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  • How does Entity Framework 4.0 determine which parameters are required for the factory method of an e

    - by Scott Davies
    Hi, I am working with Entity Framework 4.0 (VS 2010 Beta 2, NOT RC). I can model the EDM and produce the required database. When I ask VS to generate the code for the model, it generates the expected .designer.cs file. When I look at the factory methods for each entity that the designer has generated, I've noticed that it doesn't include all of the properties of the entity. Is it correct to say that the factory method only includes properties that cannot be null ? This appears to be the case, but I'm not entirely sure. Thanks, Scott

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  • I don't get prices with Amazon Product Advertising API

    - by Xarem
    I try to get prices of an ASIN number with the Amazon Product Advertising API. Code: $artNr = "B003TKSD8E"; $base_url = "http://ecs.amazonaws.de/onca/xml"; $params = array( 'AWSAccessKeyId' => self::API_KEY, 'AssociateTag' => self::API_ASSOCIATE_TAG, 'Version' => "2010-11-01", 'Operation' => "ItemLookup", 'Service' => "AWSECommerceService", 'Condition' => "All", 'IdType' => 'ASIN', 'ItemId' => $artNr); $params['Timestamp'] = gmdate("Y-m-d\TH:i:s.\\0\\0\\0\\Z", time()); $url_parts = array(); foreach(array_keys($params) as $key) $url_parts[] = $key . "=" . str_replace('%7E', '~', rawurlencode($params[$key])); sort($url_parts); $url_string = implode("&", $url_parts); $string_to_sign = "GET\necs.amazonaws.de\n/onca/xml\n" . $url_string; $signature = hash_hmac("sha256", $string_to_sign, self::API_SECRET, TRUE); $signature = urlencode(base64_encode($signature)); $url = $base_url . '?' . $url_string . "&Signature=" . $signature; $response = file_get_contents($url); $parsed_xml = simplexml_load_string($response); I think this should be correct - but I don't get offers in the response: SimpleXMLElement Object ( [OperationRequest] => SimpleXMLElement Object ( [RequestId] => ************************* [Arguments] => SimpleXMLElement Object ( [Argument] => Array ( [0] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Condition [Value] => All ) ) [1] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Operation [Value] => ItemLookup ) ) [2] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Service [Value] => AWSECommerceService ) ) [3] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => ItemId [Value] => B003TKSD8E ) ) [4] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => IdType [Value] => ASIN ) ) [5] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => AWSAccessKeyId [Value] => ************************* ) ) [6] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Timestamp [Value] => 2011-11-29T01:32:12.000Z ) ) [7] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Signature [Value] => ************************* ) ) [8] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => AssociateTag [Value] => ************************* ) ) [9] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Version [Value] => 2010-11-01 ) ) ) ) [RequestProcessingTime] => 0.0091540000000000 ) [Items] => SimpleXMLElement Object ( [Request] => SimpleXMLElement Object ( [IsValid] => True [ItemLookupRequest] => SimpleXMLElement Object ( [Condition] => All [IdType] => ASIN [ItemId] => B003TKSD8E [ResponseGroup] => Small [VariationPage] => All ) ) [Item] => SimpleXMLElement Object ( [ASIN] => B003TKSD8E [DetailPageURL] => http://www.amazon.de/Apple-iPhone-4-32GB-schwarz/dp/B003TKSD8E%3FSubscriptionId%3DAKIAI6NFQHK2DQIPRUEQ%26tag%3Dbanholzerme-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D165953%26creativeASIN%3DB003TKSD8E [ItemLinks] => SimpleXMLElement Object ( [ItemLink] => Array ( [0] => SimpleXMLElement Object ( [Description] => Add To Wishlist [URL] => http://www.amazon.de/gp/registry/wishlist/add-item.html%3Fasin.0%3DB003TKSD8E%26SubscriptionId%3DAKIAI6NFQHK2DQIPRUEQ%26tag%3Dbanholzerme-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D12738%26creativeASIN%3DB003TKSD8E ) [1] => SimpleXMLElement Object ( [Description] => Tell A Friend [URL] => http://www.amazon.de/gp/pdp/taf/B003TKSD8E%3FSubscriptionId%3DAKIAI6NFQHK2DQIPRUEQ%26tag%3Dbanholzerme-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D12738%26creativeASIN%3DB003TKSD8E ) [2] => SimpleXMLElement Object ( [Description] => All Customer Reviews [URL] => http://www.amazon.de/review/product/B003TKSD8E%3FSubscriptionId%3DAKIAI6NFQHK2DQIPRUEQ%26tag%3Dbanholzerme-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D12738%26creativeASIN%3DB003TKSD8E ) [3] => SimpleXMLElement Object ( [Description] => All Offers [URL] => http://www.amazon.de/gp/offer-listing/B003TKSD8E%3FSubscriptionId%3DAKIAI6NFQHK2DQIPRUEQ%26tag%3Dbanholzerme-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D12738%26creativeASIN%3DB003TKSD8E ) ) ) [ItemAttributes] => SimpleXMLElement Object ( [Manufacturer] => Apple Computer [ProductGroup] => CE [Title] => Apple iPhone 4 32GB schwarz ) ) ) ) Can someone please explain me why I don't get any price-information? Thank you very much

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  • How to get javascript object references or reference count?

    - by Tauren
    How to get reference count for an object Is it possible to determine if a javascript object has multiple references to it? Or if it has references besides the one I'm accessing it with? Or even just to get the reference count itself? Can I find this information from javascript itself, or will I need to keep track of my own reference counters. Obviously, there must be at least one reference to it for my code access the object. But what I want to know is if there are any other references to it, or if my code is the only place it is accessed. I'd like to be able to delete the object if nothing else is referencing it. If you know the answer, there is no need to read the rest of this question. Below is just an example to make things more clear. Use Case In my application, I have a Repository object instance called contacts that contains an array of ALL my contacts. There are also multiple Collection object instances, such as friends collection and a coworkers collection. Each collection contains an array with a different set of items from the contacts Repository. Sample Code To make this concept more concrete, consider the code below. Each instance of the Repository object contains a list of all items of a particular type. You might have a repository of Contacts and a separate repository of Events. To keep it simple, you can just get, add, and remove items, and add many via the constructor. var Repository = function(items) { this.items = items || []; } Repository.prototype.get = function(id) { for (var i=0,len=this.items.length; i<len; i++) { if (items[i].id === id) { return this.items[i]; } } } Repository.prototype.add = function(item) { if (toString.call(item) === "[object Array]") { this.items.concat(item); } else { this.items.push(item); } } Repository.prototype.remove = function(id) { for (var i=0,len=this.items.length; i<len; i++) { if (items[i].id === id) { this.removeIndex(i); } } } Repository.prototype.removeIndex = function(index) { if (items[index]) { if (/* items[i] has more than 1 reference to it */) { // Only remove item from repository if nothing else references it this.items.splice(index,1); return; } } } Note the line in remove with the comment. I only want to remove the item from my master repository of objects if no other objects have a reference to the item. Here's Collection: var Collection = function(repo,items) { this.repo = repo; this.items = items || []; } Collection.prototype.remove = function(id) { for (var i=0,len=this.items.length; i<len; i++) { if (items[i].id === id) { // Remove object from this collection this.items.splice(i,1); // Tell repo to remove it (only if no other references to it) repo.removeIndxe(i); return; } } } And then this code uses Repository and Collection: var contactRepo = new Repository([ {id: 1, name: "Joe"}, {id: 2, name: "Jane"}, {id: 3, name: "Tom"}, {id: 4, name: "Jack"}, {id: 5, name: "Sue"} ]); var friends = new Collection( contactRepo, [ contactRepo.get(2), contactRepo.get(4) ] ); var coworkers = new Collection( contactRepo, [ contactRepo.get(1), contactRepo.get(2), contactRepo.get(5) ] ); contactRepo.items; // contains item ids 1, 2, 3, 4, 5 friends.items; // contains item ids 2, 4 coworkers.items; // contains item ids 1, 2, 5 coworkers.remove(2); contactRepo.items; // contains item ids 1, 2, 3, 4, 5 friends.items; // contains item ids 2, 4 coworkers.items; // contains item ids 1, 5 friends.remove(4); contactRepo.items; // contains item ids 1, 2, 3, 5 friends.items; // contains item ids 2 coworkers.items; // contains item ids 1, 5 Notice how coworkers.remove(2) didn't remove id 2 from contactRepo? This is because it was still referenced from friends.items. However, friends.remove(4) causes id 4 to be removed from contactRepo, because no other collection is referring to it. Summary The above is what I want to do. I'm sure there are ways I can do this by keeping track of my own reference counters and such. But if there is a way to do it using javascript's built-in reference management, I'd like to hear about how to use it.

