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  • How to select a single object using Linq in vb.net

    - by Hucker
    I have done a lot of searching to what appears to be a simple LINQ problem but I can't figure out how to do grab an object out of a collection that has a specified minimum (or max value) without resorting to a sort like this: > dim customers= GetCustomers() > > dim youngest = (From c in customers > Order By c.age Ascending).ToList.First This (untested code) structure works fine with the exception that the entire customer array must be sorted and placed into a list for the only purpose of extracting the first value. That can't be the best way to get the minimum! Note that I want the whole c record in this case, not the minumum age of a customer that can be done like this (a typical example): > dim customers= GetCustomers() > > dim youngest = (From c in customers > Select c.age).Min Or even > dim customers= GetCustomers() > > dim youngest = (From c in customers > Select c).Min(Function(x) x.age) I can't for the life of me figure out how to get the whole object (or even the index) without resorting to the sort...

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  • Can I automate a loop query based on category with the page's title?

    - by jordaninternets
    To explain further, I need to get a page to display posts from a specific category. I want to automate this process so I don't have to make a template for each category. How would I do that? (keep in mind the person I'm building this is for has no coding experience.) The only way I could think off from the top of my head is to use the title or slug. So if the category is named the same thing as the slug, could I filter by category using the slug? Maybe this isn't the best way... what should I do? This is what I came up with, but it doesn't work, I'm sure due to improper use on may part, but I've been pouring over the WP codex and Google with no avail to tell me my problem. <?php $paged = (get_query_var('paged')) ? get_query_var('paged') : 1; $args= array( 'orderby' => 'date', 'order' => 'ASC', 'paged' => $paged, 'category_name' => echo the_title('\'','\'',) ); query_posts($args); ?>

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  • MySQL Query - WHERE and IF?

    - by Prash
    I'm not quite sure how to right this query. Basically, I'm going to have a table with two columns (OS and country_code) - more columns too, but those are the conditional ones. These will be either set to 0 for all, or specific ones, separated by commas. Now, what I'm trying achieve is pull data from the table if the OS and country_code = 0, or if they contain matching data (separated by commas). Then, I have a column for time. I want to select rows where the time is GREATER than the time column, unless the column time_t is set to false, in which case this shouldn't matter. I hope I explained it right? This is what I kind of have so far: $get = $db->prepare("SELECT * FROM commands WHERE country_code = 0 OR country_code LIKE :country_code AND OS = 0 OR OS LIKE :OS AND IF (time_t = 1, expiry > NOW()) "); $get->execute(array( ':country_code' => "%{$data['country_code']}%", ':OS' => "%{$data['OS']}%" ));

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  • PHP: exif_imagetype() not working?

    - by Karem
    I have this extension checker: $upload_name = "file"; $max_file_size_in_bytes = 8388608; $extension_whitelist = array("jpg", "gif", "png", "jpeg"); /* checking extensions */ $path_info = pathinfo($_FILES[$upload_name]['name']); $file_extension = $path_info["extension"]; $is_valid_extension = false; foreach ($extension_whitelist as $extension) { if (strcasecmp($file_extension, $extension) == 0) { $is_valid_extension = true; break; } } if (!$is_valid_extension) { echo "{"; echo "error: 'ext not allowed!'\n"; echo "}"; exit(0); } And then i added this: if (exif_imagetype($_FILES[$upload_name]['name']) != IMAGETYPE_GIF OR exif_imagetype($_FILES[$upload_name]['name']) != IMAGETYPE_JPEG OR exif_imagetype($_FILES[$upload_name]['name']) != IMAGETYPE_PNG) { echo "{"; echo "error: 'This is no photo..'\n"; echo "}"; exit(0); } As soon when I added this to my imageupload function, the function stops working. I dont get any errors, not even the one i made myself "this is no photo", what could be wrong? Just checked with my host. They support the function exif_imagetype()

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  • HTTP post using php and curl failing

