functionality - Page 288

[C#][Design] Appropriate programming design questions.

- by Edward

I have a few questions on good programming design. I'm going to first describe the project I'm building so you are better equipped to help me out. I am coding a Remote Assistance Tool similar to TeamViewer, Microsoft Remote Desktop, CrossLoop. It will incorporate concepts like UDP networking (using Lidgren networking library), NAT traversal (since many computers are invisible behind routers nowadays), Mirror Drivers (using DFMirage's Mirror Driver (http://www.demoforge.com/dfmirage.htm) for realtime screen grabbing on the remote computer). That being said, this program has a concept of being a client-server architecture, but I made only one program with both the functionality of client and server. That way, when the user runs my program, they can switch between giving assistance and receiving assistance without having to download a separate client or server module. I have a Windows Form that allows the user to choose between giving assistance and receiving assistance. I have another Windows Form for a file explorer module. I have another Windows Form for a chat module. I have another Windows Form form for a registry editor module. I have another Windows Form for the live control module. So I've got a Form for each module, which raises the first question: 1. Should I process module-specific commands inside the code of the respective Windows Form? Meaning, let's say I get a command with some data that enumerates the remote user's files for a specific directory. Obviously, I would have to update this on the File Explorer Windows Form and add the entries to the ListView. Should I be processing this code inside the Windows Form though? Or should I be handling this in another class (although I have to eventually pass the data to the Form to draw, of course). Or is it like a hybrid in which I process most of the data in another class and pass the final result to the Form to draw? So I've got like 5-6 forms, one for each module. The user starts up my program, enters the remote machine's ID (not IP, ID, because we are registering with an intermediary server to enable NAT traversal), their password, and connects. Now let's suppose the connection is successful. Then the user is presented with a form with all the different modules. So he can open up a File Explorer, or he can mess with the Registry Editor, or he can choose to Chat with his buddy. So now the program is sort of idle, just waiting for the user to do something. If the user opens up Live Control, then the program will be spending most of it's time receiving packets from the remote machine and drawing them to the form to provide a 'live' view. 2. Second design question. A spin off question #1. How would I pass module-specific commands to their respective Windows Forms? What I mean is, I have a class like "NetworkHandler.cs" that checks for messages from the remote machine. NetworkHandler.cs is a static class globally accessible. So let's say I get a command that enumerates the remote user's files for a specific directory. How would I "give" that command to the File Explorer Form. I was thinking of making an OnCommandReceivedEvent inside NetworkHandler, and having each form register to that event. When the NetworkHandler received a command, it would raise the event, all forms would check it to see if it was relevant, and the appropriate form would take action. Is this an appropriate/the best solution available? 3. The networking library I'm using, Lidgren, provides two options for checking networking messages. One can either poll ReadMessage() to return null or a message, or one can use an AutoResetEvent OnMessageReceived (I'm guessing this is like an event). Which one is more appropriate?

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Advice on Factory Method

- by heath

Using php 5.2, I'm trying to use a factory to return a service to the controller. My request uri would be of the format www.mydomain.com/service/method/param1/param2/etc. My controller would then call a service factory using the token sent in the uri. From what I've seen, there are two main routes I could go with my factory. Single method: class ServiceFactory { public static function getInstance($token) { switch($token) { case 'location': return new StaticPageTemplateService('location'); break; case 'product': return new DynamicPageTemplateService('product'); break; case 'user' return new UserService(); break; default: return new StaticPageTemplateService($token); } } } or multiple methods: class ServiceFactory { public static function getLocationService() { return new StaticPageTemplateService('location'); } public static function getProductService() { return new DynamicPageTemplateService('product'); } public static function getUserService() { return new UserService(); } public static function getDefaultService($token) { return new StaticPageTemplateService($token); } } So, given this, I will have a handful of generic services in which I will pass that token (for example, StaticPageTemplateService and DynamicPageTemplateService) that will probably implement another factory method just like this to grab templates, domain objects, etc. And some that will be specific services (for example, UserService) which will be 1:1 to that token and not reused. So, this seems to be an ok approach (please give suggestions if it is not) for a small amount of services. But what about when, over time and my site grows, I end up with 100s of possibilities. This no longer seems like a good approach. Am I just way off to begin with or is there another design pattern that would be a better fit? Thanks. UPDATE: @JSprang - the token is actually sent in the uri like mydomain.com/location would want a service specific to loction and mydomain.com/news would want a service specific to news. Now, for a lot of these, the service will be generic. For instance, a lot of pages will call a StaticTemplatePageService in which the token is passed in to the service. That service in turn will grab the "location" template or "links" template and just spit it back out. Some will need DynamicTemplatePageService in which the token gets passed in, like "news" and that service will grab a NewsDomainObject, determine how to present it and spit that back out. Others, like "user" will be specific to a UserService in which it will have methods like Login, Logout, etc. So basically, the token will be used to determine which service is needed AND if it is generic service, that token will be passed to that service. Maybe token isn't the correct terminology but I hope you get the purpose. I wanted to use the factory so I can easily swap out which Service I need in case my needs change. I just worry that after the site grows larger (both pages and functionality) that the factory will become rather bloated. But I'm starting to feel like I just can't get away from storing the mappings in an array (like Stephen's solution). That just doesn't feel OOP to me and I was hoping to find something more elegant.

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What is there so useful in the Decorator Pattern? My example doesn't work

- by Green

The book says: The decorator pattern can be used to extend (decorate) the functionality of a certain object I have a rabbit animal. And I want my rabbit to have, for example, reptile skin. Just want to decorate a common rabbit with reptile skin. I have the code. First I have abstract class Animal with everythig that is common to any animal: abstract class Animal { abstract public function setSleep($hours); abstract public function setEat($food); abstract public function getSkinType(); /* and more methods which for sure will be implemented in any concrete animal */ } I create class for my rabbit: class Rabbit extends Animal { private $rest; private $stomach; private $skinType = "hair"; public function setSleep($hours) { $this->rest = $hours; } public function setFood($food) { $this->stomach = $food; } public function getSkinType() { return $this->$skinType; } } Up to now everything is OK. Then I create abstract AnimalDecorator class which extends Animal: abstract class AnimalDecorator extends Animal { protected $animal; public function __construct(Animal $animal) { $this->animal = $animal; } } And here the problem comes. Pay attention that AnimalDecorator also gets all the abstract methods from the Animal class (in this example just two but in real can have many more). Then I create concrete ReptileSkinDecorator class which extends AnimalDecorator. It also has those the same two abstract methods from Animal: class ReptileSkinDecorator extends AnimalDecorator { public function getSkinColor() { $skin = $this->animal->getSkinType(); $skin = "reptile"; return $skin; } } And finaly I want to decorate my rabbit with reptile skin: $reptileSkinRabbit = ReptileSkinDecorator(new Rabbit()); But I can't do this because I have two abstract methods in ReptileSkinDecorator class. They are: abstract public function setSleep($hours); abstract public function setEat($food); So, instead of just re-decorating only skin I also have to re-decorate setSleep() and setEat(); methods. But I don't need to. In all the book examples there is always ONLY ONE abstract method in Animal class. And of course it works then. But here I just made very simple real life example and tried to use the Decorator pattern and it doesn't work without implementing those abstract methods in ReptileSkinDecorator class. It means that if I want to use my example I have to create a brand new rabbit and implement for it its own setSleep() and setEat() methods. OK, let it be. But then this brand new rabbit has the instance of commont Rabbit I passed to ReptileSkinDecorator: $reptileSkinRabbit = ReptileSkinDecorator(new Rabbit()); I have one common rabbit instance with its own methods in the reptileSkinRabbit instance which in its turn has its own reptileSkinRabbit methods. I have rabbit in rabbit. But I think I don't have to have such possibility. I don't understand the Decarator pattern right way. Kindly ask you to point on any mistakes in my example, in my understanding of this pattern. Thank you.

