Arrays

- by JoshReuben

You cant pass MultiD arrays accross the wire using WCF - you need to pass jagged arrays. heres 2 extension methods that will allow you to convert prior to serialzation and convert back after deserialization: public static T[,] ToMultiD<T>(this T[][] jArray) { int i = jArray.Count(); int j = jArray.Select(x => x.Count()).Aggregate(0, (current, c) => (current > c) ? current : c); var mArray = new T[i, j]; for (int ii = 0; ii < i; ii++) { for (int jj = 0; jj < j; jj++) { mArray[ii, jj] = jArray[ii][jj]; } } return mArray; } public static T[][] ToJagged<T>(this T[,] mArray) { var cols = mArray.GetLength(0); var rows = mArray.GetLength(1); var jArray = new T[cols][]; for (int i = 0; i < cols; i++) { jArray[i] = new T[rows]; for (int j = 0; j < rows; j++) { jArray[i][j] = mArray[i, j]; } } return jArray; } enjoy!

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What is the correct way to handle debug output in Java?

- by Federico Zancan

As my current Java projects grow bigger and bigger, I feel a likewise growing need to insert debug output in several points of my code. To enable or disable this feature appropriately, depending on the opening or closure of the test sessions, I usually put a private static final boolean DEBUG = false at the beginning of the classes my tests are inspecting, and trivially use it this way (for example): public MyClass { private static final boolean DEBUG = false; ... some code ... public void myMethod(String s) { if (DEBUG) { System.out.println(s); } } } and the like. But that doesn't bliss me out, because of course it works but there could be too many classes in which to set DEBUG to true, if you are not staring at just a couple of them. Conversely, I (like - I think - many others) wouldn't love to put the whole application in debug mode, as the amount of text being output could be overwhelming. So, is there a correct way to architecturally handle such situation or the most correct way is to use the DEBUG class member?

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C# String.format extension method

- by Paul Roe

With the addtion of Extension methods to C# we've seen a lot of them crop up in our group. One debate revolves around extension methods like this one: public static class StringExt { /// <summary> /// Shortcut for string.Format. /// </summary> /// <param name="str"></param> /// <param name="args"></param> /// <returns></returns> public static string Format(this string str, params object[] args) { if (str == null) return null; return string.Format(str, args); } } Does this extension method break any programming best practices that you can name? Would you use it anyway, if not why? If I renamed the function to "F" but left the xml comments would that be epic fail or just a wonderful savings of keystrokes?

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How do I resolve this exercise on C++? [closed]

- by user40630

(Card Shuffling and Dealing) Create a program to shuffle and deal a deck of cards. The program should consist of class Card, class DeckOfCards and a driver program. Class Card should provide: a) Data members face and suit of type int. b) A constructor that receives two ints representing the face and suit and uses them to initialize the data members. c) Two static arrays of strings representing the faces and suits. d) A toString function that returns the Card as a string in the form “face of suit.” You can use the + operator to concatenate strings. Class DeckOfCards should contain: a) A vector of Cards named deck to store the Cards. b) An integer currentCard representing the next card to deal. c) A default constructor that initializes the Cards in the deck. The constructor should use vector function push_back to add each Card to the end of the vector after the Card is created and initialized. This should be done for each of the 52 Cards in the deck. d) A shuffle function that shuffles the Cards in the deck. The shuffle algorithm should iterate through the vector of Cards. For each Card, randomly select another Card in the deck and swap the two Cards. e) A dealCard function that returns the next Card object from the deck. f) A moreCards function that returns a bool value indicating whether there are more Cards to deal. The driver program should create a DeckOfCards object, shuffle the cards, then deal the 52 cards. This above is the exercise I'm trying to solve. I'd be very much appreciated if someone could solve it and explain it to me. The main idea of the program is quite simple. What I don't get is how to build the constructor for the class DeckOfCards and how to generate the 52 cards of the deck with different suits and faces. Untill now I've managed to do this: #include <iostream> #include <vector> using namespace std; /* * */ /* a) Data members face and suit of type int. b) A constructor that receives two ints representing the face and suit and uses them to initialize the data members. c) Two static arrays of strings representing the faces and suits. d) A toString function that returns the Card as a string in the form “face of suit.” You can use the + operator to concatenate strings. */ class Card { public: Card(int, int); string toString(); private: int suit, face; static string faceNames[13]; static string suitNames[4]; }; string Card::faceNames[13] = {"Ace","Two","Three","Four","Five","Six","Seven","Eight","Nine","Ten","Queen","Jack","King"}; string Card::suitNames[4] = {"Diamonds","Clubs","Hearts","Spades"}; string Card::toString() { return faceNames[face]+" of "+suitNames[suit]; } Card::Card(int f, int s) :face(f), suit(s) { } /* Class DeckOfCards should contain: a) A vector of Cards named deck to store the Cards. b) An integer currentCard representing the next card to deal. c) A default constructor that initializes the Cards in the deck. The constructor should use vector function push_back to add each Card to the end of the vector after the Card is created and initialized. This should be done for each of the 52 Cards in the deck. d) A shuffle function that shuffles the Cards in the deck. The shuffle algorithm should iterate through the vector of Cards. For each Card, randomly select another Card in the deck and swap the two Cards. e) A dealCard function that returns the next Card object from the deck. f) A moreCards function that returns a bool value indicating whether there are more Cards to deal. */ class DeckOfCards { public: DeckOfCards(); void shuffleCards(); Card dealCard(); bool moreCards(); private: vector<Card> deck(52); int currentCard; }; int main(int argc, char** argv) { return 0; } DeckOfCards::DeckOfCards() { //I'm stuck here I have no idea of what to take out of here. //I still don't fully get the idea of class inside class and that's turning out as a problem. I try to find a way to set the suits and faces members of the class Card but I can't figure out how. for(int i=0; i<deck.size(); i++) { deck[i]//....There is no function to set them. They must be set when initialized. But how?? } } For easier reading: http://pastebin.com/pJeXMH0f

