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• Are there compelling reasons not to use Groovy?

  - by Leonard H Martin

  I'm developing a LoB application in Java after a long absence from the platform (having spent the last 8 years or so entrenched in Fortran, C, a smidgin of C++ and latterly .Net). Java, the language, is not much changed from how I remember it. I like it's strengths and I can work around its weaknesses - the platform has grown and deciding upon the myriad of different frameworks which appear to do much the same thing as one another is a different story; but that can wait for another day - all-in-all I'm comfortable with Java. However, over the last couple of weeks I've become enamoured with Groovy, and purely from a selfish point of view: but not just because it makes development against the JVM a more succinct and entertaining (and, well, "groovy") proposition than Java (the language). What strikes me most about Groovy is its inherent maintainability. We all (I hope!) strive to write well documented, easy to understand code. However, sometimes the languages we use themselves defeat us. An example: in 2001 I wrote a library in C to translate EDIFACT EDI messages into ANSI X12 messages. This is not a particularly complicated process, if slightly involved, and I thought at the time I had documented the code properly - and I probably had - but some six years later when I revisited the project (and after becoming acclimatised to C#) I found myself lost in so much C boilerplate (mallocs, pointers, etc. etc.) that it took three days of thoughtful analysis before I finally understood what I'd been doing six years previously. This evening I've written about 2000 lines of Java (it is the day of rest, after all!). I've documented as best as I know how, but, but, of those 2000 lines of Java a significant proportion is Java boiler plate. This is where I see Groovy and other dynamic languages winning through - maintainability and later comprehension. Groovy lets you concentrate on your intent without getting bogged down on the platform specific implementation; it's almost, but not quite, self documenting. I see this as being a huge boon to me when I revisit my current project (which I'll port to Groovy asap) in several years time and to my successors who will inherit it and carry on the good work. So, are there any reasons not to use Groovy?

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• ZF Autoloader to load ancestor and requested class

  - by Pekka

  I am integrating Zend Framework into an existing application. I want to switch the application over to Zend's autoloading mechanism to replace dozens of include() statements. I have a specific requirement for the autoloading mechanism, though. Allow me to elaborate. The existing application uses a core library (independent from ZF), for example: /Core/Library/authentication.php /Core/Library/translation.php /Core/Library/messages.php this core library is to remain untouched at all times and serves a number of applications. The library contains classes like class ancestor_authentication { ... } class ancestor_translation { ... } class ancestor_messages { ... } in the application, there is also a Library directory: /App/Library/authentication.php /App/Library/translation.php /App/Library/messages.php these includes extend the ancestor classes and are the ones that actually get instantiated in the application. class authentication extends ancestor_authentication { } class translation extends ancestor_translation { } class messages extends ancestor_messages { } usually, these class definitions are empty. They simply extend their ancestors and provide the class name to instantiate. $authentication = new authentication(); The purpose of this solution is to be able to easily customize aspects of the application without having to patch the core libraries. Now, the autoloader I need would have to be aware of this structure. When an object of the class authentication is requested, the autoloader would have to: 1. load /Core/Library/authentication.php 2. load /App/Library/authentication.php My current approach would be creating a custom function, and binding that to Zend_Loader_Autoloader for a specific namespace prefix. Is there already a way to do this in Zend that I am overlooking? The accepted answer in this question kind of implies there is, but that may be just a bad choice of wording. Are there extensions to the Zend Autoloader that do this? Can you - I am new to ZF - think of an elegant way, conforming with the spirit of the framework, of extending the Autoloader with this functionality? I'm not necessary looking for a ready-made implementation, some pointers (This should be an extension to the xyz method that you would call like this...) would already be enough.

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• How do I write object classes effectively when dealing with table joins?

  - by Chris

  I should start by saying I'm not now, nor do I have any delusions I'll ever be a professional programmer so most of my skills have been learned from experience very much as a hobby. I learned PHP as it seemed a good simple introduction in certain areas and it allowed me to design simple web applications. When I learned about objects, classes etc the tutor's basic examnples covered the idea that as a rule of thumb each database table should have its own class. While that worked well for the photo gallery project we wrote, as it had very simple mysql queries, it's not working so well now my projects are getting more complex. If I require data from two separate tables which require a table join I've instead been ignoring the class altogether and handling it on a case by case basis, OR, even worse been combining some of the data into the class and the rest as a separate entity and doing two queries, which to me seems inefficient. As an example, when viewing content on a forum I wrote, if you view a thread, I retrieve data from the threads table, the posts table and the user table. The queries from the user and posts table are retrieved via a join and not instantiated as an object, whereas the thread data is called using my Threads class. So how do I get from my current state of affairs to something a little less 'stupid', for want of a better word. Right now I have a DB class that deals with connection and escaping values etc, a parent db query class that deals with the common queries and methods, and all of the other classes (Thread, Upload, Session, Photo and ones thats aren't used Post, User etc ) are children of that. Do I make a big posts class that has the relevant extra attributes that I retrieve from the users (and potentially threads) table? Do I have separate classes that populate each of their relevant attributes with a single query? If so how do I do that? Because of the way my classes are written, based on what I was taught, my db update row method, or insert method both just take the attributes as an array and update all of that, if I have extra attributes from other db tables in each class then how do I rewrite those methods as obbiously updating automatically like that would result in errors? In short I think my understanding is limited right now and I'd like some pointers when it comes to the fundamentals of how to write more complex classes.

