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• PHP (A few questions) OO, refactoring, eclipse

  - by jax

  I am using PHP in eclipse. It works ok, I can connect to my remote site, there is colour coding of code elements and some code hints. I realise this may be too long to answer all questions, if you have a good answer for one part, answering just that is ok. Firstly General Coding I have found that it is easy to loose track of included files and their variables. For example if there was a database $cursor it is difficult to remember or even know that it was declared in the included file (this becomes much worse the more files you include). How are people dealing with this? How are people documenting their code - in particular the required GET and POST data? Secondly OO Development: Should I be going full OO in my development. Currently I have a functions library which I can include and have separated each "task" into a separate file. It is a bit nasty but it works. If I go OO how do I structure the directories in PHP, java uses packages - what about php? How should I name my files, should I use all lower case with _ for spaces "hello_world.php"? Should I name classes with Uppercase like Java "HelloWorld.php"? Is there a different naming convention for Classes and regular function files? Thirdly Refactoring I must say this is a real pain. If I change the name of a variable in one place I have to go through whole document and each file that included this file and change the name their too. Of course, errors everywhere is what results. How are people dealing with this problem? In Java if you change the name in one place it changes everywhere. Are there any plugins to improve php refactoring? I am using the official PHP version of Eclipse from their website. thanks

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• How do you deal with denormalization / secondary indexes in database sharding?

  - by Continuation

  Say I have a "message" table with 2 secondary indexes: "recipient_id" "sender_id" I want to shard the "message" table by "recipient_id". That way to retrieve all messages sent to a certain recipient I only need to query one shard. But at the same time, I want to be able to make a query that ask for all messages sent by a certain sender. Now I don't want to send that query to every single shard of the "message" table. One way to do this is to duplicate the data and have a "message_by_sender" table sharded by "sender_id". The problem with that approach is that every time a message has been sent, I need to insert the message into both "message" and "message_by_sender" tables. But what if after inserting into "message" the insertion into "message_by_sender" fail? In that case the message exists in "message" but not in "message_by_sender". How do I make sure that if a message exists in "message" then it also exists in "message_by_sender" without resorting to 2 phase commit? This must be a very common issue for anyone who shards their databases. How do you deal woth it?

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• How do I store complex objects in javascript?

  - by Colen

  Hello, I need to be able to store objects in javascript, and access them very quickly. For example, I have a list of vehicles, defined like so: { "name": "Jim's Ford Focus", "color": "white", isDamaged: true, wheels: 4 } { "name": "Bob's Suzuki Swift", "color": "green", isDamaged: false, wheels: 4 } { "name": "Alex's Harley Davidson", "color": "black", isDamaged: false, wheels: 2 } There will potentially be hundreds of these vehicle entries, which might be accessed thousands of times. I need to be able to access them as fast as possible, ideally in some useful way. For example, I could store the objects in an array. Then I could simply say vehicles[0] to get the Ford Focus entry, vehicles[1] to get the Suzuki Swift entry, etc. However, how do I know which entry is the Ford Focus? I want to simply ask "find me Jim's Ford Focus" and have the object returned to me, as fast as possible. For example, in another language, I might use a hash table, indexed by name. How can I do this in javascript? Or, is there a better way? Thanks.

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• asynchronous pages

  - by lockedscope

  I have just read the multi-threading and custom threading in asp.net articles. http://www.williablog.net/williablog/post/2008/12/16/Custom-Threading-in-ASPNET.aspx http://www.williablog.net/williablog/post/2008/12/16/Multi-Threading-in-ASPNET.aspx I have couple of questions. What does he mean by returning a thread to the pool? Is that thread completely removed from memory or put in to a state that it does not scheduled to CPU(is it in sleep state or whatever)? If that thread is removed from memory how could it survive after async point? How this mechanism works? Are every objects(pages class, request,response etc.) are copied to somewhere else before they are disposed? (Or, is it just waiting in a sleep state and then its waked when async call ends?) He is saying that; "Having said that, making pages asynchronous is not really about improving performance, it is about improving scalability" then he is saying; "I'm sorry to say that it will do nothing for scalability or performance." So which one is true? or for which case(s) are they true?