    - by user2916484
    I am trying to send an XML file to an external system. I am using the below code for doing so, which I got over the internet. But I observed that when i put an echo on the xml variable, it does not show me the XML as a string, but it is parsing the xml and showing me the values. Same is happening when I am sending this to external system. Which is failing. Can you please tell me a way, in which the XML is not parsed and I can send the entire XML text as a string to external system? My code is below. <?php $xml = '<?xml version=\"1.0\" encoding="UTF-8" ?><shiporder><orderID>1234</orderID> <orderperson>John Smith</orderperson></shiporder>'; $xml2 = ''; $headers = array( "Content-type: text/xml", "Content-length: " . strlen($xml), "Connection: close", ); // give the path of the Third party site $url = "http://<server>:<port>/XMII/Illuminator?service=WSMessageListener&mode=WSMessageListenerServer&NAME=shiporder&IllumLoginName=<name>&IllumLoginPassword=<pswd>"; echo $xml; echo $url; $ch = curl_init(); curl_setopt($ch, CURLOPT_URL,$url); //curl_setopt($ch, CURLOPT_MUTE, 1); curl_setopt($ch, CURLOPT_POST, 1); curl_setopt($ch, CURLOPT_TIMEOUT, 10); curl_setopt($ch, CURLOPT_HTTPHEADER, $headers); curl_setopt($ch, CURLOPT_POSTFIELDS, $xml); curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); $output = curl_exec($ch); echo $output; curl_close($ch); ?> Regards, Gita

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  • How do I display core data on second view controller?

    - by jon
    I am working on my first core data iPhone application. I am using a navigation controller, and the root view controller displays 4 rows. Clicking the first row takes me to a second table view controller. However, when I click the back button, repeat the row tap, click the back button again, and tap the row a third time, I get an error. I have been researching this for a week with no success. I can reproduce the error easily: Create a new Navigation-based Application, use Core Data for storage, call it MyTest which creates MyTestAppDelegate and RootViewController. Add new UIViewController subclass, with UITableViewController and xib, call it ListViewController. Copy code from RootViewController.h and .m to ListViewController.h and .m., changing the file names appropriately. To simplify the code, I removed the trailing “_” from all variables. In RootViewController, I added #import ListViewController.h, set up an array to display 4 rows and navigate to ListViewController when clicking the first row. In ListViewController.m, I added #import MyTestAppDelegate.h” and the following code: - (void)viewDidLoad { [super viewDidLoad]; if (managedObjectContext == nil) { managedObjectContext = [(MyTestAppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext]; } .. } The sequence that causes the error is tap row, return, tap row, return, tap row - error. managedObjectContext is synthesized for the third time. I appreciate your patience and your help, as this makes no sense to me. ADDENDUM: I may have a partial solution. http://www.iphonedevsdk.com/forum/iphone-sdk-development/41688-accessing-app-delegates-managed-object-context.html If I do not release the managedObjectContext in the .m file, the error goes away. Is that ok or will that cause me issues? - (void)dealloc { [fetchedResultsController release]; // [managedObjectContext release]; [super dealloc]; } ADDENDUM 2: See solution below. Sorry for the formatting issues - this was my first post.

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  • Easy HTTPS to PHP script

    - by Tom
    Hi, here is my scenario: I have a website with php, mySQL. I have a software application that has a login screen and sends usernames and passwords over the web by http: public String GetWebPageSource(String pURL) { try { byte[] vReceivedBytes = null; using (System.Net.WebClient vWebClient = new System.Net.WebClient()) { vReceivedBytes = vWebClient.DownloadData(pURL); } int vBomLen = 3; byte[] vStrippedBytes = new byte[vReceivedBytes.Length - vBomLen]; Array.Copy(vReceivedBytes, vBomLen, vStrippedBytes, 0, vReceivedBytes.Length - vBomLen); return System.Text.Encoding.UTF8.GetString(vStrippedBytes); } catch (Exception e) { Console.WriteLine(e.Message); return null; } } So to send a username and password I would write: GetWebPageSource("http://mywebsite.com/Login.php?username=stackoverflow&password=iscool") and the php file would spit out some text saying whether the password is accepted or denied. However this is NOT secure. So I want to make it secure... https. How easy is it to integrate https? How much will the code change? How much do I have to handle? What is transparent to me. Do I have to check if a cookie already exists and if not write the methods for authentication or is there librarys already provided that will do it for me?