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• choosing an image locally from http url and serving that image without a server round trip

  - by serverman

  Hi folks I am a complete novice to Flash (never created anything in flash). I am quite familiar with web applications (J2EE based) and have a reasonable expertise in Javascript. Here is my requirement. I want the user to select (via an html form) an image. Normally in the post, this image would be sent to server and may be stored there to be served later. I do not want that. I want to store this image locally and then serve it via HTTP to the user. So, the flow is: 1. Go to the "select image url":mywebsite.com/selectImage Browse the image and select the image This would transfer control locally to some code running on the client (Javascript or flash), which would then store the image locally at some place on the client machine. Go to the "show image url": mywebsite.com/showImage This would eventually result in some client code running on the browser that retrieves the image and renders it (without any server round trips.) I considered the following options: Use HTML5 local storage. Since I am a complete novice to flash, I looked into this. I found that it is fairly straightforward to store and retrieve images in javascript (only strings are allowed but I am hoping storing base64 encoded strings would work at least for small images). However, how do I serve the image via http url that points to my server without a server round trip? I saw the interesting article at http://hacks.mozilla.org/category/fileapi/ but that would work only in firefox and I need to work on all latest browsers (at least the ones supporting HTML5 local storage) Use flash SharedObjects. OK, this would have been good - the only thing is I am not sure where to start. Snippets of actionscripts to do this are scattered everywhere but I do not know how to use those scripts in an actual html page:) I do not need to create any movies or anything - just need to store an image and serve it locally. If I go this route, I would also use it to store other "strings" locally. If you suggest this, please give me the exact steps (could be pointers to other web sites) on how to do this. I would like to avoid paying for any flash development environment software ideally:) Thank you!

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• MVC | Linq Update Query | Help!

  - by 109221793

  Hi guys, I'm making modifications to a C# MVC application that I've inherited. I have a database, and for simplicity I'll just focus on the two tables I'm working with for this linq query. Item ItemID Int PK ItemName RepairSelection (Yes or No) RepairID Int FK Repair RepairID Int PK RepairCategory SubmissionDate DateSentForRepair Ok, so ItemID is pretty much the identifier, and the View to display the Repair details goes like this (snippet): <%= Html.LabelFor(x => x.ItemID)%> <%= Html.DisplayFor(x => x.ItemID)%><br /> <%= Html.LabelFor(x => x.Repair.RepairCategory)%> <%= Html.DisplayFor(x => x.Repair.RepairCategory, "FormTextShort")%><br /> <%= Html.LabelFor(x => x.Repair.SubmissionDate)%> <%= Html.DisplayFor(x => x.Repair.SubmissionDate)%><br /> <%= Html.LabelFor(x => x.Repair.DateSentForRepair)%> <%= Html.DisplayFor(x => x.Repair.DateSentForRepair)%><br /> <%= Html.ActionLink("Edit Repair Details", "Edit", new { ItemID= Model.ItemID})%> Here is the GET Edit action: public ActionResult Edit(Int64? itemId) { ModelContainer ctn = new ModelContainer(); var item = from i in ctn.Items where i.ItemID == itemId select i; return View(item.First()); } This is also fine, the GET Edit view displays the right details. Where I'm stuck is the linq query to update the Repair table. I have tried it so many ways today that my head is just fried (new to Linq as you may have guessed). My latest try is here (which I know is way off so go easy ;-) ): [HttpPost] public ActionResult Edit(Int64 itemId, Repair repair, Item item, FormCollection formValues) { if (formValues["cancelButton"] != null) { return RedirectToAction("View", new { ItemID = itemId }); } ModelContainer ctn = new ModelContainer(); Repair existingData = ctn.Repair.First(a => a.RepairId == item.RepairID && item.ItemID == itemId); existingData.SentForConversion = DateTime.Parse(formValues["SentForConversion"]); ctn.SaveChanges(); return RedirectToAction("View", new { ItemID = itemId }); } For the above attempt I get a Sequence Contains No Elements error. Any help or pointers would be appreciated. Thanks guys.

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• Using hidden values with jQuery (and ASP.NET MVC) -- not working?

  - by SlackerCoder

  Im using a couple of JSON calls to render data, etc etc. In order to keep the proper key value, I am storing it in a tag. I have this in several places in my code, none of which cause an issue like this one is. Here is the jQuery: The call that "sets" the value: $("a[id^='planSetupAddNewPlan']").live('click', function() { var x = $(this).attr('id'); x = x.substring(19); $("#hidPlanSetupCurrentGroupKey").val(x); $.getJSON("/GroupSetup/PlanSetupAddNewList", { GroupKey: x }, function(data) { $("#planSetupAddNew").html('' + data.TableResult + ''); alert('First Inside 2 ' + x); $.blockUI({ message: $("#planSetupAddNew") }); }); }); The call that "gets" the value: $("#ddlPlanSetupAddNewProduct").live('change', function() { var a = $("#hidPlanSetupCurrentGroupKey").val(); var prod = $(this).val(); alert(a); $.getJSON("/GroupSetup/PlanSetupChangePlanList", { GroupKey: a, Product: prod }, function(data) { if (data.Message == "Success") { $("#planSetupAddNewPlan").html('' + data.TableResult + ''); } else if (data.Message == "Error") { //Do something } }); }); Here is the html in question: <div id="planSetupAddNew" style="display:none; cursor: default;"> <input type="hidden" id="hidPlanSetupCurrentGroupKey" /> <div id="planSetupAddNewData"> </div> </div> In the first section, the alert ('First Inside 2 ' + x) returns what I expect (where x = the key value), and if I add a line to display the contents of the hidden field, that works as well: ie. var key = $("#hidPlanSetupCurrentGroupKey").val(); alert(key); In the "alert(a);" call, I am getting "undefined". I have looked at the other code in the same view and it is the same and it works. I must be missing something, or have some sort of mistype that I havent caught. Just an overview of the controller events: The first call (/GroupSetup/PlanSetupAddNewList) will return an html string building a "form" for users to enter information into. The second call (/GroupSetup/PlanSetupChangePlanList) just changes a second dropdown based on the first dropdown selection (overwriting the html in the div). If you need more info, let me know! Any thoughts/tips/pointers/suggestions?!?! Thanks for all your help :)

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• Is it any loose coupling mechanism in Objective-C + Cocoa like C# delegates or C++Qt signals+slots?