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• Is an "infinite" iterator bad design?

  - by Adamski

  Is it generally considered bad practice to provide Iterator implementations that are "infinite"; i.e. where calls to hasNext() always(*) return true? Typically I'd say "yes" because the calling code could behave erratically, but in the below implementation hasNext() will return true unless the caller removes all elements from the List that the iterator was initialised with; i.e. there is a termination condition. Do you think this is a legitimate use of Iterator? It doesn't seem to violate the contract although I suppose one could argue it's unintuitive. public class CyclicIterator<T> implements Iterator<T> { private final List<T> l; private Iterator it; public CyclicIterator<T>(List<T> l) { this.l = l; this.it = l.iterator(); } public boolean hasNext() { return !l.isEmpty(); } public T next() { T ret; if (!hasNext()) { throw new NoSuchElementException(); } else if (it.hasNext()) { ret = it.next(); } else { it = l.iterator(); ret = it.next(); } return ret; } public void remove() { it.remove(); } }

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• MS SQL datetime precision problem

  - by Nailuj

  I have a situation where two persons might work on the same order (stored in an MS SQL database) from two different computers. To prevent data loss in the case where one would save his copy of the order first, and then a little later the second would save his copy and overwrite the first, I've added a check against the lastSaved field (datetime) before saving. The code looks roughly like this: private bool orderIsChangedByOtherUser(Order localOrderCopy) { // Look up fresh version of the order from the DB Order databaseOrder = orderService.GetByOrderId(localOrderCopy.Id); if (databaseOrder != null && databaseOrder.LastSaved > localOrderCopy.LastSaved) { return true; } else { return false; } } This works for most of the time, but I have found one small bug. If orderIsChangedByOtherUser returns false, the local copy will have its lastSaved updated to the current time and then be persisted to the database. The value of lastSaved in the local copy and the DB should now be the same. However, if orderIsChangedByOtherUser is run again, it sometimes returns true even though no other user has made changes to the DB. When debugging in Visual Studio, databaseOrder.LastSaved and localOrderCopy.LastSaved appear to have the same value, but when looking closer they some times differ by a few milliseconds. I found this article with a short notice on the millisecond precision for datetime in SQL: Another problem is that SQL Server stores DATETIME with a precision of 3.33 milliseconds (0. 00333 seconds). The solution I could think of for this problem, is to compare the two datetimes and consider them equal if they differ by less than say 10 milliseconds. My question to you is then: are there any better/safer ways to compare two datetime values in MS SQL to see if they are exactly the same?

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• A problem with connected points and determining geometry figures based on points' location analysis

  - by StolePopov

  In school we have a really hard problem, and still no one from the students has solved it yet. Take a look at the picture below: http://d.imagehost.org/0422/mreza.gif That's a kind of a network of connected points, which doesn't end and each point has its own number representing it. Let say the numbers are like this: 1-23-456-78910-etc. etc.. (You can't see the number 5 or 8,9... on the picture but they are there and their position is obvious, the point in middle of 4 and 6 is 5 and so on). 1 is connected to 2 and 3, 2 is connected to 1,3,5 and 4 etc. The numbers 1-2-3 indicate they represent a triangle on the picture, but the numbers 1-4-6 do not because 4 is not directly connected with 6. Let's look at 2-3-4-5, that's a parallelogram (you know why), but 4-6-7-9 is NOT a parallelogram because the in this problem there's a rule which says all the sides must be equal for all the figures - triangles and parallelograms. Also there are hexagons, for ex. 4-5-7-9-13-12 is a hexagon - all sides must be equal here too. 12345 - that doesn't represent anything, so we ignore it. I think i explained the problem well. The actual problem which is given to us by using an input of numbers like above to determine if that's a triangle/parallelogram/hexagon(according to the described rules). For ex: 1 2 3 - triangle 11 13 24 26 -parallelogram 1 2 3 4 5 - nothing 11 23 13 25 - nothing 3 2 5 - triangle I was reading computational geometry in order to solve this, but i gave up quickly, nothing seems to help here. One friend told me this site so i decided to give it a try. If you have any ideas about how to solve this, please reply, you can use pseudo code or c++ whatever. Thank you very much.

