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  • Why use object.prototype.constructor in OOP javascript?

    - by Matt
    I've recently started reading up on OOP javascript and one thing that authors seem to skip over is when an object A has been declared and suddenly I see "A.prototype.constructor =A; For example, var A = function(){}; // This is the constructor of "A" A.prototype.constructor = A; A.prototype.value = 1; A.prototype.test = function() { alert(this.value); } var a = new A(); // create an instance of A alert(a.value); // => 1 So I run the command in firebug "var A = function(){};" and then "A.Constructor" Which reveals it's a function. I understand this. I run the code "A.prototype.constructor = A;" and I thought this changes the A constructor from Function to A. The constructor property of A has been changed right? Instead when I run "A.constructor" it gives me function () still. What's the point? I also see A.constructor.prototype.constructor.prototype.. what is going on?

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  • Unable to get data from a WCF client

    - by Scott
    I am developing a DLL that will provide sychronized time stamps to multiple applications running on the same machine. The timestamps are altered in a thread that uses a high performance timer and a scalar to provide the appearance of moving faster than real-time. For obvious reasons I want only 1 instance of this time library, and I thought I could use WCF for the other processes to connect to this and poll for timestamps whenever they want. When I connect however I never get a valid time stamp, just an empty DateTime. I should point out that the library does work. The original implementation was a single DLL that each application incorporated and each one was synced using windows messages. I'm fairly sure it has something to do with how I'm setting up the WCF stuff, to which I am still pretty new. Here are the contract definitions: public interface ITimerCallbacks { [OperationContract(IsOneWay = true)] void TimerElapsed(String id); } [ServiceContract(SessionMode = SessionMode.Required, CallbackContract = typeof(ITimerCallbacks))] public interface ISimTime { [OperationContract] DateTime GetTime(); } Here is my class definition: [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)] public class SimTimeServer: ISimTime The host setup: // set up WCF interprocess comms host = new ServiceHost(typeof(SimTimeServer), new Uri[] { new Uri("net.pipe://localhost") }); host.AddServiceEndpoint(typeof(ISimTime), new NetNamedPipeBinding(), "SimTime"); host.Open(); and the implementation of the interface function server-side: public DateTime GetTime() { if (ThreadMutex.WaitOne(20)) { RetTime = CurrentTime; ThreadMutex.ReleaseMutex(); } return RetTime; } Lastly the client-side implementation: Callbacks myCallbacks = new Callbacks(); DuplexChannelFactory pipeFactory = new DuplexChannelFactory(myCallbacks, new NetNamedPipeBinding(), new EndpointAddress("net.pipe://localhost/SimTime")); ISimTime pipeProxy = pipeFactory.CreateChannel(); while (true) { string str = Console.ReadLine(); if (str.ToLower().Contains("get")) Console.WriteLine(pipeProxy.GetTime().ToString()); else if (str.ToLower().Contains("exit")) break; }

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  • problem adding object to hashtable

    - by daemonkid
    I am trying to call a class method dynamically depending on a condition. This is how I am doing it I have three classes implement a single interface interface IReadFile { string DoStuff(); } The three classes A,B,C implement the interface above. I am trying to add them to a hashtable with the code below _HashT.Add("a", new classA()); _HashT.Add("b", new classB()); _HashT.Add("c", new classC()); This compiles fine, but gives a runtime error.{Object reference not set to an instance of an object.} I was planning to return the correct class to the interface type depending on a parameter that matches the key value. say if I send in a. ClassA is returned to the interface type and the method is called. IReadFile Obj = (IReadFile )_HashT["a"].GetType(); obj.DoStuff(); How do I correct the part above where the objects need to be added to the hashtable? Or do I need to use a different approach? All the classes are in the same assembly and namespace. Thanks for your time.

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  • SQL Server problems reading columns with a foreign key

