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• Collision Systems Implementation

  - by hrr4

  Just curious what might be a good way to implement a decent collision system. As a class inherited by a base Entity class? Currently I'm stuck and could just use a couple better ideas than my own. Any help is appreciated! Edit: Sorry, it's 2D Collisioning but honestly, I'm not looking for specific collision methods. I'm looking more about the lines of implementation. Just curious of some of the common methods of how to implement collision systems such as: Should the entire collision system be it's own class? What, if anything, should be inheritable? These are some of my questions. Sorry for the confusion.

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• Google Currency Convertor JSON API

  - by Gopinath

  There are many live currency conversion services available on the web and the popular one’s among them are – Google, Yahoo, MSN & XE. Among all these four Google is the developer’s darling and it provides a simple JSON API that can be integrated in your applications.  http://www.google.com/ig/calculator?hl=en&q=1USD=?INR Using the API is very simple and it takes two parameters as input. The first parameter “hl” is the language code in which you want output. The second parameter “q” is the conversion query in the format <number><from currency code>=?<to currency code>. In the URL give above the query requests for conversion of 1 USD in INR. JSON output for the above query would be  similar to {lhs: "1 U.S. dollar",rhs: "54.4602984 Indian rupees",error: "",icc: true} Examples: 100 USD in INR  http://www.google.com/ig/calculator?hl=en&q=100USD=?INR Example 2: 1 GBP in INR http://www.google.com/ig/calculator?hl=en&q=1GBP=?INR Example 3: 1 USD in INR, output the data in French language http://www.google.com/ig/calculator?hl=fr&q=1USD=?INR   This is an undocumented service and expect changes at any time. But as long as it works, you got a programmatic way to convert currencies.

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• MVC pattern synchronisation

  - by Hariprasad

  I am facing a problem in synchronizing my model and view threads I have a view which is table. In it, user can select a few rows. I update the view as soon as the user clicks on any row since I don't want the UI to be slow. This updating is done by a logic which runs in the controller thread below. At the same time, the controller will update the model data too, which takes place in a different thread. i.e., controller puts the query in a queue, which is then executed by the model thread - which is a single-threaded interface. As soon as the query executes, controller will get a signal. Now, In order to keep the view and model synchronized, I will update the view again based on the return value of the query (the data returned by model) - even though I updated the view already for that user action. But, I am facing issues because, its taking a lot of time for the model to return the result, by that time user would have performed multiple clicks. So, as a result of updating the view again based on the information from model, the view sometimes goes back to the state in which the previous clicks were made (Suppose user clicks thrice on different rows. I update the view as soon as the click happens. Also, I update the view when I get data back from the model - which is supposed to be same as the already updated state of the view. Now, when the user clicks third time, I get data for the first click from model. As a result, view goes back to a state which is generated by the first click) Is there any way to handle such a synchronization issue?

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• Create an array from mysql with column names and values [on hold]

  - by ScaZ

  i'm trying to create an array with PHP and MySQL, but i always get errors. The code i'm using function db_listar_usuarios(){ $link=db_connect(); $query = "select * from usuarios" or die("Problemas en el select: " . mysqli_error($link)); $result = $link->query($query); while($row = mysqli_fetch_assoc($result)) { $row['nombre'] . array(; foreach ($row as $col => $val) { $col => $val; } } } And what I want to create with this code is: array( 'john' => array('address' => 'st 123', 'age' => '25', 'surname' => 'doe'), 'ane' => array('address' => 'av 456', 'age'=> '32', 'surname' => 'smith'), ); To use then like something like this: private $contacts = db_listar_usuarios(); I use 2 files: functions.php and server.php server.php is a downloaded file example to do a REST API. Here are both of them. server.php - pastebin.com/5j54m1Mz functions.php - pastebin.com/N7jMhSBa Thank you in advance!