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  • New asp "showat" attribute required inconsistently in VS2010. Why?

    - by Patrick Karcher
    When I generate code using T4 templates in Visual Studio 2010, I get the following error for each of my asp controls when I try to compile: Control "ddState" is missing required attribute "showat". I have never gotten this error in previous versions of .NET. Further, I don't get this error when I manually construct my pages either by dragging/dropping, nor do I get it when I type out the control text myself. When I generate code, I have to manually add showat="client" to my tag for the compiler to be happy. It was my understanding that I never had to explicitly specify this tag. The following: <asp:dropdownlist id="ddState" runat="server" showat="client" /> solves the problem. Why do I have to add this to generated code but not other times? (It's a VS-2010 webforms project, using VB, in case that makes a difference.)

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  • Eclipse RCP & tycho - The type org.eclipse.swt.widgets.Button cannot be resolved. It is indirectly referenced from required .class files

    - by Skip
    Situation: I have an Eclipse RCP Application, which I am trying to build with tycho plugin for Eclipse. When I am executing my Eclipse Application inside of the IDe - the Application is executed normally. When using tycho to build the Application - the following error is thrown: The type org.eclipse.swt.widgets.Button cannot be resolved. It is indirectly referenced from required .class files What I did : In other cases where a "missing requirenments" exception was thrown, which I found - a missing transitive plugin-dependency was the reason. In my case an SWT widget "Button" is missing, so I am trying to import swt. SWT is platform dependant so I am importing swt inside of the product, as described here. Anyway, during compilation the error occurs again. Question: Do someone have any Idea, how to solve this Problem?

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  • How to implement Cocoa copyWithZone on derived object in MonoMac C#?

    - by Justin Aquadro
    I'm currently porting a small Winforms-based .NET application to use a native Mac front-end with MonoMac. The application has a TreeControl with icons and text, which does not exist out of the box in Cocoa. So far, I've ported almost all of the ImageAndTextCell code in Apple's DragNDrop example: https://developer.apple.com/library/mac/#samplecode/DragNDropOutlineView/Listings/ImageAndTextCell_m.html#//apple_ref/doc/uid/DTS40008831-ImageAndTextCell_m-DontLinkElementID_6, which is assigned to an NSOutlineView as a custom cell. It seems to be working almost perfectly, except that I have not figured out how to properly port the copyWithZone method. Unfortunately, this means the internal copies that NSOutlineView is making do not have the image field, and it leads to the images briefly vanishing during expand and collapse operations. The objective-c code in question is: - (id)copyWithZone:(NSZone *)zone { ImageAndTextCell *cell = (ImageAndTextCell *)[super copyWithZone:zone]; // The image ivar will be directly copied; we need to retain or copy it. cell->image = [image retain]; return cell; } The first line is what's tripping me up, as MonoMac does not expose a copyWithZone method, and I don't know how to otherwise call it. Update Based on current answers and additional research and testing, I've come up with a variety of models for copying an object. static List<ImageAndTextCell> _refPool = new List<ImageAndTextCell>(); // Method 1 static IntPtr selRetain = Selector.GetHandle ("retain"); [Export("copyWithZone:")] public virtual NSObject CopyWithZone(IntPtr zone) { ImageAndTextCell cell = new ImageAndTextCell() { Title = Title, Image = Image, }; Messaging.void_objc_msgSend (cell.Handle, selRetain); return cell; } // Method 2 [Export("copyWithZone:")] public virtual NSObject CopyWithZone(IntPtr zone) { ImageAndTextCell cell = new ImageAndTextCell() { Title = Title, Image = Image, }; _refPool.Add(cell); return cell; } [Export("dealloc")] public void Dealloc () { _refPool.Remove(this); this.Dispose(); } // Method 3 static IntPtr selRetain = Selector.GetHandle ("retain"); [Export("copyWithZone:")] public virtual NSObject CopyWithZone(IntPtr zone) { ImageAndTextCell cell = new ImageAndTextCell() { Title = Title, Image = Image, }; _refPool.Add(cell); Messaging.void_objc_msgSend (cell.Handle, selRetain); return cell; } // Method 4 static IntPtr selRetain = Selector.GetHandle ("retain"); static IntPtr selRetainCount = Selector.GetHandle("retainCount"); [Export("copyWithZone:")] public virtual NSObject CopyWithZone (IntPtr zone) { ImageAndTextCell cell = new ImageAndTextCell () { Title = Title, Image = Image, }; _refPool.Add (cell); Messaging.void_objc_msgSend (cell.Handle, selRetain); return cell; } public void PeriodicCleanup () { List<ImageAndTextCell> markedForDelete = new List<ImageAndTextCell> (); foreach (ImageAndTextCell cell in _refPool) { uint count = Messaging.UInt32_objc_msgSend (cell.Handle, selRetainCount); if (count == 1) markedForDelete.Add (cell); } foreach (ImageAndTextCell cell in markedForDelete) { _refPool.Remove (cell); cell.Dispose (); } } // Method 5 static IntPtr selCopyWithZone = Selector.GetHandle("copyWithZone:"); [Export("copyWithZone:")] public virtual NSObject CopyWithZone(IntPtr zone) { IntPtr copyHandle = Messaging.IntPtr_objc_msgSendSuper_IntPtr(SuperHandle, selCopyWithZone, zone); ImageAndTextCell cell = new ImageAndTextCell(copyHandle) { Image = Image, }; _refPool.Add(cell); return cell; } Method 1: Increases the retain count of the unmanaged object. The unmanaged object will persist persist forever (I think? dealloc never called), and the managed object will be harvested early. Seems to be lose-lose all-around, but runs in practice. Method 2: Saves a reference of the managed object. The unmanaged object is left alone, and dealloc appears to be invoked at a reasonable time by the caller. At this point the managed object is released and disposed. This seems reasonable, but on the downside the base type's dealloc won't be run (I think?) Method 3: Increases the retain count and saves a reference. Unmanaged and managed objects leak forever. Method 4: Extends Method 3 by adding a cleanup function that is run periodically (e.g. during Init of each new ImageAndTextCell object). The cleanup function checks the retain counts of the stored objects. A retain count of 1 means the caller has released it, so we should as well. Should eliminate leaking in theory. Method 5: Attempt to invoke the copyWithZone method on the base type, and then construct a new ImageAndTextView object with the resulting handle. Seems to do the right thing (the base data is cloned). Internally, NSObject bumps the retain count on objects constructed like this, so we also use the PeriodicCleanup function to release these objects when they're no longer used. Based on the above, I believe Method 5 is the best approach since it should be the only one that results in a truly correct copy of the base type data, but I don't know if the approach is inherently dangerous (I am also making some assumptions about the underlying implementation of NSObject). So far nothing bad has happened "yet", but if anyone is able to vet my analysis then I would be more confident going forward.

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  • What knowledge/expertize is required to port android to custom arm device ?

    - by Sunny
    Hi Friends, I am working on a system on which currently linux kernel and microwindows windowing system is running. Code of current linux system drivers is available to me. I want to port android on it, just as a hobby project. can you please tell me what all understanding of linux-kernel is required to port it? Please give me references (Books, Tutorials) to build-up understandings. Thanks, Sunny. P.S. I have basic understanding of linux. Configuration of device is 450 Mhz ARM9, 64 MB RAM, 256 MB NAND 480x272 resolution.

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  • Entity Framework insert error ("The Version field is required.")