    - by illdev
    I have a weird situation, where simple queries seem to never finish for instance SELECT top 100 ArticleID FROM Article WHERE ProductGroupID=379114 returns immediately SELECT top 1000 ArticleID FROM Article WHERE ProductGroupID=379114 never returns SELECT ArticleID FROM Article WHERE ProductGroupID=379114 never returns SELECT top 1000 ArticleID FROM Article returns immediately By 'returning' I mean 'in query analyzer the green check mark appears and it says "Query executed successfully"'. I sometimes get the rows painted to the grid in qa, but still the query goes on waiting for my client to time out - 'sometimes': SELECT ProductGroupID AS Product23_1_, ArticleID AS ArticleID1_, ArticleID AS ArticleID18_0_, Inventory_Name AS Inventory3_18_0_, Inventory_UnitOfMeasure AS Inventory4_18_0_, BusinessKey AS Business5_18_0_, Name AS Name18_0_, ServesPeople AS ServesPe7_18_0_, InStock AS InStock18_0_, Description AS Descript9_18_0_, Description2 AS Descrip10_18_0_, TechnicalData AS Technic11_18_0_, IsDiscontinued AS IsDisco12_18_0_, Release AS Release18_0_, Classifications AS Classif14_18_0_, DistributorName AS Distrib15_18_0_, DistributorProductCode AS Distrib16_18_0_, Options AS Options18_0_, IsPromoted AS IsPromoted18_0_, IsBulkyFreight AS IsBulky19_18_0_, IsBackOrderOnly AS IsBackO20_18_0_, Price AS Price18_0_, Weight AS Weight18_0_, ProductGroupID AS Product23_18_0_, ConversationID AS Convers24_18_0_, DistributorID AS Distrib25_18_0_, type AS Type18_0_ FROM Article AS articles0_ WHERE (IsDiscontinued = '0') AND (ProductGroupID = 379121) shows this behavior. I have no idea what is going on. Probably select is broken ;) I got a foreign key on ProductGroups ALTER TABLE [dbo].[Article] WITH CHECK ADD CONSTRAINT [FK_ProductGroup_Articles] FOREIGN KEY([ProductGroupID]) REFERENCES [dbo].[ProductGroup] ([ProductGroupID]) GO ALTER TABLE [dbo].[Article] CHECK CONSTRAINT [FK_ProductGroup_Articles] there are some 6000 rows and IsDiscontinued is a bit, not null, but leaving this condition out does not change the outcome. Anyone can tell me how to handle such a situation? More info, anyone? Additional Info: this does not seem to be restricted to this Foreign Key, but all/some referencing this entity.

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  • How to get the related_name of a many-to-many-field?

    - by amann
    I am trying to get the related_name of a many-to-many-field. The m2m-field is located betweeen the models "Group" and "Lection" and is declared in the group-model as following: lections = models.ManyToManyField(Lection, blank=True) The field looks like this: <django.db.models.fields.related.ManyToManyField object at 0x012AD690> The print of field.__dict__ is: {'_choices': [], '_m2m_column_cache': 'group_id', '_m2m_name_cache': 'group', '_m2m_reverse_column_cache': 'lection_id', '_m2m_reverse_name_cache': 'lection', '_unique': False, 'attname': 'lections', 'auto_created': False, 'blank': True, 'column': 'lections', 'creation_counter': 71, 'db_column': None, 'db_index': False, 'db_table': None, 'db_tablespace': '', 'default': <class django.db.models.fields.NOT_PROVIDED at 0x00FC8780>, 'editable': True, 'error_messages': {'blank': <django.utils.functional.__proxy__ object at 0x00FC 7B50>, 'invalid_choice': <django.utils.functional.__proxy__ object at 0x00FC7A50>, 'null': <django.utils.functional.__proxy__ object at 0x00FC7 A70>}, 'help_text': <django.utils.functional.__proxy__ object at 0x012AD6F0>, 'm2m_column_name': <function _curried at 0x012A88F0>, 'm2m_db_table': <function _curried at 0x012A8AF0>, 'm2m_field_name': <function _curried at 0x012A8970>, 'm2m_reverse_field_name': <function _curried at 0x012A89B0>, 'm2m_reverse_name': <function _curried at 0x012A8930>, 'max_length': None, 'name': 'lections', 'null': False, 'primary_key': False, 'rel': <django.db.models.fields.related.ManyToManyRel object at 0x012AD6B0>, 'related': <RelatedObject: mymodel:group related to lections>, 'related_query_name': <function _curried at 0x012A8670>, 'serialize': True, 'unique_for_date': None, 'unique_for_month': None, 'unique_for_year': None, 'validators': [], 'verbose_name': 'lections'} Now the field should be accessed via a lection-instance. So this is done by lection.group_set But i need to access it dynamically, so there is the need to get the related_name attribute from somewhere. Here in the documentation, there is a note that it is possible to access ManyToManyField.related_name, but this doesn't work for my somehow.. Help would be a lot appreciated. Thanks in advance.

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  • How do I make JPA POJO classes + Netbeans forms play well together?

    - by Zak
    I started using netbeans to design forms to edit the instances of various classes I have made in a small app I am writing. Basically, the app starts, an initial set of objects is selected from the DB and presented in a list, then an item in the list can be selected for editing. When the editor comes up it has form fields for many of the data fields in the class. The problem I run into is that I have to create a controller that maps each of the data elements to the correct form element, and create an inordinate number of small conversion mapping lines of code to convert numbers into strings and set the correct element in a dropdown, then another inordinate amount of code to go back and update the underlying object with all the values from the form when the save button is clicked. My question is; is there a more directly way to make the editing of the form directly modify the contents of my class instance? I would like to be able to have a default mapping "controller" that I can configure, then override the getter/setter for a particular field if needed. Ideally, there would be standard field validation for things like phone numbers, integers, floats, zip codes, etc... I'm not averse to writing this myself, I would just like to see if it is already out there and use the right tool for the right job.

