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• Hover-to-click on jQuery UI datePicker 'next month' and 'prev month' not working

  - by user316727

  Hi there, I have a calendar which is meant to look much like the calendar in Outlook. There is a big field representing the hours in a day, and there is a date navigator. The navigator is the jQuery UI Datepicker. I want users to be able to navigate to a new day by clicking on a date in the datepicker, but also to be able to drag appointments over the datepicker and drop them on a specific date. I have that working now. I also want users, while they are dragging an appointment, to be able to move to next or previous month simply by hovering over the datepicker. So I've added a mouseenter and mouseleave event: one runs a setInterval function which sends a click every 1,5 seconds; the other cancels the interval function. This is where all sorts of things go wrong. As soon as one click has been triggered, the mouseleave function no longer works: in other words, the datepicker keeps flipping over to another month every 1,5 seconds. It seems that the datePicker interferes, or that the click event causes other things to go wrong. What can I do?

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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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• How do I initialize the controls in an InsertItemTemplate?

  - by Slauma

  I have - for instance - an asp:FormView which supports Read, Insert, Update, Delete and is bound to a DataSource: <asp:FormView ID="FormView1" runat="server" DataSourceID="ObjectDataSource1" > <ItemTemplate> <asp:Label ID="Label1" runat="server" Text='<%# Bind("MyText") %>' /> </ItemTemplate> <EditItemTemplate> <asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("MyText") %>' /> </EditItemTemplate> <InsertItemTemplate> <asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("MyText") %>' /> </InsertItemTemplate> </asp:FormView> If I am in Read-Mode or Edit-Mode the control is initialized with the property MyText of the current object which is bound to the FormView. But when I go to Insert-Mode I do not have a "current object" (FormView1.DataItem is indeed null) and the controls are empty. If I want to have my TextBox control initialized with a specific value how can I do that? In which event can I hook in to set default values to the controls in the InsertItemTemplate? Especially I have in mind using an ObjectDataSource. I was expecting that the InsertItemTemplate is initialized with a business object which underlies my ObjectDataSource and which is created by the ASP.NET framework simply by using its default constructor when the InsertItemTemplate gets activated. In the default constructor I would init the class members to the default values I'd like to have in my controls of the InsertItemTemplate. But unfortunately that's not the case: No "default" object is created and bound to the FormView. So it seems I have to initialize all controls separately or to create the default object manually and bind it to the InsertItemTemplate of the FormView. But how and where can I do that? Thanks in advance!

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• Sequential access to asynchronous sockets

  - by Lars A. Brekken

  I have a server that has several clients C1...Cn to each of which there is a TCP connection established. There are less than 10,000 clients. The message protocol is request/response based, where the server sends a request to a client and then the client sends a response. The server has several threads, T1...Tm, and each of these may send requests to any of the clients. I want to make sure that only one of these threads can send a request to a specific client at any one time, while the other threads wanting to send a request to the same client will have to wait. I do not want to block threads from sending requests to different clients at the same time. E.g. If T1 is sending a request to C3, another thread T2 should not be able to send anything to C3 until T1 has received its response. I was thinking of using a simple lock statement on the socket: lock (c3Socket) { // Send request to C3 // Get response from C3 } I am using asynchronous sockets, so I may have to use Monitor instead: Monitor.Enter(c3Socket); // Before calling .BeginReceive() And Monitor.Exit(c3Socket); // In .EndReceive I am worried about stuff going wrong and not letting go of the monitor and therefore blocking all access to a client. I'm thinking that my heartbeat thread could use Monitor.TryEnter() with a timeout and throw out sockets that it cannot get the monitor for. Would it make sense for me to make the Begin and End calls synchronous in order to be able to use the lock() statement? I know that I would be sacrificing concurrency for simplicity in this case, but it may be worth it. Am I overlooking anything here? Any input appreciated.