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  • How to output multiple rows from an SQL query using the mysqli object

    - by Jonathan
    Assuming that the mysqli object is already instantiatied (and connected) with the global variable $mysql, here is the code I am trying to work with. class Listing { private $mysql; function getListingInfo($l_id = "", $category = "", $subcategory = "", $username = "", $status = "active") { $condition = "`status` = '$status'"; if (!empty($l_id)) $condition .= "AND `L_ID` = '$l_id'"; if (!empty($category)) $condition .= "AND `category` = '$category'"; if (!empty($subcategory)) $condition .= "AND `subcategory` = '$subcategory'"; if (!empty($username)) $condition .= "AND `username` = '$username'"; $result = $this->mysql->query("SELECT * FROM listing WHERE $condition") or die('Error fetching values'); $this->listing = $result->fetch_array() or die('could not create object'); foreach ($this->listing as $key => $value) : $info[$key] = stripslashes(html_entity_decode($value)); endforeach; return $info; } } there are several hundred listings in the db and when I call $result-fetch_array() it places in an array the first row in the db. however when I try to call the object, I can't seem to access more than the first row. for instance: $listing_row = new Listing; while ($listing = $listing_row-getListingInfo()) { echo $listing[0]; } this outputs an infinite loop of the same row in the db. Why does it not advance to the next row? if I move the code: $this->listing = $result->fetch_array() or die('could not create object'); foreach ($this->listing as $key => $value) : $info[$key] = stripslashes(html_entity_decode($value)); endforeach; if I move this outside the class, it works exactly as expected outputting a row at a time while looping through the while statement. Is there a way to write this so that I can keep the fetch_array() call in the class and still loop through the records?

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  • How can a B-tree node be represented?

    - by chronodekar
    We're learning B-trees in class and have been asked to implement them in code. The teacher has left choice of programming language to us and I want to try and do it in C#. My problem is that the following structure is illegal in C#, unsafe struct BtreeNode { int key_num; // The number of keys in a node int[] key; // Array of keys bool leaf; // Is it a leaf node or not? BtreeNode*[] c; // Pointers to next nodes } Specifically, one is not allowed to create a pointer to point to the structure itself. Is there some work-around or alternate approach I could use? I'm fairly certain that there MUST be a way to do this within the managed code, but I can't figure it out. EDIT: Eric's answer pointed me in the right direction. Here's what I ended up using, class BtreeNode { public List<BtreeNode> children; // The child nodes public static int MinDeg; // The Minimum Degree of the tree public bool IsLeaf { get; set; } // Is the current node a leaf or not? public List<int> key; // The list of keys ... }

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  • Using curl to submit/retrieve a forms results

    - by Jason
    I need help in trying to use curl to post data to a page and retrieve the results after the form has been submitted. I created a simple form: <form name="test" method="post" action="form.php"> <input type="text" name="name" size="40" />e <input type="text" name="comment" size="140" /> <input type="submit" name="submit" value="submit" /> </form> In addition, I have php code to handle this form in the same page. All it does is echo back the form values. The curl that I have been using is this: $h = curl_init(); curl_setopt($h, CURLOPT_URL, "path/to/form.php"); curl_setopt($h, CURLOPT_POST, true); curl_setopt($h, CURLOPT_POSTFIELDS, array( 'name' = 'yes', 'comment' = 'no' )); curl_setopt($h, CURLOPT_HEADER, false); curl_setopt($h, CURLOPT_RETURNTRANSFER, 1); $result = curl_exec($h); When I launch the page with the curl code in it, I get the form.php page contents but it doesn't not show the variables that PHP should have echo'd when the form is submitted. would appreciate any help with this. Thanks.

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  • How to do something when AVQueuePlayer finishes the last playeritem

    - by user1634529
    I've got an AVQueuePlayer which I'm creating from an array of 4 AVPlayerItems, and it all plays fine. I want to do something when the last item in the queue finishes playing, I've looked a load of answers on here and this is the one that looks most promising for what I want: The best way to execute code AFTER a sound has finished playing In my button handler i have this code: static const NSString *ItemStatusContext; [thePlayerItemA addObserver:self forKeyPath:@"status" options:0 context:&ItemStatusContext]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(playerItemDidReachEnd) name:AVPlayerItemDidPlayToEndTimeNotification object:thePlayerItemA]; theQueuePlayer = [AVQueuePlayer playerWithPlayerItem:thePlayerItemA]; [theQueuePlayer play]; and then I have a function to handle playerItemDidReachEnd: - (void)playerItemDidReachEnd:(NSNotification *)notification { // Do stuff here NSLog(@"IT REACHED THE END"); } But when I run this I get an Internal Inconsistency Exception: An -observeValueForKeyPath:ofObject:change:context: message was received but not handled. Key path: status Observed object: <AVPlayerItem: 0x735a130, asset = <AVURLAsset: 0x73559c0, URL = file://localhost/Users/mike/Library/Application%20Support/iPhone%20Simulator/5.0/Applications/A0DBEC13-2DA6-4887-B29D-B43A78E173B8/Phonics%2001.app/yes.mp3>> Change: { kind = 1; } What am I doing wrong?

