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• Is there a more useful explanation for UITableViewStylePlain?

  - by mystify

  From the docs: In the plain style, section headers and footers float above the content if the part of a complete section is visible. A table view can have an index that appears as a bar on the right hand side of the table (for example, "a" through "z"). You can touch a particular label to jump to the target section. I find that very hard to grasp. First, this one: if the part of a complete section is visible What do they mean by this? This is paradox. Which one is it? A) Table must be exactly the height of that section. If I have 5 Rows, and each row is 50px high, I must make it 5*50 high. The full section must be visible on the screen. Otherwise, if I have 100 rows but my table view is only 400 high, this will not apply. Nothing will float above my content. Sounds wrong. B) It doesn't matter how high my table view actually is. Header and Footer is floating above the content and I can scroll the section. Makes more sense. But is completely against this nonsense making sentence: 'if the part of a complete section is visible' Can anyone explain it better than they did?

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• emberjs on symfony2 dev enviroment dont work propertly

  - by rkmax

  I've builded a app with symfony2 the app expose an REST Api. now i build a simple client for consuming app.coffee - app.js App = Em.Application.create ready: -> @.entradas.load() Entrada: Em.Object.extend() entradas: Em.ArrayController.create content: [] load: -> url = 'http://localhost/api/1/entrada' me = @ $.ajax( url: url, method: 'GET', success: (data) -> me.set('content', []) for entrada in data.data.objects me.pushObject DBPlus.Entrada.create(entrada) ) MyBundle:Home:index.html.twig <script type="text/x-handlebars" src="{{ asset('js/templates/entradas.hbs') }}"></script> <script src="{{ asset('js/libs/jquery-1.7.2.min.js') }}"></script> <script src="{{ asset('js/libs/handlebars-1.0.0.beta.6.js') }}"></script> <script src="{{ asset('js/libs/ember-1.0.pre.min.js') }}"></script> <script src="{{ asset('js/app.js') }}"></script> the problem here is when i run on dev enviroment and link the template like <script type="text/x-handlebars" src="{{...}}"> the app dont work, nothing show but works fine over prod enviroment. he only way that works on dev enviroment is inline template MyBundle:Home:index.html.twig <script type="text/x-handlebars"> {% raw %} <ul class="entradas"> {{#each App.entradas}} <li class="entrada">{{nombre}}</li> {{/each}} </ul> {% endraw %} </script> can explain why this behavoir? Note: I disabled the debug profiler toolbar, and nothing

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• Unable to call RESTful web services methods

  - by Alessandro

  Hello, I'm trying to dive into the RESTful web services world and have started with the following template: [ServiceContract] [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)] public class Test { // TODO: Implement the collection resource that will contain the SampleItem instances [WebGet(UriTemplate = ""), OperationContract] public List<SampleItem> GetCollection() { // TODO: Replace the current implementation to return a collection of SampleItem instances return new List<SampleItem>() {new SampleItem() {Id = 1, StringValue = "Hello"}}; } [WebInvoke(UriTemplate = "", Method = "POST"), OperationContract] public SampleItem Create(SampleItem instance) { // TODO: Add the new instance of SampleItem to the collection throw new NotImplementedException(); } [WebGet(UriTemplate = "{id}"), OperationContract] public SampleItem Get(string id) { // TODO: Return the instance of SampleItem with the given id throw new NotImplementedException(); } [WebInvoke(UriTemplate = "{id}", Method = "PUT"), OperationContract] public SampleItem Update(string id, SampleItem instance) { return new SampleItem { Id = 99, StringValue = "Done" }; } [WebInvoke(UriTemplate = "{id}", Method = "DELETE"), OperationContract] public void Delete(string id) { // TODO: Remove the instance of SampleItem with the given id from the collection throw new NotImplementedException(); } } I am able to perform the GET operation but I am unable to perform PUT, POST or DELETE requests. Can anyone explain me how to perform these operations and how to create the correct URLs? Best regards Alessandro

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• How to continuously scroll content within a DIV using jQuery?