  - by Eye of Hell

  Hello. For a large programs, the standard way to chalenge a complexity is to divide a program code into small objects. Most of the actual programming languages offer this functionality via classes, so is Objective-C. But after source code is separated into small object, the second challenge is to somehow connect them with each over. Standard approaches, supported by most languages are compositon (one object is a member field of another), inheritance, templates (generics) and callbacks. More cryptic techniques include method-level delagates (C#) and signals+slots (C++Qt). I like the delegates / signals idea, since while connecting two objects i can connect individual methods with each over, without objects knowing anything of each over. For C#, it will look like this: var object1 = new CObject1(); var object2 = new CObject2(); object1.SomethingHappened += object2.HandleSomething; In this code, is object1 calls it's SomethingHappened delegate (like a normal method call) the HandleSomething method of object2 will be called. For C++Qt, it will look like this: var object1 = new CObject1(); var object2 = new CObject2(); connect( object1, SIGNAL(SomethingHappened()), object2, SLOT(HandleSomething()) ); The result will be exactly the same. This technique has some advantages and disadvantages, but generally i like it more than interfaces since if program code base grows i can change connections and add new ones without creating tons of interfaces. After examination of Objective-C i havn't found any way to use this technique i like :(. It seems that Objective-C supports message passing perfectly well, but it requres for object1 to have a pointer to object2 in order to pass it a message. If some object needs to be connected to lots of other objects, in Objective-C i will be forced to give him pointers to each of the objects it must be connected. So, the question :). Is it any approach in Objective-C programming that will closely resemble delegate / signal+slot types of connection, not a 'give first object an entire pointer to second object so it can pass a message to it'. Method-level connections are a bit more preferable to me than object-level connection ^_^.

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• Can't insert a number into a C++ custom streambuf/ostream

  - by 0xbe5077ed

  I have written a custom std::basic_streambuf and std::basic_ostream because I want an output stream that I can get a JNI string from in a manner similar to how you can call std::ostringstream::str(). These classes are quite simple. namespace myns { class jni_utf16_streambuf : public std::basic_streambuf<char16_t> { JNIEnv * d_env; std::vector<char16_t> d_buf; virtual int_type overflow(int_type); public: jni_utf16_streambuf(JNIEnv *); jstring jstr() const; }; typedef std::basic_ostream<char16_t, std::char_traits<char16_t>> utf16_ostream; class jni_utf16_ostream : public utf16_ostream { jni_utf16_streambuf d_buf; public: jni_utf16_ostream(JNIEnv *); jstring jstr() const; }; // ... } // namespace myns In addition, I have made four overloads of operator<<, all in the same namespace: namespace myns { // ... utf16_ostream& operator<<(utf16_ostream&, jstring) throw(std::bad_cast); utf16_ostream& operator<<(utf16_ostream&, const char *); utf16_ostream& operator<<(utf16_ostream&, const jni_utf16_string_region&); jni_utf16_ostream& operator<<(jni_utf16_ostream&, jstring); // ... } // namespace myns The implementation of jni_utf16_streambuf::overflow(int_type) is trivial. It just doubles the buffer width, puts the requested character, and sets the base, put, and end pointers correctly. It is tested and I am quite sure it works. The jni_utf16_ostream works fine inserting unicode characters. For example, this works fine and results in the stream containing "hello, world": myns::jni_utf16_ostream o(env); o << u"hello, wor" << u'l' << u'd'; My problem is as soon as I try to insert an integer value, the stream's bad bit gets set, for example: myns::jni_utf16_ostream o(env); if (o.badbit()) throw "bad bit before"; // does not throw int32_t x(5); o << x; if (o.badbit()) throw "bad bit after"; // throws :( I don't understand why this is happening! Is there some other method on std::basic_streambuf I need to be implementing????

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• string s; &s+1; Legal? UB?

  - by John Dibling

  Consider the following code: #include <cstdlib> #include <iostream> #include <string> #include <vector> #include <algorithm> using namespace std; int main() { string myAry[] = { "Mary", "had", "a", "Little", "Lamb" }; const size_t numStrs = sizeof(myStr)/sizeof(myAry[0]); vector<string> myVec(&myAry[0], &myAry[numStrs]); copy( myVec.begin(), myVec.end(), ostream_iterator<string>(cout, " ")); return 0; } Of interest here is &myAry[numStrs]: numStrs is equal to 5, so &myAry[numStrs] points to something that doesn't exist; the sixth element in the array. There is another example of this in the above code: myVec.end(), which points to one-past-the-end of the vector myVec. It's perfecly legal to take the address of this element that doesn't exist. We know the size of string, so we know where the address of the 6th element of a C-style array of strings must point to. So long as we only evaluate this pointer and never dereference it, we're fine. We can even compare it to other pointers for equality. The STL does this all the time in algorithms that act on a range of iterators. The end() iterator points past the end, and the loops keep looping while a counter != end(). So now consider this: #include <cstdlib> #include <iostream> #include <string> #include <vector> #include <algorithm> using namespace std; int main() { string myStr = "Mary"; string* myPtr = &myStr; vector<string> myVec2(myPtr, &myPtr[1]); copy( myVec2.begin(), myVec2.end(), ostream_iterator<string>(cout, " ")); return 0; } Is this code legal and well-defined? It is legal and well-defined to take the address of an array element past the end, as in &myAry[numStrs], so should it be legal and well-defined to pretend that myPtr is also an array?

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• Database Schema Versioning Strategies

  - by Jack Ryan

  I work on a project that uses a reasonably large database, the live version weighing in at somewhere around 60-80GB. The live database is the only real definitive source of our schema, and because of its size duplicating this database is too slow to be done often. This means we have ended up developing our database schema in a pretty ad hoc way, using sql compare to migrate changes from dev dbs to the live system, and only wiping our dev dbs every month or two. I am hoping to get some pointers on how to improve our database development work flow so that we have a little more control. Some things to think about: Currently nobody is really in charge of the database schema, all developers can change it if they need to, though generally these decisions are talked about before they are done. There are stored procedures, functions, and views in the database. These should probably be dumped to files so they can be reloaded on every build. Schema changes should probably be checked in as scripts. We have started to do this recently. However all our scripts must then be numbered (because there may be dependencies between them), and must be re runnable (because our build script currently runs them all in order). This makes them hard to read because they are full of conditionals that check whether tables or columns already exist. This is a step that is often forgotten by developers. Getting a new database should be quick and easy. This is currently a big problem, it takes several hours to get a copy of last nights backup and restore it onto a dev machine. Some mechanism needs to be in place to allow developers to update static data. We have tables that contain data that is never updated through the application, but does potentially need to be changed when we do a new release (often this drives dropdowns). The whole thing needs to be runnable as part of a build script. Are there any tools that can be used to help to do this? Eventually I would like to be at a point where a new DB can be built from scratch without copying any data from the live system. I don't mind writing some scripts to glue all the steps together but each part should be easily editable so that we continue to use it rather than make changes directly on DBs.