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• The sign of a true manager is delegation (C# style)

  - by MarkPearl

  Today I thought I would write a bit about delegates in C#. Up till recently I have managed to side step any real understanding of what delegates do and why they are useful – I mean, I know roughly what they do and have used them a lot, but I have never really got down dirty with them and mucked about. Recently however with my renewed interest in Silverlight delegates came up again as a possible solution to a particular problem, and suddenly I found myself opening a bland little console application to just see exactly how far I could take delegates with my limited knowledge. So, let’s first look at the MSDN definition of delegates… A delegate declaration defines a reference type that can be used to encapsulate a method with a specific signature. A delegate instance encapsulates a static or an instance method. Delegates are roughly similar to function pointers in C++; however, delegates are type-safe and secure. Well, don’t you love MSDN for such a useful definition. I must give it credit though… later on it really explains it a bit better by saying “A delegate lets you pass a function as a parameter. The type safety of delegates requires the function you pass as a delegate to have the same signature as the delegate declaration.” A little more reading up on delegates mentions that delegates are similar to interfaces in that they enable the separation of specification and implementation. A delegate declares a single method, while an interface declares a group of methods. So enough reading - lets look at some code and see a basic example of a delegate… Let’s assume we have a console application with a simple delegate declared called AdjustValue like below… class Program { private delegate int AdjustValue(int val); static void Main(string[] args) { } } In a sense, all we have said is that we will be creating one or more methods that follow the same pattern as AdjustValue – i.e. they will take one input value of type int and return an integer. We could then expand our code to have various methods that match the structure of our delegate AdjustValue (remember the structure is int xxx (int xxx)) class Program { private delegate int AdjustValue(int val); private static int Dbl(int val) { return val * 2; } private static int AlwaysOne(int val) { return 1; } static void Main(string[] args) { } }  Above I have expanded my project to have two methods, one called Dbl and the other AlwaysOne. Dbl always returns double the input val and AlwaysOne always returns 1. I could now declare a variable and assign it to be one of those functions, like the following… class Program { private delegate int AdjustValue(int val); private static int Dbl(int val) { return val * 2; } private static int AlwaysOne(int val) { return 1; } static void Main(string[] args) { AdjustValue myDelegate; myDelegate = Dbl; Console.WriteLine(myDelegate(1).ToString()); Console.ReadLine(); } } In this instance I have declared an instance of the AdjustValue delegate called myDelegate; I have then told myDelegate to point to the method Dbl, and then called myDelegate(1). What would the result be? Yes, in this instance it would be exactly the same as me calling the following code… static void Main(string[] args) { Console.WriteLine(Dbl(1).ToString()); Console.ReadLine(); }   So why all the extra work for delegates when we could just do what we did above and call the method directly? Well… that separation of specification to implementation comes to mind. So, this all seems pretty simple. Let’s take a slightly more complicated variation to the console application. Assume that my project is the same as the one previously except that my main method is adjusted as follows… static void Main(string[] args) { AdjustValue myDelegate; myDelegate = Dbl; myDelegate = AlwaysOne; Console.WriteLine(myDelegate(1).ToString()); Console.ReadLine(); } What would happen in this scenario? Quite simply “1” would be written to the console, the reason being that myDelegate was last pointing to the AlwaysOne method before it was called. Make sense? In a way, the myDelegate is a variable method that can be swapped and changed when needed. Let’s make the code a little more confusing by using a delegate in the declaration of another delegate as shown below… class Program { private delegate int AdjustValue(InputValue val); private delegate int InputValue(); private static int Dbl(InputValue val) { return val()*2; } private static int GetInputVal() { Console.WriteLine("Enter a whole number : "); return Convert.ToInt32(Console.ReadLine()); } static void Main(string[] args) { AdjustValue myDelegate; myDelegate = Dbl; Console.WriteLine(myDelegate(GetInputVal).ToString()); Console.ReadLine(); } }   Now it gets really interesting because it looks like we have passed a method into a function in the main method by declaring… Console.WriteLine(myDelegate(GetInputVal).ToString()); So, what it the output? Well, try take a guess on what will happen – then copy the code and see if you got it right. Well that brings me to the end of this short explanation of Delegates. Hopefully it made sense!

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• fastcgi-mono-server with Nginx is much slower than xsp4

  - by marxin

  We started testing our MVC4 app on xsp4 server compiled with mono-3.0.3, speed was enough and we decided to set up production fastcgi-mono-server4 (version 2.11.0.0) with nginx (1.2.6-r1). Single query that loads some JSON query took ~200ms on XSP4, but Nginx serves the query in about 1.2s and I am wondering where could be such a slow down? I followed nginx configuration: http://www.mono-project.com/FastCGI_Nginx and fastcgi-mono-server4 uses socket for listening nginx. Do you have any ideas how to log some time stamp which will help me? Thanks

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• If you need more than 3 levels of indentation, you're screwed?