    - by Graham
    I am using Silverlight 4 and RIA services. When I try to insert into my database, I get the following error: "Submit operation failed validation. Please inspect Entity.ValidationErrors for each entity in EntitiesInError for more information." Upon inspecting the ValidationErrors, I see: "The Version field is required." Isn't the Version field updated and maintained by the framework? If so, why is it null? If not, how am I supposed to set it?

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  • What are the standard/practical steps required before moving to implementation of any Project/Task?

    - by jkm
    What are the standard/practical steps required before moving to implementation of any Project/Task? Hi everyone, I liked stackoverflow very much and just got registered. As I am a beginner in programming, most of the time i just implement/code my tasks directly not even thinking of creating any dfd's, flowcharts or other tools for my new classes and methods. In some interviews i was asked what process you follow and i was confused as i am not very used to follow any standards. So If some experts can help me that what steps and in what order are the best practices for solving/approaching any task in programming. And how important these are? Thanks in advance! and sorry if this question is trivial one/already asked.

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  • Is there a standard .NET exception to throw when a class doesn't implement a required attribute?

    - by a typing monkey
    Suppose I want to throw a new exception when invoking a generic method with a type that doesn't have a required attribute. Is there a .NET exception that's appropriate for this situation, or, more likely, one that would be a suitable ancestor for a custom exception? For example: public static class ClassA { public static T DoSomething<T>(string p) { Type returnType = typeof(T); object[] typeAttributes = returnType.GetCustomAttributes(typeof(SerializableAttribute), true); if ((typeAttributes == null) || (typeAttributes.Length == 0)) { // Is there an exception type in the framework that I should use/inherit from here? throw new Exception("This class doesn't support blah blah blah"); // Maybe ArgumentException? That doesn't seem to fit right. } } } Thanks.

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  • Why is new showat attribute required when using code generation?

    - by Patrick Karcher
    When I generate code using T4 templates in Visual Studio 2010, I get the following error for each of my asp controls when I try to compile: Control "ddState" is missing required attribute "showat". I have never gotten this error in previous versions of .NET. Further, I don't get this error when I manually construct my pages either by dragging/dropping, nor do I get it when I type out the control text myself. When I generate code, I have to manually add showat="client" to my tag for the compiler to be happy. It was my understanding that I never had to explicitly specify this tag. The following: <asp:dropdownlist id="ddState" runat="server" showat="client" /> solves the problem. Why do I have to add this to generated code but not other times? (It's a VS-2010 webforms project, using VB, in case that makes a difference.)

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  • Is a live internet connection required for push notification?

    - by Heshan Perera
    This maybe a silly question, but I need confirmation and I have no one else to ask. I am trying to understand the implications of implementing my own push notification for android mobile devices. This requires a continuous TCP connection to a server, though most of the time it will be idle. My assumption is that, even when idle, for the server to be able to push data to the client through the TCP connection, an active internet connection will always be required, and if the connection is disrupted (i.e. the user switches the connection off) this push will no longer be possible. Is this assumption correct ?

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  • Are unspecified and undefined behavior required to be consistent between compiles?

    - by sharptooth
    Let's pretend my program contains a specific construct the C++ Standard states to be unspecified behavior. This basically means the implementation has to do something reasonable but is allowed not to document it. But is the implementation required to produce the same behavior every time it compiles a specific construct with unspecified behavior or is it allowed to produce different behavior in different compiles? What about undefined behavior? Let's pretend my program contains a construct that is UB according to the Standard. The implementation is allowed to exhibit any behavior. But can this behavior differ between compiles of the same program on the same compiler with same settings in the same environment? In other words, if I dereference a null pointer on line 78 in file X.cpp and the implementation formats the drive in such case does it mean that it will do the same after the program is recompiled?

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  • Registration form validation not validating