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• Generic version control strategy for select table data within a heavily normalized database

  - by leppie

  Hi Sorry for the long winded title, but the requirement/problem is rather specific. With reference to the following sample (but very simplified) structure (in psuedo SQL), I hope to explain it a bit better. TABLE StructureName { Id GUID PK, Name varchar(50) NOT NULL } TABLE Structure { Id GUID PK, ParentId GUID (FK to Structure), NameId GUID (FK to StructureName) NOT NULL } TABLE Something { Id GUID PK, RootStructureId GUID (FK to Structure) NOT NULL } As one can see, Structure is a simple tree structure (not worried about ordering of children for the problem). StructureName is a simplification of a translation system. Finally 'Something' is simply something referencing the tree's root structure. This is just one of many tables that need to be versioned, but this one serves as a good example for most cases. There is a requirement to version to any changes to the name and/or the tree 'layout' of the Structure table. Previous versions should always be available. There seems to be a few possibilities to tackle this issue, like copying the entire structure, but most approaches causes one to 'loose' referential integrity. Example if one followed this approach, one would have to make a duplicate of the 'Something' record, given that the root structure will be a new record, and have a new ID. Other avenues of possible solutions are looking into how Wiki's handle this or go a lot further and look how proper version control systems work. Currently, I feel a bit clueless how to proceed on this in a generic way. Any ideas will be greatly appreciated. Thanks leppie

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• Why am I getting "Message sent to deallocated instance" in Objective-C?

  - by Dave C

  I have several buttons on my app that are being created dynamically. They are all pointed at the button click event when pressed. When the button pressed method is called, the sender's tag (int value) is parsed into the controller's house ID. It works with one of the buttons — the first one created, to be specific — but the others throw the following error: -[CFNumber intValue]: message sent to deallocated instance 0xc4bb0ff0 I am not releasing these buttons anywhere in my code. I haven't set them to autorelease or anything like that. I'm just wondering why they are doing this on the click. The button click event: - (IBAction) ButtonClick: (id) sender { HouseholdViewController *controller = [[HouseholdViewController alloc] initWithNibName:@"HouseholdViewController" bundle:nil]; controller.delegate = self; controller.HouseID = [(NSInteger)[(UIButton *)sender tag] intValue]; //this line throws an error controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal; [self presentModalViewController:controller animated:YES]; [controller release]; } Where I am creating the buttons: UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom]; button.frame = CGRectMake(MyLongInScreenCoords, MyLatInScreenCoords, 50, 50); UIImage *buttonImageNormal = [UIImage imageNamed:@"blue_pin.png"]; UIImage *strechableButtonImageNormal = [buttonImageNormal stretchableImageWithLeftCapWidth:50 topCapHeight:50]; [button setBackgroundImage:strechableButtonImageNormal forState:UIControlStateNormal]; [self.view addSubview:button]; button.tag = [NSNumber numberWithInt:[[words objectAtIndex: i] intValue]]; ButtonPoints[CurrentHouseCount][0] = button; ButtonPoints[CurrentHouseCount][1] = [NSValue valueWithCGPoint:CGPointMake(MyActualLat, MyActualLong)]; [button addTarget:self action:@selector(ButtonClick:) forControlEvents:UIControlEventTouchUpInside]; CurrentHouseCount++;

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• Resources and techniques/methods for SCJP preparation ?

  - by BenoitParis

  I am passing the SCJP 6 exam in a month. I have the "SCJP Sun Certified Programmer for Java 6 Exam 310-065" book. It seems great for the exam. But I want your advice on this. Getting the closest possible to 100% would be great. I have found a site that answered some of the questions you ask yourself when you go trough the book. Here is it : http://www.janeg.ca/java2.html As you can see it was written for Java 2 :/ I have written another specific question here on StackOverflow about the usefulness of JVM specification and Java compiler code for the SCJP. Will Update the results here. Here it is. Please share the resources you used in preparing the exam. Please also specify any resources that you think might help. Any type of resource is welcome: books, code, specs, sites, wikies, papers, online tests, grandmas... Please also share on any method/technique that helped you prepare the exam. Please also comment on the return you got from the resource and the method (for the learning process and for points in the exam) I'll begin: Book : "SCJP Sun Certified Programmer for Java 6 Exam 310-065". Seems like the official book for the preparation. Technique : Writing code in a text editor and compiling it with javac to test a question. NO IDEs! It helps you get a a straight answer to a question you have. It helps you pay attention to every word in the code (and this is very important in the SCJP) EDIT: Added dimension: Are there good, up-to-date online tests?