  - by jokoon

  Per the Linux kernel coding style document: The answer to that is that if you need more than 3 levels of indentation, you're screwed anyway, and should fix your program. What can I deduct from this quote? On top of the fact that too long methods are hard to maintain, are they hard or impossible to optimize for the compiler? I don't really understand if this quote encourages better coding practice or is really a mathematical / algorithmic sort of truth. I also read in some C++ optimizing guide that dividing up a program into more function improves its design is a common thing taught at school, but it should be not done too much, since it can turn into a lot of JMP calls (even if the compiler can inline some methods by itself).

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• Is it okay to have many Abstract classes in your application?

  - by JoseK

  We initially wanted to implement a Strategy pattern with varying implementations of the methods in a commmon interface. These will get picked up at runtime based on user inputs. As it's turned out, we're having Abstract classes implementing 3 - 5 common methods and only one method left for a varying implementation i.e. the Strategy. Update: By many abstract classes I mean there are 6 different high level functionalities i.e. 6 packages , and each has it's Interface + AbstractImpl + (series of Actual Impl). Is this a bad design in any way? Any negative views in terms of later extensibility - I'm preparing for a code/design review with seniors.

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• Creating your own Tetris game with VB.NET - Part 3

  In this part of my series, I am going to cover the whole creation of all the shapes, and the game playing methods.

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• Best Practice to return responses from service

  - by A9S6

  I am writing a SOAP based ASP.NET Web Service having a number of methods to deal with Client objects. e.g: int AddClient(Client c) = returns Client ID when successful List GetClients() Client GetClientInfo(int clientId) In the above methods, the return value/object for each method corresponds to the "all good" scenario i.e. A client Id will be returned if AddClient was successful or a List< of Client objects will be returned by GetClients. But what if an error occurs, how do I convey the error message to the caller? I was thinking of having a Response class: Response { StatusCode, StatusMessage, Details } where Details will hold the actual response but in that case the caller will have to cast the response every time. What are your views on the above? Is there a better solution? ---------- UPDATED ----------- Is there something new in WCF for the above? What difference will it make If I change the ASP.NET Web Service to a WCF Service?

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• Information I need to know as a Java Developer [on hold]

  - by Woy

  I'm a java developer. I'm trying to get more knowledge to become a better programmer. I've listed a number of technologies to learn. Instead of what I've listed, what technologies would you suggest to learn as well for a Junior Java Developer? I realize, there's a lot of things to study. Java: - how a garbage collector works - resource management - network programming - TCP/IP HTTP - transactions, - consistency: interfaces, classes collections, hash codes, algorithms, comp. complexity concurrent programming: synchronizing, semafores steam management metability: thread-safety byte code manipulations, reflections, Aspect-Oriented Programming as base to understand frameworks such as Spring etc. Web stack: servlets, filters, socket programming Libraries: JDK, GWT, Apache Commons, Joda-Time, Dependency Injections: Spring, Nano Tools: IDE: very good knowledge - debugger - profiler - web analyzers: Wireshark, firebugs - unit testing SQL/Databases: Basics SELECTing columns from a table Aggregates Part 1: COUNT, SUM, MAX/MIN Aggregates Part 2: DISTINCT, GROUP BY, HAVING + Intermediate JOINs, ANSI-89 and ANSI-92 syntax + UNION vs UNION ALL x NULL handling: COALESCE & Native NULL handling Subqueries: IN, EXISTS, and inline views Subqueries: Correlated ITH syntax: Subquery Factoring/CTE Views Advanced Topics Functions, Stored Procedures, Packages Pivoting data: CASE & PIVOT syntax Hierarchical Queries Cursors: Implicit and Explicit Triggers Dynamic SQL Materialized Views Query Optimization: Indexes Query Optimization: Explain Plans Query Optimization: Profiling Data Modelling: Normal Forms, 1 through 3 Data Modelling: Primary & Foreign Keys Data Modelling: Table Constraints Data Modelling: Link/Corrollary Tables Full Text Searching XML Isolation Levels Entity Relationship Diagrams (ERDs), Logical and Physical Transactions: COMMIT, ROLLBACK, Error Handling

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• Cross domain LDAP

  - by Adam

  For a system we are developing we have 2 domains an internal and an external domain with bi directional trust between them. However the servers are only able to connect to their own DC's. We have an application server on the internal domain which needs to use an LDAP query to gather a list of users from a group on the external domain. How do i go about writing an LDAP query that asks one DC to go ask another DC for a list of users. I tried querying the internal DC with the same LDAP query I would use if it could hit the external DC directly but this does not work. When i use Softerra LDAP Administraor I can view the full hierarchy of the interal domain but despite the trust relationship between domains i am unable to see any of the external doamin. Any suggestions or help would be greatly appreciated

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• Overload an Operator in C# 4.0

  We will be overloading operators to use in methods.