  - by Camsoft

  Aim The aim is to a have a container DIV with a fixed height and width and have the HTML content within that DIV automatically scroll vertically continuously. Question Basically I've created the code below using jQuery to scroll (move) the child DIV vertically upwards until its outside the bounding parent box where the animation then completes which triggers an event handler which resets the position of the child DIV and starts the process again. This works fine, so the content scrolls up leaving a blank space and then starts from the bottom again and scrolls up. The problem I have is that the requirements for this is for the content to appear as if it was continuously repeating, see below diagram to better explain this, is there a way to do this? (I don't want to use 3rd party plug ins or libraries other than jQuery): What I have so far The HTML: <div id="scrollingContainer"> <div class="scroller"> <h1>This is a title</h1> <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse at orci mi, id gravida tellus. Integer malesuada ante sit amet enim pulvinar congue. Donec pulvinar dolor et arcu posuere feugiat id et felis.</p> <p>More content....</p> </div> </div> The CSS: #scrollingContainer{ height: 300px; width: 300px; overflow: hidden; } #scrollingContainer DIV.scroller{ position: relative; } The JavaScript: /** * Scrolls the content DIV */ function scroll() { if($('DIV.scroller').height() > $('#scrollingContainer').height()) { var t = $('DIV.scroller').position().top + $('DIV.scroller').height(); /* Animate */ $('DIV.scroller').animate( { top: '-=' + t + 'px' } , 4000, 'linear', animationComplete); } } function animationComplete() { $(this).css('top', $('#scrollingContainer').height()); scroll(); }

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• More than 100 connection to sql server 2008 in "sleeping" status - Solved

  - by Allende

  I have a big trouble here, well at my server. I have an ASP .net web (framework 4.x) running on muy server, all the transactions/select/update/insert are made with ADO.NET. Well my problem is that after being using for a while (a couple of updates/selects/inserts) sometimes I got more than 100 connections on "sleeping" status when check for the connections on sql server with this query: SELECT spid, a.status, hostname, program_name, cmd, cpu, physical_io, blocked, b.name, loginame FROM master.dbo.sysprocesses a INNER JOIN master.dbo.sysdatabases b ON a.dbid = b.dbid where program_name like '%TMS%' ORDER BY spid I've been checking my code and closing every time I make a connection, I'm gonna test the new class, but I'm afraid the problem doesn't be fixed. It suppose that the connection pooling, keep the connections to re-use them, but until I see don't re-use them always. Any idea besides check for close all the connections open after use them? SOLVED(now I have just one and beautiful connection on "sleeping" status): Besides the anwser of David Stratton, I would like to share this link that help explain really well how the connection pool it works: http://dinesql.blogspot.com/2010/07/sql-server-sleeping-status-and.html Just to be short, you need to close every connection (sql connection objects) in order that the connection pool can re-use the connection and use the same connectinos string, to ensure this is highly recommended use one of the webConfig. Be careful with dataReaders you sould close its connection to (that was what make got out of my mind for while).

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• Doctrine2 ArrayCollection

  - by boosis

  Ok, I have a User entity as follows <?php class User { /** * @var integer * @Id * @Column(type="integer") * @GeneratedValue */ protected $id; /** * @var \Application\Entity\Url[] * @OneToMany(targetEntity="Url", mappedBy="user", cascade={"persist", "remove"}) */ protected $urls; public function __construct() { $this->urls = new \Doctrine\Common\Collections\ArrayCollection(); } public function addUrl($url) { // This is where I have a problem } } Now, what I want to do is check if the User has already the $url in the $urls ArrayCollection before persisting the $url. Now some of the examples I found says we should do something like if (!$this->getUrls()->contains($url)) { // add url } but this doesn't work as this compares the element values. As the $url doesn't have id value yet, this will always fail and $url will be dublicated. So I'd really appreciate if someone could explain how I can add an element to the ArrayCollection without persisting it and avoiding the duplication? Edit I have managed to achive this via $p = function ($key, $element) use ($url) { if ($element->getUrlHash() == $url->getUrlHash()) { return true; } else { return false; } }; But doesn't this still load all urls and then performs the check? I don't think this is efficient as there might be thousands of urls per user.