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• Add console.profile statements to JavaScript/jQuery code on the fly.

  - by novogeek

  Hi folks, We have a thick client app using jQuery heavily and want to profile the performance of the code using firebug's console.profile API. The problem is, I don't want to change the code to write the profile statements. Take this example: var search=function(){ this.init=function(){ console.log('init'); } this.ajax=function(){ console.log('ajax'); //make ajax call using $.ajax and do some DOM manipulations here.. } this.cache=function(){ console.log('cache'); } } var instance=new search(); instance.ajax(); I want to profile my instance.ajax method, but I dont want to add profile statements in the code, as that makes it difficult to maintain the code. I'm trying to override the methods using closures, like this: http://www.novogeek.com/post/2010/02/27/Overriding-jQueryJavaScript-functions-using-closures.aspx but am not very sure how I can achieve. Any pointers on this? I think this would help many big projects to profile the code easily without a big change in code. Here is the idea. Just run the below code in firebug console, to know what I'm trying to achieve. var search=function(){ this.init=function(){ console.log('init'); } this.ajax=function(){ console.log('ajax'); //make ajax call using $.ajax and do some DOM manipulations here.. } this.cache=function(){ console.log('cache'); } } var instance=new search(); $.each(instance, function(functionName, functionBody){ (function(){ var dup=functionBody functionBody=function(){ console.log('modifying the old function: ',functionName); console.profile(functionName); dup.apply(this,arguments); console.profileEnd(functionName); } })(); console.log(functionName, '::', functionBody()); }); Now what I need is, if i say instance.ajax(), I want the new ajax() method to be called, along with the console.profile statements. Hope I'm clear with the requirement. Please improvise the above code. Regards, Krishna, http://www.novogeek.com

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• PHP Changing Class Variables Outside of Class

  - by Jamie Bicknell

  Apologies for the wording on this question, I'm having difficulties explaining what I'm after, but hopefully it makes sense. Let's say I have a class, and I wish to pass a variable through one of it's methods, then I have another method which outputs this variable. That's all fine, but what I'm after is that if I update the variable which was originally passed, and do this outside the class methods, it should be reflected in the class. I've created a very basic example: class Test { private $var = ''; function setVar($input) { $this->var = $input; } function getVar() { echo 'Var = ' . $this->var . '<br />'; } } If I run $test = new Test(); $string = 'Howdy'; $test->setVar($string); $test->getVar(); I get Var = Howdy However, this is the flow I would like: $test = new Test(); $test->setVar($string); $string = 'Hello'; $test->getVar(); $string = 'Goodbye'; $test->getVar(); Expected output to be Var = Hello Var = Goodbye I don't know what the correct naming of this would be, and I've tried using references to the original variable but no luck. I've come across this in the past, with the PDO prepared statements, see Example #2 $stmt = $dbh->prepare("INSERT INTO REGISTRY (name, value) VALUES (?, ?)"); $stmt->bindParam(1, $name); $stmt->bindParam(2, $value); // insert one row $name = 'one'; $value = 1; $stmt->execute(); // insert another row with different values $name = 'two'; $value = 2; $stmt->execute(); I know I can change the variable to public and do the following, but it isn't quite the same as how the PDO class handles it, and I'm really looking to mimic that behaviour. $test = new Test(); $test->setVar($string); $test->var = 'Hello'; $test->getVar(); $test->var = 'Goodbye'; $test->getVar(); Any help, ideas, pointers, or advice would be greatly appreciated, thanks.

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• Preg_replace regex, newlines, connection resets

  - by bob_the_destroyer

  I have mixed html, custom code, and regular text I need to examine and change frequently on several, long wiki pages. I'm working with a proprietary wiki-like application and have no control over how the application functions or validates user input. The layout of pages that users add must follow a very specific standard layout and always include very specific text in only certain places - a standard which frequently changes. If users add pages that are so far out of the standard, they will be deleted. The fact that all this is obviously a complete waste of time when alternative platforms to do exactly what's needed here exist is already understood. I've built a PHP based API to automate this post-validation and frequent restandardization process for me. I've been able set up regex patterns to handle all this mixed text, and they all work fine for handling single lines. The problem I have is this: Poorly formed regex against long text with line breaks can lead to unexpected results, such as connection resets. I have no access to server-side logs to troubleshoot. How do I overcome this? This is just one example of what I currently have: {column} and {section} tags I'm searching for below can have any number of attributes, and wrap any text. {section} may or may not exist and may or may not be one or more lines under {column}, but it has to be wrapped inside {column}. {column} itself may or may not exist, and if it doesn't, I don't care. I want to grab the inner section contents and wrap it in an html div tag. I can't recall the exact pattern I'm using offhand at the moment, but it's close enough... $pattern = "/\{column:id=summary([|]?([a-zA-Z0-9-_ ]+[:][a-zA-Z0-9-_ ]+[ ]?))\}(.*)({section([|]([a-zA-Z0-9-_ ]+[:][a-zA-Z0-9-_ ]+[ ]?))\}(.*)\{section\}(.*))?{column\}/s"; $replacement = "{html}<div id='summary'$7</div{html}"; $text = preg_replace($pattern, $replacement, $subject); Handling the {column} and {section} attributes and passing only valid HTML parameters to the new html div or a subtext of it is itself a challenge, but my main focus above right now is getting that (.*) value within {section} above without causing a connection reset. Any pointers?