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  • How to check for a null object reference when validating forms in MVC

    - by quakkels
    Hello SO, I'm experimenting with validating forms in the asp.net MVC framework. I'm focusing on server side validation for the time being. I've come across an error that I'm not sure how to rectify. System.NullReferenceException: Object reference not set to an instance of an object. The code that throws the error is: [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create([Bind(Exclude="ID")] MembersCreate mc ) { mc.Modules = ModuleListDataContext.GetModuleList(); ViewData.Model = mc; //Validation using ModelState // // //line below errors when form field is empty // if ((string)mc.Member.Username.Trim() == "") ModelState.AddModelError("Member.Username", "Username is required."); if (!ModelState.IsValid) return View(); try { // TODO: Add insert logic here return RedirectToAction("Index","Home"); } catch { return View(); } } When I put spaces in the field it performs exactly as i want, but if I leave the field blank and press submit I get the error. What's the best way to avoid this error and still validate blank form fields? Thanks all -

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  • Make Trac use a Drupal user database for authentication

    - by denisw
    I am trying to set up a Trac instance as a complement to a Drupal site and would like to give users the possibility to use their Drupal account in Trac, too, ideally in a single sign-on fashion (if the user is already logged into Drupal, he is automatically logged into Trac). The question now is how to accomplish this. I have found a plugin named DrupalIntegration which seems to implement that functionality; however, it is poorly documented - in fact, not documented at all. I managed to install it, but don't know how to configure it. Here is what I came up with from looking at the source code and the documentation of the AccountManager plugin (on which DrupalIntegration depends): [components] trac.web.auth.loginmodule = disabled acct_mgr.api = enabled acct_mgr.web_ui.LoginModule = enabled acct_mgr.web_ui.RegistrationModule = disabled TracDrupalIntegration.DrupalIntegration = enabled [account-manager] drupal_database = mysql://<usernam>:<password>@localhost/<db> password_store = DrupalIntegration (<username>, <password> and <db> are naturally substituted with the correct data). While the Trac log says: 2010-12-18 10:54:09,570 Trac[loader] DEBUG: Loading TracDrupalIntegration from /usr/lib/python2.5/site-packages/TracDrupalIntegration-0.1-py2.5.egg this doesn't seem to work: trying to log in with a Drupal username / password results in an "Invalid username or password" error. Has someone used the DrupalIntegration and can point out to me what I did wrong? Or is there any other approach you know (or even have used in the past) to integrate Drupal and Trac that way?

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  • Invoking a method overloaded where all arguments implement the same interface

    - by double07
    Hello, My starting point is the following: - I have a method, transform, which I overloaded to behave differently depending on the type of arguments that are passed in (see transform(A a1, A a2) and transform(A a1, B b) in my example below) - All these arguments implement the same interface, X I would like to apply that transform method on various objects all implementing the X interface. What I came up with was to implement transform(X x1, X x2), which checks for the instance of each object before applying the relevant variant of my transform. Though it works, the code seems ugly and I am also concerned of the performance overhead for evaluating these various instanceof and casting. Is that transform the best I can do in Java or is there a more elegant and/or efficient way of achieving the same behavior? Below is a trivial, working example printing out BA. I am looking for examples on how to improve that code. In my real code, I have naturally more implementations of 'transform' and none are trivial like below. public class A implements X { } public class B implements X { } interface X { } public A transform(A a1, A a2) { System.out.print("A"); return a2; } public A transform(A a1, B b) { System.out.print("B"); return a1; } // Isn't there something better than the code below??? public X transform(X x1, X x2) { if ((x1 instanceof A) && (x2 instanceof A)) { return transform((A) x1, (A) x2); } else if ((x1 instanceof A) && (x2 instanceof B)) { return transform((A) x1, (B) x2); } else { throw new RuntimeException("Transform not implemented for " + x1.getClass() + "," + x2.getClass()); } } @Test public void trivial() { X x1 = new A(); X x2 = new B(); X result = transform(x1, x2); transform(x1, result); }

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  • Latex multicols. Can I group content so it won't split over cols and/or suggest colbreaks?