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Bind: dns not 'spreaded'

- by realtebo

I've elfoip.net with bind $ whois elfoip.net | grep 'Name Server' Name Server: NS.ELFOIP.NET I need elfoip.net be able to serve third levels domain, like mickymouse.elfoip.net, etc... Yes, I'm trying to create an other useless dyndns clone. i've added some third level as A RR. Eg: executing this from the server itself $ dig @localhost mattinauno.elfoip.net ;; ANSWER SECTION: mattinauno.elfoip.net. 60 IN A 192.81.221.113 I was expecting in one or two days, from my pc i can digit in browser mattinauno.elfoip.net and get page a 192.81.221.113 But this is not happening. Are there any prerequisites to satisfy to allow dns of my isp to be able to forward dns resolution of *.elfoip.net to MY dns ? (Or to ask to him and then cache ?) TTL of zone is set a 5m I've not AllowQuey directive, is it necessary for other dns to cache from mine ? I've cheched the zone with bind utility named-checkzone but no error detected. How to diagnose why other dns doesn't take in account RR from mine ? from my home pc dig @ns.elfoip.net mattinauno.elfoip.net ;; ANSWER SECTION: mattinauno.elfoip.net. 60 IN A 192.81.221.113 ;; AUTHORITY SECTION: elfoip.net. 300 IN NS ns.elfoip.net. but dig @8.8.8.8 mattinauno.elfoip.net give no answers Whole zone file: note I've used nsupdate, so this file has been re-edited and re-formatted from this utility ! root@mirko:/var/named# cat elfoip.net.db $ORIGIN . $TTL 300 ; 5 minutes elfoip.net IN SOA ns.elfoip.net. hostmaster.elfoip.net. ( 2013062314 ; serial 3600 ; refresh (1 hour) 600 ; retry (10 minutes) 86400 ; expire (1 day) 60 ; minimum (1 minute) ) NS ns.elfoip.net. A 109.168.99.6 $ORIGIN elfoip.net. $TTL 60 ; 1 minute google A 173.194.35.56 maiscai A 192.81.221.113 mattinadue A 192.81.221.113 mattinauno A 192.81.221.113 $TTL 300 ; 5 minutes ns A 109.168.99.6 $TTL 60 ; 1 minute prova A 208.67.222.222 prova2 A 13.23.34.45 A 13.23.34.46 www CNAME elfoip.net. EDIT: added named.conf.local zone "elfoip.net" { type master; // file "/etc/bind/elfoip.net.db"; file "/var/named/elfoip.net.db"; allow-update { key elfoip.net ; }; }; EDIT: I've no setup list-on directive *EDIT Added a TCPDUMP after [email protected] wwww.elfoip.net from a machine which uses my company internal dns, who allow recursive query. root@mirko:~# tcpdump -i eth0 'port 53' tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes 11:57:23.293611 IP host9-210-static.22-87-b.business.telecomitalia.it.45958 > mirko.elfoip.net.domain: 61337+ A? www.elfoip.net. (32) 11:57:23.294114 IP mirko.elfoip.net.domain > host9-210-static.22-87-b.business.telecomitalia.it.45958: 61337* 2/1/1 CNAME elfoip.net., A 109.168.99.6 (95) 11:57:23.294554 IP mirko.elfoip.net.59571 > google-public-dns-a.google.com.domain: 45851+ PTR? 9.210.22.87.in-addr.arpa. (42) 11:57:23.330444 IP google-public-dns-a.google.com.domain > mirko.elfoip.net.59571: 45851 1/0/0 PTR host9-210-static.22-87-b.business.telecomitalia.it. (106) 11:57:23.331181 IP mirko.elfoip.net.44171 > google-public-dns-a.google.com.domain: 33339+ PTR? 8.8.8.8.in-addr.arpa. (38) 11:57:23.439405 IP google-public-dns-a.google.com.domain > mirko.elfoip.net.44171: 33339 1/0/0 PTR google-public-dns-a.google.com. (82) 11:57:31.350654 IP host9-210-static.22-87-b.business.telecomitalia.it.30108 > mirko.elfoip.net.domain: 38269 [1au] A? ns.elfoip.net. (42) 11:57:31.351117 IP mirko.elfoip.net.domain > host9-210-static.22-87-b.business.telecomitalia.it.30108: 38269* 1/1/1 A 109.168.99.6 (72) If i dig @8.8.8.8 www.elfoip.net, NOTHING happens in dump log !