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• Does OO, TDD, and Refactoring to Smaller Functions affect Speed of Code?

  - by Dennis

  In Computer Science field, I have noticed a notable shift in thinking when it comes to programming. The advice as it stands now is write smaller, more testable code refactor existing code into smaller and smaller chunks of code until most of your methods/functions are just a few lines long write functions that only do one thing (which makes them smaller again) This is a change compared to the "old" or "bad" code practices where you have methods spanning 2500 lines, and big classes doing everything. My question is this: when it call comes down to machine code, to 1s and 0s, to assembly instructions, should I be at all concerned that my class-separated code with variety of small-to-tiny functions generates too much extra overhead? While I am not exactly familiar with how OO code and function calls are handled in ASM in the end, I do have some idea. I assume that each extra function call, object call, or include call (in some languages), generate an extra set of instructions, thereby increasing code's volume and adding various overhead, without adding actual "useful" code. I also imagine that good optimizations can be done to ASM before it is actually ran on the hardware, but that optimization can only do so much too. Hence, my question -- how much overhead (in space and speed) does well-separated code (split up across hundreds of files, classes, and methods) actually introduce compared to having "one big method that contains everything", due to this overhead? UPDATE for clarity: I am assuming that adding more and more functions and more and more objects and classes in a code will result in more and more parameter passing between smaller code pieces. It was said somewhere (quote TBD) that up to 70% of all code is made up of ASM's MOV instruction - loading CPU registers with proper variables, not the actual computation being done. In my case, you load up CPU's time with PUSH/POP instructions to provide linkage and parameter passing between various pieces of code. The smaller you make your pieces of code, the more overhead "linkage" is required. I am concerned that this linkage adds to software bloat and slow-down and I am wondering if I should be concerned about this, and how much, if any at all, because current and future generations of programmers who are building software for the next century, will have to live with and consume software built using these practices. UPDATE: Multiple files I am writing new code now that is slowly replacing old code. In particular I've noted that one of the old classes was a ~3000 line file (as mentioned earlier). Now it is becoming a set of 15-20 files located across various directories, including test files and not including PHP framework I am using to bind some things together. More files are coming as well. When it comes to disk I/O, loading multiple files is slower than loading one large file. Of course not all files are loaded, they are loaded as needed, and disk caching and memory caching options exist, and yet still I believe that loading multiple files takes more processing than loading a single file into memory. I am adding that to my concern.

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• Finding Locked Out Users

  - by Bart Silverstrim

  Active Directory up to 2008 network (our servers are a mix of 2008, 2003...) I'm looking for a quick way to query AD to find out what users are locked out, preferably from a batch or script file, to monitor for possible issues with either user accounts being attacked by an automated attack or just anomalies in the network. I've Googled and my Google-fu has failed; I found a query off Microsoft's own knowledgebase that cites a string to use on Server 2003 with the management snap-in's saved queries (http://support.microsoft.com/kb/555131) but when I entered it, the query returned 400 users that a spot-check showed did NOT have a checkmark in the "Account is locked out" box under "account." In fact, I don't see anything wrong with their accounts. Is there a simple utility (wisesoft bulkadusers apparently uses this method behind the scenes, since it's results were also wrong) that will give a count of users and possibly their user object names? Script? Something?

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• Visual Studio 2010 and MS SQL 2008- Authentication System using asp.net ( JQuery, Json and Web servi

  how to call server side methods or functions directly using JQuery in ASP.Net Csharp.

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• Should I implement an interface directly or have the superclass do it?

  - by c_maker

  Is there a difference between public class A extends AbstractB implements C {...} versus... public class A extends AbstractB {...} AbstractB implements C {...} I understand that in both cases, class A will end up conforming to the interface. In the second case, AbstractB can provide implementation for interface methods in C. Is that the only difference? If I do NOT want to provide an implementation for any of the interface methods in AbstractB, which style should I be using? Does using one or the other have some hidden 'documentation' purpose?