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• How reliable is DateTime.UtcNow in Silverlight applications?

  - by Edward Tanguay

  I have a silverlight application which users will be running in various time zones. These applications load their data from the server upon start up, then cache it in IsolatedStorage. When I make changes to the data on the server, I want to be able to change the "last updated time" so that all silverlight clients download the newest data the next time they check this date. However, I'm a bit confused as to how to handle the time zone issue since a if the server is in New York and the update time is set to 2010-01-01 17:00:00 and a client in Seattle checks compares it to its local time of 2010-01-01 14:00:00 it won't update and will continue to provide old data for three more hours. My solution is to always post the update time in UTC time, not with the time on the server, then make the Silverlight app check with DateTime.UtcNow. Is this as easy as it sounds or are their issues with this, e.g. that timezones are not set correctly on computers and hence the SilverlightApp does not report the correct UTC time. Can anyone say from experience how likely it is that using DateTime.UtcNow like this for cache refreshing will work in all cases? If DateTime.UtcNow is not reliable, I will just use an incremented "DataVersion" integer but there are other scenarios in which getting time zone sychronization down would make it useful to thoroughly understand how to solve this in silverlight apps.

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• PHP get "Application Root" in Xampp on Windows correctly

  - by Michael Mao

  Hi all: I found this thread on StackOverflow about how to get the "Application Root" from inside my web app. However, most of the approaches suggested in that thread can hardly be applied to my Xampp on Windows. Say, I've got a "common.php" which stays inside my web app's app directory: / /app/common.php /protected/index.php In my common.php, what I've got is like this: define('DOCROOT', $_SERVER['DOCUMENT_ROOT']); define('ABSPATH', dirname(__FILE__)); define('COMMONSCRIPT', $_SERVER['PHP_SELF']); After I required the common.php inside the /protected/index.php, I found this: C:/xampp/htdocs //<== echo DOCROOT; C:\xampp\htdocs\comic\app //<== echo ABSPATH /comic/protected/index.php //<== echo COMMONSCRIPT So the most troublesome part is the path delimiters are not universal, plus, it seems all superglobals from the $_SERVER[] asso array, such as $_SERVER['PHP_SELF'], are relative to the "caller" script, not the "callee" script. It seems that I can only rely on dirname(__FILE__) to make sure this always returns an absolute path to the common.php file. I can certainly parse the returning values from DOCROOT and ABSPATH and then calculate the correct "application root". For instance, I can compare the parts after htdocs and substitute all backslashes with slashes to get a unix-like path I wonder is this the right way to handle this? What if I deploy my web app on a LAMP environment? would this environment-dependent approach bomb me out? I have used some PHP frameworks such as CakePHP and CodeIgniter, to be frank, They just work on either LAMP or WAMP, but I am not sure how they approached such a elegant solution. Many thanks in advance for all the hints and suggestions.

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• Unit Testing in the real world

  - by Malfist

  I manage a rather large application (50k+ lines of code) by myself, and it manages some rather critical business actions. To describe the program simple, I would say it's a fancy UI with the ability to display and change data from the database, and it's managing around 1,000 rental units, and about 3k tenants and all the finances. When I make changes, because it's so large of a code base, I sometimes break something somewhere else. I typically test it by going though the stuff I changed at the functional level (i.e. I run the program and work through the UI), but I can't test for every situation. That is why I want to get started with unit testing. However, this isn't a true, three tier program with a database tier, a business tier, and a UI tier. A lot of the business logic is performed in the UI classes, and many things are done on events. To complicate things, everything is database driven, and I've not seen (so far) good suggestions on how to unit test database interactions. How would be a good way to get started with unit testing for this application. Keep in mind. I've never done unit testing or TDD before. Should I rewrite it to remove the business logic from the UI classes (a lot of work)? Or is there a better way?

