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  • Partitioning requests in code among several servers

    - by Jacques René Mesrine
    I have several forum servers (what they are is irrelevant) which stores posts from users and I want to be able to partition requests among these servers. I'm currently leaning towards partitioning them by geographic location. To improve the locality of data, users will be separated into regions e.g. North America, South America and so on. Is there any design pattern on how to implement the function that maps the partioning property to the server, so that this piece of code has high availability and would not become a single point of failure ? f( Region ) -> Server IP

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  • Strategies for generating Zend Cache Keys

    - by emeraldjava
    ATM i'm manually generating a cache key based on the method name and parameters, then follow to the normal cache pattern. This is all done in the Controller and i'm calling a model class that 'extends Zend_Db_Table_Abstract'. public function indexAction() { $cache = Zend_Registry::get('cache'); $individualleaguekey = sprintf("getIndividualLeague_%d_%s",$leagueid,$division->code); if(!$leaguetable = $cache->load($individualleaguekey)) { $table = new Model_DbTable_Raceresult(); $leaguetable = $table->getIndividualLeague($leagueid,$division,$races); $cache->save($leaguetable, $individualleaguekey); } $this->view->leaguetable = $leaguetable; .... I want to avoid the duplication of parameters to the cache creation method and also to the model method, so i'm thinking of moving the caching logic away from my controller class and into model class packaged in './model/DbTable', but this seems incorrect since the DB model should only handle SQL operations. Any suggestions on how i can implement a clean patterned solution?

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  • string parsing help

    - by sprugman
    I've got a string like this: #################### Section One #################### Data A Data B #################### Section Two #################### Data C Data D etc. I want to parse it into something like: $arr( 'Section One' => array('Data A', 'Data B'), 'Section Two' => array('Data C', 'Data D') ) At first I tried this: $sections = preg_split("/(\r?\n)(\r?\n)#/", $file_content); The problem is, the file isn't perfectly clean: sometimes there are different numbers of blank lines between the sections, or blank spaces between data rows. The section head pattern itself seems to be relatively consistent: #################### Section Title #################### The number of #'s is probably consistent, but I don't want to count on it. The white space on the title line is pretty random. Once I have it split into sections, I think it'll be pretty straightforward, but any help writing a killer reg ex to get it there would be appreciated. (Or if there's a better approach than reg ex...)

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  • Why use hashing to create pathnames for large collections of files?

    - by Stephen
    Hi, I noticed a number of cases where an application or database stored collections of files/blobs using a has to determine the path and filename. I believe the intended outcome is a situation where the path never gets too deep, or the folders ever get too full - too many files (or folders) in a folder making for slower access. EDIT: Examples are often Digital libraries or repositories, though the simplest example I can think of (that can be installed in about 30s) is the Zotero document/citation database. Why do this? EDIT: thanks Mat for the answer - does this technique of using a hash to create a file path have a name? Is it a pattern? I'd like to read more, but have failed to find anything in the ACM Digital Library

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  • How to disable UI control based on domain object's state?

    - by Subb
    Here's my problem. I have a somewhat complex domain object, which, depending on its state, responds to certain actions. I think the state pattern is pretty much the solution for that. However, I need to display which actions are possible at any moment in the UI. Ex: The domain object is an audio player. Some songs can't be skipped (like ads), so I need to disable the "next" and "previous" buttons in the GUI so the user have some kind of feedback of which action he can execute. I've looked at Swing's Action class (note: this is not a Java project), but I think I would need to keep every Actions in my domain object class (audio player), so it can enable or disable them depending on its own state (thus, affecting the UI). Is it the way to do it?

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  • Favoriting system on Appengine

    - by Mateusz Cieslak
    Hi, I have the following model structure class Authors(db.Model) : nickname = db.StringProperty(required=True) fullname = db.StringProperty(required=True) class Articles(db.Model) : title = db.StringProperty(required=True) body = db.StringProperty(required=True) author = db.ReferenceProperty(Authors, required=True) class Favorites(db.Model) : who = db.ReferenceProperty(Authors, required=True) what = db.ReferenceProperty(Articles, required=True) I'd like to display 10 last articles according to this pattern: article.title, article.body, article.author(nickname), info if this article has been already favorited by the signed in user. I have added a function which I use to get the authors of these articles using only one query (it is described here) But I don't know what to do with the favorites (I'd like to know which of the displayed articles have been favorited by me using less than 10 queries (I want to display 10 articles)). Is it possible?