    - by jgray
    I am a noob when it comes to web development. I am trying to validate a registration form and to me it looks right but it will not validate.. This is what i have so far and i am validating through a repository or database. Any help would be greatly appreciated. thanks <?php session_start(); $title = "User Registration"; $keywords = "Name, contact, phone, e-mail, registration"; $description = "user registration becoming a member."; require "partials/_html_header.php"; //require "partials/_header.php"; require "partials/_menu.php"; require "DataRepository.php"; // if all validation passed save user $db = new DataRepository(); // form validation goes here $first_nameErr = $emailErr = $passwordErr = $passwordConfirmErr = ""; $first_name = $last_name = $email = $password = $passwordConfirm = ""; if(isset($_POST['submit'])) { $valid = TRUE; // check if all fields are valid { if ($_SERVER["REQUEST_METHOD"] == "POST") { if (empty($_POST["first_name"])) {$first_nameErr = "Name is required";} else { // $first_name = test_input($_POST["first_name"]); // check if name only contains letters and whitespace if (!preg_match("/^[a-zA-Z ]*$/",$first_name)) { $first_nameErr = "Only letters and white space allowed"; } } if (empty($_POST["email"])) {$emailErr = "Email is required";} else { // $email = test_input($_POST["email"]); // check if e-mail address syntax is valid if (!preg_match("/([\w\-]+\@[\w\-]+\.[\w\-]+)/",$email)) { $emailErr = "Invalid email format"; } } if (!preg_match("/(......)/",$password)) { $passwordErr = "Subject must contain THREE or more characters!"; } if ($_POST['password']!= $_POST['passwordConfirm']) { echo("Oops! Password did not match! Try again. "); } function test_input($data) { $data = trim($data); $data = stripslashes($data); $data = htmlspecialchars($data); return $data; } } } if(!$db->isEmailUnique($_POST['email'])) { $valid = FALSE; //display errors in the correct places } // if still valid save the user if($valid) { $new_user = array( 'first_name' => $_POST['first_name'], 'last_name' => $_POST['last_name'], 'email' => $_POST['email'], 'password' => $_POST['password'] ); $results = $db->saveUser($new_user); if($results == TRUE) { header("Location: login.php"); } else { echo "WTF!"; exit; } } } ?> <head> <style> .error {color: #FF0000;} </style> </head> <h1 class="center"> World Wide Web Creations' User Registration </h1> <p><span class="error"></span><p> <form method="POST" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>" onsubmit="return validate_form()" > First Name: <input type="text" name="first_name" id="first_name" value="<?php echo $first_name;?>" /> <span class="error"> <?php echo $first_nameErr;?></span> <br /> <br /> Last Name(Optional): <input type="text" name="last_name" id="last_name" value="<?php echo $last_name;?>" /> <br /> <br /> E-mail: <input type="email" name="email" id="email" value="<?php echo $email;?>" /> <span class="error"> <?php echo $emailErr;?></span> <br /> <br /> Password: <input type="password" name="password" id="password" value="" /> <span class="error"> <?php echo $passwordErr;?></span> <br /> <br /> Confirmation Password: <input type="password" name="passwordConfirm" id="passwordConfirm" value="" /> <span class="error"> <?php echo $passwordConfirmErr;?></span> <br /> <br /> <br /> <br /> <input type="submit" name="submit" id="submit" value="Submit Data" /> <input type="reset" name="reset" id="reset" value="Reset Form" /> </form> </body> </html> <?php require "partials/_footer.php"; require "partials/_html_footer.php"; ?> class DataRepository { // version number private $version = "1.0.3"; // turn on and off debugging private static $debug = FALSE; // flag to (re)initialize db on each call private static $initialize_db = FALSE; // insert test data on initialization private static $load_default_data = TRUE; const DATAFILE = "203data.txt"; private $data = NULL; private $errors = array(); private $user_fields = array( 'id' => array('required' => 0), 'created_at' => array('required' => 0), 'updated_at' => array('required' => 0), 'first_name' => array('required' => 1), 'last_name' => array('required' => 0), 'email' => array('required' => 1), 'password' => array('required' => 1), 'level' => array('required' => 0, 'default' => 2), ); private $post_fields = array( 'id' => array('required' => 0), 'created_at' => array('required' => 0), 'updated_at' => array('required' => 0), 'user_id' => array('required' => 1), 'title' => array('required' => 1), 'message' => array('required' => 1), 'private' => array('required' => 0, 'default' => 0), ); private $default_user = array( 'id' => 1, 'created_at' => '2013-01-01 00:00:00', 'updated_at' => '2013-01-01 00:00:00', 'first_name' => 'Admin Joe', 'last_name' => 'Tester', 'email' => '[email protected]', 'password' => 'a94a8fe5ccb19ba61c4c0873d391e987982fbbd3', 'level' => 1, ); private $default_post = array( 'id' => 1, 'created_at' => '2013-01-01 00:00:00', 'updated_at' => '2013-01-01 00:00:00', 'user_id' => 1, 'title' => 'My First Post', 'message' => 'This is the message of the first post.', 'private' => 0, ); // constructor will load existing data into memory // if it does not exist it will create it and initialize if desired public function __construct() { // check if need to reset if(DataRepository::$initialize_db AND file_exists(DataRepository::DATAFILE)) { unlink(DataRepository::DATAFILE); } // if file doesn't exist, create the initial datafile if(!file_exists(DataRepository::DATAFILE)) { $this->log("Data file does not exist. Attempting to create it... (".__FUNCTION__.":".__LINE__.")"); // create initial file $this->data = array( 'users' => array( ), 'posts' => array() ); // load default data if needed if(DataRepository::$load_default_data) { $this->data['users'][1] = $this->default_user; $this->data['posts'][1] = $this->default_post; } $this->writeTheData(); } // load the data into memory for use $this->loadTheData(); } private function showErrors($break = TRUE, $type = NULL) { if(count($this->errors) > 0) { echo "<div style=\"color:red;font-weight: bold;font-size: 1.3em\":<h3>$type Errors</h3><ol>"; foreach($this->errors AS $error) { echo "<li>$error</li>"; } echo "</ol></div>"; if($break) { "</br></br></br>Exiting because of errors!"; exit; } } } private function writeTheData() { $this->log("Attempting to write the datafile: ".DataRepository::DATAFILE." (".__FUNCTION__.":".__LINE__.")"); file_put_contents(DataRepository::DATAFILE, json_encode($this->data)); $this->log("Datafile written: ".DataRepository::DATAFILE." (line: ".__LINE__.")"); } private function loadTheData() { $this->log("Attempting to load the datafile: ".DataRepository::DATAFILE." (".__FUNCTION__.":".__LINE__.")"); $this->data = json_decode(file_get_contents(DataRepository::DATAFILE), true); $this->log("Datafile loaded: ".DataRepository::DATAFILE." (".__FUNCTION__.":".__LINE__.")", $this->data); } private function validateFields(&$info, $fields, $pre_errors = NULL) { // merge in any pre_errors if($pre_errors != NULL) { $this->errors = array_merge($this->errors, $pre_errors); } // check all required fields foreach($fields AS $field => $reqs) { if(isset($reqs['required']) AND $reqs['required'] == 1) { if(!isset($info[$field]) OR strlen($info[$field]) == 0) { $this->errors[] = "$field is a REQUIRED field"; } } // set any default values if not present if(isset($reqs['default']) AND (!isset($info[$field]) OR $info[$field] == "")) { $info[$field] = $reqs['default']; } } $this->showErrors(); if(count($this->errors) == 0) { return TRUE; } else { return FALSE; } } private function validateUser(&$user_info) { // check if the email is already in use $this->log("About to check pre_errors: ".DataRepository::DATAFILE." (".__FUNCTION__.":".__LINE__.")", $user_info); $pre_errors = NULL; if(isset($user_info['email'])) { if(!$this->isEmailUnique($user_info['email'])) { $pre_errors = array('The email: '.$user_info['email'].' is already used in our system'); } } $this->log("After pre_error check: ".DataRepository::DATAFILE." (".__FUNCTION__.":".__LINE__.")", $pre_errors); return $this->validateFields($user_info, $this->user_fields, $pre_errors); } private function validatePost(&$post_info) { // check if the user_id in the post actually exists $this->log("About to check pre_errors: ".DataRepository::DATAFILE." (".__FUNCTION__.":".__LINE__.")", $post_info); $pre_errors = NULL; if(isset($post_info['user_id'])) { if(!isset($this->data['users'][$post_info['user_id']])) { $pre_errors = array('The posts must belong to a valid user. (User '.$post_info['user_id'].' does not exist in the data'); } } $this->log("After pre_error check: ".DataRepository::DATAFILE." (".__FUNCTION__.":".__LINE__.")", $pre_errors); return $this->validateFields($post_info, $this->post_fields, $pre_errors); } private function log($message, $data = NULL) { $style = "background-color: #F8F8F8; border: 1px solid #DDDDDD; border-radius: 3px; font-size: 13px; line-height: 19px; overflow: auto; padding: 6px 10px;"; if(DataRepository::$debug) { if($data != NULL) { $dump = "<div style=\"$style\"><pre>".json_encode($data, JSON_PRETTY_PRINT)."</pre></div>"; } else { $dump = NULL; } echo "<code><b>Debug:</b> $message</code>$dump<br />"; } } public function saveUser($user_info) { $this->log("Entering saveUser: (".__FUNCTION__.":".__LINE__.")", $user_info); $mydata = array(); $update = FALSE; // check for existing data if(isset($user_info['id']) AND $this->data['users'][$user_info['id']]) { $mydata = $this->data['users'][$user_info['id']]; $this->log("Loaded prior user: ".print_r($mydata, TRUE)." (".__FUNCTION__.":".__LINE__.")"); } // copy over existing values $this->log("Before copying over existing values: (".__FUNCTION__.":".__LINE__.")", $mydata); foreach($user_info AS $k => $v) { $mydata[$k] = $user_info[$k]; } $this->log("After copying over existing values: (".__FUNCTION__.":".__LINE__.")", $mydata); // check required fields if($this->validateUser($mydata)) { // hash password if new if(isset($mydata['password'])) { $mydata['password'] = sha1($mydata['password']); } // if no id, add the next available one if(!isset($mydata['id']) OR (int)$mydata['id'] < 1) { $this->log("No id set: ".DataRepository::DATAFILE." (".__FUNCTION__.":".__LINE__.")"); if(count($this->data['users']) == 0) { $mydata['id'] = 1; $this->log("Setting id to 1: ".DataRepository::DATAFILE." (".__FUNCTION__.":".__LINE__.")"); } else { $mydata['id'] = max(array_keys($this->data['users']))+1; $this->log("Found max id and added 1 [".$mydata['id']."]: ".DataRepository::DATAFILE." (".__FUNCTION__.":".__LINE__.")"); } } // set created date if null if(!isset($mydata['created_at'])) { $mydata['created_at'] = date ("Y-m-d H:i:s", time()); } // update modified time $mydata['modified_at'] = date ("Y-m-d H:i:s", time()); // copy into data and save $this->log("Before data save: (".__FUNCTION__.":".__LINE__.")", $this->data); $this->data['users'][$mydata['id']] = $mydata; $this->writeTheData(); } return TRUE; } public function getUserById($id) { if(isset($this->data['users'][$id])) { return $this->data['users'][$id]; } else { return array(); } } public function isEmailUnique($email) { // find the user that has the right username/password foreach($this->data['users'] AS $k => $v) { $this->log("Checking unique email: {$v['email']} == $email (".__FUNCTION__.":".__LINE__.")", NULL); if($v['email'] == $email) { $this->log("FOUND NOT unique email: {$v['email']} == $email (".__FUNCTION__.":".__LINE__.")", NULL); return FALSE; break; } } $this->log("Email IS unique: $email (".__FUNCTION__.":".__LINE__.")", NULL); return TRUE; } public function login($username, $password) { // hash password for validation $password = sha1($password); $this->log("Attempting to login with $username / $password: (".__FUNCTION__.":".__LINE__.")", NULL); $user = NULL; // find the user that has the right username/password foreach($this->data['users'] AS $k => $v) { if($v['email'] == $username AND $v['password'] == $password) { $user = $v; break; } } $this->log("Exiting login: (".__FUNCTION__.":".__LINE__.")", $user); return $user; } public function savePost($post_info) { $this->log("Entering savePost: (".__FUNCTION__.":".__LINE__.")", $post_info); $mydata = array(); // check for existing data if(isset($post_info['id']) AND $this->data['posts'][$post_info['id']]) { $mydata = $this->data['posts'][$post_info['id']]; $this->log("Loaded prior posts: ".print_r($mydata, TRUE)." (".__FUNCTION__.":".__LINE__.")"); } $this->log("Before copying over existing values: (".__FUNCTION__.":".__LINE__.")", $mydata); foreach($post_info AS $k => $v) { $mydata[$k] = $post_info[$k]; } $this->log("After copying over existing values: (".__FUNCTION__.":".__LINE__.")", $mydata); // check required fields if($this->validatePost($mydata)) { // if no id, add the next available one if(!isset($mydata['id']) OR (int)$mydata['id'] < 1) { $this->log("No id set: ".DataRepository::DATAFILE." (".__FUNCTION__.":".__LINE__.")"); if(count($this->data['posts']) == 0) { $mydata['id'] = 1; $this->log("Setting id to 1: ".DataRepository::DATAFILE." (".__FUNCTION__.":".__LINE__.")"); } else { $mydata['id'] = max(array_keys($this->data['posts']))+1; $this->log("Found max id and added 1 [".$mydata['id']."]: ".DataRepository::DATAFILE." (".__FUNCTION__.":".__LINE__.")"); } } // set created date if null if(!isset($mydata['created_at'])) { $mydata['created_at'] = date ("Y-m-d H:i:s", time()); } // update modified time $mydata['modified_at'] = date ("Y-m-d H:i:s", time()); // copy into data and save $this->data['posts'][$mydata['id']] = $mydata; $this->log("Before data save: (".__FUNCTION__.":".__LINE__.")", $this->data); $this->writeTheData(); } return TRUE; } public function getAllPosts() { return $this->loadPostsUsers($this->data['posts']); } public function loadPostsUsers($posts) { foreach($posts AS $id => $post) { $posts[$id]['user'] = $this->getUserById($post['user_id']); } return $posts; } public function dump($line_number, $temp = 'NO') { // if(DataRepository::$debug) { if($temp == 'NO') { $temp = $this->data; } echo "<pre>Dumping from line: $line_number\n"; echo json_encode($temp, JSON_PRETTY_PRINT); echo "</pre>"; } } } /* * Change Log * * 1.0.0 * - first version * 1.0.1 * - Added isEmailUnique() function for form validation and precheck on user save * 1.0.2 * - Fixed getAllPosts() to include the post's user info * - Added loadPostsUsers() to load one or more posts with their user info * 1.0.3 * - Added autoload to always add admin Joe. */