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• JPA - Can I create an Entity class, using an @DiscriminatorValue, that doesn't have its own table?

  - by DaveyDaveDave

  Hi - this is potentially a bit complex, so I'll do my best to describe my situation - it's also my first post here, so please forgive formatting mistakes, etc! I'm using JPA with joined inheritance and a database structure that looks like: ACTION --------- ACTION_ID ACTION_MAPPING_ID ACTION_TYPE DELIVERY_CHANNEL_ACTION -------------------------- ACTION_ID CHANNEL_ID OVERRIDE_ADDRESS_ACTION -------------------------- ACTION_ID (various fields specific to this action type) So, in plain English, I have multiple different types of action, all share an ACTION_MAPPING, which is referenced from the 'parent' ACTION table. DELIVERY_CHANNEL_ACTION and OVERRIDE_ADDRESS_ACTION both have extra, supplementary data of their own, and are mapped to ACTION with a FK. Real-world, I also have a 'suppress' action, but this doesn't have any supplementary data of its own, so it doesn't have a corresponding table - all it needs is an ACTION_MAPPING, which is stored in the ACTION table. Hopefully you're with me so far... I'm creating a new project from scratch, so am pretty flexible in what I can do, but obviously would like to get it right from the outset! My current implementation, which works, has three entities loosely defined as follows: @Entity @Table(name="ACTION") @Inheritance(strategy=InheritanceType.JOINED) @DiscriminatorValue("SUPPRESS") public class Action @Entity @Table(name="DELIVERY_CHANNEL_ACTION") @DiscriminatorValue("DELIVERY_CHANNEL") public class DeliveryChannelAction extends Action @Entity @Table(name="OVERRIDE_ADDRESS_ACTION") @DiscriminatorValue("OVERRIDE_ADDRESS") public class OverrideAddressAction extends Action That is - I have a concrete base class, Action, with a Joined inheritance strategy. DeliveryChannelAction and OverrideAddressAction both extend Action. What feels wrong here though, is that my Action class is the base class for these two actions, but also forms the concrete implementation for the suppress action. For the time being this works, but at some point more actions are likely to be added, and there's every chance that some of them will, like SUPPRESS, have no supplementary data, which will start to get difficult! So... what I would like to do, in the object model world, is to have Action be abstract, and create a SuppressAction class, which is empty apart from having a @DiscriminatorValue("SUPPRESS"). I've tried doing exactly what is described above, so, changing Action to: @Entity @Table(name="ACTION") @Inheritance(strategy=InheritanceType.JOINED) public abstract class Action and creating: @DiscriminatorValue("SUPPRESS") public class SuppressAction extends Action but no luck - it seems to work fine for DeliveryChannelAction and OverrideAddressAction, but when I try to create a SuppressAction and persist it, I get: java.lang.IllegalArgumentException: Object: com.mypackage.SuppressAction[actionId=null] is not a known entity type. at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.registerNewObjectForPersist(UnitOfWorkImpl.java:4147) at org.eclipse.persistence.internal.jpa.EntityManagerImpl.persist(EntityManagerImpl.java:368) at com.mypackage.test.util.EntityTestUtil.createSuppressAction(EntityTestUtil.java:672) at com.mypackage.entities.ActionTest.testCRUDAction(ActionTest.java:27) which I assume is down to the fact that SuppressAction isn't registered as an entity, but I don't know how I can do that, given that it doesn't have an associated table. Any pointers, either complete answers or hints for things to Google (I'm out of ideas!), most welcome :) EDIT: to correct my stacktrace.

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• Is it possible to create a C++ factory system that can create an instance of any "registered" object

  - by chrensli

  Hello, I've spent my entire day researching this topic, so it is with some scattered knowledge on the topic that i come to you with this inquiry. Please allow me to describe what I am attempting to accomplish, and maybe you can either suggest a solution to the immediate question, or another way to tackle the problem entirely. I am trying to mimic something related to how XAML files work in WPF, where you are essentially instantiating an object tree from an XML definition. If this is incorrect, please inform. This issue is otherwise unrelated to WPF, C#, or anything managed - I solely mention it because it is a similar concept.. So, I've created an XML parser class already, and generated a node tree based on ObjectNode objects. ObjectNode objects hold a string value called type, and they have an std::vector of child ObjectNode objects. The next step is to instantiate a tree of objects based on the data in the ObjectNode tree. This intermediate ObjectNode tree is needed because the same ObjectNode tree might be instantiated multiple times or delayed as needed. The tree of objects that is being created is such that the nodes in the tree are descendants of a common base class, which for now we can refer to as MyBase. Leaf nodes can be of any type, not necessarily derived from MyBase. To make this more challenging, I will not know what types of MyBase derived objects might be involved, so I need to allow for new types to be registered with the factory. I am aware of boost's factory. Their docs have an interesting little design paragraph on this page: o We may want a factory that takes some arguments that are forwarded to the constructor, o we will probably want to use smart pointers, o we may want several member functions to create different kinds of objects, o we might not necessarily need a polymorphic base class for the objects, o as we will see, we do not need a factory base class at all, o we might want to just call the constructor - without #new# to create an object on the stack, and o finally we might want to use customized memory management. I might not be understanding this all correctly, but that seems to state that what I'm trying to do can be accomplished with boost's factory. But all the examples I've located, seem to describe factories where all objects are derived from a base type. Any guidance on this would be greatly appreciated. Thanks for your time!