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• "more than 3 levels of indentation, you're screwed" How should I understand this quote ?

  - by jokoon

  The answer to that is that if you need more than 3 levels of indentation, you're screwed anyway, and should fix your program. What can I deduct from this quote ? On top of the fact that too long methods are hard to maintain, are they hard or impossible to optimize for the compiler ? I don't really understand if this quote encourages better coding practice or is really a mathematical/algorithmic sort of truth... I also read in some C++ optimizing guide that dividing up a program into more function improves its design is a common thing taught at school, but it should be not done too much, since it can turn into a lot of JMP calls (even if the compiler can inline some methods by itself).

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• How is this "interface"-like structure/pattern called?

  - by Sebastian Negraszus

  Let's assume we have an XmlDoc class that contains basic functionality for dealing with an XML data structure and saving/loading data to/from a file. Now we have several subclasses, A, B and C. They all inherit from XmlDoc and add component-specific methods for setting and getting lots of data. They are like "interfaces" but also add an implementation for the signatures. Finally, we have an ABCDoc class that joins all the "interfaces" via virtual multiple inheritence and adds some ABCDoc-specific stuff, such as using XMLDoc-methods to set an appropriate doc type. We may also have an ADoc class for only saving A data. How is this pattern called? "Interface" is not really the right word since interfaces usually do not contain an implementation. Bonus points for C++ code conventions.

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• Best approach for tracking dependent state

  - by Pace

  Let's pretend I work on a project tracking application. The application is a database backed, server hosted, web application. In this application there are Projects which have many Activities which have many Tasks. A Task has two date fields an originalDueDate and a projectedDueDate. In addition, there are dynamic fields on the Activities and the Projects which indicate whether the Activity or Project is behind schedule based on the projected due dates of the child tasks and various other variables such as remaining buffer time, etc. There are a number of things that can cause the projectedDueDate to change. For example, an employee working on the project may (via a server request) enter in a shipping delay. Alternatively, a site may (via a server request) enter in an unexpected closure. When any of these things occur I need to not only update the projectedDueDate of the Task but also trigger the corresponding Project and Activity to update as well. What is the best way to do this? I've thought of the observer pattern but I don't keep a single copy of all these objects in memory. When a request comes in, I query the Task in from the database, at that point there is no associated Activity in memory that would be a listener. I could remove the ability to query for Tasks and force the application to query first by Project, then by Activity (in context of Project), then by task (in context of Activity) adding the observer relationships at each step but I'm not sure if that is the best way. I could setup a database event listening system so when a Task modified event is dispatched I have a handler which queries for the Activity at that point. I could simply setup a two-way relationship between Task and Activity so that the Task knows about the parent Activity and when the Task updates his state the Task grabs his parent and updates state. Right now I'm stuck considering all the options and am wondering if any single approach (doesn't have to be a listed approach) is jumping out at others as the best approach.

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• Imperative vs. component based programming [closed]

  - by AlexW

  I've been thinking about how programming and more specifically the teaching of programming is advocated amongst the community (online). Often I've heard that Ruby and RoR is an ideal platform for learning to program. I completely disagree... RoR and Ruby are based on the application of the component based paradigm, which means they are ideal for rapid application development. This is much like the MVC model in PHP and ASP.NET But, learning a proper imperative language like Java or C/C++ (or even Perl and PHP) is the only way for a new programmer to explore logic itself, and not get too bogged down in architectural concerns like the need for separation of concerns, and the preference for components. Maybe it's a personal preference thing. I rather think that the most interesting aspects to programming are the procedural bits of code I write that actually do stuff rather than the project planning, and modelling that comes about from fully object oriented engineering or simply using the MVC model. I know this may sound confused to some of you. I feel strongly though that the best way for programming to be taught is through imperative and procedural methods. Architectural (component) methods come later, if at all. After all, none of the amazing algorithms that exist were based on OOP practice! It's all procedural code when it comes to the 'magic'. OOP is useful in creating products and utilities. Algorithms are what makes things happen, and move data around, and so imperative (and/or procedural) code are what matters most. When I see programmers recommending Ruby on Rails to newbie developers, I think it's just so wrong. Just because you write less code with Ruby does not make it easier to do! It's the opposite... you have to know loads more to appreciate its succinct nature. New coders who really want to understand the nuts and bolts of coding need to go away and figure out writing methods/functions (i.e. imperative programming) and working in procedural style, in order to grasp the fundamentals, first, before looking into architectural ways of working. So, my question is: should Ruby ever be recommended as a first language? I think no (obviously)... what arguments are there for it?