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• Javascript storing properties and functions in variables

  - by richard

  Hello, I'm having trouble with my programming style and I hope to get some feedback here. I recently bought Javascript: The Good Parts and while I find this a big help, I'm still having trouble designing this application. Especially when it comes to writing function and methods. Example: I have a function that let's the user switches games in my app. This function updates game-specific information in the current view. var games = { active: Titanium.App.Properties.getString('active_game'), gameswitcher_positions: { 'Game 1': 0, 'Game 2': 1, 'Game 3': 2, 'Game 4': 3, 'Game 5': 4 }, change: function(game) { if (active_game !== game) { gameswitcher.children[this.gameswitcher_positions[this.active]].backgroundImage = gameswitcher.children[this.gameswitcher_positions[this.active]].backgroundImage.replace('_selected', ''); gameswitcher.children[this.gameswitcher_positions[game]].backgroundImage = gameswitcher.children[this.gameswitcher_positions[game]].backgroundImage.replace('.png', '_selected.png'); events.update(game); this.active = game; } }, init: function() { gameswitcher.children[this.gameswitcher_positions[this.active]].backgroundImage = gameswitcher.children[this.gameswitcher_positions[this.active]].backgroundImage.replace('.png', '_selected.png'); events.update(this.active); } }; gameswitcher is a container view which contains buttons to switch games. I am not satisfied with this approach but I cannot think of a better one. Should I place the gameswitcher_positions outside of the variable in a seperate variable instead of as a property? And what about the active game? Please give me feedback, what am I doing wrong?

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• How to properly implement the Strategy pattern in a web MVC framework?

  - by jboxer

  In my Django app, I have a model (lets call it Foo) with a field called "type". I'd like to use Foo.type to indicate what type the specific instance of Foo is (possible choices are "Number", "Date", "Single Line of Text", "Multiple Lines of Text", and a few others). There are two things I'd like the "type" field to end up affecting; the way a value is converted from its normal type to text (for example, in "Date", it may be str(the_date.isoformat())), and the way a value is converted from text to the specified type (in "Date", it may be datetime.date.fromtimestamp(the_text)). To me, this seems like the Strategy pattern (I may be completely wrong, and feel free to correct me if I am). My question is, what's the proper way to code this in a web MVC framework? In a client-side app, I'd create a Type class with abstract methods "serialize()" and "unserialize()", override those methods in subclasses of Type (such as NumberType and DateType), and dynamically set the "type" field of a newly-instantiated Foo to the appropriate Type subclass at runtime. In a web framework, it's not quite as straightforward for me. Right now, the way that makes the most sense is to define Foo.type as a Small Integer field and define a limited set of choices (0 = "Number", 1 = "Date", 2 = "Single Line of Text", etc.) in the code. Then, when a Foo object is instantiated, use a Factory method to look at the value of the instance's "type" field and plug in the correct Type subclass (as described in the paragraph above). Foo would also have serialize() and unserialize() methods, which would delegate directly to the plugged-in Type subclass. How does this design sound? I've never run into this issue before, so I'd really like to know if other people have, and how they've solved it.

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• Something about Stream

  - by sforester

  I've been working on something that make use of streams and I found myself not clear about some stream concepts( you can also view another question posted by me at http://stackoverflow.com/questions/2933923/about-redirected-stdout-in-system-diagnostics-process ). 1.how do you indicate that you have finished writing a stream, writing something like a EOF? 2.follow the previous question, if I have written a EOF(or something like that) to a stream but didn't close the stream, then I want to write something else to the same stream, can I just start writing to it and no more set up required? 3.if a procedure tries to read a stream(like the stdin ) that no one has written anything to it, the reading procedure will be blocked,finally some data arrives and the procedure will just read till the writing is done,which is indicated by getting a return of 0 count of bytes read rather than being blocked, and now if the procedure issues another read to the same stream, it will still get a 0 count and return immediately while I was expecting it will be blocked since no one is writing to the stream now. So does the stream holds different states when the stream is opened but no one has written to it yet and when someone has finished a writing session? I'm using Windows the .net framework if there will by any thing platform specific. Thanks a lot!