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Best way to add an extra (nested) form in the middle of a tabbed form

- by Scharrels

I've got a web application, consisting mainly of a big form with information. The form is split into multiple tabs, to make it more readable for the user: <form> <div id="tabs"> <ul> <li><a href="#tab1">Tab1</a></li> <li><a href="#tab2">Tab2</a></li> </ul> <div id="tab1">A big table with a lot of input rows</div> <div id="tab2">A big table with a lot of input rows</div> </div> </form> The form is dynamically extended (extra rows are added to the tables). Every 10 seconds the form is serialized and synchronized with the server. I now want to add an interactive form on one of the tabs: when a user enters a name in a field, this information is sent to the server and an id associated with that name is returned. This id is used as an identifier for some dynamically added form fields. A quick sketchup of such a page would look like this: <form action="bigform.php"> <div id="tabs"> <ul> <li><a href="#tab1">Tab1</a></li> <li><a href="#tab2">Tab2</a></li> </ul> <div id="tab1">A big table with a lot of input rows</div> <div id="tab2"> <div class="associatedinfo"> <p>Information for Joe</p> <ul> <li><input name="associated[26][]" /></li> <li><input name="associated[26][]" /></li> </ul> </div> <div class="associatedinfo"> <p>Information for Jill</p> <ul> <li><input name="associated[12][]" /></li> <li><input name="associated[12][]" /></li> </ul> </div> <div id="newperson"> <form action="newform.php"> <p>Add another person:</p> <input name="extra" /><input type="submit" value="Add" /> </form> </div> </div> </div> </form> The above will not work: nested forms are not allowed in HTML. However, I really need to display the form on that tab: it's part of the functionality of that page. I also want the behaviour of a separate form: when the user hits return in the form field, the "Add" submit button is pressed and a submit action is triggered on the partial form. What is the best way to solve this problem?

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Data munging and data import scripting

- by morpheous

I need to write some scripts to carry out some tasks on my server (running Ubuntu server 8.04 TLS). The tasks are to be run periodically, so I will be running the scripts as cron jobs. I have divided the tasks into "group A" and "group B" - because (in my mind at least), they are a bit different. Task Group A import data from a file and possibly reformat it - by reformatting, I mean doing things like santizing the data, possibly normalizing it and or running calculations on 'columns' of the data Import the munged data into a database. For now, I am mostly using mySQL for the vast majority of imports - although some files will be imported into a sqlLite database. Note: The files will be mostly text files, although some of the files are in a binary format (my own proprietary format, written by a C++ application I developed). Task Group B Extract data from the database Perform calculations on the data and either insert or update tables in the database. My coding experience is is primarily as a C/C++ developer, although I have been using PHP as well for the last 2 years or so. I am from a windows background so I am still finding my feet in the linux environment. My question is this - I need to write scripts to perform the tasks I described above. Although I suppose I could write a few C++ applications to be used in the shell scripts, I think it may be better to write them in a scripting language (maybe this is a flawed assumption?). My thinking is that it would be easier to modify thins in a script - no need to rebuild etc for changes to functionality. Additionally, C++ data munging in C++ tends to involve more lines of code than "natural" scripting languages such as Perl, Python etc. Assuming that the majority of people on here agree that scripting is the way to go, herein lies my dilema. Which scripting language to use to perform the tasks above (giving my background). My gut instinct tells me that Perl (shudder) would be the most obvious choice for performing all of the above tasks. BUT (and that is a big BUT). The mere mention of Perl makes my toes curl, as I had a very, very bag experience with it a while back. The syntax seems quite unnatural to me - despite how many times I have tried to learn it - so if possible, I would really like to give it a miss. PHP (which I already know), also am not sure is a good candidate for scripting on the CLI (I have not seen many examples on how to do this etc - so I may be wrong). The last thing I must mention is that IF I have to learn a new language in order to do this, I cannot afford (time constraint) to spend more than a day, in learning the key commands/features required in order to do this (I can always learn the details of the language later, once I have actually deployed the scripts). So, which scripting language would you recommend (PHP, Python, Perl, [insert your favorite here]) - and most importantly WHY?. Or, should I just stick to writing little C++ applications that I call in a shell script?. Lastly, if you have suggested a scripting language, can you please show with a FEW lines (Perl mongers - I'm looking in your direction [nothing to cryptic!] ;) ) how I can use the language you suggested to do what I want to do. Hopefully, the lines you present will convince me that it can be done easily and elegantly in the language you suggested.

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Algorithm for dragging objects on a fixed grid

- by FlyingStreudel

Hello, I am working on a program for the mapping and playing of the popular tabletop game D&D :D Right now I am working on getting the basic functionality like dragging UI elements around, snapping to the grid and checking for collisions. Right now every object when released from the mouse immediately snaps to the nearest grid point. This causes an issue when something like a player object snaps to a grid point that has a wall -or other- adjacent. So essentially when the player is dropped they wind up with some of the wall covering them. This is fine and working as intended, however the problem is that now my collision detection is tripped whenever you try to move this player because its sitting underneath a wall and because of this you cant drag the player anymore. Here is the relevant code: void UIObj_MouseMove(object sender, MouseEventArgs e) { blocked = false; if (dragging) { foreach (UIElement o in ((Floor)Parent).Children) { if (o.GetType() != GetType() && o.GetType().BaseType == typeof(UIObj) && Math.Sqrt(Math.Pow(((UIObj)o).cX - cX, 2) + Math.Pow(((UIObj)o).cY - cY, 2)) < Math.Max(r.Height + ((UIObj)o).r.Height, r.Width + ((UIObj)o).r.Width)) { double Y = e.GetPosition((Floor)Parent).Y; double X = e.GetPosition((Floor)Parent).X; Geometry newRect = new RectangleGeometry(new Rect(Margin.Left + (X - prevX), Margin.Top + (Y - prevY), Margin.Right + (X - prevX), Margin.Bottom + (Y - prevY))); GeometryHitTestParameters ghtp = new GeometryHitTestParameters(newRect); VisualTreeHelper.HitTest(o, null, new HitTestResultCallback(MyHitTestResultCallback), ghtp); } } if (!blocked) { Margin = new Thickness(Margin.Left + (e.GetPosition((Floor)Parent).X - prevX), Margin.Top + (e.GetPosition((Floor)Parent).Y - prevY), Margin.Right + (e.GetPosition((Floor)Parent).X - prevX), Margin.Bottom + (e.GetPosition((Floor)Parent).Y - prevY)); InvalidateVisual(); } prevX = e.GetPosition((Floor)Parent).X; prevY = e.GetPosition((Floor)Parent).Y; cX = Margin.Left + r.Width / 2; cY = Margin.Top + r.Height / 2; } } internal virtual void SnapToGrid() { double xPos = Margin.Left; double yPos = Margin.Top; double xMarg = xPos % ((Floor)Parent).cellDim; double yMarg = yPos % ((Floor)Parent).cellDim; if (xMarg < ((Floor)Parent).cellDim / 2) { if (yMarg < ((Floor)Parent).cellDim / 2) { Margin = new Thickness(xPos - xMarg, yPos - yMarg, xPos - xMarg + r.Width, yPos - yMarg + r.Height); } else { Margin = new Thickness(xPos - xMarg, yPos - yMarg + ((Floor)Parent).cellDim, xPos - xMarg + r.Width, yPos - yMarg + ((Floor)Parent).cellDim + r.Height); } } else { if (yMarg < ((Floor)Parent).cellDim / 2) { Margin = new Thickness(xPos - xMarg + ((Floor)Parent).cellDim, yPos - yMarg, xPos - xMarg + ((Floor)Parent).cellDim + r.Width, yPos - yMarg + r.Height); } else { Margin = new Thickness(xPos - xMarg + ((Floor)Parent).cellDim, yPos - yMarg + ((Floor)Parent).cellDim, xPos - xMarg + ((Floor)Parent).cellDim + r.Width, yPos - yMarg + ((Floor)Parent).cellDim + r.Height); } } } Essentially I am looking for a simple way to modify the existing code to allow the movement of a UI element that has another one sitting on top of it. Thanks!

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Custom Online Backup Solution Advice

- by Martín Marconcini

I have to implement a way so our customers can backup their SQL 2000/5/8 databasase online. The application they use is a C#/.NET35 Winforms application that connects to a SQL Server (can be 2000/2005/2008, sometimes express editions). The SQL Server is on the same LAN. Our application has a very specific UI and we must code each form following those guidelines. There’s lots of GDI+ to give it the look and feel we want. For that reason, using a 3rd party application is not a very good idea. We need to charge the customer on a monthly/annual basis for the service. Preferably, the customer doesn’t need to care about bandwidth and storage space. It must be transparent. Given the above reqs., my first thoughts are: Solution 1: Code some sort of FTP basic functionality with behind the scenes SQL Backup mechanism, then hire a Hosting service and compress-transfer the .BAK to the Hosting. Maintain a series of Folders (for each customer). They won’t see what’s happening. They will just see a list of their files and a big “Backup now” button that will perform the SQL backup, compress it and upload it (and update the file list) ;) Pros: Not very complicated to implement, simple to use, fairly simple to configure (could have a dedicated ftp user/pass) Cons: Finding a “ftp” only hosting plan is not probably going to be easy, they usually come with a bunch of stuff. FTP is not always the best protocol. more? Solution 2: Similar to 1, but instead of FTP, find a cloud computing service like Amazon S3, Mosso or similar. Pros: Cloud Storage is fast, reliable, etc. It’s kind of easy to implement (specially if there are APIs like AWS or Mosso). Cons: I have been unable to come up with a service optimized for resellers where I can give multiple sub-accounts (one for each customer). Billing is going to be a nightmare cuz these services bill per/GB and with One account it’s impossible to differentiate each customer. Solution 3: Similar to 2, but letting the user create their own account on Amazon S3 (for example). Pros: You forget about billing and such. Cons: A mess for the customer who has to open the Amazon (or whatever) account, will be charged for that and not from you. You can’t really charge the customer (since you’re just not doing anything). Solution 4: Use one of the many backup online solutions that use the tech in cloud storage. Pros: many of these include SQL Server backup, and a lot of features that we’d have to implement. Plus web access and stuff like that will come included. Cons: Still have the billing problem described in number 2. Little of these companies (if any) offers “reseller” accounts. You have to eventually use their software (some offer certain branding). Any better approach? Summary: You have a software (.NET Winapp). You want your users to be able to backup their SQL Server databases online (and be able to retrieve the backups if needed). You ideally would like to charge the customer for this service (i.e. XX € a year).