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  • Looking for a good explanation of the table generation macro idiom

    - by detly
    I want to make this clear up front : I know how this trick works, what I want is a link to a clear explanation to share with others. One of the answers to a C macro question talks about the "X macro" or "not yet defined macro" idiom. This involves defining something like: #define MAGIC_LIST \ X(name_1, default_1) \ X(name_2, default_2) \ ... Then to create, say, an array of values with named indices you do: typedef enum { #define X(name, val) name, MAGIC_LIST #undef X } NamedDefaults; You can repeat the procedure with a different #define for X() to create an array of values, and maybe debugging strings, etc. I'd like a link to a clear explanation of how this works, pitched at someone who is passably familiar with C. I have no idea what everyone usually calls this pattern, though, so my attempts to search the web for it have failed thus far. (If there is such an explanation on SO, that'd be fine...)

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  • Can we you the attached properties in C# class library?

    - by Manas Agarwal
    Hi I have implemented the Observer Pattern with lazy load. The class that requests the data from the database is a singleton class. Now I am able to load the data from one database (located in one datacenter) very easily. But I need to get the data from other data centers too and display on the same UI. I can somehow pass the address of second data center and fetch the data from there also. But once I will get the data from second data center, it will be added to earlier list only. So later it will be thought for me to distinguish between the data. So I thought of attaching a property with the result set, so that while displaying the output I can show the data for both the data centers separately but on the same UI. I thought of attached property as an option where I can attach the data center name with the list of the data obtained. How is it possible to do in C#? Thanks Manas

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  • php regex replace slashes and spaces and hyphens

    - by Muhammad Shahzad
    I have fews combinations of strings that I need to bring in to one pattern, that is multiple spaces should be removed, double hyphens should be replaced with single hypen, and single space should be replaced with single hyphen. I have already tried this expression. $output = preg_replace( "/[^[:space:]a-z0-9]/e", "", $output ); $output = trim( $output ); $output = preg_replace( '/\s+/', '-', $output ); But this fails in few combinations. I need help in making all of these combinations to work perfectly: steel-black steel- black steel black I should also remove any of these as well "\r\n\t".

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  • what is the return value of BeautifulSoup.find ?

    - by prosseek
    I run to get some value as score. score = soup.find('div', attrs={'class' : 'summarycount'}) I run 'print score' to get as follows. <div class=\"summarycount\">524</div> I need to extract the number part. I used re module but failed. m = re.search("[^\d]+(\d+)", score) TypeError: expected string or buffer function search in re.py at line 142 return _compile(pattern, flags).search(string) What's the return type of the find function? How to get the number from the score variable? Is there any easy way to let BeautifulSoup to return the value(in this case 524) itself?

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  • Zend Framework Custom Validation Class Error Message

    - by remlabm
    The validation fails as it should but does not return the error message. $form->addElement('text', 'phone_number', array( 'required' => true, 'validators' => array( array('NotEmpty', true, array('messages' => 'Enter a valid Phone Number')), array('regex', false, array('pattern' => '/\([0-9]{3}\)\s[0-9]{3}-[0-9]{4}/', 'messages' => 'Enter a valid Phone Number' )), 'CheckPhoneNumber'), ), )); Custom Class: class Custom_Validators_CheckPhoneNumber extends Zend_Validate_Abstract{ const IN_USE = 'inUse'; protected $_messageTemplates = array( self::IN_USE => "'%value%' is currently in use" ); public function isValid($value) { $this->_setValue($value); $user_check = Users::getActive(preg_replace("/[^0-9]/", "", $value)); if($user_check->id){ $this->_error(self::IN_USE); return false; } return true; } } Just fails does not give the "IN_USE" error.

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  • creative way for implementing Data object with its corresponding business logic class in java

    - by ekeren
    I have a class that need to be serialized (for both persistentcy and client-server communication) for simplicity's sake let's call the classes Business a BusinessData and I prefix for their Interfaces. All the getter and setter are delegated from Business class to BusinessData class. I thought about implementing IBusinessData interface that will contain all the getter and setters and IBusiness interface that will extend it. I can either make Business extend BuisnessData so I will not need to implement all getter and setter delegates, or make some abstract class ForwardingBusinessData that will only delegate getter and setters. Any of the above option I lose my hierarchy freedom, do any of you have any creative solutions for this problem... I also reviewed DAO pattern: http://java.sun.com/blueprints/patterns/DAO.html

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  • C# Using singleton instead of a global static instance

    - by Farstucker
    I ran into a problem today and a friend recommended I use a global static instance or more elegantly a singleton pattern. I spent a few hours reading about singletons but a few things still escape me. Background: What Im trying to accomplish is creating an instance of an API and use this one instance in all my classes (as opposed to making a new connection, etc). There seems to be about 100 ways of creating a singleton but with some help from yoda I found some thread safe examples. ..so given the following code: public sealed class Singleton { public static Singleton Instance { get; private set; } static Singleton() { Instance = new Singleton(); } } How/Where would you instantiate the this new class and how should it be called from a separate class? Thanks for your help.