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• WYSIWYG with Qt - font size woes

  - by Rob

  I am creating a custom Qt widget that mimics an A4 printed page and am having problems getting fonts to render at the correct size. My widget uses QPainter::setViewport and QPainter::setWindow to mimic the A4 page, using units of 10ths of a millimetre which enables me to draw easily. However, attempting to create a font at a specific point size doesn't seem to work and using QFont:setPixelSize isn't accurate. Here is some code: View::View(QWidget *parent) : QWidget(parent), printer(new QPrinter) { printer->setPaperSize(QPrinter::A4); printer->setFullPage(true); } void View::paintEvent(QPaintEvent*) { QPainter painter(this); painter.setWindow(0, 0, 2100, 2970); painter.setViewport(0, 0, printer->width(), printer->height()); // Draw a rect at x = 1cm, y = 1cm, 6cm wide and 1 inch high painter.drawRect(100, 100, 600, 254); // Create a 72pt (1 inch) high font QFont font("Arial"); font.setPixelSize(254); painter.setFont(font); // Draw in the same box // The font is too large painter.drawText(QRect(100, 100, 600, 254), tr("Wg\u0102")); // Ack - the actual font size reported by the metrics is 283 pixels! const QFontMetrics fontMetrics = painter.fontMetrics(); qDebug() << "Font height = " << fontMetrics.height(); } So I'm asking for a 254 high font (1 inch, 72 pts) and it's too big and sure enough when I query for the font height via QFontMetrics it is 283 high. Does anyone else know how to use font sizes in points when using custom mapping modes like this? It must be possible. Note that I cannot see how to convert between logical/device points either (i.e. the Win32 DPtoLP/LPtoDP equivalents.)

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• Trouble with building up a string in Clojure

  - by Aki Iskandar

  Hi gang - [this may seem like my problem is with Compojure, but it isn't - it's with Clojure] I've been pulling my hair out on this seemingly simple issue - but am getting nowhere. I am playing with Compojure (a light web framework for Clojure) and I would just like to generate a web page showing showing my list of todos that are in a PostgreSQL database. The code snippets are below (left out the database connection, query, etc - but that part isn't needed because specific issue is that the resulting HTML shows nothing between the <body> and </body> tags). As a test, I tried hard-coding the string in the call to main-layout, like this: (html (main-layout "Aki's Todos" "Haircut<br>Study Clojure<br>Answer a question on Stackoverfolw")) - and it works fine. So the real issue is that I do not believe I know how to build up a string in Clojure. Not the idiomatic way, and not by calling out to Java's StringBuilder either - as I have attempted to do in the code below. A virtual beer, and a big upvote to whoever can solve it! Many thanks! ============================================================= ;The master template (a very simple POC for now, but can expand on it later) (defn main-layout "This is one of the html layouts for the pages assets - just like a master page" [title body] (html [:html [:head [:title title] (include-js "todos.js") (include-css "todos.css")] [:body body]])) (defn show-all-todos "This function will generate the todos HTML table and call the layout function" [] (let [rs (select-all-todos) sbHTML (new StringBuilder)] (for [rec rs] (.append sbHTML (str rec "<br><br>"))) (html (main-layout "Aki's Todos" (.toString sbHTML))))) ============================================================= Again, the result is a web page but with nothing between the body tags. If I replace the code in the for loop with println statements, and direct the code to the repl - forgetting about the web page stuff (ie. the call to main-layout), the resultset gets printed - BUT - the issue is with building up the string. Thanks again. ~Aki

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• Effective books for learning the intricacies of business application development?