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  • A Communication System for XAML Applications

    - by psheriff
    In any application, you want to keep the coupling between any two or more objects as loose as possible. Coupling happens when one class contains a property that is used in another class, or uses another class in one of its methods. If you have this situation, then this is called strong or tight coupling. One popular design pattern to help with keeping objects loosely coupled is called the Mediator design pattern. The basics of this pattern are very simple; avoid one object directly talking to another object, and instead use another class to mediate between the two. As with most of my blog posts, the purpose is to introduce you to a simple approach to using a message broker, not all of the fine details. IPDSAMessageBroker Interface As with most implementations of a design pattern, you typically start with an interface or an abstract base class. In this particular instance, an Interface will work just fine. The interface for our Message Broker class just contains a single method “SendMessage” and one event “MessageReceived”. public delegate void MessageReceivedEventHandler( object sender, PDSAMessageBrokerEventArgs e); public interface IPDSAMessageBroker{  void SendMessage(PDSAMessageBrokerMessage msg);   event MessageReceivedEventHandler MessageReceived;} PDSAMessageBrokerMessage Class As you can see in the interface, the SendMessage method requires a type of PDSAMessageBrokerMessage to be passed to it. This class simply has a MessageName which is a ‘string’ type and a MessageBody property which is of the type ‘object’ so you can pass whatever you want in the body. You might pass a string in the body, or a complete Customer object. The MessageName property will help the receiver of the message know what is in the MessageBody property. public class PDSAMessageBrokerMessage{  public PDSAMessageBrokerMessage()  {  }   public PDSAMessageBrokerMessage(string name, object body)  {    MessageName = name;    MessageBody = body;  }   public string MessageName { get; set; }   public object MessageBody { get; set; }} PDSAMessageBrokerEventArgs Class As our message broker class will be raising an event that others can respond to, it is a good idea to create your own event argument class. This class will inherit from the System.EventArgs class and add a couple of additional properties. The properties are the MessageName and Message. The MessageName property is simply a string value. The Message property is a type of a PDSAMessageBrokerMessage class. public class PDSAMessageBrokerEventArgs : EventArgs{  public PDSAMessageBrokerEventArgs()  {  }   public PDSAMessageBrokerEventArgs(string name,     PDSAMessageBrokerMessage msg)  {    MessageName = name;    Message = msg;  }   public string MessageName { get; set; }   public PDSAMessageBrokerMessage Message { get; set; }} PDSAMessageBroker Class Now that you have an interface class and a class to pass a message through an event, it is time to create your actual PDSAMessageBroker class. This class implements the SendMessage method and will also create the event handler for the delegate created in your Interface. public class PDSAMessageBroker : IPDSAMessageBroker{  public void SendMessage(PDSAMessageBrokerMessage msg)  {    PDSAMessageBrokerEventArgs args;     args = new PDSAMessageBrokerEventArgs(      msg.MessageName, msg);     RaiseMessageReceived(args);  }   public event MessageReceivedEventHandler MessageReceived;   protected void RaiseMessageReceived(    PDSAMessageBrokerEventArgs e)  {    if (null != MessageReceived)      MessageReceived(this, e);  }} The SendMessage method will take a PDSAMessageBrokerMessage object as an argument. It then creates an instance of a PDSAMessageBrokerEventArgs class, passing to the constructor two items: the MessageName from the PDSAMessageBrokerMessage object and also the object itself. It may seem a little redundant to pass in the message name when that same message name is part of the message, but it does make consuming the event and checking for the message name a little cleaner – as you will see in the next section. Create a Global Message Broker In your WPF application, create an instance of this message broker class in the App class located in the App.xaml file. Create a public property in the App class and create a new instance of that class in the OnStartUp event procedure as shown in the following code: public partial class App : Application{  public PDSAMessageBroker MessageBroker { get; set; }   protected override void OnStartup(StartupEventArgs e)  {    base.OnStartup(e);     MessageBroker = new PDSAMessageBroker();  }} Sending and Receiving Messages Let’s assume you have a user control that you load into a control on your main window and you want to send a message from that user control to the main window. You might have the main window display a message box, or put a string into a status bar as shown in Figure 1. Figure 1: The main window can receive and send messages The first thing you do in the main window is to hook up an event procedure to the MessageReceived event of the global message broker. This is done in the constructor of the main window: public MainWindow(){  InitializeComponent();   (Application.Current as App).MessageBroker.     MessageReceived += new MessageReceivedEventHandler(       MessageBroker_MessageReceived);} One piece of code you might not be familiar with is accessing a property defined in the App class of your XAML application. Within the App.Xaml file is a class named App that inherits from the Application object. You access the global instance of this App class by using Application.Current. You cast Application.Current to ‘App’ prior to accessing any of the public properties or methods you defined in the App class. Thus, the code (Application.Current as App).MessageBroker, allows you to get at the MessageBroker property defined in the App class. In the MessageReceived event procedure in the main window (shown below) you can now check to see if the MessageName property of the PDSAMessageBrokerEventArgs is equal to “StatusBar” and if it is, then display the message body into the status bar text block control. void MessageBroker_MessageReceived(object sender,   PDSAMessageBrokerEventArgs e){  switch (e.MessageName)  {    case "StatusBar":      tbStatus.Text = e.Message.MessageBody.ToString();      break;  }} In the Page 1 user control’s Loaded event procedure you will send the message “StatusBar” through the global message broker to any listener using the following code: private void UserControl_Loaded(object sender,  RoutedEventArgs e){  // Send Status Message  (Application.Current as App).MessageBroker.    SendMessage(new PDSAMessageBrokerMessage("StatusBar",      "This is Page 1"));} Since the main window is listening for the message ‘StatusBar’, it will display the value “This is Page 1” in the status bar at the bottom of the main window. Sending a Message to a User Control The previous example sent a message from the user control to the main window. You can also send messages from the main window to any listener as well. Remember that the global message broker is really just a broadcaster to anyone who has hooked into the MessageReceived event. In the constructor of the user control named ucPage1 you can hook into the global message broker’s MessageReceived event. You can then listen for any messages that are sent to this control by using a similar switch-case structure like that in the main window. public ucPage1(){  InitializeComponent();   // Hook to the Global Message Broker  (Application.Current as App).MessageBroker.    MessageReceived += new MessageReceivedEventHandler(      MessageBroker_MessageReceived);} void MessageBroker_MessageReceived(object sender,  PDSAMessageBrokerEventArgs e){  // Look for messages intended for Page 1  switch (e.MessageName)  {    case "ForPage1":      MessageBox.Show(e.Message.MessageBody.ToString());      break;  }} Once the ucPage1 user control has been loaded into the main window you can then send a message using the following code: private void btnSendToPage1_Click(object sender,  RoutedEventArgs e){  PDSAMessageBrokerMessage arg =     new PDSAMessageBrokerMessage();   arg.MessageName = "ForPage1";  arg.MessageBody = "Message For Page 1";   // Send a message to Page 1  (Application.Current as App).MessageBroker.SendMessage(arg);} Since the MessageName matches what is in the ucPage1 MessageReceived event procedure, ucPage1 can do anything in response to that event. It is important to note that when the message gets sent it is sent to all MessageReceived event procedures, not just the one that is looking for a message called “ForPage1”. If the user control ucPage1 is not loaded and this message is broadcast, but no other code is listening for it, then it is simply ignored. Remove Event Handler In each class where you add an event handler to the MessageReceived event you need to make sure to remove those event handlers when you are done. Failure to do so can cause a strong reference to the class and thus not allow that object to be garbage collected. In each of your user control’s make sure in the Unloaded event to remove the event handler. private void UserControl_Unloaded(object sender, RoutedEventArgs e){  if (_MessageBroker != null)    _MessageBroker.MessageReceived -=         _MessageBroker_MessageReceived;} Problems with Message Brokering As with most “global” classes or classes that hook up events to other classes, garbage collection is something you need to consider. Just the simple act of hooking up an event procedure to a global event handler creates a reference between your user control and the message broker in the App class. This means that even when your user control is removed from your UI, the class will still be in memory because of the reference to the message broker. This can cause messages to still being handled even though the UI is not being displayed. It is up to you to make sure you remove those event handlers as discussed in the previous section. If you don’t, then the garbage collector cannot release those objects. Instead of using events to send messages from one object to another you might consider registering your objects with a central message broker. This message broker now becomes a collection class into which you pass an object and what messages that object wishes to receive. You do end up with the same problem however. You have to un-register your objects; otherwise they still stay in memory. To alleviate this problem you can look into using the WeakReference class as a method to store your objects so they can be garbage collected if need be. Discussing Weak References is beyond the scope of this post, but you can look this up on the web. Summary In this blog post you learned how to create a simple message broker system that will allow you to send messages from one object to another without having to reference objects directly. This does reduce the coupling between objects in your application. You do need to remember to get rid of any event handlers prior to your objects going out of scope or you run the risk of having memory leaks and events being called even though you can no longer access the object that is responding to that event. NOTE: You can download the sample code for this article by visiting my website at http://www.pdsa.com/downloads. Select “Tips & Tricks”, then select “A Communication System for XAML Applications” from the drop down list.