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• Inlining an array of non-default constructible objects in a C++ class

  - by porgarmingduod

  C++ doesn't allow a class containing an array of items that are not default constructible: class Gordian { public: int member; Gordian(int must_have_variable) : member(must_have_variable) {} }; class Knot { Gordian* pointer_array[8]; // Sure, this works. Gordian inlined_array[8]; // Won't compile. Can't be initialized. }; As even beginner C++ users know, the language guarantees that all members are initialized when constructing a class. And it doesn't trust the user to initialize everything in the constructor - one has to provide valid arguments to the constructors of all members before the body of the constructor even starts. Generally, that's a great idea as far as I'm concerned, but I've come across a situation where it would be a lot easier if I could actually have an array of non-default constructible objects. The obvious solution: Have an array of pointers to the objects. This is not optimal in my case, as I am using shared memory. It would force me to do extra allocation from an already contended resource (that is, the shared memory). The entire reason I want to have the array inlined in the object is to reduce the number of allocations. This is a situation where I would be willing to use a hack, even an ugly one, provided it works. One possible hack I am thinking about would be: class Knot { public: struct dummy { char padding[sizeof(Gordian)]; }; dummy inlined_array[8]; Gordian* get(int index) { return reinterpret_cast<Gordian*>(&inlined_array[index]); } Knot() { for (int x = 0; x != 8; x++) { new (get(x)) Gordian(x*x); } } }; Sure, it compiles, but I'm not exactly an experienced C++ programmer. That is, I couldn't possibly trust my hacks less. So, the questions: 1) Does the hack I came up with seem workable? What are the issues? (I'm mainly concerned with C++0x on newer versions of GCC). 2) Is there a better way to inline an array of non-default constructible objects in a class?

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• Correct use of a "for...in" loop in javascript?

  - by jnkrois

  Hello everybody, before I ask my question I wanted to let everybody know that I appreciate the fact that there's always somebody out there willing to help, and on my end I'll try to give back to the community as much as I can. Thanks Now, I would like to get some pointers as to how to properly take advantage of the "for...in" loop in JavaScript, I already did some research and tried a couple things but it is still not clear to me how to properly use it. Let's say I have a random number of "select" tags in an HTML form, and I don't require the user to select an option for all of them, they can leave some untouched if they want. However I need to know if they selected none or at least one. The way I'm trying to find out if the user selected any of them is by using the "for...in" loop. For example: var allSelected = $("select option:selected"); var totalSelected = $("select option:selected").length; The first variable produces an array of all the selected options. The second variable tells me how many selected options I have in the form (select tags could be more than one and it changes every time). Now, in order to see if any has been selected I loop through each element (selected option), and retrieve the "value" attribute. The default "option" tag has a value="0", so if any selected option returns a value greater than 0, I know at least one option has been selected, however it does not have to be in order, this is my loop so far: for(var i = 0; i < totalSelected; i++){ var eachOption = $(allSelected[i]).val(); var defaultValue = 0; if(eachOption == defaultValue){ ...redirect to another page }else if(eachOption > defaultValue){ ... I display an alert } } My problem here is that as soon as the "if" matches a 0 value, it sends the user to the next page without testing the rest of the elements in the array, and the user could have selected the second or third options. What I really want to do is check all the elements in the array and then take the next action, in my mind this is how I could do it, but I'm not getting it right: var randomValue = 25; for(randomValue in allSelected){ var found = true; var notFound = false if(found){ display an alert }else{ redirect to next page } } This loop or the logic I'm using are flawed (I'm pretty sure), what I want to do is test all the elements in the array against a single variable and take the next action accordingly. I hope this makes some sense to you guys, any help would be appreciated. Thanks, JC

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• Problem intialising 2D array

  - by TeeJay

  Ok, so I have a 2D Array that is initialised with values from a file (format: x y z). My file reads in the values correctly but when adding the z value to the matrix/2DArray, I run into a segfault and I have no idea why. It is possibly incorrect use of pointers? I still don't quite have the hang of them yet. This is my intialiser, works fine, even intialises all "z" values to 0. int** make2DArray(int rows, int columns) { int** newArray; newArray = (int**)malloc(rows*sizeof(int*)); if (newArray == NULL) { printf("out of memory for newArray.\n"); } for (int i = 0; i < rows; i++) { newArray[i] = (int*)malloc(columns*sizeof(int)); if (newArray[i] == NULL) { printf("out of memory for newArray[%d].\n", i); } } //intialise all values to 0 for (int i = 0; i < rows; i++) { for (int j = 0; j < columns; j++) { newArray[i][j] = 0; } } return newArray; } This is how I call the initialiser (and problem function). int** map = make2DArray(rows, columns); fillMatrix(&map, mapFile); And this is the problem code. void fillMatrix(int*** inMatrix, FILE* inFile) { int x, y, z; char line[100]; while(fgets(line, sizeof(line), inFile) != NULL) { sscanf(line, "%d %d %d", &x, &y, &z); *inMatrix[x][y] = z; } } From what I can gather through the use of ddd, the problem comes when y gets to 47. The map file has a max "x" value of 47 and a max "y" value of 63, I'm pretty sure I haven't got the order mixed up, so I don't know why the program is segfault-ing? I'm sure it's some newbie mistake...

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• How to ensure structures are completly initialized (by name) in GCC?

  - by Steven Spark

  How do I ensure each and every field of my structures are initialized in GCC when using designated initializers? (I'm especially interested in function pointers.) (I'm using C not C++.) Here is an example: typedef struct { int a; int b; } foo_t; typedef struct { void (*Start)(void); void (*Stop)(void); } bar_t; foo_t fooo = { 5 }; foo_t food = { .b=4 }; bar_t baro = { NULL }; bar_t bard = { .Start = NULL }; -Wmissing-field-initializers does not help at all. It works for fooo only in GCC (mingw 4.7.3, 4.8.1), and clang does only marginally better (no warnings for food and bard). I'm sure there is a reason for not producing warnings for designated initializer (even when I explicitly ask for them) but I want/need them. I do not want to initialize structures based on order/position because that is more error prone (for example swapping Start and Stop won't even give any warning). And neither gcc nor clang will give any warning that I failed to explicitly initialize a field (when initializing by name). I also don't want to litter my code with if(x.y==NULL) lines for multiple reasons, one of which is I want compile time warnings and not runtime errors. At least splint will give me warnings on all 4 cases, but unfortunately I cannot use splint all the time (it chokes on some of the code (fails to parse some C99, GCC extensions)). Note: If I'm using a real function instead of NULL GCC will also show a warning for baro (but not bard). I searched google and stack overflow but only found related questions and have not found answer for this specific problem. The best match I have found is 'Ensure that all elements in a structure are initialized' Ensure that all elements in a structure are initialized Which asks pretty much the same question, but has no satisfying answer. Is there a better way dealing with this that I have not mentioned? (Maybe other code analysis tool? Preferably something (free) that can be integrated into Eclipse or Visual Studio...)