  - by OffApps Cory

  I am a self taught "developer". I use the term loosely because I only know enough to make myself dangerous. I have no theory background, and I only pick up things to get this little tool to work or make that control do what I want. That said, I am looking for some reading material that explains some of the theory behind application development especially from a business standpoint. Really I need to understand what all of these terms that float around really talk about. Business Logic Layer, UI abstraction level and all that. Anyone got a reading list that they feel helped them understand this stuff? I know how to code stuff up so that it works. It is not pretty mostly because I don't know the elegant way of doing it, and it is not planned out very well (I also don't know how to plan an application). Any help would be appreciated. I have read a number of books on what I thought was the subject, but they all seem to rehash basic coding and what-not. This doesn't have to be specific to VB.NET or WPF (or Entity Framework) but anything with those items would be quite helpful.

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• Search dir using wildcard string, return filename, and loop.

  - by Charlie Murphy

  Hello all, I'm having some problems, and looking for some help. I'm trying to create a photo gallery in javascript, that will be able to 'update' it's self automatically. I need to be able to search a directory, and grab a file with a specific prefix. I need to output the followng HTML code: <li><a href="images/resize_FILENAME.ext"><img src="images/thumb_FILENAME.ext"></a></li> The 'resize_' and 'thumb_' use a timestamp to identify, so they have the same ending, just a different prefix. So, for example, if I search the directory for an image with a prefix of 'resize_', I need to insert that into the a tag, and then remove the '_resize' prefix, and add the '_thumb' prefix for the img tag. I then need to be able to do that for each image in the directory. Any help would be greatly appreciated. Oh, I should add: I'm assuming php would be easiest for this, but if an alternative exists that would work too. I'm also using jQuery if javascript would be better.

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• TextArea component is null on applicationComplete event

  - by Alan G.

  I have a weird issue (weird because it is specific to one component) with applicationComplete in a fairly simple application. All the UI components are declared in MXML. I can access them all in applicationComplete, but not a spark.components.TextArea component, named taStatus here; it is null in the handler. MXML looks sort of like this (there are lots of other components, but nothing special) <s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark" xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="710" minHeight="640" applicationComplete="onApplicationComplete(event)" width="710" height="640"> <mx:TabNavigator left="15" right="15" top="15" bottom="340" paddingTop="0"> <s:NavigatorContent label="General" width="100%" height="100%"> <s:Label x="93" y="71" text="Label" id="lblTest"/> </s:NavigatorContent> <s:NavigatorContent label="Status" width="100%" height="100%"> <s:TextArea id="taStatus" width="100%" height="100%" text="Startup." editable="false"/> </s:NavigatorContent> </mx:TabNavigator> <fx:Script source="main.as" /> </s:Application> Here is the handler in main.as protected function onApplicationComplete(event: FlexEvent) : void { lblTest.text = 'abc789'; // OK taStatus.text = 'abc789'; // Fail } TypeError: Error #1009: Cannot access a property or method of a null object reference. So taStatus is null... What is so special about this TextArea?

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• Need a VB Script to check if service exist

  - by Shorabh Upadhyay

  I want to write a VBS script which will check if specific service is installed/exist or not locally. If it is not installed/exist, script will display message (any text) and disabled the network interface i.e. NIC. If service exist and running, NO Action. Just exit. If service exist but not running, same action, script will display message (any text) and disabled the network interface i.e. NIC. i have below given code which is displaying a message in case one service is stop but it is not - Checking if service exist or not Disabling the NIC strComputer = "." Set objWMIService = Getobject("winmgmts:"_ & "{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2") Set colRunningServices = onjWMIService.ExecQuery _ ("select State from Win32_Service where Name = 'dhcp'") For Each objService in colRunningServices If objService.State <> "Running" Then errReturn = msgbox ("Stopped") End If Next Please help. Thanks in advance.