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  • Efficient persistent storage for simple id to table of values map for java

    - by wds
    I need to store some data that follows the simple pattern of mapping an "id" to a full table (with multiple rows) of several columns (i.e. some integer values [u, v, w]). The size of one of these tables would be a couple of KB. Basically what I need is to store a persistent cache of some intermediary results. This could quite easily be implemented as simple sql, but there's a couple of problems, namely I need to compress the size of this structure on disk as much as possible. (because of amount of values I'm storing) Also, it's not transactional, I just need to write once and simply read the contents of the entire table, so a relational DB isn't actually a very good fit. I was wondering if anyone had any good suggestions? For some reason I can't seem to come up with something decent atm. Especially something with an API in java would be nice.

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  • Entity Framework 4: C# !(ReferenceEquals()) vs !=

    - by Eric J.
    Unless a class specifically overrides the behavior defined for Object, ReferenceEquals and == do the same thing... compare references. In property setters, I have commonly used the pattern private MyType myProperty; public MyType MyProperty { set { if (myProperty != value) { myProperty = value; // Do stuff like NotifyPropertyChanged } } } However, in code generated by Entity Framework, the if statement is replaced by if (!ReferenceEquals(myProperty, value)) Using ReferenceEquals is more explicit (as I guess not all C# programmers know that == does the same thing if not overridden). Is there any difference that's escaping me between the two if-variants? Are they perhaps accounting for the possibility that POCO designers may have overridden ==? In short, if I have not overridden ==, am I save using != instead of ReferencEquals()?

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  • Do I still have to implement a singleton class by hand in .net, even when using .Net4.0?

    - by Hamish Grubijan
    Once the singleton pattern is understood, writing subsequent singleton classes in C# is a brainless exercise. I would hope that the framework would help you by providing an interface or a base class to do that. Here is how I envision it: public sealed class Schablone : ISingleton<Schablone> { // Stuff forced by the interface goes here // Extra logic goes here } Does what I am looking for exist? Is there some syntactic sugar for constructing a singleton class - whether with an interface, a class attribute, etc.? Can one write a useful and bullet-proof ISingleton themselves? Care to try? Thanks!

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  • Styling a list as tabs with a background overflowing into content

    - by Litso
    I couldn't think of any better way to name this question, but I'll explain. I have a mediawiki website with a background pattern (like parchment) behind the articles. At the top of each article I want to have tabs like wikipedia does (with page | talk | edit etc links). The problem is, the tabs should seamlessly fit with the article's background and I can't figure out if this is actually possible. The way I was trying to do it was positioning the list inside the actual content div and give the <li items a transparent background, but as far as I can see there's no way to color the rest of the <ul's background black without affecting the <li's in there. Anyone have an idea? (example url: http://dev.mansonwiki.com/wiki/Sandbox )

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  • Why state cannot be part of Presenter in MVP?

    - by rFactor
    I read http://www.codeproject.com/KB/architecture/MVC_MVP_MVVM_design.aspx and it said: As powerful as they are, both MVC and MVP have their problems. One of them is persistence of the View’s state. For instance, if the Model, being a domain object, does not know anything about the UI, and the View does not implement any business logic, then where would we store the state of the View’s elements such as selected items? Fowler comes up with a solution in the form of a Presentation Model pattern. I wonder why Presenter can't hold View state? It already holds all View logic. As far as I understand, in MVC and MVP the state is kept in View. In PM and MVVM the state is kept in the Presentation Model. Why can't Presenter follow PM in this particular case and contain the state of the view? Here is another article which says Presenter does not hold View state, instead the view does: http://www.codeproject.com/KB/aspnet/ArchitectureComparison.aspx

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  • Thread used for ServiceConnection callback (Android)

    - by Jannick
    Hi I'm developing an activity that binds to a local service (in onCreate of the activity): bindService(new Intent(this, CommandService.class), svcConn, BIND_AUTO_CREATE); I would like to be able to call methods through the IBinder in my lifecycle methods, but can not be sure that onServiceConnected have been called prior to these. I'm thinking of handling this by adding a queue of sorts in the ServiceConnection implementation, so that the method calls (Command pattern) will be executed once the connection is established. My questions are then: Is this stupid, any better ways? :) Are there any specification for which thread will be used to execute the ServiceConnection callbacks? More to the point, do I need to worry about synchronizing a queue datastructure? Edit - something like: public void onServiceConnected(ComponentName name, IBinder service) { dispatchService = (DispatchAsync)service; for(ExecutionTask task : queue){ dispatchService.execute(task.getCommand(), task); } }