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Defend PHP; convince me it isn't horrible

- by Jason L

I made a tongue-in-cheek comment in another question thread calling PHP a terrible language and it got down-voted like crazy. Apparently there are lots of people here who love PHP. So I'm genuinely curious. What am I missing? What makes PHP a good language? Here are my reasons for disliking it: PHP has inconsistent naming of built-in and library functions. Predictable naming patterns are important in any design. PHP has inconsistent parameter ordering of built-in functions, eg array_map vs. array_filter which is annoying in the simple cases and raises all sorts of unexpected behaviour or worse. The PHP developers constantly deprecate built-in functions and lower-level functionality. A good example is when they deprecated pass-by-reference for functions. This created a nightmare for anyone doing, say, function callbacks. A lack of consideration in redesign. The above deprecation eliminated the ability to, in many cases, provide default keyword values for functions. They fixed this in PHP 5, but they deprecated the pass-by-reference in PHP 4! Poor execution of name spaces (formerly no name spaces at all). Now that name spaces exist, what do we use as the dereference character? Backslash! The character used universally for escaping, even in PHP! Overly-broad implicit type conversion leads to bugs. I have no problem with implicit conversions of, say, float to integer or back again. But PHP (last I checked) will happily attempt to magically convert an array to an integer. Poor recursion performance. Recursion is a fundamentally important tool for writing in any language; it can make complex algorithms far simpler. Poor support is inexcusable. Functions are case insensitive. I have no idea what they were thinking on this one. A programming language is a way to specify behavior to both a computer and a reader of the code without ambiguity. Case insensitivity introduces much ambiguity. PHP encourages (practically requires) a coupling of processing with presentation. Yes, you can write PHP that doesn't do so, but it's actually easier to write code in the incorrect (from a sound design perspective) manner. PHP performance is abysmal without caching. Does anyone sell a commercial caching product for PHP? Oh, look, the designers of PHP do. Worst of all, PHP convinces people that designing web applications is easy. And it does indeed make much of the effort involved much easier. But the fact is, designing a web application that is both secure and efficient is a very difficult task. By convincing so many to take up programming, PHP has taught an entire subgroup of programmers bad habits and bad design. It's given them access to capabilities that they lack the understanding to use safely. This has led to PHP's reputation as being insecure. (However, I will readily admit that PHP is no more or less secure than any other web programming language.) What is it that I'm missing about PHP? I'm seeing an organically-grown, poorly-managed mess of a language that's spawning poor programmers. So convince me otherwise!

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How do I get a button to show on mouseover using jQuery?

- by sharataka

I am trying to get a button to appear over an image when there is a mouseover event over the image. I have multiple images on the screen that I would like to have the same functionality. I'm having trouble getting this to work as the button is always present. Any advice on how to get it to work? Below is the rendered html and javascript. javascript <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js"></script> <script src="http://code.jquery.com/jquery.min.js" type="text/javascript"></script> <script type = "text/javascript"> $(document).ready(function() { $('.image').mouseover(function(){ $('.munchbutton').show(); }); }); </script> css div.munchbutton{ position: absolute; bottom: 5px; right: 0px; left: 60px; } div.wrapper{ float:left; /* important */ position:relative; /* important(so we can absolutely position the description div */ padding: 5px; } html  <div class='wrapper'>  <div class="image" style="position: relative; left: 0; top: 0;"> <a href="/partners/Business/CNNMoney" > <img src="/static/CNNMoney.png" style="position: relative; top: 0; left: 0;"/> </a>  <div class='munchbutton'> <form method='post'><div style='display:none'><input type='hidden' name='csrfmiddlewaretoken' value='7wq8pRYNCDkXUGRv7eU6qI1BU7RKyoT8' /></div> <input type="hidden" name="channel" id="channel" value="CNNMoney" /> <input type='submit' class = 'add' value='Add to plate'/> </form> </div>  </div>  </div>   <div class='wrapper'>  <div class="image" style="position: relative; left: 0; top: 0;"> <a href="/partners/Business/EconomistMagazine" > <img src="/static/EconomistMagazine.png" style="position: relative; top: 0; left: 0;"/> </a>  <div class='munchbutton'> <form method='post'><div style='display:none'><input type='hidden' name='csrfmiddlewaretoken' value='7wq8pRYNCDkXUGRv7eU6qI1BU7RKyoT8' /></div> <input type="hidden" name="channel" id="channel" value="EconomistMagazine" /> <input type='submit' class = 'add' value='Add to plate'/> </form> </div>  </div>  </div>

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Event handle in drop-down menu.

- by QLiu

Hello fellows, I am trying to develop a dynamic drop down menu by a customized widget style The custom widget has two main features: Read user's location cookies variable to set the proper contact phone number in the CP pages When users select on the drop down menu, it triggers onChange event, it re-select the contact phone number based on users' selections, but it won't reset the location cookies. My widgets conatins two files: Controller.php: Simply one, it uses to handle get cookies variables class serial extends Widget { function __construct() { parent::__construct(); } function generateWidgetInformation() { $this->info['notes'] = "Serial Number search Box"; } function getData() { //Get cookies code will go here, and pass to view.php $this->data['locale'] = 'gb';// for test purpose now } } view.php is about Presentation layer contains HTML, which get the data from my controller <div style="border: 1px solid black; display: block;" id="<?=$this->instanceID;?>"></div> <script>locale2contact('<?=$this->data['locale']?>', '<?=$this->instanceID;?>');</script> And then the Javascript function, call locale2contact var element_id =''; //Define Global Variables, //Receive the cookies locale, and instance id from view.php function locale2contact(locale, instance_id) { var details = ''; this.element_id=instance_id; //assing the instance id into global variable // alert(instance_id); //Check whether we got the instance id from view files if (locale == 'gb') details = 'UK Contact Details<br>' + build_dropdown(locale); else if (locale == 'fr') details = 'French Contact Details<br>'+build_dropdown(locale); else if (locale == 'be') details = 'Belgian Contact Details<br>'+ build_dropdown(locale); else details = 'Unknown Contact Detail'; writeContactInfo(details); } //Build the drop down menu with pre-selected option by using cookies. function build_dropdown(locale) { var dropdown = '<select onChange=changeContactInfo(this.options[selectedIndex].text)>'; dropdown += '<option' + (locale == 'gb' ? ' selected' : '') + '>UK</option>'; dropdown += '<option' + (locale == 'be' ? ' selected' : '') + '>Belgium</option>'; dropdown += '</select>'; return dropdown; } // Not smart way in here, once the people select the drop down box, it reselect the drop down menu and reset the contact info function changeContactInfo(selected) { var details =''; //alert(this.element_id); //alert(locale); if (selected == 'UK') details = 'UK Contact Details<br>' + build_dropdown2(selected); else if (selected == 'fr') details = 'French Contact Details<br>'+ build_dropdown2(selected); else if (selected == 'Belgium') details = 'Belgian Contact Details<br>'+ build_dropdown2(selected); else details = 'Unknown Contact Detail'; writeContactInfo(details); } //Build the drop down menu function build_dropdown2(selected) { var dropdown = '<select onChange=changeContactInfo(this.options[selectedIndex].text)>'; dropdown += '<option' + (selected == 'UK' ? ' selected' : '') + '>UK</option>'; dropdown += '<option' + (selected == 'Belgium' ? ' selected' : '') + '>Belgium</option>'; dropdown += '</select>'; return dropdown; } //Back to view function writeContactInfo(details) { document.getElementById(this.element_id).innerHTML = details; //update the instance field in view } Javascript function is not efficient. As you see, I got two similar duplicate functions to handle events. Users go to the page, the widget read the cookies variable to display contact info (locale2contact)and preselect the drop-down menu (function build_dropdown) If users select the drop down menu, the displya contact info change (function changeContactInfo), and then I need to rebuild the drop down menu with user previously selection (function build_dropdown2). I am looking for best practices for adding this functionality to RightNow widget. Thank you. I really do not like the way i am doing now. It works; but the code looks bad.