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• Java: Help constructing a fillTextFields() method

  - by Holly

  I have a Java project where I am to connect to a database and create buttons (next, new, save, delete, previous) to navigate through the database content where there are appropriate text fields and labels for the specific information. I'll use the code below as an example (each button is set up very similar)... I have it as follows: JButton jbtnNext = new JButton("Next ->"); jbtnNext.addActionListener(this); if (e.getSource() == jbtnNext) jbtnNext_Click(); private void jbtnNext_Click() { JOptionPane.showMessageDialog(null, "Next" ,"Button Pressed", JOptionPane.INFORMATION_MESSAGE); try { if (rset.next()) { fillTextFields(true); }else{ //Display result in a dialog box JOptionPane.showMessageDialog(null, "Not found"); } } catch (SQLException ex) { ex.printStackTrace(); } } The professor gave the following outline of logic to construct the fillTextFields() method: Construct the method to provide reusable code that would fill the JTextFields on the GUI with appropriate values from current record from the database (when "Previous or "Next" buttons are pressed) or blank values (when the new Button is pressed). To determine when the current record was to provide values (next and previous) or the value would be blank (new button) pass a boolean argument into the method. If data from the current record was to be used as fill values, pass true for both previous and next button code after moving the record pointer. If the new button was pressed and want to fill with blank values, pass false to the method. Inside the method, use a conditional expression to evaluate the boolean variable. If true, The appropriate get----() resultset method is used to fill the JTextFields. If false, fill them with "". The .setText() method of the JTextField is used to fill each JTextField. Make sure the fillTextFields method throws the appropriate exception. I understand and have the previous and next button methods passing true, while the new button method is passing false, but I don't quite understand how to set up the fillTextFields() method correctly or how to "throw the appropriate exception"... Any help would really be appreciated, thank you!

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• How to make ActiveRecord work with legacy partitioned/sharded databases/tables?

  - by Utensil

  thanks for your time first...after all the searching on google, github and here, and got more confused about the big words(partition/shard/fedorate),I figure that I have to describe the specific problem I met and ask around. My company's databases deals with massive users and orders, so we split databases and tables in various ways, some are described below: way database and table name shard by (maybe it's should be called partitioned by?) YZ.X db_YZ.tb_X order serial number last three digits YYYYMMDD. db_YYYYMMDD.tb date YYYYMM.DD db_YYYYMM.tb_ DD date too The basic concept is that databases and tables are seperated acording to a field(not nessissarily the primary key), and there are too many databases and too many tables, so that writing or magically generate one database.yml config for each database and one model for each table isn't possible or at least not the best solution. I looked into drnic's magic solutions, and datafabric, and even the source code of active record, maybe I could use ERB to generate database.yml and do database connection in around filter, and maybe I could use named_scope to dynamically decide the table name for find, but update/create opertions are bounded to "self.class.quoted_table_name" so that I couldn't easily get my problem solved. And even I could generate one model for each table, because its amount is up to 30 most. But this is just not DRY! What I need is a clean solution like the following DSL: class Order < ActiveRecord::Base shard_by :order_serialno do |key| [get_db_config_by(key), #because some or all of the databaes might share the same machine in a regular way or can be configed by a hash of regex, and it can also be a const get_db_name_by(key), get_tb_name_by(key), ] end end Can anybody enlight me? Any help would be greatly appreciated~~~~

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• Trying to make a plugin system in C++/Qt