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• WPF DataValidation on a DataTemplate object in an ItemsControl

  - by Matt H.

  I have two datatemplates, both very similar... here is one of them: <DataTemplate x:Key="HeadingTemplate"> <Grid x:Name="mainHeadingGrid" Margin="5,5,30,0" HorizontalAlignment="Stretch"> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto" /> <ColumnDefinition /> </Grid.ColumnDefinitions> <TextBlock Grid.Column="1" Margin="30,3,10,0" Foreground="Black" FontWeight="Bold" HorizontalAlignment="Left" TextWrapping="Wrap"> <TextBlock.Text> <MultiBinding Converter="{StaticResource myHeadingConverter}" ConverterParameter="getRNHeadingTitle" Mode="TwoWay"> <Binding Path="num"/> <Binding Path="name"/> </MultiBinding> </TextBlock.Text> </TextBlock> <TextBox Grid.Column="1" Text="{Binding Path=moreInfo}"/> </Grid> </DataTemplate> I use an selector in my ItemsControl to choose between the two, based on the object it is bound to. I want to use validation to check through all of the properties and put a big exclamation point in front of the whole datatemplate as it is displayed in the itemscontrol. how do I do this? All of the examples I've found explain how to set a ValidationRule on a specific control in the datatemplate, in that control's binding. I want to apply my validation rule to the entire template... Help! :)

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• Cocos2D: Problem Rotating a CCMenu

  - by srikanth rongali

  If I try to do actions over menuItems but the actions are not running as expected. I think code below should make the menuItem rotate by 90 degrees but when I run it, the menuItem translates from its coordinates to another coordinate then returns to its original coordinate. The complete translation takes 3 seconds. What I need is for the menuItem to rotate by 90 degrees in place within a 3 seconds duration. Please explain where I have done wrong? CCMenuItemImage *targetE;//Globally declared CCMenu *menu;//Globally declared -(id)init { if( (self = [super init]) ) { isTouchEnabled = YES; CGSize windowSize = [[CCDirector sharedDirector] winSize]; targetE = [CCMenuItemImage itemFromNormalImage:@"grossinis_sister1.png" selectedImage:@"grossinis_sister1.png" target:self selector:@selector(touch:)]; menu = [CCMenu menuWithItems:targetE,nil]; id action4 = [CCRotateBy actionWithDuration:3.0 angle:90]; [menu runAction: [CCSequence actions: action4, nil]]; menu.position = ccp(windowSize.width/2 + 200, windowSize.height/2); [self addChild: menu z:10]; } return self; } @end Thank You.

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• Linq: the linked objects are null, why?

  - by user46503

  Hello, I have several linked tables (entities). I'm trying to get the entities using the following linq: ObjectQuery<Location> locations = context.Location; ObjectQuery<ProductPrice> productPrice = context.ProductPrice; ObjectQuery<Product> products = context.Product; IQueryable<ProductPrice> res1 = from pp in productPrice join loc in locations on pp.Location equals loc join prod in products on pp.Product equals prod where prod.Title.ToLower().IndexOf(Word.ToLower()) > -1 select pp; This query returns 2 records, ProductPrice objects that have linked object Location and Product but they are null and I cannot understand why. If I try to fill them in the linq as below: res = from pp in productPrice join loc in locations on pp.Location equals loc join prod in products on pp.Product equals prod where prod.Title.ToLower().IndexOf(Word.ToLower()) > -1 select new ProductPrice { ProductPriceId = pp.ProductPriceId, Product = prod }; I have the exception "The entity or complex type 'PBExplorerData.ProductPrice' cannot be constructed in a LINQ to Entities query" Could someone please explain me what happens and what I need to do? Thanks

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• detecting pauses in a spoken word audio file using pymad, pcm, vad, etc