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  • jQuery/javascript events - prototype event handler

    - by Brian M. Hunt
    The following code doesn't work as I intuitively expect it to: function MyObject(input) { input.change(this._foo); this.X = undefined; } MyObject.prototype._foo = function() { alert("This code is never called"); // but if it did this.X = true; } var test_input = $("input#xyz"); // a random, existing input var m = MyObject(test_input); // attach handler (or try to) test_input.change(); // trigger event alert(m.X); // undefined I'd expect that _foo() would be called (and, if that ever happens, that the this variable in _foo() would be an instantiation of MyObject. Does anyone know why this doesn't work, and of any alternative pattern for passing an object to an event handler? Thank you for reading. Brian

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  • Convert inline image tags like [image:123:title:size] into HTML img tags

    - by Jacques Joubert
    I am looking for help with regular expression $pattern to convert inline image tags like [image:123:title:size] into HTML img tags. here is the code: //[image:ID:caption:size] $content = '[image:38:title:800x900]'; preg_match_all( '/\[image:(\d+)(:?)([^\]]*)\]/i', $content, $images ); if( !empty( $images[0] ) ) { // There are image inline tags in the content foreach( $images[0] as $i => $tag ) { $link_ID = (int)$images[1][$i]; $caption = empty( $images[2][$i] ) ? '#' : $images[3][$i]; $size = empty( $images[4][$i] ) ? '#' : $images[4][$i]; } echo '<br />'; echo 'ID: '.$link_ID.'<br />'; echo 'Tag: '.$caption.'<br />'; echo 'size: '.$size.'<br />'; } which outputs: ID: 12 Tag: caption:size size: # Any help would be great!

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  • Different background colors for the top and bottom of a UITableView

    - by Aaron Brethorst
    If you look at your Inbox in iPhone OS 3.0's Mail app, you'll see that swiping down displays a grayish background color above the UISearchBar. Now, if you scroll down to the bottom of the table, you'll see that the background color at that end is white. I can think of a couple ways of solving this problem, but they're pretty hacky: Change the table view's background color depending on the current scrollOffset by overriding -scrollViewDidScroll: Give the UITableView a clear background color and then set its superview's backgroundColor to a gradient pattern image. Does anyone know what the "best practice" solution is for this problem? thanks.

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  • Is it a bad idea to have a login dialog inside an iframe?

    - by AyKarsi
    We're creating a website where we will be giving out code snippets to our users which they can place on their own websites. These snippets contain a link a javascript include. When clicking the link, an iframe containing the login dialog to our site opens. The user then authenticates inside the iframe, does his work and when he leaves the iframe his session is closed. We've got it working allready and it's very slick. Our main concern though is phishing. The user has absolutely now way of veryifying where the login page is really coming from. On the other hand, phising attacks are also succesfull even if the user can see the fake-url in the address bar. Would you enter your (OpenId) credentials in an iframe? Does anyone know a pattern with which we could minimise the chances of a phishing attack?

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  • Restrict violation of architecture - asp.net MVP

    - by Srikanth
    If we had a defined hierarchy in an application. For ex a 3 - tier architecture, how do we restrict subsequent developers from violating the norms? For ex, in case of MVP (not asp.net MVC) architecture, the presenter should always bind the model and view. This helps in writing proper unit test programs. However, we had instances where people directly imported the model in view and called the functions violating the norms and hence the test cases couldn't be written properly. Is there a way we can restrict which classes are allowed to inherit from a set of classes? I am looking at various possibilities, including adopting a different design pattern, however a new approach should be worth the code change involved.

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  • How would MVVM be for games?

    - by Benny Jobigan
    Particularly for 2d games, and particularly silverlight/wpf games. If you think about it, you can divide a game object into its view (the graphic on the screen) and a view-model/model (the state, ai, and other data for the object). In silverlight, it seems common to make each object a user control, putting the model and view into a single object. I suppose the advantage of this is simplicity. But, perhaps it's less clean or has some disadvantages in terms of the underlying "game engine". What are your thoughts on this matter? What are some advantages and disadvantages of using the MVVM pattern for game development? How about performance? All thoughts are welcome.

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