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Does my GetEnumerator cause a deadlock?

- by Scott Chamberlain

I am starting to write my first parallel applications. This partitioner will enumerate over a IDataReader pulling chunkSize records at a time from the data-source. TLDR; version private object _Lock = new object(); public IEnumerator GetEnumerator() { var infoSource = myInforSource.GetEnumerator(); //Will this cause a deadlock if two threads lock (_Lock) //use the enumator at the same time? { while (infoSource.MoveNext()) { yield return infoSource.Current; } } } full code protected class DataSourcePartitioner<object[]> : System.Collections.Concurrent.Partitioner<object[]> { private readonly System.Data.IDataReader _Input; private readonly int _ChunkSize; public DataSourcePartitioner(System.Data.IDataReader input, int chunkSize = 10000) : base() { if (chunkSize < 1) throw new ArgumentOutOfRangeException("chunkSize"); _Input = input; _ChunkSize = chunkSize; } public override bool SupportsDynamicPartitions { get { return true; } } public override IList<IEnumerator<object[]>> GetPartitions(int partitionCount) { var dynamicPartitions = GetDynamicPartitions(); var partitions = new IEnumerator<object[]>[partitionCount]; for (int i = 0; i < partitionCount; i++) { partitions[i] = dynamicPartitions.GetEnumerator(); } return partitions; } public override IEnumerable<object[]> GetDynamicPartitions() { return new ListDynamicPartitions(_Input, _ChunkSize); } private class ListDynamicPartitions : IEnumerable<object[]> { private System.Data.IDataReader _Input; int _ChunkSize; private object _ChunkLock = new object(); public ListDynamicPartitions(System.Data.IDataReader input, int chunkSize) { _Input = input; _ChunkSize = chunkSize; } public IEnumerator<object[]> GetEnumerator() { while (true) { List<object[]> chunk = new List<object[]>(_ChunkSize); lock(_Input) { for (int i = 0; i < _ChunkSize; ++i) { if (!_Input.Read()) break; var values = new object[_Input.FieldCount]; _Input.GetValues(values); chunk.Add(values); } if (chunk.Count == 0) yield break; } var chunkEnumerator = chunk.GetEnumerator(); lock(_ChunkLock) //Will this cause a deadlock? { while (chunkEnumerator.MoveNext()) { yield return chunkEnumerator.Current; } } } } IEnumerator IEnumerable.GetEnumerator() { return ((IEnumerable<object[]>)this).GetEnumerator(); } } } I wanted IEnumerable object it passed back to be thread safe (the MSDN example was so I am assuming PLINQ and TPL could need it) will the lock on _ChunkLock near the bottom help provide thread safety or will it cause a deadlock? From the documentation I could not tell if the lock would be released on the yeld return. Also if there is built in functionality to .net that will do what I am trying to do I would much rather use that. And if you find any other problems with the code I would appreciate it.

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How do you place an Excel Sheet/Workbook onto a C# .NET Winform?

- by incognick

I am trying to create a stand alone application in Visual Studio 2008 C# .Net that will house Excel Workbooks (2007). I am using Office.Interop in order to create the Excel application and I open the workbooks via Workbooks.Open(...). The Interop does not provide any functionality to "move" the workbooks onto a form so I turned to P/Invoke Win32 library. I am able to move the entire excel application onto a WinForm with great success: // pseudo code to give you the idea excel = new Excel.ApplicationClass(); SetParent(excel.Hwnd, form.handle); This allows me to customize the form and control user input. All right click commands and formula editing work properly. Now, the issue I run into is when I want to open two workbooks in two separate forms. I do this by creating two excel application classes and placing each of those in their own form. When I try to reference one workbook to another workbook via =[Book2]Sheet1!A1, for example, it does not update. This is expected as each application is running under its own thread/process. Here are the alternatives I have tried. If you have any suggestions I would be greatly appreciative.(OLE is not an option. VSTO must be available) Create a single application class and move the workbook window into my form. Results: The window moves into my form and displays correctly, however, no right click or left click works on the form and it never gains focus. (I have tried to manually set focus and it does not work either). My guess is, by moving the window outside of the XLDESK application (viewable in Spy++ for Excel Application), the workbook application (EXCEL7) does not receive the correct window messages to gain focus and to behave properly. This leads me to: Move the XLDESK window handle into my form. Results: This allows the workbook to be click-able again but also has an undesired result of moving all child windows into the same form. Create a main excel application that creates workbooks. Create a new excel application for each new window. Move the workbook under the new excel application XLDESK window. Results: This also has the same effect of the 1st option. Unable to click in the workbook. This must mean that the thread that created the workbook is also responsible for the events. Create a windows hook that watches the WndProc procedure. Results: No events watched. The targeted thread must export the hook proc in a DLL export call. Excel does not do this and thus you cannot inject into it's DLL (unless someone can prove me wrong). I am able to watch all threads within my own process but not from an outside process. Excel is created as a separate process. Subclass NativeWindow. Results: Same as #4. After I move the window into my form, all events are captured up until the mouse is directly over the excel sheet making the sheet seem unclickable. One idea I haven't tried yet is just to continually save the excel sheet as the user edits it. This should update all references but I would feel this would cause poor system performance. There will be numerous chart references as well and I'm not sure if this solution would cause problems further down the road. I think in the end, all the workbooks need to be created by the same Excel Application and then moved to get the desired results but I can't seem to find the correct way to move the windows without disabling the user input in the process. Any suggestions?

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Agile: User Stories for Machine Learning Project?

- by benjismith

I've just finished up with a prototype implementation of a supervised learning algorithm, automatically assigning categorical tags to all the items in our company database (roughly 5 million items). The results look good, and I've been given the go-ahead to plan the production implementation project. I've done this kind of work before, so I know how the functional components of the software. I need a collection of web crawlers to fetch data. I need to extract features from the crawled documents. Those documents need to be segregated into a "training set" and a "classification set", and feature-vectors need to be extracted from each document. Those feature vectors are self-organized into clusters, and the clusters are passed through a series of rebalancing operations. Etc etc etc etc. So I put together a plan, with about 30 unique development/deployment tasks, each with time estimates. The first stage of development -- ignoring some advanced features that we'd like to have in the long-term, but aren't high enough priority to make it into the development schedule yet -- is slated for about two months worth of work. (Keep in mind that I already have a working prototype, so the final implementation is significantly simpler than if the project was starting from scratch.) My manager said the plan looked good to him, but he asked if I could reorganize the tasks into user stories, for a few reasons: (1) our project management software is totally organized around user stories; (2) all of our scheduling is based on fitting entire user stories into sprints, rather than individually scheduling tasks; (3) other teams -- like the web developers -- have made great use of agile methodologies, and they've benefited from modelling all the software features as user stories. So I created a user story at the top level of the project: As a user of the system, I want to search for items by category, so that I can easily find the most relevant items within a huge, complex database. Or maybe a better top-level story for this feature would be: As a content editor, I want to automatically create categorical designations for the items in our database, so that customers can easily find high-value data within our huge, complex database. But that's not the real problem. The tricky part, for me, is figuring out how to create subordinate user stories for the rest of the machine learning architecture. Case in point... I know that the algorithm requires two major architectural subdivisions: (A) training, and (B) classification. And I know that the training portion of the architecture requires construction of a cluster-space. All the Agile Development literature I've read seems to indicate that a user story should be the "smallest possible implementation that provides any business value". And that makes a lot of sense when designing a piece of end-user software. Start small, and then incrementally add value when users demand additional functionality. But a cluster-space, in and of itself, provides zero business value. Nor does a crawler, or a feature-extractor. There's no business value (not for the end-user, or for any of the roles internal to the company) in a partial system. A trained cluster-space is only possible with the crawler and feature extractor, and only relevant if we also develop an accompanying classifier. I suppose it would be possible to create user stories where the subordinate components of the system act as the users in the stories: As a supervised-learning cluster-space construction routine, I want to consume data from a feature extractor, so that I can exist. But that seems really weird. What benefit does it provide me as the developer (or our users, or any other stakeholders, for that matter) to model my user stories like that? Although the main story can be easily divided along architectural-component boundaries (crawler, trainer, classifier, etc), I can't think of any useful decomposition from a user's perspective. What do you guys think? How do you plan Agile user stories for sophisticated, indivisible, non-user-facing components?