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  • What is the most efficient way to handle points / small vectors in JavaScript?

    - by Chris
    Currently I'm creating an web based (= JavaScript) application thata is using a lot of "points" (= small, fixed size vectors). There are basically two obvious ways of representing them: var pointA = [ xValue, yValue ]; and var pointB = { x: xValue, y: yValue }; So translating my point a bit would look like: var pointAtrans = [ pointA[0] + 3, pointA[1] + 4 ]; var pointBtrans = { x: pointB.x + 3, pointB.y + 4 }; Both are easy to handle from a programmer point of view (the object variant is a bit more readable, especially as I'm mostly dealing with 2D data, seldom with 3D and hardly with 4D - but never more. It'll allways fit into x,y,z and w) But my question is now: What is the most efficient way from the language perspective - theoretically and in real implementations? What are the memory requirements? What are the setup costs of an array vs. an object? ... My target browsers are FireFox and the Webkit based ones (Chromium, Safari), but it wouldn't hurt to have a great (= fast) experience under IE and Opera as well...

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  • PHP OOP class Sensative To Counter field name !

    - by Mac Taylor
    hey guys recently i managed to write a class for my stories , and everything is fine , unless counter field that stores page's hits here is my class : class nk_posts { var $data = array(); public function _data() { global $db; $result = $db->sql_query(" SELECT bt_stories.*, bt_tags.*, bt_topics.*, group_concat(DISTINCT bt_tags.tag ) as mytags, group_concat(DISTINCT bt_topics.topicname ) as mytopics FROM bt_stories,bt_tags,bt_topics WHERE CONCAT( ' ', bt_stories.tags, ' ' ) LIKE CONCAT( '%', bt_tags.tid, '%' ) AND CONCAT( ' ', bt_stories.associated, ' ' ) LIKE CONCAT( '%', bt_topics.topicid, '%' ) AND time<=now() AND section='news' AND approved='1' GROUP BY bt_stories.sid ORDER BY bt_stories.sid DESC "); while ($this->data = $db->sql_fetchrow($result)) { $this->sid = $this->data['sid']; $this->title = $this->data['title']; $this->counter = $this->data['counter']; //------Rest of Fields ------ $this->_output(); } } public function _output() { themeindex( $this->sid, $this->title, $this->counter, //------Rest of Fields ------ ); } } problem this class can't show counter filed value , but if i change counter field name to other thing like hit , .. everything goes fine im sure its okay if i write it in normal php mysql way , but i need this to be in OOP way any comment why it's sensitive to counter field name ?!

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  • Automatically update php loop with data pulled from database

    - by John Svensson
    SQL STRUCTURE CREATE TABLE IF NOT EXISTS `map` ( `id` int(11) NOT NULL AUTO_INCREMENT, `x` int(11) NOT NULL, `y` int(11) NOT NULL, `type` varchar(50) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ; http://localhost/map.php?x=0&y=0 When I update the x and y via POST or GET, I would like to pull the new data from the database without refreshing the site, how would I manage that? Could someone give me some examples, because I am really stuck here. <?php mysql_connect('localhost', 'root', ''); mysql_select_db('hol'); $startX = $_GET['x']; $startY = $_GET['y']; $fieldHeight = 6; $fieldWidth = 6; $sql = "SELECT id, x, y, type FROM map WHERE x BETWEEN ".$startX." AND ".($startX+$fieldWidth). " AND y BETWEEN ".$startY." AND ".($startY+$fieldHeight); $result = mysql_query($sql); $positions = array(); while ($row = mysql_fetch_assoc($result)) { $positions[$row['x']][$row['y']] = $row; } echo "<table>"; for($y=$startY; $y<$startY+$fieldHeight; $y++) { echo "<tr>"; for($x=$startX; $x<$startX+$fieldWidth; $x++) { echo "<td>"; if(isset($positions[$x][$y])) { echo $positions[$x][$y]['type']; } else { echo "(".$x.",".$y.")"; } echo "</td>"; } echo "</tr>"; } echo "</table>"; ?>

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  • Blackberry screen navigation probelm