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• Using COM objects in scripting languages -- Part 2 (Python)

  Article shows how to instantiate a COM object in Python and use its methods and properties.

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• Need Information On Importing Data Into The Oracle Product Hub?

  - by LuciaC

  One of the key challenges of implementing a Master Data Management solution is importing data into the system. Oracle Product Hub offers numerous ways of importing the setup data and the actual product data.  Review all available methods to import data in the White Paper Doc ID 1504980.1 which provides details and examples of each method, discusses special cases, and provides some troubleshooting tips.The methods reviewed include:     FNDLOAD     iSetup     Interfaces and Public APIs     Import from Excel     Web Application Desktop Integrator     Webservices

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• Need help for array when no checkbox is selected [closed]

  - by darlene

  Hi guys I have created a form that has checkboxes, the code works great when a checkbox is selcted however when no checkboxes are selected I get errors such as "Undefined index: onemon in and Warning: Invalid argument supplied for foreach()" Please help:) FORM 1. Had a cold, fever or headache? input type="checkbox" name="onemon[]" value="q1" if(isset($_GET['onemon']) && $_GET['onemon']= "q1") 2. Had dental extractions or teeth cleaning? input type="checkbox" name="onemon[]" value="q2" if(isset($_GET['onemon']) && $_GET['onemon']= "q2") 3. Had minor outpatient sugery? input type="checkbox" name="onemon[]" value="q3" if(isset($_GET['onemon']) && $_GET['onemon']= "q3") 4. Had any vaccines? input type="checkbox" name="onemon[]" value="q4" if(isset($_GET['onemon']) && $_GET['onemon']= "q4") PHP $date = date('Y-m-d'); $onemon = $_POST ['onemon']; { $con = mysql_connect("localhost","root","") or die ("Could not connect to DB Server"); $db_selected = mysql_select_db("nbtsdb", $con) or die("Could not locate the DB"); // You have to loop through the array of checked box values ... $ques=""; foreach($onemon as $entry){ $ques .= $entry.","; } //$addPersonalSql holds the insert SQL query string $query = "INSERT INTO defferal(defid, intdate, onemonth) VALUES('','$date','$ques')"; $addMemberSql = $query or die ("Unable to Insert Data into defferal Table"); mysql_query($addMemberSql); }

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• "Collection Wrapper" pattern - is this common?

  - by Prog

  A different question of mine had to do with encapsulating member data structures inside classes. In order to understand this question better please read that question and look at the approach discussed. One of the guys who answered that question said that the approach is good, but if I understood him correctly - he said that there should be a class existing just for the purpose of wrapping the collection, instead of an ordinary class offering a number of public methods just to access the member collection. For example, instead of this: class SomeClass{ // downright exposing the concrete collection. Things[] someCollection; // other stuff omitted Thing[] getCollection(){return someCollection;} } Or this: class SomeClass{ // encapsulating the collection, but inflating the class' public interface. Thing[] someCollection; // class functionality omitted. public Thing getThing(int index){ return someCollection[index]; } public int getSize(){ return someCollection.length; } public void setThing(int index, Thing thing){ someCollection[index] = thing; } public void removeThing(int index){ someCollection[index] = null; } } We'll have this: // encapsulating the collection - in a different class, dedicated to this. class SomeClass{ CollectionWrapper someCollection; CollectionWrapper getCollection(){return someCollection;} } class CollectionWrapper{ Thing[] someCollection; public Thing getThing(int index){ return someCollection[index]; } public int getSize(){ return someCollection.length; } public void setThing(int index, Thing thing){ someCollection[index] = thing; } public void removeThing(int index){ someCollection[index] = null; } } This way, the inner data structure in SomeClass can change without affecting client code, and without forcing SomeClass to offer a lot of public methods just to access the inner collection. CollectionWrapper does this instead. E.g. if the collection changes from an array to a List, the internal implementation of CollectionWrapper changes, but client code stays the same. Also, the CollectionWrapper can hide certain things from the client code - from example, it can disallow mutation to the collection by not having the methods setThing and removeThing. This approach to decoupling client code from the concrete data structure seems IMHO pretty good. Is this approach common? What are it's downfalls? Is this used in practice?

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