    - by valadil
    Hi. I'm trying to learn LaTeX. I've been googling this one for a couple days, but I don't speak enough LaTeX to be able to search for it effectively and what documentation I have found is either too simple or goes way over my head (http://www.uoregon.edu/~dspivak/files/multicol.pdf) I have a document using the multicol package. (I'm actually using multicols* so that the first col fills before the second begins instead of trying to balance them, but I don't think that's relevant here.) The columns output nicely, but I want to be able to indicate that some content won't be broken up into different columns. For instance, aaaaaaaa bbbbbbb aaaaaaaa bbbbbbb aaaaaaaa ccccccc bbbbbbbb ccccccc That poor attempt at ascii art columns is what's happening. I'd like to indicate that the b block is a whole unit that shouldn't be broken up into different columns. Since it doesn't fit under the a block, the entirety of the b block should be moved to the second column. Should b be wrapped in something? Is there a block/float/section/box/minipage/paragraph structure I can use? Something specific to multicol? Alternatively is there a way that I can suggest a columnbreak? I'm thinking of something like \- that suggests a hyphenated line break if its convenient, but this would go between blocks. Thanks!

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  • Ad distribution problem: an optimal solution?

    - by Mokuchan
    I'm asked to find a 2 approximate solution to this problem: You’re consulting for an e-commerce site that receives a large number of visitors each day. For each visitor i, where i € {1, 2 ..... n}, the site has assigned a value v[i], representing the expected revenue that can be obtained from this customer. Each visitor i is shown one of m possible ads A1, A2 ..... An as they enter the site. The site wants a selection of one ad for each customer so that each ad is seen, overall, by a set of customers of reasonably large total weight. Thus, given a selection of one ad for each customer, we will define the spread of this selection to be the minimum, over j = 1, 2 ..... m, of the total weight of all customers who were shown ad Aj. Example Suppose there are six customers with values 3, 4, 12, 2, 4, 6, and there are m = 3 ads. Then, in this instance, one could achieve a spread of 9 by showing ad A1 to customers 1, 2, 4, ad A2 to customer 3, and ad A3 to customers 5 and 6. The ultimate goal is to find a selection of an ad for each customer that maximizes the spread. Unfortunately, this optimization problem is NP-hard (you don’t have to prove this). So instead give a polynomial-time algorithm that approximates the maximum spread within a factor of 2. The solution I found is the following: Order visitors values in descending order Add the next visitor value (i.e. assign the visitor) to the Ad with the current lowest total value Repeat This solution actually seems to always find the optimal solution, or I simply can't find a counterexample. Can you find it? Is this a non-polinomial solution and I just can't see it?

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  • Why does GetWindowThreadProcessId return 0 when called from a service

    - by Marve
    When using the following class in a console application, and having at least one instance of Notepad running, GetWindowThreadProcessId correctly returns a non-zero thread id. However, if the same code is included in a Windows Service, GetWindowThreadProcessId always returns 0 and no exceptions are thrown. Changing the user the service launches under to be the same as the one running the console application didn't alter the result. What causes GetWindowThreadProcessId to return 0 even if it is provided with a valid hwnd? And why does it function differently in the console application and the service? Note: I am running Windows 7 32-bit and targeting .NET 3.5. public class TestClass { [DllImport("user32.dll")] static extern uint GetWindowThreadProcessId(IntPtr hWnd, IntPtr ProcessId); public void AttachToNotepad() { var processesToAttachTo = Process.GetProcessesByName("Notepad") foreach (var process in processesToAttachTo) { var threadID = GetWindowThreadProcessId(process.MainWindowHandle, IntPtr.Zero); .... } } } Console Code: class Program { static void Main(string[] args) { var testClass = new TestClass(); testClass.AttachToNotepad(); } } Service Code: public class TestService : ServiceBase { private TestClass testClass = new TestClass(); static void Main() { ServiceBase.Run(new TestService()); } protected override void OnStart(string[] args) { testClass.AttachToNotepad(); base.OnStart(args); } protected override void OnStop() { ... } }

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  • How to allow multiple filters to be selected - pagination?