    - by dalandroid
    I have a Screen name DownloaderScreen when the screen start it will start download some file and when download is complete it will go forward to next screen autometically. I using the following code. public DownloaderScreen() { super(NO_VERTICAL_SCROLL | NO_HORIZONTAL_SCROLL | USE_ALL_HEIGHT | USE_ALL_WIDTH); this.application = UiApplication.getUiApplication(); HorizontalFieldManager outerBlock = new HorizontalFieldManager(USE_ALL_HEIGHT); VerticalFieldManager innerBlock = new VerticalFieldManager(USE_ALL_WIDTH | FIELD_VCENTER); innerBlock.setPadding(0, 10, 0, 10); outerBlock.setBackground(BackgroundFactory .createBitmapBackground(LangValue.dlBgimg)); outerBlock.add(innerBlock); add(outerBlock); phraseHelper = new PhraseHelper(); final String[][] phraseList = phraseHelper.getDownloadList(); gaugeField = new GaugeField("Downloading ", 0, phraseList.length, 0, GaugeField.PERCENT); innerBlock.add(gaugeField); Thread dlTread = new Thread() { public void run() { startDownload(phraseList); } }; dlTread.start(); } private void startDownload(String[][] phraseList){ if(phraseList.length!=0){ for(int i=0; i < phraseList.length ; i++){// gaugeField.setValue(i); // code for download } } goToNext(); } private void goToNext() { final Screen currentScreen = application.getActiveScreen(); if (UiApplication.isEventDispatchThread()) { application.popScreen(currentScreen); application.pushScreen(new HomeScreen()); } else { application.invokeLater(new Runnable() { public void run() { application.popScreen(currentScreen); application.pushScreen(new HomeScreen()); } }); } } The code is working fine and starts download files and when download is completed it is going forward to next screen. But when there is no file to download phraseList array length is zero, it is not going forward. What is problem in my code?

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  • TCP/IP Implementation General Questions

    - by user2971023
    I've implemented the concepts shown here; http://wiki.unity3d.com/index.php/Simple_TCP/IP_Client_-_Server outside of unity and it works. (though i had to create the TCPIPServerApp from scratch as i could not find the base project anywhere). I have some general questions on how to use tcp/ip properly however. I've done some research on tcp/ip itself but I'm still a little confused. It seems like using the method above doesn't guarantee that I'll see the message (res). It just checks on every update to see if there is a different message in res. What if multiple messages are sent and the program lags or something, will i miss the earlier packet(s)? Should i instead do an array so it stores the last X messages? How do i know the data was received? Do I need to add a message id and build in my own ack into the data? Should i check to see if the port is in use before setting up a connection? Sorry for all the questions. This is all new to me but I enjoy this very much! ... Below already answered By Anton, Thanks It sounds like tcp uses its own packet numbering to ensure the packets end up in the right order on the other side. What if a packet is missed, are the subsequent packets thrown away? Or is this numbering and packet ordering, only for handling data that is broken out into multiple packets? TCP will automatically break the data into multiple packets if necessary right?

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  • is_dir does not recognize folders

    - by Rakoon
    Hi I am trying to make a function that scans a folder for subfolders and then returns a numeric array with the names of those folders. This is the code i use for testing. Once i get it to print out the folder names and not just "." and ".." for present and above folder all will be well, and I can finish the function. <?php function super_l_getthemes($dir="themes") { if ($handle = opendir($dir)) { echo "Handle: {$handle}\n"; echo "Files:\n"; while (false !== ($file = readdir($handle))) { echo "{$file}<br>"; } closedir($handle); } ?> The above code works fine, and prints out all the contents of the folder: files, subfolders and the "." and ".." but if i replace: while (false !== ($file = readdir($handle))) { echo "{$file}<br>"; } with: while (false !== ($file = readdir($handle))) { if(file_exists($file) && is_dir($file)){echo "{$file}";} } The function only prints "." and ".." , not the two folder names that I'd like it to print. Any help is appreciated.

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  • Why is it possible to enumerate a LinqToSql query after calling Dispose() on the DataContext?