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Custom Configuration Section Handlers

Most .NET developers who need to store something in configuration tend to use appSettings for this purpose, in my experience. More recently, the framework itself has helped things by adding the <connectionStrings /> section so at least these are in their own section and not adding to the appSettings clutter that pollutes most apps. I recommend avoiding appSettings for several reasons. In addition to those listed there, I would add that strong typing and validation are additional reasons to go the custom configuration section route. For my ASP.NET Tips and Tricks talk, I use the following example, which is a simple DemoSettings class that includes two fields. The first is an integer representing how many attendees there are present for the talk, and the second is the title of the talk. The setup in web.config is as follows: <configSections> <section name="DemoSettings" type="ASPNETTipsAndTricks.Code.DemoSettings" /> </configSections> <DemoSettings sessionAttendees="100" title="ASP.NET Tips and Tricks DevConnections Spring 2010" /> Referencing the values in code is strongly typed and straightforward. Here I have a page that exposes two properties which internally get their values from the configuration section handler: public partial class CustomConfig1 : System.Web.UI.Page { public string SessionTitle { get { return DemoSettings.Settings.Title; } } public int SessionAttendees { get { return DemoSettings.Settings.SessionAttendees; } } } Note that the settings are only read from the config file once after that they are cached so there is no need to be concerned about excessive file access. Now weve seen how to set it up on the config file and how to refer to the settings in code. All that remains is to see the file itself: public class DemoSettings : ConfigurationSection { private static DemoSettings settings = ConfigurationManager.GetSection("DemoSettings") as DemoSettings; public static DemoSettings Settings{ get { return settings;} } [ConfigurationProperty("sessionAttendees" , DefaultValue = 200 , IsRequired = false)] [IntegerValidator(MinValue = 1 , MaxValue = 10000)] public int SessionAttendees { get { return (int)this["sessionAttendees"]; } set { this["sessionAttendees"] = value; } } [ConfigurationProperty("title" , IsRequired = true)] [StringValidator(InvalidCharacters = "~!@#$%^&*()[]{}/;\"|\\")] public string Title { get { return (string)this["title"]; } set { this["title"] = value; } } } The class is pretty straightforward, but there are some important components to note. First, it must inherit from System.Configuration.ConfigurationSection. Next, as a convention I like to have a static settings member that is responsible for pulling out the section when the class is first referenced, and further to expose this collection via a static readonly property, Settings. Note that the types of both of these are the type of my class, DemoSettings. The properties of the class, SessionAttendees and Title, should map to the attributes of the config element in the XML file. The [ConfigurationProperty] attribute allows you to map the attribute name to the property name (thus using both XML standard naming conventions and C# naming conventions). In addition, you can specify a default value to use if nothing is specified in the config file, and whether or not the setting must be provided (IsRequired). If it is required, then it doesnt make sense to include a default value. Beyond defaults and required, you can specify more advanced validation rules for the configuration values using additional C# attributes, such as [IntegerValidator] and [StringValidator]. Using these, you can declaratively specify that your configuration values be in a given range, or omit certain forbidden characters, for instance. Of course you can write your own custom validation attributes, and there are others specified in System.Configuration. Individual sections can also be loaded from separate files, using syntax like this: <DemoSettings configSource="demosettings.config" /> Summary Using a custom configuration section handler is not hard. If your application or component requires configuration, I recommend creating a custom configuration handler dedicated to your app or component. Doing so will reduce the clutter in appSettings, will provide you with strong typing and validation, and will make it much easier for other developers or system administrators to locate and understand the various configuration values that are necessary for a given application. Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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GameplayScreen does not contain a definition for GraphicsDevice