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• unable to find a MessageBodyReader

  - by Cristian Boariu

  Hi guys, I have this interface: @Path("inbox") public interface InboxQueryResourceTest { @POST @Path("{membershipExternalId}/query") @Consumes(MediaType.APPLICATION_XML) @Produces("multipart/mixed") public MultipartOutput query(@PathParam("membershipExternalId") final String membershipExternalId, @QueryParam("page") @DefaultValue("0") final int page, @QueryParam("pageSize") @DefaultValue("10") final int pageSize, @QueryParam("sortProperty") final List<String> sortPropertyList, @QueryParam("sortReversed") final List<Boolean> sortReversed, @QueryParam("sortType") final List<String> sortTypeString, final InstanceQuery instanceQuery) throws IOException; } I have implemented the method to return a MultipartOutput. I am posting an xml query from Fiddler and i receive the result without any problem. BUT i have done an integration test for the same interface, i send the same objects and i put the response like: final MultipartOutput multiPartOutput = getClient().query(getUserRestAuth(), 0, 25, null, null, null, instanceQuery); But here, so from integration tests, i receive a strange error: Unable to find a MessageBodyReader of content-type multipart/mixed;boundary="74c5b6b4-e820-452d-abea-4c56ffb514bb" and type class org.jboss.resteasy.plugins.providers.multipart.MultipartOutput Anyone has any ideea why only in integration tests i receive this error? PS: Some of you will say that i do not send application/xml as ContentType but multipart, which of course is false because the objects are annotated with the required @XmlRootElement etc, otherways neither the POST from Fiddler would work.

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• What would be the safest way to store objects of classes derived from a common interface in a common

  - by Svenstaro

  I'd like to manage a bunch of objects of classes derived from a shared interface class in a common container. To illustrate the problem, let's say I'm building a game which will contain different actors. Let's call the interface IActor and derive Enemy and Civilian from it. Now, the idea is to have my game main loop be able to do this: // somewhere during init std::vector<IActor> ActorList; Enemy EvilGuy; Civilian CoolGuy; ActorList.push_back(EvilGuy); ActorList.push_back(CoolGuy); and // main loop while(!done) { BOOST_FOREACH(IActor CurrentActor, ActorList) { CurrentActor.Update(); CurrentActor.Draw(); } } ... or something along those lines. This example obviously won't work but that is pretty much the reason I'm asking here. I'd like to know: What would be the best, safest, highest-level way to manage those objects in a common heterogeneous container? I know about a variety of approaches (Boost::Any, void*, handler class with boost::shared_ptr, Boost.Pointer Container, dynamic_cast) but I can't decide which would be the way to go here. Also I'd like to emphasize that I want to stay away as far as possible from manual memory management or nested pointers. Help much appreciated :).

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• In Perl, is a while loop generally faster than a for loop?

  - by Mike

  I've done a small experiment as will be shown below and it looks like that a while loop is faster than a for loop in Perl. But since the experiment was rather crude, and the subject might be a lot more complicated than it seems, I'd like to hear what you have to say about this. Thanks as always for any comments/suggestions :) In the following two small scripts, I've tried while and for loops separately to calcaulte the factorial of 100,000. The one that has the while loop took 57 minutes 17 seconds to finish while the for loop equivalent took 1 hour 7 minutes 54 seconds. Script that has while loop: use strict; use warnings; use bigint; my $now = time; my $n =shift; my $s=1; while(1){ $s *=$n; $n--; last if $n==2; } print $s*$n; $now = time - $now; printf("\n\nTotal running time: %02d:%02d:%02d\n\n", int($now / 3600), int(($now % 3600) / 60), int($now % 60)); Script that has for loop: use strict; use warnings; use bigint; my $now = time; my $n =shift; my $s=1; for (my $i=2; $i<=$n;$i++) { $s = $s*$i; } print $s; $now = time - $now; printf("\n\nTotal running time: %02d:%02d:%02d\n\n", int($now / 3600), int(($now % 3600) / 60), int($now % 60));