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  • Metro: Understanding Observables

    - by Stephen.Walther
    The goal of this blog entry is to describe how the Observer Pattern is implemented in the WinJS library. You learn how to create observable objects which trigger notifications automatically when their properties are changed. Observables enable you to keep your user interface and your application data in sync. For example, by taking advantage of observables, you can update your user interface automatically whenever the properties of a product change. Observables are the foundation of declarative binding in the WinJS library. The WinJS library is not the first JavaScript library to include support for observables. For example, both the KnockoutJS library and the Microsoft Ajax Library (now part of the Ajax Control Toolkit) support observables. Creating an Observable Imagine that I have created a product object like this: var product = { name: "Milk", description: "Something to drink", price: 12.33 }; Nothing very exciting about this product. It has three properties named name, description, and price. Now, imagine that I want to be notified automatically whenever any of these properties are changed. In that case, I can create an observable product from my product object like this: var observableProduct = WinJS.Binding.as(product); This line of code creates a new JavaScript object named observableProduct from the existing JavaScript object named product. This new object also has a name, description, and price property. However, unlike the properties of the original product object, the properties of the observable product object trigger notifications when the properties are changed. Each of the properties of the new observable product object has been changed into accessor properties which have both a getter and a setter. For example, the observable product price property looks something like this: price: { get: function () { return this.getProperty(“price”); } set: function (value) { this.setProperty(“price”, value); } } When you read the price property then the getProperty() method is called and when you set the price property then the setProperty() method is called. The getProperty() and setProperty() methods are methods of the observable product object. The observable product object supports the following methods and properties: · addProperty(name, value) – Adds a new property to an observable and notifies any listeners. · backingData – An object which represents the value of each property. · bind(name, action) – Enables you to execute a function when a property changes. · getProperty(name) – Returns the value of a property using the string name of the property. · notify(name, newValue, oldValue) – A private method which executes each function in the _listeners array. · removeProperty(name) – Removes a property and notifies any listeners. · setProperty(name, value) – Updates a property and notifies any listeners. · unbind(name, action) – Enables you to stop executing a function in response to a property change. · updateProperty(name, value) – Updates a property and notifies any listeners. So when you create an observable, you get a new object with the same properties as an existing object. However, when you modify the properties of an observable object, then you can notify any listeners of the observable that the value of a particular property has changed automatically. Imagine that you change the value of the price property like this: observableProduct.price = 2.99; In that case, the following sequence of events is triggered: 1. The price setter calls the setProperty(“price”, 2.99) method 2. The setProperty() method updates the value of the backingData.price property and calls the notify() method 3. The notify() method executes each function in the collection of listeners associated with the price property Creating Observable Listeners If you want to be notified when a property of an observable object is changed, then you need to register a listener. You register a listener by using the bind() method like this: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price observableProduct.price = 2.99; } }; app.start(); })(); In the code above, the bind() method is used to associate the price property with a function. When the price property is changed, the function logs the new value of the price property to the Visual Studio JavaScript console. The price property is associated with the function using the following line of code: // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); Coalescing Notifications If you make multiple changes to a property – one change immediately following another – then separate notifications won’t be sent. Instead, any listeners are notified only once. The notifications are coalesced into a single notification. For example, in the following code, the product price property is updated three times. However, only one message is written to the JavaScript console. Only the last value assigned to the price property is written to the JavaScript Console window: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price observableProduct.price = 3.99; observableProduct.price = 2.99; observableProduct.price = 1.99; Only the last value assigned to price, the value 1.99, appears in the console: If there is a time delay between changes to a property then changes result in different notifications. For example, the following code updates the price property every second: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Add 1 to price every second window.setInterval(function () { observableProduct.price += 1; }, 1000); In this case, separate notification messages are logged to the JavaScript Console window: If you need to prevent multiple notifications from being coalesced into one then you can take advantage of promises. I discussed WinJS promises in a previous blog entry: http://stephenwalther.com/blog/archive/2012/02/22/windows-web-applications-promises.aspx Because the updateProperty() method returns a promise, you can create different notifications for each change in a property by using the following code: // Change the price observableProduct.updateProperty("price", 3.99) .then(function () { observableProduct.updateProperty("price", 2.99) .then(function () { observableProduct.updateProperty("price", 1.99); }); }); In this case, even though the price is immediately changed from 3.99 to 2.99 to 1.99, separate notifications for each new value of the price property are sent. Bypassing Notifications Normally, if a property of an observable object has listeners and you change the property then the listeners are notified. However, there are certain situations in which you might want to bypass notification. In other words, you might need to change a property value silently without triggering any functions registered for notification. If you want to change a property without triggering notifications then you should change the property by using the backingData property. The following code illustrates how you can change the price property silently: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price silently observableProduct.backingData.price = 5.99; console.log(observableProduct.price); // Writes 5.99 The price is changed to the value 5.99 by changing the value of backingData.price. Because the observableProduct.price property is not set directly, any listeners associated with the price property are not notified. When you change the value of a property by using the backingData property, the change in the property happens synchronously. However, when you change the value of an observable property directly, the change is always made asynchronously. Summary The goal of this blog entry was to describe observables. In particular, we discussed how to create observables from existing JavaScript objects and bind functions to observable properties. You also learned how notifications are coalesced (and ways to prevent this coalescing). Finally, we discussed how you can use the backingData property to update an observable property without triggering notifications. In the next blog entry, we’ll see how observables are used with declarative binding to display the values of properties in an HTML document.