- by Dave Voyles

Long story short: I'm trying to intergrate my game with Microsoft's Game State Management. In doing so I've run into some errors, and the latest one is in the title. I'm not able to display my HUD for the reasons listed above. Previously, I had much of my code in my Game.cs class, but the GSM has a bit of it in Game1, and most of what you have drawn for the main screen in your GameplayScreen class, and that is what is causing confusion on my part. I've created an instance of the GameplayScreen class to be used in the HUD class (as you can see below). Before integrating with the GSM however, I created an instance of my Game class, and all worked fine. It seems that I need to define my graphics device somewhere, but I am not sure of where exactly. I've left some code below to help you understand. public class GameStateManagementGame : Microsoft.Xna.Framework.Game { #region Fields GraphicsDeviceManager graphics; ScreenManager screenManager; // Creates a new intance, which is used in the HUD class public static Game Instance; // By preloading any assets used by UI rendering, we avoid framerate glitches // when they suddenly need to be loaded in the middle of a menu transition. static readonly string[] preloadAssets = { "gradient", }; #endregion #region Initialization /// <summary> /// The main game constructor. /// </summary> public GameStateManagementGame() { Content.RootDirectory = "Content"; graphics = new GraphicsDeviceManager(this); graphics.PreferredBackBufferWidth = 1280; graphics.PreferredBackBufferHeight = 720; graphics.IsFullScreen = false; graphics.ApplyChanges(); // Create the screen manager component. screenManager = new ScreenManager(this); Components.Add(screenManager); // Activate the first screens. screenManager.AddScreen(new BackgroundScreen(), null); //screenManager.AddScreen(new MainMenuScreen(), null); screenManager.AddScreen(new PressStartScreen(), null); } namespace Pong { public class HUD { public void Update(GameTime gameTime) { // Used in the Draw method titleSafeRectangle = new Rectangle (GameplayScreen.Instance.GraphicsDevice.Viewport.TitleSafeArea.X, GameplayScreen.Instance.GraphicsDevice.Viewport.TitleSafeArea.Y, GameplayScreen.Instance.GraphicsDevice.Viewport.TitleSafeArea.Width, GameplayScreen.Instance.GraphicsDevice.Viewport.TitleSafeArea.Height); } } } class GameplayScreen : GameScreen { #region Fields ContentManager content; public static GameStates gamestate; private GraphicsDeviceManager graphics; public int screenWidth; public int screenHeight; private Texture2D backgroundTexture; private SpriteBatch spriteBatch; private Menu menu; private SpriteFont arial; private HUD hud; Animation player; // Creates a new intance, which is used in the HUD class public static GameplayScreen Instance; public GameplayScreen() { TransitionOnTime = TimeSpan.FromSeconds(1.5); TransitionOffTime = TimeSpan.FromSeconds(0.5); } protected void Initialize() { lastScored = false; menu = new Menu(); resetTimer = 0; resetTimerInUse = true; ball = new Ball(content, new Vector2(screenWidth, screenHeight)); SetUpMulti(); input = new Input(); hud = new HUD(); // Places the powerup animation inside of the surrounding box // Needs to be cleaned up, instead of using hard pixel values player = new Animation(content.Load<Texture2D>(@"gfx/powerupSpriteSheet"), new Vector2(103, 44), 64, 64, 4, 5); // Used by for the Powerups random = new Random(); vec = new Vector2(100, 50); vec2 = new Vector2(100, 100); promptVec = new Vector2(50, 25); timer = 10000.0f; // Starting value for the cooldown for the powerup timer timerVector = new Vector2(10, 10); //JEP - one time creation of powerup objects playerOnePowerup = new Powerup(); playerOnePowerup.Activated += PowerupActivated; playerOnePowerup.Deactivated += PowerupDeactivated; playerTwoPowerup = new Powerup(); playerTwoPowerup.Activated += PowerupActivated; playerTwoPowerup.Deactivated += PowerupDeactivated; //JEP - moved from events since these only need set once activatedVec = new Vector2(100, 125); deactivatedVec = new Vector2(100, 150); powerupReady = false; }

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Local Entities with NHibernate

- by Ricardo Peres

You may know that Entity Framework Code First has a nice property called Local which lets you iterate through all the entities loaded by the current context (first level cache). This comes handy at times, so I decided to check if it would be difficult to have it on NHibernate. It turned out it is not, so here it is! Another nice addition to an NHibernate toolbox! public static class SessionExtensions { public static IEnumerable<T> Local<T>(this ISession session) { ISessionImplementor impl = session.GetSessionImplementation(); IPersistenceContext pc = impl.PersistenceContext; foreach (Object key in pc.EntityEntries.Keys) { if (key is T) { yield return ((T) key); } } } } //simple usage IEnumerable<Post> localPosts = session.Local<Post>(); SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.all();

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Read All Text from Textfile with Encoding in Windows RT

- by jdanforth

A simple extension for reading all text from a text file in WinRT with a specific encoding, made as an extension to StorageFile: public static class StorageFileExtensions { async public static Task<string> ReadAllTextAsync(this StorageFile storageFile) { var buffer = await FileIO.ReadBufferAsync(storageFile); var fileData = buffer.ToArray(); var encoding = Encoding.GetEncoding("Windows-1252"); var text = encoding.GetString(fileData, 0, fileData.Length); return text; } }

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Unauthorized response from Server with API upload

- by Ethan Shafer

I'm writing a library in C# to help me develop a Windows application. The library uses the Ubuntu One API. I am able to authenticate and can even make requests to get the Quota (access to Account Admin API) and Volumes (so I know I have access to the Files API at least) Here's what I have as my Upload code: public static void UploadFile(string filename, string filepath) { FileStream file = File.OpenRead(filepath); byte[] bytes = new byte[file.Length]; file.Read(bytes, 0, (int)file.Length); RestClient client = UbuntuOneClients.FilesClient(); RestRequest request = UbuntuOneRequests.BaseRequest(Method.PUT); request.Resource = "/content/~/Ubuntu One/" + filename; request.AddHeader("Content-Length", bytes.Length.ToString()); request.AddParameter("body", bytes, ParameterType.RequestBody); client.ExecuteAsync(request, webResponse => UploadComplete(webResponse)); } Every time I send the request I get an "Unauthorized" response from the server. For now the "/content/~/Ubuntu One/" is hardcoded, but I checked and it is the location of my root volume. Is there anything that I'm missing? UbuntuOneClients.FilesClient() starts the url with "https://files.one.ubuntu.com" UbuntuOneRequests.BaseRequest(Method.{}) is the same requests that I use to send my Quota and Volumes requests, basically just provides all of the parameters needed to authenticate. EDIT:: Here's the BaseRequest() method: public static RestRequest BaseRequest(Method method) { RestRequest request = new RestRequest(method); request.OnBeforeDeserialization = resp => { resp.ContentType = "application/json"; }; request.AddParameter("realm", ""); request.AddParameter("oauth_version", "1.0"); request.AddParameter("oauth_nonce", Guid.NewGuid().ToString()); request.AddParameter("oauth_timestamp", DateTime.Now.ToString()); request.AddParameter("oauth_consumer_key", UbuntuOneRefreshInfo.UbuntuOneInfo.ConsumerKey); request.AddParameter("oauth_token", UbuntuOneRefreshInfo.UbuntuOneInfo.Token); request.AddParameter("oauth_signature_method", "PLAINTEXT"); request.AddParameter("oauth_signature", UbuntuOneRefreshInfo.UbuntuOneInfo.Signature); //request.AddParameter("method", method.ToString()); return request; } and the FilesClient() method: public static RestClient FilesClient() { return (new RestClient("https://files.one.ubuntu.com")); }