    - by NewSOuser
    Hey, I am still trying to allow multiple filters to be selected for my pagination script but not sure how to do it being very new to php and programing in general. So in my pagination, when a user clicks the 'marketing' button(link) it queries the database just for the category that = marketing. The same goes for the other 2 filter buttons as seen in the script below. (automotive, sports). The problem is, I want to be able to select multiple filters like only marketing and auomotive or automotive and sports, for example if I click the marketing filter and then the automotive, it would display the categories that equal marketing, and automotive. I have no idea how to accomplish this, so I have come to the experts to help me out. This is the script I am working on: <h3>Filter results by:</h3> <a href='pagi_test.php?category=marketing'>marketing</a> <a href='pagi_test.php?category=automotive'>automotive</a> <a href='pagi_test.php?category=sports'>sports</a> <br /> <h3>Results:</h3> <?php //connecting to the database $error = "Could not connect to the database"; mysql_connect('localhost','root','root') or die($error); mysql_select_db('ajax_demo') or die($error); //max displayed per page $per_page = 3; //get start variable $start = $_GET['start']; $category = mysql_real_escape_string($_GET['category']); //count records $record_count = mysql_num_rows(mysql_query("SELECT * FROM explore WHERE category='$category'")); //count max pages $max_pages = $record_count / $per_page; //may come out as decimal if (!$start) $start = 0; //display data $get = mysql_query("SELECT * FROM explore WHERE category='$category' LIMIT $start, $per_page"); ?> <table width="800px"> <?php while ($row = mysql_fetch_assoc($get)) { // get data $id = $row['id']; $site_name = $row['site_name']; $site_description = $row['site_description']; ?> <tr> <td><?php echo $id; ?></td> <td><?php echo $site_name; ?></td> <td><?php echo $site_description; ?></td> </tr> <?php } //setup prev and next variables $prev = $start - $per_page; $next = $start + $per_page; //show prev button if (!($start<=0)) echo "<a href='pagi_test.php?category=$category&start=$prev'>Prev</a> "; //show page numbers //set variable for first page $i=1; for ($x=0;$x<$record_count;$x=$x+$per_page) { if ($start!=$x) echo " <a href='pagi_test.php?category=$category&start=$x'>$i</a> "; else echo " <a href='pagi_test.php?category=$category&start=$x'><b>$i</b></a> "; $i++; } //show next button if (!($start>=$record_count-$per_page)) echo " <a href='pagi_test.php?category=$category&start=$next'>Next</a>"; ?> Any help on this would be great. Thank you. -- EDIT -- If anyone has a better method of doing a pagination system with multiple filters than the one above, please let me know.

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  • Some specific questions about object oriented and MVC design.

    - by Samn
    I have two objects, Users and Mail. Users create Mail objects and send them to other users. If I wanted to get all mail for a User, I could create a method like GetMail() that would return an array of Mail objects owned by that User. But if I wanted to get all mail across the system, what "type" of object would be responsible for that? To solve this problem, I usually create a Manager, which is an object responsible for dealing with a collection of a particular type of object. MailManager deals with collections of Mail objects. GetMailForUser() is one method, GetAllMail() is another method. The User objects invokes the MailManager and executes GetMailForUser(me). Is this stupid? When a user executes the controller CreateMail, a new instance of the Mail object is created. The Mail object, seeing it is creating a new Mail of type 'sent', decides to go ahead and create a second Mail object for the recipient, of type 'received'. Creating one Mail object triggers the creation of a second Mail object. Is this stupid? Should the controller have created both Mail objects, or just the first 'sent' one? When two Users are friends, the association is stored in a table of Relationships. I use a simple object for Relationships. A RelationshipManager has a method called GetFriendsForUser(). The User object has a method GetFriends(), which invokes the RelationshipManager. Is this stupid?

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  • Creating an element and insertBefore is not working...

    - by sologhost
    Ok, I've been banging my head up against the wall on this and I have no clue why it isn't creating the element. Maybe something very small that I overlooked here. Basically, there is this Javascript code that is in a PHP document being outputted, like somewhere in the middle of when the page gets loaded, NOW, unfortunately it can't go into the header. Though I'm not sure that that is the problem anyways, but perhaps it is... hmmmmm. // Setting the variables needed to be set. echo ' <script type="text/javascript" src="' . $settings['default_theme_url'] . '/scripts/dpShoutbox.js"></script>'; echo ' <script type="text/javascript"> var refreshRate = ', $params['refresh_rate'], '; createEventListener(window); window.addEventListener("load", loadShouts, false); function loadShouts() { var alldivs = document.getElementsByTagName(\'div\'); var shoutCount = 0; var divName = "undefined"; for (var i = 0; i<alldivs.length; i++) { var is_counted = 0; divName = alldivs[i].getAttribute(\'name\'); if (divName.indexOf(\'dp_Reserved_Shoutbox\') < 0 && divName.indexOf(\'dp_Reserved_Counted\') < 0) continue; else if(divName == "undefined") continue; else { if (divName.indexOf(\'dp_Reserved_Counted\') == 0) { is_counted = 0; shoutCount++; continue; } else { shoutCount++; is_counted = 1; } } // Empty out the name attr. alldivs[i].name = \'dp_Reserved_Counted\'; var shoutId = \'shoutbox_area\' + shoutCount; // Build the div to be inserted. var shoutHolder = document.createElement(\'div\'); shoutHolder.setAttribute(\'id\', [shoutId]); shoutHolder.setAttribute(\'class\', \'dp_control_flow\'); shoutHolder.style.cssText = \'padding-right: 6px;\'; alldivs[i].parentNode.insertBefore(shoutHolder, alldivs[i]); if (is_counted == 1) { startShouts(refreshRate, shoutId); break; } } } </script>'; Also, I'm sure the other functions that I'm linking to within these functions work just fine. The problem here is that within this function, the div never gets created at all and I can't understand why? Furthermore Firefox, FireBug is telling me that the variable divName is undefined, even though I have attempted to take care of this within the function, though not sure why. Anyways, I need the created div element to be inserted just before the following HTML: echo ' <div name="dp_Reserved_Shoutbox" style="padding-bottom: 9px;"></div>'; I'm using name here instead of id because I don't want duplicate id values which is why I'm changing the name value and incrementing, since this function may be called more than 1 time. For example if there are 3 shoutboxes on the same page (Don't ask why...lol), I need to skip the other names that I already changed to "dp_Reserved_Counted", which I believe I am doing correctly. In any case, if I could I would place this into the header and have it called just once, but this isn't possible as these are loaded and no way of telling which one's they are, so it's directly hard-coded into the actual output on the page of where the shoutbox is within the HTML. Basically, not sure if that is the problem or not, but there must be some sort of work-around, unless the problem is within my code above... arrg Please help me. Thanks :)