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• How to arrange business logic in a Kohana 3 project

  - by Pekka

  I'm looking for advice, tutorials and links at how to set up a mid-sized web application with Kohana 3. I have implemented MVC patterns in the past but never worked against a "formalized" MVC framework so I'm still getting my head around the terminology - toying around with basic examples, building views and templates, and so on. I'm progressing fairly well but I want to set up a real-world web project (one of my own that I've been planning for quite some time now) as a learning object. I learn best by example, but example-based documentation is a bit sparse for Kohana 3 right now - they say so themselves on the site. While I'm not worried about learning the framework as I go along, I want to make sure the code base is healthily structured from the start - i.e. controllers are split nicely, named well and according to standards, and most importantly the business logic is separated into appropriately sized models. My application could, in its core, be described as a business directory with a range of search and listing functions, and a login area for each entry owner. The actual administrative database backend is already taken care of. Supposing I have all the API worked out and in place already - list all businesses, edit business, list businesses by street name, create offer logged in as business, and so on, and I'm just looking for how to fit the functionality into a MVC pattern and into a Kohana application structure that can be easily extended. Do you know real-life examples of "database-heavy" applications like directories, online communities... with a log-in area built on Kohana 3, preferably Open Source so I could take a peek how they do it? Are there conventions or best practices on how to structure an extendable login area for end users in a Kohana project that is not only able to handle a business directory page, but further products on separate pages as well? Do you know any good resources on building complex applications with Kohana? Have you built something similar and could give me recommendations on a project structure?

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• using XSL to replace XML nodes with new nodes

  - by iHeartGreek

  I need an XSL solution to replace XML nodes with new nodes. Say I have the following existing XML structure: <root> <criteria> <criterion>AAA</criterion> </criteria> </root> And I want to replace the one criterion node with: <criterion>BBB</criterion> <criterion>CCC</criterion> <criterion>DDD</criterion> So that the final XML result is: <root> <criteria> <criterion>BBB</criterion> <criterion>CCC</criterion> <criterion>DDD</criterion> </criteria> </root> I have tried using substring-before and substring-after to just copy the first half of the structure, then just copy the second half (in order to fill in my new nodes in between the two halves) but it appears that the substring functions only recognize text in between the nodes' tags, and not the tags themselves like I want them to. :( :( Any other solutions?

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• DIY intellisense on XPath - design approach? (WinForms app)

  - by Cheeso

  I read the DIY Intellisense article on code project, which was referenced from the Mimic Intellisense? question here on SO. I wanna do something similar, DIY intellisense, but for XPath not C#. The design approach used there makes sense to me: maintain a tree of terms, and when the "completion character" is pressed, in the case of C#, a dot, pop up the list of possible completions in a textfield. Then allow the user to select a term from the textfield either through typing, arrow keys, or double-click. How would you apply this to XPath autocompletion? should there be an autocomplete key? In XPath there is no obvious separator key like "dot" in C#. should the popup be triggered explicitly in some other way, let's say ctrl-. ? or should the parser try to autocomplete continuously? If I do the autocomplete continuously, how to scale it properly? There are 93 xpath functions, not counting overloads. I certainly don't want to popup a list of 93 choices. How do I decide when I've narrowed it enough to offer a useful lsit of possible completions? How to populate the tree of possible completions? For C#, it's easy: walk the type space via reflection. At a first level, the "syntax tree" for C# seems like a single tree, and the list of completions at any point depends on the graph of nodes you've traversed to that point. Typing System.Console. traverses to a certain node in that tree, and the list of completions is the set of child nodes available at that node in the tree. On the other hand, the xpath syntax seems like it is a "flatter" tree - function names, axis names, literals. Does this make sense? what have I not considered?

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• Why avoid increment ("++") and decrement ("--") operators in JavaScript?