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what does composition example vs aggregation

- by meWantToLearn

Composition and aggregation both are confusion to me. Does my code sample below indicate composition or aggregation? class A { public static function getData($id) { //something } public static function checkUrl($url) { // something } class B { public function executePatch() { $data = A::getData(12); } public function readUrl() { $url = A::checkUrl('http/erere.com'); } public function storeData() { //something not related to class A at all } } } Is class B a composition of class A or is it aggregation of class A? Does composition purely mean that if class A gets deleted class B does not works at all and aggregation if class A gets deleted methods in class B that do not use class A will work?

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ReSharper C# Live Template for Read-Only Dependency Property and Routed Event Boilerplate

- by Bart Read

Following on from my previous post, where I shared a Live Template for quickly declaring a normal read-write dependency property and its associated property change event boilerplate, here's an unsurprisingly similar template for creating a read-only dependency property. #region $PROPNAME$ Read-Only Property and Property Change Routed Event private static readonly DependencyPropertyKey $PROPNAME$PropertyKey = DependencyProperty.RegisterReadOnly( "$PROPNAME$", typeof ( $PROPTYPE$ ), typeof ( $DECLARING_TYPE$ ), new PropertyMetadata( $DEF_VALUE$ , On$PROPNAME$Changed ) ); public static readonly DependencyProperty $PROPNAME$Property = $PROPNAME$PropertyKey.DependencyProperty; public $PROPTYPE$ $PROPNAME$ { get { return ( $PROPTYPE$ ) GetValue( $PROPNAME$Property ); } private set { SetValue( $PROPNAME$PropertyKey, value ); } } public static readonly RoutedEvent $PROPNAME$ChangedEvent = EventManager.RegisterRoutedEvent( "$PROPNAME$Changed", RoutingStrategy.$ROUTINGSTRATEGY$, typeof( RoutedPropertyChangedEventHandler< $PROPTYPE$ > ), typeof( $DECLARING_TYPE$ ) ); public event RoutedPropertyChangedEventHandler< $PROPTYPE$ > $PROPNAME$Changed { add { AddHandler( $PROPNAME$ChangedEvent, value ); } remove { RemoveHandler( $PROPNAME$ChangedEvent, value ); } } private static void On$PROPNAME$Changed( DependencyObject d, DependencyPropertyChangedEventArgs e) { var $DECLARING_TYPE_var$ = d as $DECLARING_TYPE$; var args = new RoutedPropertyChangedEventArgs< $PROPTYPE$ >( ( $PROPTYPE$ ) e.OldValue, ( $PROPTYPE$ ) e.NewValue ); args.RoutedEvent = $DECLARING_TYPE$.$PROPNAME$ChangedEvent; $DECLARING_TYPE_var$.RaiseEvent( args );$END$ } #endregion The only real difference here is the addition of the DependencyPropertyKey, which allows your implementation to set the value of the dependency property without exposing the setter code to consumers of your type. You'll probably find that you create read-only dependency properties much less often than read-write properties, but this should still save you some typing when you do need to do so. Technorati Tags: resharper,live template,c#,dependency property,read-only,routed events,property change,boilerplate,wpf

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How to remove java.sql.BatchUpdateException in Grails? [closed]

- by aman.nepid

I have a domain like this: class BusinessOrganization { static hasMany = [organizationBusinessTypes:OrganizationBusinessType] String name String icon static constraints = { name(blank:false,unique:true) icon(unique:true) } String toString() { return "${name}" } } When I save some data for first time it works fine. But when by the next time it shows this error : Error 500: Internal Server Error URI /nLocatePortal/businessOrganization/save Class java.sql.BatchUpdateException Message Batch entry 0 insert into business_organization (version, icon, name, id) values ('0', '', 'dddd', '2') was aborted. Call getNextException to see the cause. **Around line 24 of grails-app/controllers/com/nlocate/portal/BusinessOrganizationController.groovy** 21: 22: def save() { 23: def businessOrganizationInstance = new BusinessOrganization(params) 24: if (!businessOrganizationInstance.save(flush: true)) { 25: render(view: "create", model: [businessOrganizationInstance: businessOrganizationInstance]) 26: return 27: } Please someone help me why this is happening. I am new to Grails. I have not modified the controllers but still I get this error.