    - by DanM
    I'm using the Repository Pattern with some LinqToSql objects. My repository objects all implement IDisposable, and the Dispose() method does only thing--calls Dispose() on the DataContext. Whenever I use a repository, I wrap it in a using person, like this: public IEnumerable<Person> SelectPersons() { using (var repository = _repositorySource.GetNew<Person>(dc => dc.Person)) { return repository.GetAll(); } } This method returns an IEnumerable<Person>, so if my understanding is correct, no querying of the database actually takes place until Enumerable<Person> is traversed (e.g., by converting it to a list or array or by using it in a foreach loop), as in this example: var persons = gateway.SelectPersons(); // Dispose() is fired here var personViewModels = ( from b in persons select new PersonViewModel { Id = b.Id, Name = b.Name, Age = b.Age, OrdersCount = b.Order.Count() }).ToList(); // executes queries In this example, Dispose() gets called immediately after setting persons, which is an IEnumerable<Person>, and that's the only time it gets called. So, a couple questions: How does this work? How can a disposed DataContext still query the database for results when I walk the IEnumerable<Person>? What does Dispose() actually do? I've heard that it is not necessary (e.g., see this question) to dispose of a DataContext, but my impression was that it's not a bad idea. Is there any reason not to dispose of it?

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  • Thread-Safe lazy instantiating using MEF

    - by Xaqron
    // Member Variable private static readonly object _syncLock = new object(); // Now inside a static method foreach (var lazyObject in plugins) { if ((string)lazyObject.Metadata["key"] = "something") { lock (_syncLock) { // It seems the `IsValueCreated` is not up-to-date if (!lazyObject.IsValueCreated) lazyObject.value.DoSomething(); } return lazyObject.value; } } Here I need synchronized access per loop. There are many threads iterating this loop and based on the key they are looking for, a lazy instance is created and returned. lazyObject should not be created more that one time. Although Lazy class is for doing so and despite of the used lock, under high threading I have more than one instance created (I track this with a Interlocked.Increment on a volatile static int and log it somewhere). The problem is I don't have access to definition of Lazy and MEF defines how the Lazy class create objects. I should notice the CompositionContainer has a thread-safe option in constructor which is already used. My questions: 1) Why the lock doesn't work ? 2) Should I use an array of locks instead of one lock for performance improvement ?

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  • Are there concurrency problems when using -performSelector:withObject:afterDelay: ?

    - by mystify
    For example, I often use this: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:someDelay]; Now, lets say I call this 10 times to perform at the exact same delay, like: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; - (void)doSomethingAfterDelay:(id)someObject { /* access an array, read stuff, write stuff, do different things that would suffer in multithreaded environments .... all operations are nonatomic! */ } I have observed pretty strange behavior when doing things like this. For my understanding, this method schedules a timer to fire on the current thread, so in this case the main thread. But since it doesn't create new threads, it actually should not be possible to run into concurrency problems, right?

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  • Are there concurrency problems when using -performSelector:withObject:afterDelay: ?

    - by mystify
    For example, I often use this: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:someDelay]; Now, lets say I call this 10 times to perform at the exact same delay, like: [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; [self performSelector:@selector(doSomethingAfterDelay:) withObject:someObject afterDelay:2.0]; - (void)doSomethingAfterDelay:(id)someObject { /* access an array, read stuff, write stuff, do different things that would suffer in multithreaded environments .... all operations are nonatomic! */ } I have observed pretty strange behavior when doing things like this. For my understanding, this method schedules a timer to fire on the current thread, so in this case the main thread. But since it doesn't create new threads, it actually should not be possible to run into concurrency problems, right?

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  • How to know the type of an object in a list?

    - by nacho4d
    Hi, I want to know the type of object (or type) I have in my list so I wrote this: void **list; //list of references list = new void * [2]; Foo foo = Foo(); const char *not_table [] = {"tf", "ft", 0 }; list[0] = &foo; list[1] = not_table; if (dynamic_cast<LogicProcessor*>(list[0])) { //ERROR here ;( printf("Foo was found\n"); } if (dynamic_cast<char*> (list[0])) { //ERROR here ;( printf("char was found\n"); } but I get : error: cannot dynamic_cast '* list' (of type 'void*') to type 'class Foo*' (source is not a pointer to class) error: cannot dynamic_cast '* list' (of type 'void*') to type 'char*' (target is not pointer or reference to class) Why is this? what I am doing wrong here? Is dynamic_cast what I should use here? Thanks in advance EDIT: I know above code is much like plain C and surely sucks from the C++ point of view but is just I have the following situation and I was trying something before really implementing it: I have two arrays of length n but both arrays will never have an object at the same index. Hence, or I have array1[i]!=NULL or array2[i]!=NULL. This is obviously a waste of memory so I thought everything would be solved if I could have both kind of objects in a single array of length n. I am looking something like Cocoa's (Objective-C) NSArray where you don't care about the type of the object to be put in. Not knowing the type of the object is not a problem since you can use other method to get the class of a certain later. Is there something like it in c++ (preferably not third party C++ libraries) ? Thanks in advance ;)