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  • Deal with undefined values in code or in the template?

    - by David
    I'm writing a web application (in Python, not that it matters). One of the features is that people can leave comments on things. I have a class for comments, basically like so: class Comment: user = ... # other stuff where user is an instance of another class, class User: name = ... # other stuff And of course in my template, I have <div>${comment.user.name}</div> Problem: Let's say I allow people to post comments anonymously. In that case comment.user is None (undefined), and of course accessing comment.user.name is going to raise an error. What's the best way to deal with that? I see three possibilities: Use a conditional in the template to test for that case and display something different. This is the most versatile solution, since I can change the way anonymous comments are displayed to, say, "Posted anonymously" (instead of "Posted by ..."), but I've often been told that templates should be mindless display machines and not include logic like that. Also, other people might wind up writing alternate templates for the same application, and I feel like I should be making things as easy as possible for the template writer. Implement an accessor method for the user property of a Comment that returns a dummy user object when the real user is undefined. This dummy object would have user.name = 'Anonymous' or something like that and so the template could access it and print its name with no error. Put an actual record in my database corresponding to a user with user.name = Anonymous (or something like that), and just assign that user to any comment posted when nobody's logged in. I know I've seen some real-world systems that operate this way. (phpBB?) Is there a prevailing wisdom among people who write these sorts of systems about which of these (or some other solution) is the best? Any pitfalls I should watch out for if I go one way vs. another? Whoever gives the best explanation gets the checkmark.

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  • Nullability (Regular Expressions)

    - by danportin
    In Brzozowski's "Derivatives of Regular Expressions" and elsewhere, the function d(R) returning ? if a R is nullable, and Ø otherwise, includes clauses such as the following: d(R1 + R2) = d(R1) + d(R2) d(R1 · R2) = d(R1) ? d(R2) Clearly, if both R1 and R2 are nullable then (R1 · R2) is nullable, and if either R1 or R2 is nullable then (R1 + R2) is nullable. It is unclear to me what the above clauses are supposed to mean, however. My first thought, mapping (+), (·), or the Boolean operations to regular sets is nonsensical, since in the base case, d(a) = Ø (for all a ? S) d(?) = ? d(Ø) = Ø and ? is not a set (nor is the return type of d, which is a regular expression). Furthermore, this mapping isn't indicated, and there is a separate notation for it. I understand nullability, but I'm lost on the definition of the sum, product, and Boolean operations in the definition of d: how are ? or Ø returned from d(R1) ? d(R2), for instance, in the definition off d(R1 · R2)?

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  • SQL-Server: Is there an equivalent of a trigger for general stored procedure execution

    - by Arj
    Hi All, Hope you can help. Is there a way to reliably detect when a stored proc is being run on SQL Server without altering the SP itself? Here's the requirement. We need to track users running reports from our enterprise data warehouse as the core product we use doesn't allow for this. Both core product reports and a slew of in-house ones we've added all return their data from individual stored procs. We don't have a practical way of altering the parts of the product webpages where reports are called from. We also can't change the stored procs for the core product reports. (It would be trivial to add a logging line to the start/end of each of our inhouse ones). What I'm trying to find therefore, is whether there's a way in SQL Server (2005 / 2008) to execute a logging stored proc whenever any other stored procedure runs, without altering those stored procedures themselves. We have general control over the SQL Server instance itself as it's local, we just don't want to change the product stored procs themselves. Any one have any ideas? Is there a kind of "stored proc executing trigger"? Is there an event model for SQL Server that we can hook custom .Net code into? (Just to discount it from the start, we want to try and make a change to SQL Server rather than get into capturing the report being run from the products webpages etc) Thoughts appreciated Thanks

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  • How do I connect to SQL Server with VB?