  - by Pirate for Profit

  I'm making a task-based program that needs to have plugins. Tasks need to have properties which can be easily edited, I think this can be done with Qt's Meta-Object Compiler reflection capabilities (I could be wrong, but I should be able to stick this in a QtPropertyBrowser?) So here's the base: class Task : public QObject { Q_OBJECT public: explicit Task(QObject *parent = 0) : QObject(parent){} virtual void run() = 0; signals: void taskFinished(bool success = true); } Then a plugin might have this task: class PrinterTask : public Task { Q_OBJECT public: explicit PrinterTask(QObject *parent = 0) : Task(parent) {} void run() { Printer::getInstance()->Print(this->getData()); // fictional emit taskFinished(true); } inline const QString &getData() const; inline void setData(QString data); Q_PROPERTY(QString data READ getData WRITE setData) // for reflection } In a nutshell, here's what I want to do: // load plugin // find all the Tasks interface implementations in it // have user able to choose a Task and edit its specific Q_PROPERTY's // run the TASK It's important that one .dll has multiple tasks, because I want them to be associated by their module. For instance, "FileTasks.dll" could have tasks for deleting files, making files, etc. The only problem with Qt's plugin setup is I want to store X amount of Tasks in one .dll module. As far as I can tell, you can only load one interface per plugin (I could be wrong?). If so, the only possible way to do accomplish what I want is to create a FactoryInterface with string based keys which return the objects (as in Qt's Plug-And-Paint example), which is a terrible boilerplate that I would like to avoid. Anyone know a cleaner C++ plugin architecture than Qt's to do what I want? Also, am I safely assuming Qt's reflection capabilities will do what I want (i.e. able to edit an unknown dynamically loaded tasks' properties with the QtPropertyBrowser before dispatching)?

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• Scientific Algorithms that can produce imagery, pseudocode perhaps?

  - by Ross

  Hello, I have a client who are based in the field of mathematics. We are developing, amongst other things, a website. I like to create a mock-up of a drawing tool that an produce some imagery in the background based on some scientific algorithms. The intention being that the may client, later, may create there own. (They use emacs for everything, great client.) I'm look for an answer of where or what to go looking for. Not code specific, pseudocode even, as we can adapt and have not yet settled on a platform. I'm afraid my mathematic stops at the power of two and some trigonometry. Appreciated if they're are any mathematics related students/academics how could enlighten me? What to search for will be accepted? Edit: To summarise/clarify, I want to draw pretty pictures (the design perspective). I want them to have some context (i.e. not just for the sake of pretty images but have some explanation available). In essence I would to create a rendering engine which we can draw the images and we set the style parameters: line, colour, etc... But to pursue this option I want to experiment myself. Thanks Ross

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• Can I use foreign key restrictions to return meaningful UI errors with PHP

  - by Shane

  I want to start by saying that I am a big fan of using foreign keys and have a tendency to use them even on small projects to keep my database from being filled with orphaned data. On larger projects I end up with gobs of keys which end up covering upwards of 8 - 10 layers of data. I want to know if anyone could suggest a graceful way of handling 'expected errors' from the MySQL database in a way that I can construct meaningful messages for the end user. I will explain 'expected errors' with an example. Lets say I have a set of tables used for basic discussions: discussion questions responses users Hierarchically they would probably look something like this: -users --discussion ---questions ----responses When I attempt to delete a user the FKs will check discussions and if any discussion exist the deletion is restricted, deleting discussion checks questions, deleting questions checks responses. An 'expected error' in this case would be attempting to delete a user--unless they are newly created I can anticipate that one or more foreign keys will fail causing an error. What I WANT to do is to catch that error on deletion and be able to tell the end user something like 'We're sorry, but all discussions must be removed before you can delete this user...'. Now I know I can keep and maintain matching arrays in PHP and map specific errors to messages but that is messy and prone to becoming stagnant, or I could manually run a set of selects prior to attempting the deletion, but then I am doing just as much work as without using FKs. Any help here would be greatly appreciated, or if I am just looking at this completely wrong then please let me know. On a side note I generally use CodeIgniter for my application development, so if that would open up an avenue through that framework please consider that in your answers. Thanks in Advance

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• How do i set the Transaction Isolation in EJB?

  - by Nitesh Panchal

  Hello, I am not able to find a way to set TransactionIsolation in ejb. Can anybody tell me how do i set it? I am using persistence. I have looked the following classes : EntityManager , EntityManagerFactory, UserTransaction. None of them seems to have any method like setTransactionIsolation or such. Do we need to change persistence.xml? I just read a book named Mastering EJB 3.0 4th edition. They gave a full 10 page theory about Isolation level that this problems occur and that occurs and such things but at the end they gave this paragraph :- "As we now know, the EJB standard does not deal with isolation levels directly, and rightly so. EJB is a component specification. It defines the behavior and contracts of a business component with clients and middleware infrastructure (containers) such that the component can be rendered as various middleware services properly. EJBs therefore are transactional components that interact with resource managers, such as the JDBC resource manager or JMS resource manager, via JTS, as part of a transaction. They are not, hence, resource components in themselves. Since isolation levels are very specific to the behavior and capabilities of the underlying resources, they should therefore be specified at the resource API levels. " What exactly does it mean? What is meant by resource level APIs? Please help me. If persistence has no way to set Isolation Level then why do they give such huge theory in an EJB book and make it heavy in weight unnecessarily :(