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Problem with large number of markers on the map...

- by bobetko

I am working on an Android app that already exists on iPhone. In the app, there is a Map activity that has (I counted) around 800 markers in four groups marked by drawable in four different colors. Each group can be turned on or off. Information about markers I have inside List. I create a mapOverlay for each group, then I attach that overlay to the map. I strongly believe that coding part I did properly. But I will attach my code anyway... The thing is, my Nexus One can't handle map with all those markers. It takes around 15 seconds just to draw 500 markers. Then when all drawn, map is not quite smooth. It is sort of hard to zoom and navigate around. It can be done, but experience is bad and I would like to see if something can be done there. iPhone seems doesn't have problems showing all these markers. It takes roughly about 1-2 seconds to show all of them and zooming and panning is not that bad. Slow down is noticeable but still acceptable. I personally think it is no good to draw all those markers, but app is designed by somebody else and I am not supposed to make any drastic changes. I am not sure what to do here. It seems I will have to come up with different functionality, maybe use GPS location, if known, and draw only markers within some radius, or, if location not known, use center of the screen(map) and draw markers around that. I will have to have reasonable explanation for my bosses in case I make these changes. I appreciate if anybody has any idas. And the code: ... for (int m = 0; m < ArrList.size(); m++) { tName = ArrList.get(m).get("name").toString(); tId = ArrList.get(m).get("id").toString(); tLat = ArrList.get(m).get("lat").toString();; tLng = ArrList.get(m).get("lng").toString();; try { lat = Double.parseDouble(tLat); lng = Double.parseDouble(tLng); p1 = new GeoPoint( (int) (lat * 1E6), (int) (lng * 1E6)); OverlayItem overlayitem = new OverlayItem(p1, tName, tId); itemizedoverlay.addOverlay(overlayitem); } catch (NumberFormatException e) { Log.d(TAG, "NumberFormatException" + e); } } mapOverlays.add(itemizedoverlay); mapView.postInvalidate(); ................................ public class HelloItemizedOverlay extends ItemizedOverlay<OverlayItem> { private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>(); private Context mContext; public HelloItemizedOverlay(Drawable defaultMarker, Context context) { super(boundCenterBottom(defaultMarker)); mContext = context; } public void addOverlay(OverlayItem overlay) { mOverlays.add(overlay); populate(); } @Override protected OverlayItem createItem(int i) { return mOverlays.get(i); } @Override public int size() { return mOverlays.size(); } @Override protected boolean onTap(int index) { final OverlayItem item = mOverlays.get(index); ... EACH MARKER WILL HAVE ONCLICK EVENT THAT WILL PRODUCE CLICABLE ... BALOON WITH MARKER'S NAME. return true; } }

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Faulty to use memcache together with a php web-browser-game in this way?

- by Crowye

Background We are currently working on a strategy web-browser game based on php, html and javascript. The plan is to have 10,000+ users playing within the same world. Currently we are using memcached to: store json static data, language files store changeable serialized php class objects (such as armies, inventorys, unit-containers, buildings, etc) In the back we have a mysql server running and holding all the game data aswell. When a object is loaded through our ObjectLoader it loads in this order: checks a static hashmap in the script for the object checks memcache if it has already been loaded into it otherwise loads from database, and saves it into memcache and the static temp hashmap We have built the whole game using a class-object-oriented approach where functionality is always made between objects. Beause of this we think we have managed to get a nice structure, and with the help of memcached we have received good request times from client-server when interacting with the game. I'm aware that memcache is not synchronized, and also is not commonly used for holding a full game in memory. In the beginning after a server's startup the load times when loading objects into memcache for the first time will be high, but after the server's been online for a while and most loads are from memcache, the loads will be well reduced. Currently we are saving changed objects into memcache and database at the same time. Earlier we had an idea to save objects into db only after a certain time or at intervals, but due to risk inconsistency if the memcache/server went down, we skipped it for now. Client requests to server often return object's status simple json-format without changing the object, which in turn is represented in the browser visually with images and javascript. But from time to time depending on when an object was last updated, it updates them with new information (e.g. a build-queue holding planned buildings time-progress is increased, and/or planned-queue-items-array has changed). Questions: Do you see how this could work or are we walking in blindness here? Do you expect us to have a lot of inconsistency issues if someone loads and updates the a memcache objects while someone else does the same? Is it even doable to do it in the way he have done it? Seems to be working fine atm, but so far we have only been 4 people online at the same time.. Is some other cache program more fit for this class-object approach than memcached? Is there any other tips you have for this situation? UPDATE Since it is simply a "normal webpage" (no applet, flash, etc), we are implementing the game so that the server is the only one holding a "real game-state".. the state of the different javascript-objects on the client is more like a approximative version of the server's game state. From time to time and before you do certain things important things, the client's visual state is updated to the server's state (e.g. the client things he can afford a barracks, asks the server to build a barracks, server updates current resources according to income-data on server and then tries to build a barracks or casts an error-message, and then sends the current server-state on resources, buildings back to the client).. It is not a fast-paced game lika real strategy game. More like a quite slow 3-4 months playtime game, where buildings can take +1 minute up to several days to complete.

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Log4j: Events appear in the wrong logfile

- by Markus

Hi there! To be able to log and trace some events I've added a LoggingHandler class to my java project. Inside this class I'm using two different log4j logger instances - one for logging an event and one for tracing an event into different files. The initialization block of the class looks like this: public void initialize() { System.out.print("starting logging server ..."); // create logger instances logLogger = Logger.getLogger("log"); traceLogger = Logger.getLogger("trace"); // create pattern layout String conversionPattern = "%c{2} %d{ABSOLUTE} %r %p %m%n"; try { patternLayout = new PatternLayout(); patternLayout.setConversionPattern(conversionPattern); } catch (Exception e) { System.out.println("error: could not create logger layout pattern"); System.out.println(e); System.exit(1); } // add pattern to file appender try { logFileAppender = new FileAppender(patternLayout, logFilename, false); traceFileAppender = new FileAppender(patternLayout, traceFilename, false); } catch (IOException e) { System.out.println("error: could not add logger layout pattern to corresponding appender"); System.out.println(e); System.exit(1); } // add appenders to loggers logLogger.addAppender(logFileAppender); traceLogger.addAppender(traceFileAppender); // set logger level logLogger.setLevel(Level.INFO); traceLogger.setLevel(Level.INFO); // start logging server loggingServer = new LoggingServer(logLogger, traceLogger, serverPort, this); loggingServer.start(); System.out.println(" done"); } To make sure that only only thread is using the functionality of a logger instance at the same time each logging / tracing method calls the logging method .info() inside a synchronized-block. One example looks like this: public void logMessage(String message) { synchronized (logLogger) { if (logLogger.isInfoEnabled() && logFileAppender != null) { logLogger.info(instanceName + ": " + message); } } } If I look at the log files, I see that sometimes a event appears in the wrong file. One example: trace 10:41:30,773 11080 INFO masterControl(192.168.2.21): string broadcast message was pushed from 1267093 to vehicle 1055293 (slaveControl 1) trace 10:41:30,784 11091 INFO masterControl(192.168.2.21): string broadcast message was pushed from 1156513 to vehicle 1105792 (slaveControl 1) trace 10:41:30,796 11103 INFO masterControl(192.168.2.21): string broadcast message was pushed from 1104306 to vehicle 1055293 (slaveControl 1) trace 10:41:30,808 11115 INFO masterControl(192.168.2.21): vehicle 1327879 was pushed to slave control 1 10:41:30,808 11115 INFO masterControl(192.168.2.21): string broadcast message was pushed from 1101572 to vehicle 106741 (slaveControl 1) trace 10:41:30,820 11127 INFO masterControl(192.168.2.21): string broadcast message was pushed from 1055293 to vehicle 1104306 (slaveControl 1) I think that the problem occures everytime two event happen at the same time (here: 10:41:30,808). Does anybody has an idea how to solve my problem? I already tried to add a sleep() after the method call, but that doesn't helped ... BR, Markus Edit: logtrace 11:16:07,75511:16:07,755 1129711297 INFOINFO masterControl(192.168.2.21): string broadcast message was pushed from 1291400 to vehicle 1138272 (slaveControl 1)masterControl(192.168.2.21): vehicle 1333770 was added to slave control 1 or log 11:16:08,562 12104 INFO 11:16:08,562 masterControl(192.168.2.21): string broadcast message was pushed from 117772 to vehicle 1217744 (slaveControl 1) 12104 INFO masterControl(192.168.2.21): vehicle 1169775 was pushed to slave control 1 Edit 2: It seems like the problem only occurs if logging methods are called from inside a RMI thread (my client / server exchange information using RMI connections). ... Edit 3: I solved the problem by myself: It seems like log4j is NOT completely thread-save. After synchronizing all log / trace methods using a separate object everything is working fine. Maybe the lib is writing the messages to a thread-unsafe buffer before writing them to file?