  - by james

  First I am going to broadly state what I'm trying to do and ask for advice. Then I will explain my current approach and ask for answers to my current problems. Problem I have an MP3 file of a person speaking. I'd like to split it up into segments roughly corresponding to a sentence or phrase. (I'd do it manually, but we are talking hours of data.) If you have advice on how to do this programatically or for some existing utilities, I'd love to hear it. (I'm aware of voice activity detection and I've looked into it a bit, but I didn't see any freely available utilities.) Current Approach I thought the simplest thing would be to scan the MP3 at certain intervals and identify places where the average volume was below some threshold. Then I would use some existing utility to cut up the mp3 at those locations. I've been playing around with pymad and I believe that I've successfully extracted the PCM (pulse code modulation) data for each frame of the mp3. Now I am stuck because I can't really seem to wrap my head around how the PCM data translates to relative volume. I'm also aware of other complicating factors like multiple channels, big endian vs little, etc. Advice on how to map a group of pcm samples to relative volume would be key. Thanks!

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• ruby 1.9 ri problem

  - by Yousui

  hi all, i'm using windows xp sp2, and installed ruby through ruby 1.9 one click installer. then when i try to using ri, i get the following response, can anyone help me with my problem? great thanks. C:\Documents and Settings\eyang>ruby --version ruby 1.9.1p243 (2009-07-16 revision 24175) [i386-mingw32] C:\Documents and Settings\eyang>ri --version ri 2.2.2 C:\Documents and Settings\eyang>ri String Updating class cache with 0 classes... Nothing known about String C:\Documents and Settings\eyang>ri Updating class cache with 0 classes... No ri data found If you've installed Ruby yourself, you need to generate documentation using: make install-doc from the same place you ran `make` to build ruby. If you installed Ruby from a packaging system, then you may need to install an additional package, or ask the packager to enable ri generation. C:\Documents and Settings\eyang> by the way, when i try to use gem, i got the following error messages too, anyone can explain it ? great thanks. C:\Documents and Settings\eyang>gem --version 1.3.5 C:\Documents and Settings\eyang>gem query --remote *** REMOTE GEMS *** ERROR: While executing gem ... (Errno::ENOMEM) Not enough space - <STDOUT> C:\Documents and Settings\eyang>

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• Is possible to reuse subqueries?

  - by Gothmog

  Hello, I'm having some problems trying to perform a query. I have two tables, one with elements information, and another one with records related with the elements of the first table. The idea is to get in the same row the element information plus several records information. Structure could be explain like this: table [ id, name ] [1, '1'], [2, '2'] table2 [ id, type, value ] [1, 1, '2009-12-02'] [1, 2, '2010-01-03'] [1, 4, '2010-01-03'] [2, 1, '2010-01-02'] [2, 2, '2010-01-02'] [2, 2, '2010-01-03'] [2, 3, '2010-01-07'] [2, 4, '2010-01-07'] And this is want I would like to achieve: result [id, name, Column1, Column2, Column3, Column4] [1, '1', '2009-12-02', '2010-01-03', , '2010-01-03'] [2, '2', '2010-01-02', '2010-01-02', '2010-01-07', '2010-01-07'] The following query gets the proper result, but it seems to me extremely inefficient, having to iterate table2 for each column. Would be possible in anyway to do a subquery and reuse it? SELECT a.id, a.name, (select min(value) from table2 t where t.id = subquery.id and t.type = 1 group by t.type) as Column1, (select min(value) from table2 t where t.id = subquery.id and t.type = 2 group by t.type) as Column2, (select min(value) from table2 t where t.id = subquery.id and t.type = 3 group by t.type) as Column3, (select min(value) from table2 t where t.id = subquery.id and t.type = 4 group by t.type) as Column4 FROM (SELECT distinct id FROM table2 t WHERE (t.type in (1, 2, 3, 4)) AND t.value between '2010-01-01' and '2010-01-07') as subquery LEFT JOIN table a ON a.id = subquery.id

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• Apache rewrite rules redux