  - by artlung

  I'm a big fan of Douglas Crockford's writing on JavaScript, particularly his book JavaScript: The Good Parts. It's made me a better JavaScript programmer and a better programmer in general. One of his tips for his jslint tool is this : ++ and -- The ++ (increment) and -- (decrement) operators have been known to contribute to bad code by encouraging excessive trickiness. They are second only to faulty architecture in enabling to viruses and other security menaces. There is a plusplus option that prohibits the use of these operators. This has always struck my gut as "yes, that makes sense," but has annoyed me when I've needed a looping condition and can't figure out a better way to control the loop than a while( a < 10 )do { a++ } or for (var i=0;i<10;i++) { } and use jslint. It's challenged me to write it differently. I also know in the distant past using things, in say PHP like $foo[$bar++] has gotten me in trouble with off-by-one errors. Are there C-like languages or other languages with similarities that that lack the "++" and "--" syntax or handle it differently? Are there other rationales for avoiding "++" and "--" that I might be missing? UPDATE -- April 9, 2010: In the video Crockford on JavaScript -- Part 5: The End of All Things, Douglas Crockford addresses the ++ issue more directly and with more detail. It appears at 1:09:00 in the timeline. Worth a watch.

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• Link to RSS/Atom feed, relative, doesn't work in Firefox

  - by Adrian Smith

  I have a weird problem. I generate a HTML page, hosted let's say at http://www.x.com/stuff which contains <head> <link type="application/atom+xml" rel="alternate" href="/stuff/feed"/> .. </head> The result is: In IE7 all works well - you can click on the feed icon in the browser and the feed is displayed In Firefox, view source, click on the linked /stuff/feed and you see the source of the feed, so that works as expected In Firefox, view the page (not source), then click on the feed icon in the address bar, I get an error that it can't retrieve the URL feed://http//www.x.com/stuff/feed So the problem is, that it's appending feed:// to the front of the URL and then taking out the colon : after the http. I understand that feed: is HTTP anyway so perhaps the adding of that isn't a big problem. But anyway, the fact is, that URL Firefox generates out of my <link> tag doesn't work. I have considered making the URL absolute, but I haven't found any evidence that those URLs have to be absolute, nor can I understand why that would be the case. And for various reasons it would be inconvenient in my code to generate an absolute URL. I can do it if necessary but I would prefer to see proof (e.g. specification, or Mozilla bug report) that it's necessary before making my code messy What do you think? Does anyone know of any evidence that the URL should be absolute? Or am I doing something else wrong? It seems such a simple/obvious tag, where nothing could go wrong, but I can't get it to work.

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• Should DAL always return business objects in MVP

  - by Chathuranga

  In Model View Presenter (MVP) pattern, it is said that our DAL always should returns business models. But let's say if I want to get just a number from database like the last ClientID (the latest clients ID) which is a string, should my DAL method returns a ClientInfo object which has about 10 other fields as well like ClientName, Address etc.? If I want to get a list of business objects from my DAL, is it acceptable to do it as follows or better to get a DataTable from DAL and then in the applications BLL, converts it a List? public List<Employee> GetNewEmployees() { string selectStatement = "SELECT Employee.Emp_ID, Employee.Initials + ' ' + Employee.Surname AS Name,..."; using (SqlConnection sqlConnection = new SqlConnection(db.GetConnectionString)) { using (SqlCommand sqlCommand = new SqlCommand(selectStatement, sqlConnection)) { sqlConnection.Open(); using (SqlDataReader dataReader = sqlCommand.ExecuteReader()) { List<Employee> list = new List<Employee>(); while (dataReader.Read()) { list.Add ( new EpfEtfMaster { EmployeeID = (int) dataReader ["emp_id"], EmployeeName = (string) dataReader ["Name"], AppointmentDate = (DateTime) dataReader["appointment_date"], }); } return list; } } } }

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• How to Deserialize Missing Fields To Nulls