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  • Should pathfinder in A* hold closedSet and openedSet or each object should hold its sets?

    - by Patryk
    I am about to implement A* pathfinding algorithm and I wonder how should I implement this - from the point of view of architecture. I have the pathfinder as a class - I think I will instantiate only one object of this class (or maybe make it a Singleton - this is not so important). The hardest part for me is whether the closedSet and openedSet should be attached to objects that can find the path for them or should be stored in pathfinder class ? I am opened to any hints and critique whatsoever. What is the best practice considering pathfinding in terms of design ?

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  • Cost Comparison Hard Disk Drive to Solid State Drive on Price per Gigabyte - dispelling a myth!

    - by tonyrogerson
    It is often said that Hard Disk Drive storage is significantly cheaper per GiByte than Solid State Devices – this is wholly inaccurate within the database space. People need to look at the cost of the complete solution and not just a single component part in isolation to what is really required to meet the business requirement. Buying a single Hitachi Ultrastar 600GB 3.5” SAS 15Krpm hard disk drive will cost approximately £239.60 (http://scan.co.uk, 22nd March 2012) compared to an OCZ 600GB Z-Drive R4 CM84 PCIe costing £2,316.54 (http://scan.co.uk, 22nd March 2012); I’ve not included FusionIO ioDrive because there is no public pricing available for it – something I never understand and personally when companies do this I immediately think what are they hiding, luckily in FusionIO’s case the product is proven though is expensive compared to OCZ enterprise offerings. On the face of it the single 15Krpm hard disk has a price per GB of £0.39, the SSD £3.86; this is what you will see in the press and this is what sales people will use in comparing the two technologies – do not be fooled by this bullshit people! What is the requirement? The requirement is the database will have a static size of 400GB kept static through archiving so growth and trim will balance the database size, the client requires resilience, there will be several hundred call centre staff querying the database where queries will read a small amount of data but there will be no hot spot in the data so the randomness will come across the entire 400GB of the database, estimates predict that the IOps required will be approximately 4,000IOps at peak times, because it’s a call centre system the IO latency is important and must remain below 5ms per IO. The balance between read and write is 70% read, 30% write. The requirement is now defined and we have three of the most important pieces of the puzzle – space required, estimated IOps and maximum latency per IO. Something to consider with regard SQL Server; write activity requires synchronous IO to the storage media specifically the transaction log; that means the write thread will wait until the IO is completed and hardened off until the thread can continue execution, the requirement has stated that 30% of the system activity will be write so we can expect a high amount of synchronous activity. The hardware solution needs to be defined; two possible solutions: hard disk or solid state based; the real question now is how many hard disks are required to achieve the IO throughput, the latency and resilience, ditto for the solid state. Hard Drive solution On a test on an HP DL380, P410i controller using IOMeter against a single 15Krpm 146GB SAS drive, the throughput given on a transfer size of 8KiB against a 40GiB file on a freshly formatted disk where the partition is the only partition on the disk thus the 40GiB file is on the outer edge of the drive so more sectors can be read before head movement is required: For 100% sequential IO at a queue depth of 16 with 8 worker threads 43,537 IOps at an average latency of 2.93ms (340 MiB/s), for 100% random IO at the same queue depth and worker threads 3,733 IOps at an average latency of 34.06ms (34 MiB/s). The same test was done on the same disk but the test file was 130GiB: For 100% sequential IO at a queue depth of 16 with 8 worker threads 43,537 IOps at an average latency of 2.93ms (340 MiB/s), for 100% random IO at the same queue depth and worker threads 528 IOps at an average latency of 217.49ms (4 MiB/s). From the result it is clear random performance gets worse as the disk fills up – I’m currently writing an article on short stroking which will cover this in detail. Given the work load is random in nature looking at the random performance of the single drive when only 40 GiB of the 146 GB is used gives near the IOps required but the latency is way out. Luckily I have tested 6 x 15Krpm 146GB SAS 15Krpm drives in a RAID 0 using the same test methodology, for the same test above on a 130 GiB for each drive added the performance boost is near linear, for each drive added throughput goes up by 5 MiB/sec, IOps by 700 IOps and latency reducing nearly 50% per drive added (172 ms, 94 ms, 65 ms, 47 ms, 37 ms, 30 ms). This is because the same 130GiB is spread out more as you add drives 130 / 1, 130 / 2, 130 / 3 etc. so implicit short stroking is occurring because there is less file on each drive so less head movement required. The best latency is still 30 ms but we have the IOps required now, but that’s on a 130GiB file and not the 400GiB we need. Some reality check here: a) the drive randomness is more likely to be 50/50 and not a full 100% but the above has highlighted the effect randomness has on the drive and the more a drive fills with data the worse the effect. For argument sake let us assume that for the given workload we need 8 disks to do the job, for resilience reasons we will need 16 because we need to RAID 1+0 them in order to get the throughput and the resilience, RAID 5 would degrade performance. Cost for hard drives: 16 x £239.60 = £3,833.60 For the hard drives we will need disk controllers and a separate external disk array because the likelihood is that the server itself won’t take the drives, a quick spec off DELL for a PowerVault MD1220 which gives the dual pathing with 16 disks 146GB 15Krpm 2.5” disks is priced at £7,438.00, note its probably more once we had two controller cards to sit in the server in, racking etc. Minimum cost taking the DELL quote as an example is therefore: {Cost of Hardware} / {Storage Required} £7,438.60 / 400 = £18.595 per GB £18.59 per GiB is a far cry from the £0.39 we had been told by the salesman and the myth. Yes, the storage array is composed of 16 x 146 disks in RAID 10 (therefore 8 usable) giving an effective usable storage availability of 1168GB but the actual storage requirement is only 400 and the extra disks have had to be purchased to get the  IOps up. Solid State Drive solution A single card significantly exceeds the IOps and latency required, for resilience two will be required. ( £2,316.54 * 2 ) / 400 = £11.58 per GB With the SSD solution only two PCIe sockets are required, no external disk units, no additional controllers, no redundant controllers etc. Conclusion I hope by showing you an example that the myth that hard disk drives are cheaper per GiB than Solid State has now been dispelled - £11.58 per GB for SSD compared to £18.59 for Hard Disk. I’ve not even touched on the running costs, compare the costs of running 18 hard disks, that’s a lot of heat and power compared to two PCIe cards!Just a quick note: I've left a fair amount of information out due to this being a blog! If in doubt, email me :)I'll also deal with the myth that SSD's wear out at a later date as well - that's just way over done still, yes, 5 years ago, but now - no.