  - by AlexanderJohannesen

  I've got a REST framework that when plopped into any directory should Just Work(TM), and it seems to work fine when I've got projects in subdirectories, but not if it's in root. So, given a few example directories; / /project1 /bingo/project2 /hoopla/doopla/minor/project3 All of these works fine, except I'm getting "funnies"* when the project runs in the root directory (bit hard to explain, I suppose, but the second level rewrites are not working properly). Here's my attempt at a generic .htaccess file: RewriteEngine On RewriteRule ^static/ - [L] RewriteCond %{REQUEST_URI} ^$ RewriteRule .* ./ [R,L] RewriteRule ^index.php - [L] RewriteRule (.*) index.php?q=$1 [QSA,PT] (And yes, all projects have a subdirectory ./static which is ignored by rewrites) What I'm trying to achieve is a set of rewrite rules that work for most cases (which is, again, plonking the project in a directory the webserver serves). I'm not a rewrite rules wiz by a long shot, and any good advice and gotchas would be appreciated (and yes, I've gone through too many introductory articles. I need some serious juice.) More info on the funnies; my webserver has docroot in one spot (under /usr/share/apache2/default-site/), but a set of rules that says that /projects is pulled in from somewhere else that's not a subdirectory of docroot (/home/user/Projects/). When I go there, I get a list of /projects subdirectories, and if one of those subdirectories gets called (restmapp) with the proposed rewrite rules, I get ; The requested URL /home/user/Projects/restmapp/index.php was not found on this server.

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• Should we have a database independent SQL like query language in Django? [closed]

  - by Yugal Jindle

  Note : I know we have Django ORM already that keeps things database independent and converts to the database specific SQL queries. Once things starts getting complicated it is preferred to write raw SQL queries for better efficiency. When you write raw sql queries your code gets trapped with the database you are using. I also understand its important to use the full power of your database that can-not be achieved with the django orm alone. My Question : Until I use any database specific feature, why should one be trapped with the database. For instance : We have a query with multiple joins and we decided to write a raw sql query. Now, that makes my website postgres specific. Even when I have not used any postgres specific feature. I feel there should be some fake sql language which can translate to any database's sql query. Even Django's ORM can be built over it. So, that if you go out of ORM but not database specific - you can still remain database independent. I asked the same question to Jacob Kaplan Moss (In person) : He advised me to stay with the database that I like and endure its whole power, to which I agree. But my point was not that we should be database independent. My point is we should be database independent until we use a database specific feature. Please explain, why should be there a fake sql layer over the actual sql ?

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• SeriesInterpolate - removing data at start of array

  - by Allan Jardine

  Hello all, I've been experimenting with Flex Charts (in Flash Builder 4) recently, but have run into one area which didn't quite work as I was expecting. Specifically, when adding and removing a data point from an array, with SeriesInterpolate set. I've put up three examples, as I expect these will make a lot more sense than me trying to explain it with words only!: http://sprymedia.co.uk/media/misc/flex/linechart/LineChart-Add.swf - Clicking the button in the top right adds a new data point to the end of the data array, and the chart is smoothly updated (almost smoothly there is a 1px shift when animating which is odd...) http://sprymedia.co.uk/media/misc/flex/linechart/LineChart-Delete.swf - Clicking the button (which is now labelled incorrectly) will remove the item at the start of the data array - but the chart draws this as if it were removing the end element. http://sprymedia.co.uk/media/misc/flex/linechart/LineChart-AddDelete.swf - This is sort of what I'm eventually aiming for - a smooth side scroll chart, where new data is added at the end and the old data is sifted off the front. However the delete behaviour makes this look a bit odd. Does anyone know if there is a way to get the smooth transition I'm looking with SeriesInterpolate? Or is it possible to implement a custom transition? Many thanks, Allan

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• Learning AES: the KeyBytes