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Manipulating Collections Without Loops with lambdaj

A thread safe library of static methods that provides an internal DSL to manipulate Java collections without loops

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How to get MAC address from c# [migrated]

- by Andrew Simpson

I have a C# application. In a routine I have code to get the MAC address from using SendARP. It works on Windows 7 but does not work on Windows XP. I just get a null string returned. This is my code. Thanks... System.Runtime.InteropServices.DllImport("iphlpapi.dll", ExactSpelling = true)] static extern int SendARP(int DestIP, int SrcIP, byte[] pMacAddr, ref int PhyAddrLen); public static PhysicalAddress GetMacAddress(IPAddress ipAddress) { const int MacAddressLength = 6; //i know it is has a length of 6 int length = MacAddressLength; var macBytes = new byte[MacAddressLength]; SendARP(BitConverter.ToInt32(ipAddress.GetAddressBytes(), 0), 0, macBytes, ref length); return new PhysicalAddress(macBytes); }

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Node Serialization in NetBeans Platform 7.0

- by Geertjan

Node serialization makes sense when you're not interested in the data (since that should be serialized to a database), but in the state of the application. For example, when the application restarts, you want the last selected node to automatically be selected again. That's not the kind of information you'll want to store in a database, hence node serialization is not about data serialization but about application state serialization. I've written about this topic in October 2008, here and here, but want to show how to do this again, using NetBeans Platform 7.0. Somewhere I remember reading that this can't be done anymore and that's typically the best motivation for me, i.e., to prove that it can be done after all. Anyway, in a standard POJO/Node/BeanTreeView scenario, do the following: Remove the "@ConvertAsProperties" annotation at the top of the class, which you'll find there if you used the Window Component wizard. We're not going to use property-file based serialization, but plain old java.io.Serializable instead. In the TopComponent, assuming it is named "UserExplorerTopComponent", typically at the end of the file, add the following: @Override public Object writeReplace() { //We want to work with one selected item only //and thanks to BeanTreeView.setSelectionMode, //only one node can be selected anyway: Handle handle = NodeOp.toHandles(em.getSelectedNodes())[0]; return new ResolvableHelper(handle); } public final static class ResolvableHelper implements Serializable { private static final long serialVersionUID = 1L; public Handle selectedHandle; private ResolvableHelper(Handle selectedHandle) { this.selectedHandle = selectedHandle; } public Object readResolve() { WindowManager.getDefault().invokeWhenUIReady(new Runnable() { @Override public void run() { try { //Get the TopComponent: UserExplorerTopComponent tc = (UserExplorerTopComponent) WindowManager.getDefault().findTopComponent("UserExplorerTopComponent"); //Get the display text to search for: String selectedDisplayName = selectedHandle.getNode().getDisplayName(); //Get the root, which is the parent of the node we want: Node root = tc.getExplorerManager().getRootContext(); //Find the node, by passing in the root with the display text: Node selectedNode = NodeOp.findPath(root, new String[]{selectedDisplayName}); //Set the explorer manager's selected node: tc.getExplorerManager().setSelectedNodes(new Node[]{selectedNode}); } catch (PropertyVetoException ex) { Exceptions.printStackTrace(ex); } catch (IOException ex) { Exceptions.printStackTrace(ex); } } }); return null; } } Assuming you have a node named "UserNode" for a type named "User" containing a property named "type", add the bits in bold below to your "UserNode": public class UserNode extends AbstractNode implements Serializable { static final long serialVersionUID = 1L; public UserNode(User key) { super(Children.LEAF); setName(key.getType()); } @Override public Handle getHandle() { return new CustomHandle(this, getName()); } public class CustomHandle implements Node.Handle { static final long serialVersionUID = 1L; private AbstractNode node = null; private final String searchString; public CustomHandle(AbstractNode node, String searchString) { this.node = node; this.searchString = searchString; } @Override public Node getNode() { node.setName(searchString); return node; } } } Run the application and select one of the user nodes. Close the application. Start it up again. The user node is not automatically selected, in fact, the window does not open, and you will see this in the output: Caused: java.io.InvalidClassException: org.serialization.sample.UserNode; no valid constructor Read this article and then you'll understand the need for this class: public class BaseNode extends AbstractNode { public BaseNode() { super(Children.LEAF); } public BaseNode(Children kids) { super(kids); } public BaseNode(Children kids, Lookup lkp) { super(kids, lkp); } } Now, instead of extending AbstractNode in your UserNode, extend BaseNode. Then the first non-serializable superclass of the UserNode has an explicitly declared no-args constructor, Do the same as the above for each node in the hierarchy that needs to be serialized. If you have multiple nodes needing serialization, you can share the "CustomHandle" inner class above between all the other nodes, while all the other nodes will also need to extend BaseNode (or provide their own non-serializable super class that explicitly declares a no-args constructor). Now, when I run the application, I select a node, then I close the application, restart it, and the previously selected node is automatically selected when the application has restarted.