  - by Nathan

  I am working on a .NET project where several versions of the same type of object have been created over the life of the project - most new versions add a field or two. However, now I am looking to mitigate problems for users with an old version. My goal is that when a user tries to open an old version of the serialized object with the new program, the program will automatically assign default values to the fields that are missing from the depreciated version of the file. For example, say I had a class with two boolean fields - RepeatSound and RepeatForever. The first version of the program doesn't know how to repeat forever, so it only saved RepeatSound: <anyType xsi:type="Sound"> <RepeatSound>true</RepeatSound> </anyType> but the new files look like this: <anyType xsi:type="Sound"> <RepeatSound>true</RepeatSound> <RepeatForever>true</RepeatForever> </anyType> My goal is that when I deserialize the first file in the new program that it will create the Sound object but simply default the value of RepeatForever to false. Right now trying to deserialize the first object would throw an exception. Thank you in advance for any responses

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• Why use SQL database?

  - by martinthenext

  I'm not quite sure stackoverflow is a place for such a general question, but let's give it a try. Being exposed to the need of storing application data somewhere, I've always used MySQL or sqlite, just because it's always done like that. As it seems like the whole world is using these databases, most of all software products, frameworks, etc. It is rather hard for a beginning developer like me to ask a question - why? Ok, say we have some object-oriented logic in our application, and objects are related to each other somehow. We need to map this logic to the storage logic, so we need relations between database objects too. This leads us to using relational database and I'm ok with that - to put it simple, our database rows sometimes will need to have references to other tables' rows. But why do use SQL language for interaction with such a database? SQL query is a text message. I can understand this is cool for actually understanding what it does, but isn't it silly to use text table and column names for a part of application that no one ever seen after deploynment? If you had to write a data storage from scratch, you would have never used this kind of solution. Personally, I would have used some 'compiled db query' bytecode, that would be assembled once inside a client application and passed to the database. And it surely would name tables and colons by id numbers, not ascii-strings. In the case of changes in table structure those byte queries could be recompiled according to new db schema, stored in XML or something like that. What are the problems of my idea? Is there any reason for me not to write it myself and to use SQL database instead?

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• Help understanding the Single Responsibility Principle

  - by user204588

  I'm trying to understand what a responsibility actually is so I want to use an example of something I'm currently working on. I have a app that imports product information from one system to another system. The user of the apps gets to choose various settings for which product fields in one system that want to use in the other system. So I have a class, say ProductImporter and it's responsibility is to import products. This class is large, probably too large. The methods in this class are complex and would be for example, getDescription. This method doesn't simply grab a description from the other system but sets a product description based on various settings set by the user. If I were to add a setting and a new way to get a description, this class could change. So, is that two responsibilities? Is there one that imports products and one that gets a description. It would seem this way, almost every method I have would be in it's own class and that seems like overkill. I really need a good description of this principle because it's hard for me to completely understand. I don't want needless complexity.

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• Finding values from a table that are *not* in a grouping of another table and what group that value

  - by Bkins

  I hope I am not missing something very simple here. I have done a Google search(es) and searched through stackoverflow. Here is the situation: For simplicity's sake let's say I have a table called "PeoplesDocs", in a SQL Server 2008 DB, that holds a bunch of people and all the documents that they own. So one person can have several documents. I also have a table called "RequiredDocs" that simply holds all the documents that a person should have. Here is sort of what it looks like: PeoplesDocs: PersonID DocID -------- ----- 1 A 1 B 1 C 1 D 2 C 2 D 3 A 3 B 3 C RequiredDocs: DocID DocName ----- --------- A DocumentA B DocumentB C DocumentC D DocumentD How do I write a SQL query that returns some variation of: PersonID MissingDocs -------- ----------- 2 DocumentA 2 DocumentB 3 DocumentD I have tried, and most of my searching has pointed to, something like: SELECT DocID FROM DocsRequired WHERE NOT EXIST IN ( SELECT DocID FROM PeoplesDocs) but obviously this will not return anything in this example because everyone has at least one of the documents. Also, if a person does not have any documents then there will be one record in the PeoplesDocs table with the DocID set to NULL. Thank you in advance for any help you can provide, Ben

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• Comparing two date ranges within the same table