  - by Tom Brito

  I got the following example from here: import java.security.Security; import javax.crypto.Cipher; import javax.crypto.spec.SecretKeySpec; public class MainClass { public static void main(String[] args) throws Exception { Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider()); byte[] input = "www.java2s.com".getBytes(); byte[] keyBytes = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17 }; SecretKeySpec key = new SecretKeySpec(keyBytes, "AES"); Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding", "BC"); System.out.println(new String(input)); // encryption pass cipher.init(Cipher.ENCRYPT_MODE, key); byte[] cipherText = new byte[cipher.getOutputSize(input.length)]; int ctLength = cipher.update(input, 0, input.length, cipherText, 0); ctLength += cipher.doFinal(cipherText, ctLength); System.out.println(new String(cipherText)); System.out.println(ctLength); // decryption pass cipher.init(Cipher.DECRYPT_MODE, key); byte[] plainText = new byte[cipher.getOutputSize(ctLength)]; int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0); ptLength += cipher.doFinal(plainText, ptLength); System.out.println(new String(plainText)); System.out.println(ptLength); } } I imagine that the byte[] keyBytes should be random generated, so I gone to test the max size before do it. When adding one more byte 0x18 to the array, the exception raised: InvalidKeyException: Key length not 128/192/256 bits. But the original 18 bytes (from 0 to 17) are not multiple of nither 128, 192 or 256. I would like to understand the math here.. can anyone explain me? Thanks!

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• Java SortedMap to Scala TreeMap

  - by Dave

  I'm having trouble converting a java SortedMap into a scala TreeMap. The SortedMap comes from deserialization and needs to be converted into a scala structure before being used. Some background, for the curious, is that the serialized structure is written through XStream and on desializing I register a converter that says anything that can be assigned to SortedMap[Comparable[_],_] should be given to me. So my convert method gets called and is given an Object that I can safely cast because I know it's of type SortedMap[Comparable[_],_]. That's where it gets interesting. Here's some sample code that might help explain it. // a conversion from comparable to ordering scala> implicit def comparable2ordering[A <: Comparable[A]](x: A): Ordering[A] = new Ordering[A] { | def compare(x: A, y: A) = x.compareTo(y) | } comparable2ordering: [A <: java.lang.Comparable[A]](x: A)Ordering[A] // jm is how I see the map in the converter. Just as an object. I know the key // is of type Comparable[_] scala> val jm : Object = new java.util.TreeMap[Comparable[_], String]() jm: java.lang.Object = {} // It's safe to cast as the converter only gets called for SortedMap[Comparable[_],_] scala> val b = jm.asInstanceOf[java.util.SortedMap[Comparable[_],_]] b: java.util.SortedMap[java.lang.Comparable[_], _] = {} // Now I want to convert this to a tree map scala> collection.immutable.TreeMap() ++ (for(k <- b.keySet) yield { (k, b.get(k)) }) <console>:15: error: diverging implicit expansion for type Ordering[A] starting with method Tuple9 in object Ordering collection.immutable.TreeMap() ++ (for(k <- b.keySet) yield { (k, b.get(k)) })

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• When does a WPF adorner layer first become available?

  - by aoven

  I'm trying to add an overlay effect to my UserControl and I know that's what adorners are used for in WPF. But I'm a bit confused about how they supposedly work. I figured that adorner layer is implicitly handled by WPF runtime, and as such, should always be available. But when I create an instance of my UserControl in code, there is no adorner layer there. The following code fails with exception: var view = new MyUserControl(); var target = view.GetAdornerTarget(); // This returns a specific UI control. var layer = AdornerLayer.GetAdornerLayer(target); if (layer == null) { throw new Exception("No adorner layer at the moment."); } Can someone please explain to me, how this is supposed to work? Do I need to place the UserControl instance into a top-level Window first? Or do I need to define the layer myself somehow? Digging through documentation got me nowhere. Thank you!

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• Convert 4 bytes to int

  - by Oscar Reyes

  I'm reading a binary file like this: InputStream in = new FileInputStream( file ); byte[] buffer = new byte[1024]; while( ( in.read(buffer ) > -1 ) { int a = // ??? } What I want to do it to read up to 4 bytes and create a int value from those but, I don't know how to do it. I kind of feel like I have to grab 4 bytes at a time, and perform one "byte" operation ( like << & FF and stuff like that ) to create the new int What's the idiom for this? EDIT Ooops this turn out to be a bit more complex ( to explain ) What I'm trying to do is, read a file ( may be ascii, binary, it doesn't matter ) and extract the integers it may have. For instance suppose the binary content ( in base 2 ) : 00000000 00000000 00000000 00000001 00000000 00000000 00000000 00000010 The integer representation should be 1 , 2 right? :- / 1 for the first 32 bits, and 2 for the remaining 32 bits. 11111111 11111111 11111111 11111111 Would be -1 and 01111111 11111111 11111111 11111111 Would be Integer.MAX_VALUE ( 2147483647 )