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Visual Tree Enumeration

- by codingbloke

I feel compelled to post this blog because I find I’m repeatedly posting this same code in silverlight and windows-phone-7 answers in Stackoverflow. One common task that we feel we need to do is burrow into the visual tree in a Silverlight or Windows Phone 7 application (actually more recently I found myself doing this in WPF as well). This allows access to details that aren’t exposed directly by some controls. A good example of this sort of requirement is found in the “Restoring exact scroll position of a listbox in Windows Phone 7” question on stackoverflow. This required that the scroll position of the scroll viewer internal to a listbox be accessed. A caveat One caveat here is that we should seriously challenge the need for this burrowing since it may indicate that there is a design problem. Burrowing into the visual tree or indeed burrowing out to containing ancestors could represent significant coupling between module boundaries and that generally isn’t a good idea. Why isn’t this idea just not cast aside as a no-no? Well the whole concept of a “Templated Control”, which are in extensive use in these applications, opens the coupling between the content of the visual tree and the internal code of a control. For example, I can completely change the appearance and positioning of elements that make up a ComboBox. The ComboBox control relies on specific template parts having set names of a specified type being present in my template. Rightly or wrongly this does kind of give license to writing code that has similar coupling. Hasn’t this been done already? Yes it has. There are number of blogs already out there with similar solutions. In fact if you are using Silverlight toolkit the VisualTreeExtensions class already provides this feature. However I prefer my specific code because of the simplicity principle I hold to. Only write the minimum code necessary to give all the features needed. In this case I add just two extension methods Ancestors and Descendents, note I don’t bother with “Get” or “Visual” prefixes. Also I haven’t added Parent or Children methods nor additional “AndSelf” methods because all but Children is achievable with the addition of some other Linq methods. I decided to give Descendents an additional overload for depth hence a depth of 1 is equivalent to Children but this overload is a little more flexible than simply Children. So here is the code:- VisualTreeEnumeration public static class VisualTreeEnumeration { public static IEnumerable<DependencyObject> Descendents(this DependencyObject root, int depth) { int count = VisualTreeHelper.GetChildrenCount(root); for (int i = 0; i < count; i++) { var child = VisualTreeHelper.GetChild(root, i); yield return child; if (depth > 0) { foreach (var descendent in Descendents(child, --depth)) yield return descendent; } } } public static IEnumerable<DependencyObject> Descendents(this DependencyObject root) { return Descendents(root, Int32.MaxValue); } public static IEnumerable<DependencyObject> Ancestors(this DependencyObject root) { DependencyObject current = VisualTreeHelper.GetParent(root); while (current != null) { yield return current; current = VisualTreeHelper.GetParent(current); } } } Usage examples The following are some examples of how to combine the above extension methods with Linq to generate the other axis scenarios that tree traversal code might require. Missing Axis Scenarios var parent = control.Ancestors().Take(1).FirstOrDefault(); var children = control.Descendents(1); var previousSiblings = control.Ancestors().Take(1) .SelectMany(p => p.Descendents(1).TakeWhile(c => c != control)); var followingSiblings = control.Ancestors().Take(1) .SelectMany(p => p.Descendents(1).SkipWhile(c => c != control).Skip(1)); var ancestorsAndSelf = Enumerable.Repeat((DependencyObject)control, 1) .Concat(control.Ancestors()); var descendentsAndSelf = Enumerable.Repeat((DependencyObject)control, 1) .Concat(control.Descendents()); You might ask why I don’t just include these in the VisualTreeEnumerator. I don’t on the principle of only including code that is actually needed. If you find that one or more of the above is needed in your code then go ahead and create additional methods. One of the downsides to Extension methods is that they can make finding the method you actually want in intellisense harder. Here are some real world usage scenarios for these methods:- Real World Scenarios //Gets the internal scrollviewer of a ListBox ScrollViewer sv = someListBox.Descendents().OfType<ScrollViewer>().FirstOrDefault(); // Get all text boxes in current UserControl:- var textBoxes = this.Descendents().OfType<TextBox>(); // All UIElement direct children of the layout root grid:- var topLevelElements = LayoutRoot.Descendents(0).OfType<UIElement>(); // Find the containing `ListBoxItem` for a UIElement:- var container = elem.Ancestors().OfType<ListBoxItem>().FirstOrDefault(); // Seek a button with the name "PinkElephants" even if outside of the current Namescope:- var pinkElephantsButton = this.Descendents() .OfType<Button>() .FirstOrDefault(b => b.Name == "PinkElephants"); //Clear all checkboxes with the name "Selector" in a Treeview foreach (CheckBox checkBox in elem.Descendents() .OfType<CheckBox>().Where(c => c.Name == "Selector")) { checkBox.IsChecked = false; } The last couple of examples above demonstrate a common requirement of finding controls that have a specific name. FindName will often not find these controls because they exist in a different namescope. Hope you find this useful, if not I’m just glad to be able to link to this blog in future stackoverflow answers.

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Which Programming Languages Support the Following Features?

- by donalbain

My personal programming background is mainly in Java, with a little bit of Ruby, a tiny bit of Scheme, and most recently, due to some iOS development, Objective-C. In my move from Java to Objective-C I've really come to love some features that Objective-C has that Java doesn't. These include support for both static and dynamic typing, functional programming, and closures, which I'm trying to leverage in my code more often. Unfortunately there are trade-offs, including lack of support for generics and (on iOS at least) no garbage collection. These contrasts have lead me to start a search for some of the programming languages that support the following features: Object Oriented Functional Programming Support Closures Generics Support for both Static and Dynamic Typing Module Management to avoid classpath/dll hell Garbage Collection Available Decent IDE Support Admittedly some of these features(IDE support, Module Management) may not be specific to the language itself, but obviously influence the ease of development in the language. Which languages fit these criteria?

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What are some reasonable stylistic limits on type inference?