  - by Danny Herran

  I have a table with sales per store as follows: SQL> select * from sales; ID ID_STORE DATE TOTAL ---------- -------- ---------- -------------------------------------------------- 1 1 2010-01-01 500.00 2 1 2010-01-02 185.00 3 1 2010-01-03 135.00 4 1 2009-01-01 165.00 5 1 2009-01-02 175.00 6 5 2010-01-01 130.00 7 5 2010-01-02 135.00 8 5 2010-01-03 130.00 9 6 2010-01-01 100.00 10 6 2010-01-02 12.00 11 6 2010-01-03 85.00 12 6 2009-01-01 135.00 13 6 2009-01-02 400.00 14 6 2009-01-07 21.00 15 6 2009-01-08 45.00 16 8 2009-01-09 123.00 17 8 2009-01-10 581.00 17 rows selected. What I need to do is to compare two date ranges within that table. Lets say I need to know the differences in sales between 01 Jan 2009 to 10 Jan 2009 AGAINST 01 Jan 2010 to 10 Jan 2010. I'd like to build a query that returns something like this: ID_STORE_A DATE_A TOTAL_A ID_STORE_B DATE_B TOTAL_B ---------- ---------- --------- ---------- ---------- ------------------- 1 2010-01-01 500.00 1 2009-01-01 165.00 1 2010-01-02 185.00 1 2009-01-02 175.00 1 2010-01-03 135.00 1 NULL NULL 5 2010-01-01 130.00 5 NULL NULL 5 2010-01-02 135.00 5 NULL NULL 5 2010-01-03 130.00 5 NULL NULL 6 2010-01-01 100.00 6 2009-01-01 135.00 6 2010-01-02 12.00 6 2009-01-02 400.00 6 2010-01-03 85.00 6 NULL NULL 6 NULL NULL 6 2009-01-07 21.00 6 NULL NULL 6 2009-01-08 45.00 6 NULL NULL 8 2009-01-09 123.00 6 NULL NULL 8 2009-01-10 581.00 So, even if there are no sales in one range or another, it should just fill the empty space with NULL. So far, I've come up with this quick query, but I the "dates" from sales to sales2 sometimes are different in each row: SELECT sales.*, sales2.* FROM sales LEFT JOIN sales AS sales2 ON (sales.id_store=sales2.id_store) WHERE sales.date >= '2010-01-01' AND sales.date <= '2010-01-10' AND sales2.date >= '2009-01-01' AND sales2.date <= '2009-01-10' ORDER BY sales.id_store ASC, sales.date ASC, sales2.date ASC What am I missing?

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• advanced Visual Studio kung-fu test -- Calling functions from the Immediate Window during debugging

  - by kizzx2

  I see some related questions have been asked, but they're either too advanced for me to grasp or lacking a step-by-step guide from start to finish (most of them end up being insider talk of their own experiment results). OK here it is, given this simple program: #include <stdio.h> #include <string.h> int main() { FILE * f; char buffer[100]; memset(buffer, 0, 100); fun(); f = fopen("main.cpp", "r"); fread(buffer, 1, 99, f); printf(buffer); fclose(f); return 0; } What it does is basically print itself (assume file name is main.cpp). Question How can I have it print another file, say foobar.txt without modifying the source code? It has something to do with running it through VS's, stepping through the functions and hijacking the FILE pointer right before fread() is called. No need to worry about leaking resources by calling fclose(). I tried the simple f = fopen("foobar.txt", "r") which gave CXX0017: Error: symbol "fopen" not found Any ideas? Edit I found out the solution accidentally on Debugging Mozilla on Windows FAQ. The correct command to put into the Immediate Window is f = {,,MSVCR100D}fopen("foo.txt", "r") However, it doesn't really answer this question: I still don't understand what is going on here. How to systematically find out the {,,MSVCR100D} part for any given method? I know the MSVCR version changes from system to system. How can I find that out? Could anyone explain the curly brace syntax, especially, what are those two commas doing there? Are there more hidden gems using this syntax?

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