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• Weak event handler model for use with lambdas

  - by Benjol

  OK, so this is more of an answer than a question, but after asking this question, and pulling together the various bits from Dustin Campbell, Egor, and also one last tip from the 'IObservable/Rx/Reactive framework', I think I've worked out a workable solution for this particular problem. It may be completely superseded by IObservable/Rx/Reactive framework, but only experience will show that. I've deliberately created a new question, to give me space to explain how I got to this solution, as it may not be immediately obvious. There are many related questions, most telling you you can't use inline lambdas if you want to be able to detach them later: Weak events in .Net? Unhooking events with lambdas in C# Can using lambdas as event handlers cause a memory leak? How to unsubscribe from an event which uses a lambda expression? Unsubscribe anonymous method in C# And it is true that if YOU want to be able to detach them later, you need to keep a reference to your lambda. However, if you just want the event handler to detach itself when your subscriber falls out of scope, this answer is for you.

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• Scalaz: request for use case for Cokleisli composition

  - by oxbow_lakes

  This question isn't meant as flame-bait! As it might be apparent, I've been looking at Scalaz recently. I'm trying to understand why I need some of the functionality that the library provides. Here's something: import scalaz._ import Scalaz._ type NEL[A] = NonEmptyList[A] val NEL = NonEmptyList I put some println statements in my functions to see what was going on (aside: what would I have done if I was trying to avoid side effects like that?). My functions are: val f: NEL[Int] => String = (l: NEL[Int]) => {println("f: " + l); l.toString |+| "X" } val g: NEL[String] => BigInt = (l: NEL[String]) => {println("g: " + l); BigInt(l.map(_.length).sum) } Then I combine them via a cokleisli and pass in a NEL[Int] val k = cokleisli(f) =>= cokleisli(g) println("RES: " + k( NEL(1, 2, 3) )) What does this print? f: NonEmptyList(1, 2, 3) f: NonEmptyList(2, 3) f: NonEmptyList(3) g: NonEmptyList(NonEmptyList(1, 2, 3)X, NonEmptyList(2, 3)X, NonEmptyList(3)X) RES: 57 The RES value is the character count of the (String) elements in the final NEL. Two things occur to me: How could I have known that my NEL was going to be reduced in this manner from the method signatures involved? (I wasn't expecting the result at all) What is the point of this? Can a reasonably simple and easy-to-follow use case be distilled for me? This question is a thinly-veiled plea for some lovely person like retronym to explain how this powerful library actually works.

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• LINQ - is SkipWhile broken?

  - by Judah Himango

  I'm a bit surprised to find the results of the following code, where I simply want to remove all 3s from a sequence of ints: var sequence = new [] { 1, 1, 2, 3 }; var result = sequence.SkipWhile(i => i == 3); // Oh noes! Returns { 1, 1, 2, 3 } Why isn't 3 skipped? My next thought was, OK, the Except operator will do the trick: var sequence = new [] { 1, 1, 2, 3 }; var result = sequence.Except(i => i == 3); // Oh noes! Returns { 1, 2 } In summary, Except removes the 3, but also removes non-distinct elements. Grr. SkipWhile doesn't skip the last element, even if it matches the condition. Grr. Can someone explain why SkipWhile doesn't skip the last element? And can anyone suggest what LINQ operator I can use to remove the '3' from the sequence above?