- by Jon Purdy

C++0x adds pretty darn comprehensive type inference support. I'm sorely tempted to use it everywhere possible to avoid undue repetition, but I'm wondering if removing explicit type information all over the place is such a good idea. Consider this rather contrived example: Foo.h: #include <set> class Foo { private: static std::set<Foo*> instances; public: Foo(); ~Foo(); // What does it return? Who cares! Just forward it! static decltype(instances.begin()) begin() { return instances.begin(); } static decltype(instances.end()) end() { return instances.end(); } }; Foo.cpp: #include <Foo.h> #include <Bar.h> // The type need only be specified in one location! // But I do have to open the header to find out what it actually is. decltype(Foo::instances) Foo::instances; Foo() { // What is the type of x? auto x = Bar::get_something(); // What does do_something() return? auto y = x.do_something(*this); // Well, it's convertible to bool somehow... if (!y) throw "a constant, old school"; instances.insert(this); } ~Foo() { instances.erase(this); } Would you say this is reasonable, or is it completely ridiculous? After all, especially if you're used to developing in a dynamic language, you don't really need to care all that much about the types of things, and can trust that the compiler will catch any egregious abuses of the type system. But for those of you that rely on editor support for method signatures, you're out of luck, so using this style in a library interface is probably really bad practice. I find that writing things with all possible types implicit actually makes my code a lot easier for me to follow, because it removes nearly all of the usual clutter of C++. Your mileage may, of course, vary, and that's what I'm interested in hearing about. What are the specific advantages and disadvantages to radical use of type inference?

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IDirect3DDevice9Ex and D3DPOOL_MANAGED?

- by bluescrn

So I wanted to switch to IDirect3DDevice9Ex, purely for the SetFrameLatency function, as fullscreen vsynced D3D seemed to produce noticable input lag. But then it tells me 'ha ha ha! now you can't use D3DPOOL_MANAGED!': Direct3D9: (ERROR) :D3DPOOL_MANAGED is not valid with IDirect3DDevice9Ex Is this really as unpleasant as it looks (when you're relying quite heavily on managed resources) - or is there a simple solution? If it really does mean manual management of everything (reloading all static textures, VBs, and IBs on a device reset), is it worth the hassle, will IDirect3DDevice9Ex bring enough benefit to make it worth writing a new resource manager? Starting to think I must be doing something wrong, due to this: Direct3D9: (ERROR) :Lock is not supported for textures allocated with POOL_DEFAULT unless they are marked D3DUSAGE_DYNAMIC. So if I put my (static) textures in POOL_DEFAULT, they need flagging as D3DUSAGE_DYNAMIC, just because I lock them once to load the data in?

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problem with task switcher and ccsm

- by user2427

I'm trying to make a simpler task switcher work, instead of the default with unity. I installed ccsm, and then the extras to be able to access to static task switcher. The problem right now is that I can enable static task switcher but only if I run ccsm as sudo. When I try to enable running ccsm without sudo it doesn't let me enable anything. All the checkboxes are disabled. And enabling as sudo doesn't make the task switcher work. Does anyone know how to make this work?

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Missing return statement when using .charAt [migrated]

- by Timothy Butters

I need to write a code that returns the number of vowels in a word, I keep getting an error in my code asking for a missing return statement. Any solutions please? :3 import java.util.*; public class vowels { public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.println("Please type your name."); String name = input.nextLine(); System.out.println("Congratulations, your name has "+ countVowels(name) +" vowels."); } public static int countVowels(String str) { int count = 0; for (int i=0; i < str.length(); i++) { // char c = str.charAt(i); if (str.charAt(i) == 'a' || str.charAt(i) == 'e' || str.charAt(i) == 'o' || str.charAt(i) == 'i' || str.charAt(i) == 'u') count = count + 1; } } }

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setup dhcp server - "Job failed to start"

- by jdicarreira

I have an eth0 and eth1, eth0 has dynamic ip and on eth1 i setup static ip: auto lo iface lo inet loopback auto eth0 iface eth0 inet dhcp auto eth1 iface eth1 inet static address 10.10.0.1 netmask 255.0.0.0 gateway 10.10.0.1 ` and then i setup the "isc-dhcp-server" with the fowling command: INTERFACES="eth1" Finally... I went to this one "dhcpd.conf", with the fowling comand: default-lease-time 650; max-lease-time 79520; option subnet-mask 255.0.0.0; option broadcast-address 10.10.0.255; option routers 10.10.0.2; subnet 10.10.0.0 netmask 255.0.0.0 { range 10.10.0.10 10.10.0.250; } When I try to "sudo /etc/init.d/isc-dhcp-server start", I get "start: Job failed to start" Anyone knows whats wrong? :/

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Unknown error XNA cannot detect importer for "program.cs"

- by Evan Kohilas

I am not too sure what I have done to cause this, but even after undoing all my edits, this error still appears Error 1 Cannot autodetect which importer to use for "Program.cs". There are no importers which handle this file type. Specify the importer that handles this file type in your project. (filepath)\Advanced Pong\AdvancedPongContent\Program.cs Advanced Pong After receiving this error, everything between #if and #endif in the program.cs fades grey using System; namespace Advanced_Pong { #if WINDOWS || XBOX static class Program { /// <summary> /// The main entry point for the application. /// </summary> static void Main(string[] args) { using (Game1 game = new Game1()) { game.Run(); } } } #endif } I have searched this and could not find a solution anywhere. Any help is appreciated.

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