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JQuery help, How to Hide all button in JQuery

- by user303518

Hi guys, I'm trying to make a request/reply section in my project. I want to achieve these functionality in that code (that I'm not able to implement; so guys please help me out): 1 When user click on reply button; other reply area(text-area +button) should be hide (means at a time only one reply area should be visible to the user). 2 when user click on reply button text-area will focus and page will slide down (suppose user reply 10 comment focus will automatically set to the 10 number text area and page will slide down to that position accordingly). Here is my so far code guys: //method call on the click of reply link. function linkReply_Clicked(issueId) { Id = issueId; textId = "text_" + issueId + count; btnReply = "btnReply_" + issueId + count; btnCancel = "btnCancel_" + issueId + count; var textareasArray = document.getElementsByTagName("textarea"); var btnArray = document.getElementsByTagName("input"); for (i = 0; i < textareasArray.length; i++) { textareasArray[i].style.display = "none"; btnArray[i].style.display = "none"; } var str = "<table cellpadding='3' cellspacing='0' width='58%'>"; str += "<tr><td valign='top' align='left'>"; str += "<textarea id=" + textId + " rows='5' cols='60'></textarea>"; str += "</td></tr>"; str += "<tr><td valign='top' align='right'>"; str += "<input id=" + btnReply + " type='button' onclick='btnReply_Clicked(Id ,textId)' value='Reply' /> "; str += "<input id=" + btnCancel + " type='button' onclick='btnCancel_Clicked(Id ,textId)' value='Cancel' /> "; str += "</td></tr>"; str += "</table>"; document.getElementById("divOuter_" + issueId).innerHTML = str; $("#" + textId + "").focus(); } // submit user reply and try to hide that reply area. function btnReply_Clicked(issueId, textID) { var comment = document.getElementById(textID).value; if (comment != '') { $.getJSON("/Issue/SaveComment", { IssueId: issueId, Comment: comment }, null); $("#text_" + issueId + count).hide(); $("#btnReply_" + issueId + count).hide(); $("#btnCancel_" + issueId + count).hide(); document.getElementById(textID).value = ''; count = count + 1; } } // cancel user reply and try to hide that reply area. function btnCancel_Clicked(issueId, textId) { $("#text_" + issueId + count).hide(); $("#btnReply_" + issueId + count).hide(); $("#btnCancel_" + issueId + count).hide(); document.getElementById(textId).value = ''; count = count + 1; }

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How can I hit my database with an AJAX call using javascript?

- by tmedge

I am pretty new at this stuff, so bear with me. I am using ASP.NET MVC. I have created an overlay to cover the page when someone clicks a button corresponding to a certain database entry. Because of this, ALL of my code for this functionality is in a .js file contained within my project. What I need to do is pull the info corresponding to my entry from the database itself using an AJAX call, and place that into my textboxes. Then, after the end-user has made the desired changes, I need to update that entry's values to match the input. I've been surfing the web for a while, and have failed to find an example that fits my needs effectively. Here is my code in my javascript file thus far: function editOverlay(picId) { //pull up an overlay $('body').append('<div class="overlay" />'); var $overlayClass = $('.overlay'); $overlayClass.append('<div class="dataModal" />'); var $data = $('.dataModal'); overlaySetup($overlayClass, $data); //set up form $data.append('<h1>Edit Picture</h1><br /><br />'); $data.append('Picture name:  '); $data.append('<input class="picName" /> <br /><br /><br />'); $data.append('Relative url:  '); $data.append('<input class="picRelURL" /> <br /><br /><br />'); $data.append('Description:  '); $data.append('<textarea class="picDescription" /> <br /><br /><br />'); var $nameBox = $('.picName'); var $urlBox = $('.picRelURL'); var $descBox = $('.picDescription'); var pic = null; //this is where I need to pull the actual object from the db //var imgList = for (var temp in imgList) { if (temp.Id == picId) { pic= temp; } } /* $nameBox.attr('value', pic.Name); $urlBox.attr('value', pic.RelativeURL); $descBox.attr('value', pic.Description); */ //close buttons $data.append('<input type="button" value="Save Changes" class="saveButton" />'); $data.append('<input type="button" value="Cancel" class="cancelButton" />'); $('.saveButton').click(function() { /* pic.Name = $nameBox.attr('value'); pic.RelativeURL = $urlBox.attr('value'); pic.Description = $descBox.attr('value'); */ //make a call to my Save() method in my repository CloseOverlay(); }); $('.cancelButton').click(function() { CloseOverlay(); }); } The stuff I have commented out is what I need to accomplish and/or is not available until prior issues are resolved. Any and all advice is appreciated! Remember, I am VERY new to this stuff (two weeks, to be exact) and will probably need highly explicit instructions. BTW: overlaySetup() and CloseOverlay() are functions I have living someplace else. Thanks!

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Problem using delete[] (Heap corruption) when implementing operator+= (C++)

- by Darel

I've been trying to figure this out for hours now, and I'm at my wit's end. I would surely appreciate it if someone could tell me when I'm doing wrong. I have written a simple class to emulate basic functionality of strings. The class's members include a character pointer data (which points to a dynamically created char array) and an integer strSize (which holds the length of the string, sans terminator.) Since I'm using new and delete, I've implemented the copy constructor and destructor. My problem occurs when I try to implement the operator+=. The LHS object builds the new string correctly - I can even print it using cout - but the problem comes when I try to deallocate the data pointer in the destructor: I get a "Heap Corruption Detected after normal block" at the memory address pointed to by the data array the destructor is trying to deallocate. Here's my complete class and test program: #include <iostream> using namespace std; // Class to emulate string class Str { public: // Default constructor Str(): data(0), strSize(0) { } // Constructor from string literal Str(const char* cp) { data = new char[strlen(cp) + 1]; char *p = data; const char* q = cp; while (*q) *p++ = *q++; *p = '\0'; strSize = strlen(cp); } Str& operator+=(const Str& rhs) { // create new dynamic memory to hold concatenated string char* str = new char[strSize + rhs.strSize + 1]; char* p = str; // new data char* i = data; // old data const char* q = rhs.data; // data to append // append old string to new string in new dynamic memory while (*p++ = *i++) ; p--; while (*p++ = *q++) ; *p = '\0'; // assign new values to data and strSize delete[] data; data = str; strSize += rhs.strSize; return *this; } // Copy constructor Str(const Str& s) { data = new char[s.strSize + 1]; char *p = data; char *q = s.data; while (*q) *p++ = *q++; *p = '\0'; strSize = s.strSize; } // destructor ~Str() { delete[] data; } const char& operator[](int i) const { return data[i]; } int size() const { return strSize; } private: char *data; int strSize; }; ostream& operator<<(ostream& os, const Str& s) { for (int i = 0; i != s.size(); ++i) os << s[i]; return os; } // Test constructor, copy constructor, and += operator int main() { Str s = "hello"; // destructor for s works ok Str x = s; // destructor for x works ok s += "world!"; // destructor for s gives error cout << s << endl; cout << x << endl; return 0; }