    - by Wayne Werner
    Hi, I'm trying to connect to a SQL server from VB. The SQL server is across the network uses my windows login for authentication. I can access the server using the following python code: import odbc conn = odbc.odbc('SignInspection') c = conn.cursor() c.execute("SELECT * FROM list_domain") c.fetchone() This code works fine, returning the first result of the SELECT. However, I've been trying to use the SqlClient.SqlConnection in VB, and it fails to connect. I've tried several different connection strings but this is the current code: Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim conn As New SqlClient.SqlConnection conn.ConnectionString = "data source=signinspection;initial catalog=signinspection;integrated security=SSPI" Try conn.Open() MessageBox.Show("Sweet Success") 'Insert some code here, woo Catch ex As Exception MessageBox.Show("Failed to connect to data source.") MessageBox.Show(ex.ToString()) Finally conn.Close() End Try End Sub It fails miserably, and it gives me an error that says "A network-related or instance-specific error occurred... (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) I'm fairly certain it's my connection string, but nothing I've found has given me any solid examples (server=mySQLServer is not a solid example) of what I need to use. Thanks! -Wayne

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  • How to use form_tag to update params

    - by Tryskele
    I have been struggling with a problem in Rails for a couple of days and still could not find the solution. Could you help me with that? Problem: I have a search box that puts a :search_string entry in the params structure. I use a form_tag for that and it works fine. <% form_tag :controller=> 'items', :action => 'find' do %> <%= text_field_tag :search_string, params[:search_string] %> <% end %> The problem is when I want to add and update other params key-value (in another view), for instance :start_date, to filter the search_string result. Here is the code snipped that I use in the view: <% form_tag :controller=> "items", :action => "find", :params => params do %> <%= hidden_field_tag :date_start, '2010-04-01' %> <%= submit_tag 'April' %> <% end %> <% form_tag :controller=> "items", :action => "find", :params => params do %> <%= hidden_field_tag :date_start, '2010-03-01' %> <%= submit_tag 'March' %> <% end %> When I first click on "April" submit button, then the params is correctly passed to the controller (i.e. there is a params[:start_date]='April'). However when I try to click "March" button afterwards, the params[:start_date] is not updated. I definitely think this is a stupid newbie mistake, but I cannot figure out how to properly use the form_tag. Could you tell me if I am doing something work? Otherwise, could you advise me which is the best way to update the params using form_tag's ? Thank you very much in advance. Miquel

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  • Amazone API ItemSearch returns (400) Bad Request.

    - by BuzzBubba
    I'm using a simple example from Amazon documentation for ItemSearch and I get a strange error: "The remote server returned an unexpected response: (400) Bad Request." This is the code: public static void Main() { //Remember to create an instance of the amazon service, including you Access ID. AWSECommerceServicePortTypeClient service = new AWSECommerceServicePortTypeClient(new BasicHttpBinding(), new EndpointAddress( "http://webservices.amazon.com/onca/soap?Service=AWSECommerceService")); AWSECommerceServicePortTypeClient client = new AWSECommerceServicePortTypeClient( new BasicHttpBinding(), new EndpointAddress("http://webservices.amazon.com/onca/soap?Service=AWSECommerceService")); // prepare an ItemSearch request ItemSearchRequest request = new ItemSearchRequest(); request.SearchIndex = "Books"; request.Title = "Harry+Potter"; request.ResponseGroup = new string[] { "Small" }; ItemSearch itemSearch = new ItemSearch(); itemSearch.Request = new ItemSearchRequest[] { request }; itemSearch.AWSAccessKeyId = accessKeyId; // issue the ItemSearch request try { ItemSearchResponse response = client.ItemSearch(itemSearch); // write out the results foreach (var item in response.Items[0].Item) { Console.WriteLine(item.ItemAttributes.Title); } } catch(Exception e) { Console.ForegroundColor = ConsoleColor.Red; Console.WriteLine(e.Message); Console.ForegroundColor = ConsoleColor.White; Console.WriteLine("Press any key to quit..."); Clipboard.SetText(e.Message); } Console.ReadKey(); What is wrong?

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  • Does C# allow method overloading, PHP style (__call)?