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  • Top n items in a List ( including duplicates )

    - by Krishnan
    Trying to find an efficient way to obtain the top N items in a very large list, possibly containing duplicates. I first tried sorting & slicing, which works. But this seems unnnecessary. You shouldn't need to sort a very large list if you just want the top 20 members. So I wrote a recursive routine which builds the top-n list. This also works, but is very much slower than the non-recursive one! Question: Which is my second routine (elite2) so much slower than elite, and how do I make it faster ? My code is attached below. Thanks. import scala.collection.SeqView import scala.math.min object X { def elite(s: SeqView[Int, List[Int]], k:Int):List[Int] = { s.sorted.reverse.force.slice(0,min(k,s.size)) } def elite2(s: SeqView[Int, List[Int]], k:Int, s2:List[Int]=Nil):List[Int] = { if( k == 0 || s.size == 0) s2.reverse else { val m = s.max val parts = s.force.partition(_==m) val whole = if( parts._1.size > 1) parts._1.tail:::parts._2 else parts._2 elite2( whole.view, k-1, m::s2 ) } } def main(args:Array[String]) = { val N = 1000000/3 val x = List(N to 1 by -1).flatten.map(x=>List(x,x,x)).flatten.view println(elite2(x,20)) println(elite(x,20)) } }

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  • Creating a Variable From Two Others

    - by John
    Hello, In the HTML table below, I would like to add a third column that equals $row["countSubmissions"] times 10 plus $row["countComments"]. How could I do this? Thanks in advance, John $sqlStr = "SELECT l.loginid, l.username, COALESCE(s.total, 0) AS countSubmissions, COALESCE(c.total, 0) AS countComments FROM login l LEFT JOIN ( SELECT loginid, COUNT(1) AS total FROM submission GROUP BY loginid ) s ON l.loginid = s.loginid LEFT JOIN ( SELECT loginid, COUNT(1) AS total FROM comment GROUP BY loginid ) c ON l.loginid = c.loginid GROUP BY l.loginid ORDER BY countSubmissions DESC LIMIT 10"; $result = mysql_query($sqlStr); $arr = array(); echo "<table class=\"samplesrec1edit\">"; while ($row = mysql_fetch_array($result)) { echo '<tr>'; echo '<td class="sitename1edit1"><a href="http://www...com/.../members/index.php?profile='.$row["username"].'">'.stripslashes($row["username"]).'</a></td>'; echo '<td class="sitename1edit2">'.stripslashes($row["countSubmissions"]).'</td>'; echo '<td class="sitename1edit2">'.stripslashes($row["countComments"]).'</td>'; echo '</tr>'; } echo "</table>";

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  • How do I display a sting, based on which id is set as selected?

    - by Cam
    I'd like to display a text string (to be positioned above ul) depending on which link is set to selected by the chgClass fuction. The ids for each display via an alert right now, but I can't seem to make them appear in "english". I know I can set up an array stating "id=text string" but when I do it seems to break the code I already have... <script type="text/javascript"> var Lst; function CngClass(obj){ if (typeof(obj)=='string') obj=document.getElementById(obj); if (Lst) Lst.className=''; obj.className='selected'; Lst=obj; alert(obj.id); } </script> </head> <body onload="CngClass('POSITION_WITHOUT_NOTIFY')"> <div class="slider"> <ul class="bar"> <li class="deny"><a onclick="CngClass(this);" id="POSITION_NOT_ALLOWED" href="#">Deny</a></li> <li class="askDeny"><a onclick="CngClass(this);" id="NOTIFY_POSITION_IF_GRANTED" href="#">Ask Deny</a></li> <li class="askAllow"><a onclick="CngClass(this);" id="NOTIFY_POSITION_IF_NO_RESPONSE" href="#">Ask Allow</a></li> <li class="notify"><a onclick="CngClass(this);" id="NOTIFY_POSITION" href="#">Notfiy</a></li> <li class="allow"><a onclick="CngClass(this);" id="POSITION_WITHOUT_NOTIFY" href="#">Allow</a></li> </ul> </div> </body> </html>

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