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How to debug KVO

- by user8472

In my program I use KVO manually to observe changes to values of object properties. I receive an EXC_BAD_ACCESS signal at the following line of code inside a custom setter: [self willChangeValueForKey:@"mykey"]; The weird thing is that this happens when a factory method calls the custom setter and there should not be any observers around. I do not know how to debug this situation. Update: The way to list all registered observers is observationInfo. It turned out that there was indeed an object listed that points to an invalid address. However, I have no idea at all how it got there. Update 2: Apparently, the same object and method callback can be registered several times for a given object - resulting in identical entries in the observed object's observationInfo. When removing the registration only one of these entries is removed. This behavior is a little counter-intuitive (and it certainly is a bug in my program to add multiple entries at all), but this does not explain how spurious observers can mysteriously show up in freshly allocated objects (unless there is some caching/reuse going on that I am unaware of). Modified question: How can I figure out WHERE and WHEN an object got registered as an observer? Update 3: Specific sample code. ContentObj is a class that has a dictionary as a property named mykey. It overrides: + (BOOL)automaticallyNotifiesObserversForKey:(NSString *)theKey { BOOL automatic = NO; if ([theKey isEqualToString:@"mykey"]) { automatic = NO; } else { automatic=[super automaticallyNotifiesObserversForKey:theKey]; } return automatic; } A couple of properties have getters and setters as follows: - (CGFloat)value { return [[[self mykey] objectForKey:@"value"] floatValue]; } - (void)setValue:(CGFloat)aValue { [self willChangeValueForKey:@"mykey"]; [[self mykey] setObject:[NSNumber numberWithFloat:aValue] forKey:@"value"]; [self didChangeValueForKey:@"mykey"]; } The container class has a property contents of class NSMutableArray which holds instances of class ContentObj. It has a couple of methods that manually handle registrations: + (BOOL)automaticallyNotifiesObserversForKey:(NSString *)theKey { BOOL automatic = NO; if ([theKey isEqualToString:@"contents"]) { automatic = NO; } else { automatic=[super automaticallyNotifiesObserversForKey:theKey]; } return automatic; } - (void)observeContent:(ContentObj *)cObj { [cObj addObserver:self forKeyPath:@"mykey" options:0 context:NULL]; } - (void)removeObserveContent:(ContentObj *)cObj { [cObj removeObserver:self forKeyPath:@"mykey"]; } - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { if (([keyPath isEqualToString:@"mykey"]) && ([object isKindOfClass:[ContentObj class]])) { [self willChangeValueForKey:@"contents"]; [self didChangeValueForKey:@"contents"]; } } There are several methods in the container class that modify contents. They look as follows: - (void)addContent:(ContentObj *)cObj { [self willChangeValueForKey:@"contents"]; [self observeDatum:cObj]; [[self contents] addObject:cObj]; [self didChangeValueForKey:@"contents"]; } And a couple of others that provide similar functionality to the array. They all work by adding/removing themselves as observers. Obviously, anything that results in multiple registrations is a bug and could sit somewhere hidden in these methods. My question targets strategies on how to debug this kind of situation. Alternatively, please feel free to provide an alternative strategy for implementing this kind of notification/observer pattern.

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LINQ-like or SQL-like DSL for end-users to run queries to select (not modify) data?

- by Mark Rushakoff

For a utility I'm working on, the client would like to be able to generate graphic reports on the data that has been collected. I can already generate a couple canned graphs (using ZedGraph, which is a very nice library); however, the utility would be much more flexible if the graphs were more programmable or configurable by the end-user. TLDR version I want users to be able to use something like SQL to safely extract and select data from a List of objects that I provide and can describe. What free tools or libraries will help me accomplish this? Full version I've given thought to using IronPython, IronRuby, and LuaInterface, but frankly they're all a bit overpowered for what I want to do. My classes are fairly simple, along the lines of: class Person: string Name; int HeightInCm; DateTime BirthDate; Weight[] WeighIns; class Weight: int WeightInKg; DateTime Date; Person Owner; (exact classes have been changed to protect the innocent). To come up with the data for the graph, the user will choose whether it's a bar graph, scatter plot, etc., and then to actually obtain the data, I would like to obtain some kind of List from the user simply entering something SQL-ish along the lines of SELECT Name, AVG(WeighIns) FROM People SELECT WeightInKg, Owner.HeightInCm FROM Weights And as a bonus, it would be nice if you could actually do operations as well: SELECT WeightInKg, (Date - Owner.BirthDate) AS Age FROM Weights The DSL doesn't have to be compliant SQL in any way; it doesn't even have to resemble SQL, but I can't think of a more efficient descriptive language for the task. I'm fine filling in blanks; I don't expect a library to do everything for me. What I would expect to exist (but haven't been able to find in any way, shape, or form) is something like Fluent NHibernate (which I am already using in the project) where I can declare a mapping, something like var personRequest = Request<Person>(); personRequest.Item("Name", (p => p.Name)); personRequest.Item("HeightInCm", (p => p.HeightInCm)); personRequest.Item("HeightInInches", (p => p.HeightInCm * CM_TO_INCHES)); // ... var weightRequest = Request<Weight>(); weightRequest.Item("Owner", (w => w.Owner), personRequest); // Indicate a chain to personRequest // ... var people = Table<Person>("People", GetPeopleFromDatabase()); var weights = Table<Weight>("Weights", GetWeightsFromDatabase()); // ... TryRunQuery(userInputQuery); LINQ is so close to what I want to do, but AFAIK there's no way to sandbox it. I don't want to expose any unnecessary functionality to the end user; meaning I don't want the user to be able to send in and process: from p in people select (p => { System.IO.File.Delete("C:\\something\\important"); return p.Name }) So does anyone know of any free .NET libraries that allow something like what I've described above? Or is there some way to sandbox LINQ? cs-script is close too, but it doesn't seem to offer sandboxing yet either. I'd be hesitant to expose the NHibernate interface either, as the user should have a read-only view of the data at this point in the usage. I'm using C# 3.5, and pure .NET solutions would be preferred. The bottom line is that I'm really trying to avoid writing my own parser for a subset of SQL that would only apply to this single project.

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Windows App. Thread Aborting Issue

- by Patrick

I'm working on an application that has to make specific decisions based on files that are placed into a folder being watched by a file watcher. Part of this decision making process involves renaming files before moving them off to another folder to be processed. Since I'm working with files of all different sizes I created an object that checks the file in a seperate thread to verify that it is "available" and when it is it fires an event. When I run the rename code from inside this available event it works. public void RenameFile_Test() { string psFilePath = @"C:\File1.xlsx"; tgt_File target = new FileObject(psFilePath); target.FileAvailable += new FileEventHandler(OnFileAvailable); target.FileUnAvailable += new FileEventHandler(OnFileUnavailable); } private void OnFileAvailable(object source, FileEventArgs e) { ((FileObject)source).RenameFile(@"C:\File2.xlsx"); } The problem I'm running into is that when the extensions are different from the source file and the rename to file I am making a call to a conversion factory that returns a factory object based on the type of conversion and then converts the file accordingly before doing the rename. When I run that particular piece of code in unit test it works, the factory object is returned, and the conversion happens correctly. But when I run it within the process I get up to the... moExcelApp = new Application(); part of converting an .xls or .xlsx to a .csv and i get a "Thread was being Aborted" error. Any thoughts? Update: There is a bit more information and a bit of map of how the application works currently. Client Application running FSW On File Created event Creates a FileObject passing in the path of the file. On construction the file is validated: if file exists is true then, Thread toAvailableCheck = new Thread(new ThreadStart(AvailableCheck)); toAvailableCheck.Start(); The AvailableCheck Method repeatedly tries to open a streamreader to the file until the reader is either created or the number of attempts times out. If the reader is opened, it fires the FileAvailable event, if not it fires the FileUnAvailable event, passing back itself in the event. The client application is wired to catch those events from inside the Oncreated event of the FSW. the OnFileAvailable method then calls the rename functionality which contains the excel interop call. If the file is being renamed (not converted, extensions stay the same) it does a move to change the name from the old file name to the new, and if its a conversion it runs a conversion factory object which returns the correct type of conversion based on the extensions of the source file and the destination file name. If it is a simple rename it works w/o a problem. If its a conversion (which is the XLS to CSV object that is returned as a part of the factory) the very first thing it does is create a new application object. That is where the application bombs. When i test the factory and conversion/rename process outside of the thread and in its own unit test the process works w/o a problem. Update: I tested the Excel Interop inside a thread by doing this: [TestMethod()] public void ExcelInteropTest() { Thread toExcelInteropThreadTest = new Thread(new ThreadStart(Instantiate_App)); toExcelInteropThreadTest.Start(); } private void Instantiate_App() { Application moExcelApp = new Application(); moExcelApp.Quit(); } And on the line where the application is instatntiated I got the 'A first chance exception of type 'System.Threading.ThreadAbortException' error. So I added; toExcelInteropThreadTest.SetApartmentState(ApartmentState.MTA); after the thread instantiation and before the thread start call and still got the same error. I'm getting the notion that I'm going to have to reconsider the design.

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Tool or library for end-users to run queries to select (not modify) data?