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• Re-order form fields on submit url

  - by user2521764

  I have a get form with several visible and hidden input fields. When the form is submitted, selected fileds with their values are appended to the url in the order they are placed in the form. Is there a way to re-order the parameters in the url using jQuery? Note that for the reasons of usability, I can not re-order the elements on the form itself. I know it beggs the question "why would I want to do it?", but the reason is that I will be hitting a static page, so the order of the parameters have to be exactly how they are in the static page url. For example, my form returns a url: http://someurl??names=comm&search=all&type=list while the static page has a url: http://someurl??search=all&type=list&names=comm A simplified form example is here: <form id="search_form" method="get" action="http://www.cbif.gc.ca/pls/pp/ppack.jump" > <h2>Choose which names you want to be displayed</h2> <select name="names"> <option value="comm">Common names</option> <option value="sci">Scientific names</option> </select> <h2>Choose how you want to view the results</h2> <input type="radio" name="search" value="all" id="complete" checked = "checked" /> <label for="complete" id="completeLabel">Complete list</label> <br/> <input type="radio" name="p_null" value="house" id="house" /> <label for="house" id="houseLabel">House plants only</label> <br/> <input type="radio" name="p_null" value="illust" id="illustrat" /> <label for="illustrat" id="illustratLabel">Plants with Illustrations</label> <br/> <input type="hidden" name="type" value="list" /> <input type="submit" value="Submit" /> </form> I can get form fields with values using $(#search_form).serializeArray() and massage the array like I want to, but I don't know how to set it back, i.e. modify the serialized values so that the submitted url has my order of parameters. I'm not even sure if this is the right way to go about it, so any pointers would be greatly appreciated.

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• showing content in profile box from another file

  - by fusion

  i'm stuck at this facebook application, not knowing how do i go ahead. for the canvas, the app works quite perfectly. i've two pages, quote.html and quote.php. in quote.html, quote.php [which gets the quotes from the database] is called through ajax which displays a quote randomly for 10 secs. however, for the wall tab/profile box, i can't seem to know where i'm going wrong. i created a page called 'profile_box.php', call quote.php for the quotes, setFBML. while this works on canvas [sans the timing], it doesn't display anything on the wall tab. <?php include 'quote.php'; $row = mysql_fetch_array($result, MYSQL_ASSOC); if ( !$row ) { echo "Empty"; } else{ $fb_box = "<p>" . h($row['cArabic']) . "</p>"; $fb_box .= "<p>" . h($row['cQuotes']) . "</p>"; $fb_box .= "<p>" . h($row['vAuthor']) . "</p>"; $fb_box .= "<p>" . h($row['vReference']) . "</p>"; } try{ $url="http://website/name/quote.html"; $facebook->api_client->fbml_refreshRefUrl($url); $fbml = "<fb:ref url='$url'/>"; if(isset($_REQUEST['fb_sig_page_id'])){ $page_id = $_REQUEST['fb_sig_page_id']; $profile_type = $_REQUEST['fb_sig_type']; $facebook->api_client->profile_setFBML($appapikey, $page_id, "$fbml", NULL, NULL, "$fb_box"); } else { $is_tab = isset($_REQUEST['fb_sig_in_profile_tab']); if( !$is_tab ) $user_id = $facebook->require_login(); $result = $facebook->api_client->profile_setFBML($appapikey, $user_id, "$fbml", NULL, NULL, "$fb_box"); } } catch(Exception $ex){ echo 'Caught exception: ', $ex->getMessage(), "\n"; } echo "<fb:add-section-button section=\"profile\" /><br />"; ?> can anyone please give any pointers?

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• best alternative to in-definition initialization of static class members? (for SVN keywords)

  - by Jeff

  I'm storing expanded SVN keyword literals for .cpp files in 'static char const *const' class members and want to store the .h descriptions as similarly as possible. In short, I need to guarantee single instantiation of a static member (presumably in a .cpp file) to an auto-generated non-integer literal living in a potentially shared .h file. Unfortunately the language makes no attempt to resolve multiple instantiations resulting from assignments made outside class definitions and explicitly forbids non-integer inits inside class definitions. My best attempt (using static-wrapping internal classes) is not too dirty, but I'd really like to do better. Does anyone have a way to template the wrapper below or have an altogether superior approach? // Foo.h: class with .h/.cpp SVN info stored and logged statically class Foo { static Logger const verLog; struct hInfoWrap; public: static hInfoWrap const hInfo; static char const *const cInfo; }; // Would like to eliminate this per-class boilerplate. struct Foo::hInfoWrap { hInfoWrapper() : text("$Id$") { } char const *const text; }; ... // Foo.cpp: static inits called here Foo::hInfoWrap const Foo::hInfo; char const *const Foo::cInfo = "$Id$"; Logger const Foo::verLog(Foo::cInfo, Foo::hInfo.text); ... // Helper.h: output on construction, with no subsequent activity or stored fields class Logger { Logger(char const *info1, char const *info2) { cout << info0 << endl << info1 << endl; } }; Is there a way to get around the static linkage address issue for templating the hInfoWrap class on string literals? Extern char pointers assigned outside class definitions are linguistically valid but fail in essentially the same manner as direct member initializations. I get why the language shirks the whole resolution issue, but it'd be very convenient if an inverted extern member qualifier were provided, where the definition code was visible in class definitions to any caller but only actually invoked at the point of a single special declaration elsewhere. Anyway, I digress. What's the best solution for the language we've got, template or otherwise? Thanks!

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• How can data not stored in a DB be accessed from any activity in Android?