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• what is the exact way to use Endorsed directory in jdk1.6

  - by raticulin

  I want to upgrade my jaxws to 2.2 (jdk1.6 comes bundled with jaxws 2.1). My jdk is (I did not install public jre): java version "1.6.0_20" Java(TM) SE Runtime Environment (build 1.6.0_20-b02) Java HotSpot(TM) Client VM (build 16.3-b01, mixed mode) In jaxws' own doc they explain how to do it: One way to fix this is to copy jaxws-api.jar and jaxb-api.jar into JRE endorsed directory, which is $JAVA_HOME/lib/endorsed (or $JDK_HOME/jre/lib/endorsed) But I am not sure this is having any effect in my installation. For starters I have only defined %JAVA_HOME%. And folder $JAVA_HOME/lib/endorsed is inexistant, so I created and copied the two jars. But if I do (wsgen is a tool from jaxws) wsgen -version I still get: JAX-WS RI 2.1.6 in JDK 6 I also tried creating folder JAVA_HOME\jre\lib\endorsed (notice that in the doc they say JDK_HOME, but as I only have JAVA_HOME I used this path). Still same wsgen output. My questions are: What is the difference between JAVA_HOME and JDK_HOME in the doc page? anything significant or just two ways to refer to JAVA_HOME ? Is 'wsgen -version' a valid way to check jaxws version that is used or this always calls the exe in the original jdk, but it does not mean endorsed jars will be used? Anyone knows very detailed steps to install jaxws2.2 in a jdk.16?

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• Wrappers/law of demeter seems to be an anti-pattern...

  - by Robert Fraser

  I've been reading up on this "Law of Demeter" thing, and it (and pure "wrapper" classes in general) seem to generally be anti patterns. Consider an implementation class: class Foo { void doSomething() { /* whatever */ } } Now consider two different implementations of another class: class Bar1 { private static Foo _foo = new Foo(); public static Foo getFoo() { return _foo; } } class Bar2 { private static Foo _foo = new Foo(); public static void doSomething() { _foo.doSomething(); } } And the ways to call said methods: callingMethod() { Bar1.getFoo().doSomething(); // Version 1 Bar2.doSomething(); // Version 2 } At first blush, version 1 seems a bit simpler, and follows the "rule of Demeter", hide Foo's implementation, etc, etc. But this ties any changes in Foo to Bar. For example, if a parameter is added to doSomething, then we have: class Foo { void doSomething(int x) { /* whatever */ } } class Bar1 { private static Foo _foo = new Foo(); public static Foo getFoo() { return _foo; } } class Bar2 { private static Foo _foo = new Foo(); public static void doSomething(int x) { _foo.doSomething(x); } } callingMethod() { Bar1.getFoo().doSomething(5); // Version 1 Bar2.doSomething(5); // Version 2 } In both versions, Foo and callingMethod need to be changed, but in Version 2, Bar also needs to be changed. Can someone explain the advantage of having a wrapper/facade (with the exception of adapters or wrapping an external API or exposing an internal one).

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• Need help figuring out scala compiler errors.

  - by klactose

  Hello all, I have been working on a project in scala, but I am getting some error messages that I don't quite understand. The classes that I am working with are relatively simple. For example: abstract class Shape case class Point(x: Int, y: Int) extends Shape case class Polygon(points: Point*) extends Shape Now suppose that I create a Polygon: val poly = new Polygon(new Point(2,5), new Point(7,0), new Point(3,1)) Then if I attempt to determine the location and size of the smallest possible rectangle that could contain the polygon, I get various errors that I don't quite understand. Below are snippets of different attempts and the corresponding error messages that they produce. val upperLeftX = poly.points.reduceLeft(Math.min(_.x, _.x)) Gives the error: "missing parameter type for expanded function ((x$1) = x$1.x)" val upperLeftX = poly.points.reduceLeft((a: Point, b: Point) => (Math.min(a.x, b.x))) Gives this error: "type mismatch; found : (Point, Point) = Int required: (Any, Point) = Any" I am very confused about both of these error messages. If anyone could explain more clearly what I am doing incorrectly, I would really appreciate it. Yes, I see that the second error says that I need type "Any" but I don't understand exactly how to implement a change that would work as I need it. Obviously simply changing "a: Point" to "a: Any" is not a viable solution, so what am I missing?

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