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• Digitally sign MS Office (Word, Excel, etc..) and PDF files on the server

  - by Sébastien Nussbaumer

  I need to digitally sign MS Office and PDF files that are stored on a server. I really mean a digital signature that is integrated in the document, according to each specific file formats. This is the process I had in mind : Create a hash of the file's content Send the hash to a custom written java applet in the browser The user encrypts the hash with his/her private key (on an usb token via PKCS#11 for example), thus effectively signing the file. The applet then sends the signature to the server On the server I would then incorporate the signature in the file's (MS Office and PDF files can do that without changing the file's content, probably by just setting some metadata field) What is cool is that you never have to download and upload the complete file to the server again. What is even cooler, the customer doesn't need Office or PDF Writer to sign the files. Parts 2, 3 and 4 are OK for me, my company bought all the JAVA technology I need for that for a previous project I worked on. Problem : I can't seem to find any documentation/examples to do parts 1 and 5 for Office files . Are my google skills failing me this time ? Do you have any pointers to documentation or examples for doing that for MS Office files ? The underlying technology isn't that important to me : I can use Java, .Net, COM, any working technology is OK ! Note : I'm 95% sure I can nail points 1 and 5 for PDF files using iText Thanks ** Edit : If I can't do that with hashes and must download the complete file to the client, it's also possible. But then I still need the documentation to be able to sign Office file... in java this time (from an applet)

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• Strict pointer aliasing: is access through a 'volatile' pointer/reference a solution?

  - by doublep

  On the heels of a specific problem, a self-answer and comments to it, I'd like to understand if it is a proper solution, workaround/hack or just plain wrong. Specifically, I rewrote code: T x = ...; if (*reinterpret_cast <int*> (&x) == 0) ... As: T x = ...; if (*reinterpret_cast <volatile int*> (&x) == 0) ... with a volatile qualifier to the pointer. Let's just assume that treating T as int in my situation makes sense. Does this accessing through a volatile reference solve pointer aliasing problem? For a reference, from specification: [ Note: volatile is a hint to the implementation to avoid aggressive optimization involving the object because the value of the object might be changed by means undetectable by an implementation. See 1.9 for detailed semantics. In general, the semantics of volatile are intended to be the same in C++ as they are in C. — end note ] EDIT: The above code did solve my problem at least on GCC 4.5.

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• Is there a JavaScript event that fires when a tab index switch is triggered? (TABINDEX does not work for inputs in IFRAME)

  - by treeface

  My specific use case is that I have a WYSIWYG editor which is basically an editable iframe. To the user, however, it looks like a standard-issue textarea. My problem is that I have inputs that sit before and after this editor in the (perceived) tab index and I'd like the user to be able to press tab (or the equivalent on his platform of choice) to get to the WYSIWYG editor when he's in the previous element and shift-tab to get to it when he's in the latter element. I know this can be faked using the key events and checking whether or not the tab key was pressed, but I'm curious if there's a better way. UPDATE. treeface clarified the actual problem in the comments. PROBLEM: In normal case, you can use "TABINDEX" attribute of the <input> element to control that, when tabbing out of "Subject" input field (in an email form), the focus lands on "Body" input field in the e-mail. This is done simply by assigning correctly ordered values to "TABINDEX" attribute of both input fields. The problem is that TABINDEX attribute only orders elements within the same frame. So, if "Body" input field is actually in an internal IFRAME, you can't tab out of "Subject" in the parent frame straight into "Body" in the IFRAME using TABINDEX order.

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