  - by jul

  hi, I'm passing data to a ListView to display some restaurant names. Now when clicking on an item I'd like to start another activity to display more restaurant data. I'm not sure about how to do it. Shall I pass all the restaurant data in a bundle through the intent object? Or shall I just pass the restaurant id and get the data in the other activity? In that case, how can I access my restaurantList from the other activity? In any case, how can I get data from the restaurant I clicked on (the view only contains the name)? Any help, pointers welcome! Thanks Jul ListView lv= (ListView)findViewById(R.id.listview); lv.setAdapter( new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,restaurantList.getRestaurantNames())); lv.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> parent, View view, int position, long id) { Intent i = new Intent(Atable.this, RestaurantEdit.class); Bundle b = new Bundle(); //b.putInt("id", ? ); startActivityForResult(i, ACTIVITY_EDIT); } }); RestaurantList.java package org.digitalfarm.atable; import java.util.ArrayList; import java.util.List; public class RestaurantList { private List<Restaurant> restaurants = new ArrayList<Restaurant>(); public List<Restaurant> getRestaurants() { return this.restaurants; } public void setRestaurants(List<Restaurant> restaurants) { this.restaurants = restaurants; } public List<String> getRestaurantNames() { List<String> restaurantNames = new ArrayList<String>(); for (int i=0; i<this.restaurants.size(); i++) { restaurantNames.add(this.restaurants.get(i).getName()); } return restaurantNames; } } Restaurant.java package org.digitalfarm.atable; public class Restaurant { private int id; private String name; private float latitude; private float longitude; public int getId() { return this.id; } public void setId(int id) { this.id = id; } public String getName() { return this.name; } public void setName(String name) { this.name = name; } public float getLatitude() { return this.latitude; } public void setLatitude(float latitude) { this.latitude = latitude; } public float getLongitude() { return this.longitude; } public void setLongitude(float longitude) { this.longitude = longitude; } }

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• iPhone OpenGL scrolling background jumps when texture is drawn for first time

  - by Magnum39

  I have been fighting a problem for a while now and would appreciate any help anybody could give. I have a sprite that moves within a landscape. The sprite remains in the center of the screen and the background moves to simulate that the sprite is moving within the landscape. I have split the landscape into sections so that I only draw the sections of the landscape that I need (are on screen). The Problem: As a new texture section of the screen appears on the screen (is drawn for the first time) the movement jumps. Almost like a frame is missed. I have done some timing experiments and I do not thinks a frame is missed. My processing is well below the 30fps that I have the animation set to. It only happens the first time the texture section is drawn. Is there something extra that is done the first time a texture is drawn? Here is the code: - (void) render{ // Sets up an array of values to use as the sprite vertices. const GLfloat sVerts[] = { -1.6f, -1.6f, 1.6f, -1.6f, -1.6f, 1.6f, 1.6f, 1.6f, }; static const GLfloat sTexCoords[] = { 0.0, 1.0, 1.0, 1.0, 0.0, 0.0, 1.0, 0.0 }; glDisableClientState(GL_COLOR_ARRAY); glEnableClientState(GL_VERTEX_ARRAY); glEnableClientState(GL_TEXTURE_COORD_ARRAY); // Setup opengl to draw the object in correct orientation, size, position, etc glLoadIdentity(); // Enable use of the texture glEnable(GL_TEXTURE_2D); glVertexPointer(2, GL_FLOAT, 0, sVerts); glTexCoordPointer(2, GL_FLOAT, 0, sTexCoords); // draw the texture // set the position of the first tile float xOffset = -4.8; float yOffset = 4.8; int i; int y; int currentTexture = textureA; for(i=0; i<2; i++) { for(y=0; y<2; y++) { // test for the texture tile on the screen if not on screen then do not draw float localX = xOffset+(3.21*y); float localY = yOffset-(3.21*i); float xDiff = monkeyX - localX; float yDiff = monkeyY - localY; if(((xDiff < 3.2) && (xDiff > -3.2)) && ((yDiff <2.7) && (yDiff > -2.7))) { // bind the texture and set the vertex data pointers glBindTexture(GL_TEXTURE_2D, spriteTexture[currentTexture]); // move to draw position for the texture glLoadIdentity(); glTranslatef((localX+self.positionX), (localY+self.positionY), 0.0); //draw the texture glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); } currentTexture++; } } }

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• safe dereferencing and deletion

  - by serejko

  Hi, I'm relatively new to C++ and OOP in general and currently trying to make such a class that allows to dereference and delete a dead or invalid pointer without any care of having undefined behavior or program fault in result, and I want to ask you is it a good idea and is there something similar which is already implemented by someone else? or maybe I'm doing something completely wrong? I've just started making it and here is the code I currently have: template<class T> class SafeDeref { public: T& operator *() { hash_set<T*>::iterator it = theStore.find(reinterpret_cast<T*>(ptr)); if (it != theStore.end()) return *this; return theDefaultObject; } T* operator ->() { hash_set<T*>::iterator it = theStore.find(reinterpret_cast<T*>(ptr)); if (it != theStore.end()) return this; return &theDefaultObject; } void* operator new(size_t size) { void* ptr = malloc(size * sizeof(T)); if (ptr != 0) theStore.insert(reinterpret_cast<T*>(ptr)); return ptr; } void operator delete(void* ptr) { hash_set<T*>::iterator it = theStore.find(reinterpret_cast<T*>(ptr)); if (it != theStore.end()) { theStore.erase(it); free(ptr); } } protected: static bool isInStore(T* ptr) { return theStore.find(ptr) != theStore.end(); } private: static T theDefaultObject; static hash_set<T*> theStore; }; The idea is that each class with the safe dereference should be inherited from it like this: class Foo : public SafeDeref<Foo> { void doSomething(); }; So... Any advices? Thanks in advance. P.S. If you're wondering why I need this... well, I'm creating a set of native functions for some scripting environment, and all of them use pointers to internally allocated objects as handles to them and they're able to delete them as well (input data can be wrong), so this is kinda protection from damaging host application's memory And I really sorry for my bad English

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