    - by mr.b
    In PHP, there is a special method named __call($calledMethodName, $arguments), which allows class to catch calls to non-existing methods, and do something about it. Since most of classic languages are strongly typed, compiler won't allow calling a method that does not exist, I'm clear with that part. What I want to accomplish (and I figured this is how I would do it in PHP, but C# is something else) is to proxy calls to a class methods and log each of these calls. Right now, I have code similar to this: class ProxyClass { static logger; public AnotherClass inner { get; private set; } public ProxyClass() { inner = new AnotherClass(); } } class AnotherClass { public void A() {} public void B() {} public void C() {} // ... } // meanwhile, in happyCodeLandia... ProxyClass pc = new ProxyClass(); pc.inner.A(); pc.inner.B(); // ... So, how can I proxy calls to an object instance in extensible way? Extensible, meaning that I don't have to modify ProxyClass whenever AnotherClass changes. In my case, AnotherClass can have any number of methods, so it wouldn't be appropriate to overload or wrap all methods to add logging. I am aware that this might not be the best approach for this kind of problem, so if anyone has idea what approach to use, shoot. Thanks!

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  • Do I really ned bindParam?

    - by sandelius
    Hi there! I'm trying to do a little PDO CRUD to learn some PDO. I have a question about bindParam. Here's my update method right now: public static function update($conditions = array(), $data = array(), $table = '') { self::instance(); // Late static bindings (PHP 5.3) $table = ($table === '') ? self::table() : $table; // Check which data array we want to use $values = (empty($data)) ? self::$_fields : $data; $sql = "UPDATE $table SET "; foreach ($values as $f => $v) { $sql .= "$f = ?, "; } // let's build the conditions self::build_conditions($conditions); // fix our WHERE, AND, OR, LIKE conditions $extra = self::$condition_string; // querystring $sql = rtrim($sql, ', ') . $extra; // let's merge the arrays into on $v_val = array_values($values); $c_val = array_values($conditions); $array = array_merge($v_val, self::$condition_array); $stmt = self::$db->prepare($sql); return $stmt->execute($array); } in my "self::$condition_array" I get all the right values from the ?. SO the query looks like this: UPDATE table SET this = ?, another = ? WHERE title = ? AND time = ? as you can see I dont use bindParams instead I pass the right values in the right order ($array) directly into the execute($array) method. This works like a charm BUT is it safe not use use bindParam here? If not then how can I do it? Thanks from Sweden Tobias

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  • What should i do for accomodating large scale data storage and retrieval?

    - by kailashbuki
    There's two columns in the table inside mysql database. First column contains the fingerprint while the second one contains the list of documents which have that fingerprint. It's much like an inverted index built by search engines. An instance of a record inside the table is shown below; 34 "doc1, doc2, doc45" The number of fingerprints is very large(can range up to trillions). There are basically following operations in the database: inserting/updating the record & retrieving the record accoring to the match in fingerprint. The table definition python snippet is: self.cursor.execute("CREATE TABLE IF NOT EXISTS `fingerprint` (fp BIGINT, documents TEXT)") And the snippet for insert/update operation is: if self.cursor.execute("UPDATE `fingerprint` SET documents=CONCAT(documents,%s) WHERE fp=%s",(","+newDocId, thisFP))== 0L: self.cursor.execute("INSERT INTO `fingerprint` VALUES (%s, %s)", (thisFP,newDocId)) The only bottleneck i have observed so far is the query time in mysql. My whole application is web based. So time is a critical factor. I have also thought of using cassandra but have less knowledge of it. Please suggest me a better way to tackle this problem.

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  • What is the proper way to use a Logger in a Serializable Java class?

    - by Tim Visher
    I have the following (doctored) class in a system I'm working on and Findbugs is generating a SE_BAD_FIELD warning and I'm trying to understand why it would say that before I fix it in the way that I thought I would. The reason I'm confused is because the description would seem to indicate that I had used no other non-serializable instance fields in the class but bar.model.Foo is also not serializable and used in the exact same way (as far as I can tell) but Findbugs generates no warning for it. import bar.model.Foo; import java.io.File; import java.io.Serializable; import java.util.List; import org.slf4j.Logger; import org.slf4j.LoggerFactory; public class Demo implements Serializable { private final Logger logger = LoggerFactory.getLogger(this.getClass()); private final File file; private final List<Foo> originalFoos; private Integer count; private int primitive = 0; public Demo() { for (Foo foo : originalFoos) { this.logger.debug(...); } } ... } My initial blush at a solution is to get a logger reference from the factory right as I use it: public DispositionFile() { Logger logger = LoggerFactory.getLogger(this.getClass()); for (Foo foo : originalFoos) { this.logger.debug(...); } } That doesn't seem particularly efficient, though. Thoughts?

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