- by Mark Rushakoff

For a utility I'm working on, the client would like to be able to generate graphic reports on the data that has been collected. I can already generate a couple canned graphs (using ZedGraph, which is a very nice library); however, the utility would be much more flexible if the graphs were more programmable or configurable by the end-user. TLDR version I want users to be able to use something like SQL to safely extract and select data from a List of objects that I provide and can describe. What free tools or libraries will help me accomplish this? Full version I've given thought to using IronPython, IronRuby, and LuaInterface, but frankly they're all a bit overpowered for what I want to do. My classes are fairly simple, along the lines of: class Person: string Name; int HeightInCm; DateTime BirthDate; Weight[] WeighIns; class Weight: int WeightInKg; DateTime Date; Person Owner; (exact classes have been changed to protect the innocent). To come up with the data for the graph, the user will choose whether it's a bar graph, scatter plot, etc., and then to actually obtain the data, I would like to obtain some kind of List from the user simply entering something SQL-ish along the lines of SELECT Name, AVG(WeighIns) FROM People SELECT WeightInKg, Owner.HeightInCm FROM Weights And as a bonus, it would be nice if you could actually do operations as well: SELECT WeightInKg, (Date - Owner.BirthDate) AS Age FROM Weights The DSL doesn't have to be compliant SQL in any way; it doesn't even have to resemble SQL, but I can't think of a more efficient descriptive language for the task. I'm fine filling in blanks; I don't expect a library to do everything for me. What I would expect to exist (but haven't been able to find in any way, shape, or form) is something like Fluent NHibernate (which I am already using in the project) where I can declare a mapping, something like var personRequest = Request<Person>(); personRequest.Item("Name", (p => p.Name)); personRequest.Item("HeightInCm", (p => p.HeightInCm)); personRequest.Item("HeightInInches", (p => p.HeightInCm * CM_TO_INCHES)); // ... var weightRequest = Request<Weight>(); weightRequest.Item("Owner", (w => w.Owner), personRequest); // Indicate a chain to personRequest // ... var people = Table<Person>("People", GetPeopleFromDatabase()); var weights = Table<Weight>("Weights", GetWeightsFromDatabase()); // ... TryRunQuery(userInputQuery); LINQ is so close to what I want to do, but AFAIK there's no way to sandbox it. I don't want to expose any unnecessary functionality to the end user; meaning I don't want the user to be able to send in and process: from p in people select (p => { System.IO.File.Delete("C:\\something\\important"); return p.Name }) So does anyone know of any free .NET libraries that allow something like what I've described above? Or is there some way to sandbox LINQ? cs-script is close too, but it doesn't seem to offer sandboxing yet either. I'd be hesitant to expose the NHibernate interface either, as the user should have a read-only view of the data at this point in the usage. I'm using C# 3.5, and pure .NET solutions would be preferred. The bottom line is that I'm really trying to avoid writing my own parser for a subset of SQL that would only apply to this single project.

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Trying to reinvent the wheel of StackOverflow to have a good learning experience. Need some suggesti

- by Legend

I want to learn and am not able to do it unless I have a real "mission" to complete. SO is my favorite and I can't imagine a better experience than actually recreating it but not in ASP. I'd like to use PHP+MySQL+jQuery. So far, I have been a self-taught programmer but I would like to master one paradigm that forces you to adhere to the standards. For instance, recently, jQuery forced me to use some "rules". The plugins were supposed to be written in a particular way and that's it. When I started off, everything seemed like Greek and Latin but when I finished a very small plugin, I felt really happy because it forced me to program in a certain way. I am looking for something like this only in a larger project. I've heard a lot about MVC and all but I am confused about the various frameworks out there. Zend seems awesome but looks heavy at the same time and also requires you to have a lot more control over the web-server whereas CakePHP is a good and a fast framework that needs only little control. Do I use one of these or just write my own MVC? I have the following goals: Goals: Site should be fast - I know this depends on my coding skills but I will learn on my way. The framework itself should not slow me down) Setting up the site should not require you to use command-line - This requirement is ok during development. But some frameworks like Symphony require you to initialize certain things through command-line Should support pluggable modules - For instance, if I want to be able to use the FCK editor, I should be able to organize things in a good way. Should be possible to extend - For instance, SO is mainly a Q&A site but I should be able to logically extend it into an Idea Management System (optional but I'm curious). This goes more into code re-usability I guess. I am comfortable with MySQL so I should be done with database design etc. with some serious effort. As for PHP, I can write code on my own but haven't really used any frameworks that much. jQuery, I started off recently and love it. I would be glad if someone can guide me during these initial steps. Precisely, when designing something like SO, I have the following questions: Do I use a framework? If yes, should it be MVC? If MVC, which one is a good and a scalable one? (I'd love something like jQuery that will not die anytime soon) How do I balance the functionality? The same logic can sometimes be made server centric or client centric. (more Ajax?). Is it a good idea to make a heavy javascript site considering the recent advances on client-side JS processing? Just in case anyone is wondering, I am not interested in commercializing any of this. I need a reason to learn something :)

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Multiple Notifications Not Firing

- by motionpotion

I'm scheduling two notifications as shown below. The app is a long-lived app. One local notification is scheduled to run every hour. The other is scheduled to run once per day. Only the second scheduled notification (the hourly notifcation) fires. - (void)scheduleNotification { LogInfo(@"IN scheduleNotification - DELETEYESTERDAY NOTIFICATION SCHEDULED."); UILocalNotification *notif = [[UILocalNotification alloc] init]; NSDictionary *deleteDict = [NSDictionary dictionaryWithObject:@"DeleteYesterday" forKey:@"DeleteYesterday"]; NSCalendar *calendar = [NSCalendar currentCalendar]; NSDateComponents *components = [[NSDateComponents alloc] init]; components = [[NSCalendar currentCalendar] components:NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit fromDate:[NSDate date]]; NSInteger day = [components day]; NSInteger month = [components month]; NSInteger year = [components year]; [components setDay: day]; [components setMonth: month]; [components setYear: year]; [components setHour: 00]; [components setMinute: 45]; [components setSecond: 0]; [calendar setTimeZone: [NSTimeZone systemTimeZone]]; NSDate *dateToFire = [calendar dateFromComponents:components]; notif.fireDate = dateToFire; notif.timeZone = [NSTimeZone systemTimeZone]; notif.repeatInterval = NSDayCalendarUnit; notif.userInfo = deleteDict; [[UIApplication sharedApplication] scheduleLocalNotification:notif]; } and then I schedule this after above: - (void)scheduleHeartBeat { LogInfo(@"IN scheduleHeartBeat - HEARTBEAT NOTIFICATION SCHEDULED."); UILocalNotification *heartbeat = [[UILocalNotification alloc] init]; NSDictionary *heartbeatDict = [NSDictionary dictionaryWithObject:@"HeartBeat" forKey:@"HeartBeat"]; heartbeat.userInfo = heartbeatDict; NSCalendar *calendar = [NSCalendar currentCalendar]; NSDateComponents *components = [[NSDateComponents alloc] init]; components = [[NSCalendar currentCalendar] components:NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit fromDate:[NSDate date]]; NSInteger day = [components day]; NSInteger month = [components month]; NSInteger year = [components year]; [components setDay: day]; [components setMonth: month]; [components setYear: year]; [components setHour: 00]; [components setMinute: 50]; [components setSecond: 0]; [calendar setTimeZone: [NSTimeZone systemTimeZone]]; NSDate *dateToFire = [calendar dateFromComponents:components]; heartbeat.fireDate = dateToFire; heartbeat.timeZone = [NSTimeZone systemTimeZone]; heartbeat.repeatInterval = NSHourCalendarUnit; [[UIApplication sharedApplication] scheduleLocalNotification:heartbeat]; } The above are scheduled when the app launches in the viewDidLoad of the main view controller. - (void)viewDidLoad { [self scheduleNotification]; [self scheduleHeartBeat]; [super viewDidLoad]; //OTHER CODE HERE } Then in the appdelegate I have the following: - (void)application:(UIApplication *)application didReceiveLocalNotification:(UILocalNotification *)notification { LogInfo(@"IN didReceiveLocalNotification NOTIFICATION RECEIVED."); NSString *notificationHeartBeat = nil; NSString *notificationDeleteYesterday = nil; application.applicationIconBadgeNumber = 0; if (notification) { notificationHeartBeat = [notification.userInfo objectForKey:@"HeartBeat"]; notificationDeleteYesterday = [notification.userInfo objectForKey:@"DeleteYesterday"]; LogInfo(@"IN didReceiveLocalNotification HEARTBEAT NOTIFICATION TYPE: %@", notificationHeartBeat); LogInfo(@"IN didReceiveLocalNotification DELETEYESTERDAY NOTIFICATION TYPE: %@", notificationDeleteYesterday); } if ([notificationHeartBeat isEqualToString:@"HeartBeat"]) { //CREATE THE HEARTBEAT LogInfo(@"CREATING THE HEARTBEAT."); //CALL THE FUNCTIONALITY HERE THAT CREATES HEARTBEAT. } if ([notificationDeleteYesterday isEqualToString:@"DeleteYesterday"]) { //DELETE YESTERDAYS RECORDS LogInfo(@"DELETING YESTERDAYS RECORDS."); } } The notification that is scheduled last (scheduleHeartBeat) is the only notification that is fired. Could somebody help me figure out why this is happening?

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