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  • How to structure game states in an entity/component-based system

    - by Eva
    I'm making a game designed with the entity-component paradigm that uses systems to communicate between components as explained here. I've reached the point in my development that I need to add game states (such as paused, playing, level start, round start, game over, etc.), but I'm not sure how to do it with my framework. I've looked at this code example on game states which everyone seems to reference, but I don't think it fits with my framework. It seems to have each state handling its own drawing and updating. My framework has a SystemManager that handles all the updating using systems. For example, here's my RenderingSystem class: public class RenderingSystem extends GameSystem { private GameView gameView_; /** * Constructor * Creates a new RenderingSystem. * @param gameManager The game manager. Used to get the game components. */ public RenderingSystem(GameManager gameManager) { super(gameManager); } /** * Method: registerGameView * Registers gameView into the RenderingSystem. * @param gameView The game view registered. */ public void registerGameView(GameView gameView) { gameView_ = gameView; } /** * Method: triggerRender * Adds a repaint call to the event queue for the dirty rectangle. */ public void triggerRender() { Rectangle dirtyRect = new Rectangle(); for (GameObject object : getRenderableObjects()) { GraphicsComponent graphicsComponent = object.getComponent(GraphicsComponent.class); dirtyRect.add(graphicsComponent.getDirtyRect()); } gameView_.repaint(dirtyRect); } /** * Method: renderGameView * Renders the game objects onto the game view. * @param g The graphics object that draws the game objects. */ public void renderGameView(Graphics g) { for (GameObject object : getRenderableObjects()) { GraphicsComponent graphicsComponent = object.getComponent(GraphicsComponent.class); if (!graphicsComponent.isVisible()) continue; GraphicsComponent.Shape shape = graphicsComponent.getShape(); BoundsComponent boundsComponent = object.getComponent(BoundsComponent.class); Rectangle bounds = boundsComponent.getBounds(); g.setColor(graphicsComponent.getColor()); if (shape == GraphicsComponent.Shape.RECTANGULAR) { g.fill3DRect(bounds.x, bounds.y, bounds.width, bounds.height, true); } else if (shape == GraphicsComponent.Shape.CIRCULAR) { g.fillOval(bounds.x, bounds.y, bounds.width, bounds.height); } } } /** * Method: getRenderableObjects * @return The renderable game objects. */ private HashSet<GameObject> getRenderableObjects() { return gameManager.getGameObjectManager().getRelevantObjects( getClass()); } } Also all the updating in my game is event-driven. I don't have a loop like theirs that simply updates everything at the same time. I like my framework because it makes it easy to add new GameObjects, but doesn't have the problems some component-based designs encounter when communicating between components. I would hate to chuck it just to get pause to work. Is there a way I can add game states to my game without removing the entity-component design? Does the game state example actually fit my framework, and I'm just missing something? EDIT: I might not have explained my framework well enough. My components are just data. If I was coding in C++, they'd probably be structs. Here's an example of one: public class BoundsComponent implements GameComponent { /** * The position of the game object. */ private Point pos_; /** * The size of the game object. */ private Dimension size_; /** * Constructor * Creates a new BoundsComponent for a game object with initial position * initialPos and initial size initialSize. The position and size combine * to make up the bounds. * @param initialPos The initial position of the game object. * @param initialSize The initial size of the game object. */ public BoundsComponent(Point initialPos, Dimension initialSize) { pos_ = initialPos; size_ = initialSize; } /** * Method: getBounds * @return The bounds of the game object. */ public Rectangle getBounds() { return new Rectangle(pos_, size_); } /** * Method: setPos * Sets the position of the game object to newPos. * @param newPos The value to which the position of the game object is * set. */ public void setPos(Point newPos) { pos_ = newPos; } } My components do not communicate with each other. Systems handle inter-component communication. My systems also do not communicate with each other. They have separate functionality and can easily be kept separate. The MovementSystem doesn't need to know what the RenderingSystem is rendering to move the game objects correctly; it just need to set the right values on the components, so that when the RenderingSystem renders the game objects, it has accurate data. The game state could not be a system, because it needs to interact with the systems rather than the components. It's not setting data; it's determining which functions need to be called. A GameStateComponent wouldn't make sense because all the game objects share one game state. Components are what make up objects and each one is different for each different object. For example, the game objects cannot have the same bounds. They can have overlapping bounds, but if they share a BoundsComponent, they're really the same object. Hopefully, this explanation makes my framework less confusing.

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  • What is a good alternative to Camtasia Studio (screen recording not required)?

    - by tnorthcutt
    I'm looking for a good alternative to Camtasia Studio - really just the video editing part. My current workflow looks like this: Record audio (with Audacity) Save screenshots of the subject matter (websites) Import audio and screenshots into Camtasia Use the zoom and callout tools in Camtasia to go along with the spoken audio and highlight certain parts of the sites Given that Camtasia costs $300 (I've been using a trial version), I'd like to find something else that can do this well. I suspect that a lot of the pricetag for Camtasia is because of the screencasting features. I've tried Sony Vegas Movie Studio, but it was really a lot more than I need. I'd like something relatively simple (so that new users can pick it up relatively quickly), with the zoom and callout functionality that Camtasia has. Any suggestions? Edit for clarity: I'm looking for a program that will let me combine the screenshots and audio, and (most importantly) that has features equal to or better than Camtasia for text overlays, highlighting areas on the screen, etc.

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  • Multiple validation using jquery

    - by Prasenjit
    <script type="text/javascript">           $(document).ready(                 function() {                     $("input[id$='btnOK']").click(function(event) {                         $("#form1").validate({                             rules: {                                 txtName: { required: true },                                 txtEmail: { required: true, email: true },                                 txtPostalAddress: { required: true, maxlength: 50 }                             },                             messages: {}, onsubmit: true                         });                     });                     $("input[id$='Button1']").click(function(event) {                         $("#form1").validate({                             rules: {                                 txtName: { required: true }                                                             },                             messages: {}, onsubmit: true                         });                     });                 });                             </script>

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  • How do I resolve "No JSON object could be decoded" on mythbuntu live CD?

    - by Neil
    I have been running a MythTV frontend on my laptop for some time against a MythTV backend installed in Linux Mint 12 on another computer, and everything works fine. Now, I'm trying out the Mythbuntu Live CD (12.04.1 32-bit) on the laptop, to turn it into a dedicated front end. It's connecting to the network just fine, and I can see my server. When I click on the frontend icon on the desktop, it asks me for the security code, which I've verified against mythtv-setup on the server. However, when I test that code, it shows the error message "No JSON object could be decoded". I've looked in the control center to see if there's something else I should be setting up. The message above implies to me that it can't find the server, but I can find no place in the control center to tell it where to find my myth backend, which I find a little odd. Does the live CD not work against a backend server on another machine?

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  • UML class diagram - can aggregated object be part of two aggregated classes?

    - by user970696
    Some sources say that aggregation means that the class owns the object and shares reference. Lets assume an example where a company class holds a list of cars but departments of that company has list of cars used by them. class Department { list<Car> listOfCars; } class Company { list<Car> listOfCars; //initialization of the list } So in UML class diagram, I would do it like this. But I assume this is not allowed because it would imply that both company and department own the objects.. [COMPANY]<>------[CAR] [DEPARTMENT]<>---| //imagine this goes up to the car class

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  • 10Gbe sfp+ Cross Over Cable required? Is there such a thing?

    - by dc-patos
    To preface, this is my first experience with 10GBe networking and I have encountered an issue which research does not seem to document a solution for... I have two servers (older DL580G5 and DL380G5), each with a HP NC522SFP 10Gbe dual sfp+ port adapter. I have purchased copper "passive" direct connect adapter cables (which look like twinax), which seem to work well when I connect them to the sfp+ ports on my Dell 5524 switch. However, if I directly connect the two servers with the same cable, the link doesn't come up. I am running WS2012 standard on each server. My intention is to use one of these servers as a home brew SAN and I would like to enable mutiple 10Gbe paths for iSCSI traffic. My question(s): Can I connect the two adapters to each other, such as I would with other less speedy generations of ethernet? If I can, do I require a crossover cable, or some type of other sfp+ cable solution to do this? My 10Gbe sfp+ switch ports are premium, but server to server connections are doable in small numbers for me and I would really like the multiple paths this would give me. Is there a simple solution?

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  • Windows Malicious Software Removal Tool log says it can't do all required actions. Should I be conce

    - by Tom
    Here's what the log file c:/Windows/debug/mrt.log of my Windows 7 install says: WARNING: Security policy doesn't allow for all actions MSRT may require. ->Scan ERROR: resource process://pid:6080 (code 0x00000005 (5)) ->Scan ERROR: resource process://pid:5300 (code 0x00000057 (87)) ->Scan ERROR: resource process://pid:3512 (code 0x00000057 (87)) I use the default setup. I didn't change anything. This is the first time I checked the log file and this warning is in there from the start. Can I do something about it? Or I shouldn't be concerned, because it can do everything what's necessary anyway? Do you have this warning in your logfile?

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