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• How to store wiki sites (vcs)

  - by Eugen

  Hello, as a personal project I am trying to write a wiki with the help of django. I'm a beginner when it comes to web development. I am at the (early) point where I need to decide how to store the wiki sites. I have three approaches in mind and would like to know your suggestion. Flat files I considered a flat file approach with a version control system like git or mercurial. Firstly, I would have some example wikis to look at like http://hatta.sheep.art.pl/. Secondly, the vcs would probably deal with editing conflicts and keeping the edit history, so I would not have to reinvent the wheel. And thirdly, I could probably easily clone the wiki repository, so I (or for that matter others) can have an offline copy of the wiki. On the other hand, as far as I know, I can not use django models with flat files. Then, if I wanted to add fields to a wiki site, like a category, I would need to somehow keep a reference to that flat file in order to associate the fields in the database with the flat file. Besides, I don't know if it is a good idea to have all the wiki sites in one repository. I imagine it is more natural to have kind of like a repository per wiki site resp. file. Last but not least, I'm not sure, but I think using flat files would limit my deploying capabilities because web hosts maybe don't allow creating files (I'm thinking, for example, of Google App Engine) Storing in a database By storing the wiki sites in the database I can utilize django models and associate arbitrary fields with the wiki site. I probably would also have an easier life deploying the wiki. But I would not get vcs features like history and conflict resolving per se. I searched for django-extensions to help me and I found django-reversion. However, I do not fully understand if it fit my needs. Does it track model changes like for example if I change the django model file, or does it track the content of the models (which would fit my need). Plus, I do not see if django reversion would help me with edit conflicts. Storing a vcs repository in a database field This would be my ideal solution. It would combine the advantages of both previous approaches without the disadvantages. That is; I would have vcs features but I would save the wiki sites in a database. The problem is: I have no idea how feasible that is. I just imagine saving a wiki site/source together with a git/mercurial repository in a database field. Yet, I somehow doubt database fields work like that. So, I'm open for any other approaches but this is what I came up with. Also, if you're interested, you can find the crappy early test I'm working on here http://github.com/eugenkiss/instantwiki-test

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• Soon to be PhD in Computer Science - Which Path to Follow?

  - by mttr

  I am going to submit my PhD thesis within the next six months. My PhD is on managing the availabiity of large-scale distributed systems, so I have some experience actually building non-trivial systems (+ I have four years experience working as a programmer). I am now trying to figure out what I should do following the PhD. I enjoy research (a quick definition: identify problem, come up with solution, ask interesting questions, find ways to answer them, build system, experiment, contribute some new knowledge and publish). I also like teaching and supervising students. It would seem that a career in academia is the ideal thing to do (can work on non-trivial problems and contribute something of use to some or more people). However, a career in academia has two significant drawbacks. First, it can be difficult to gain access to real systems with real users which then display real problems. This creates the danger that you do work that seems important (to you and maybe to some of your colleagues), but is not really relevant to anything or anyone. Second, the pay is pretty sad. Apparently, you have to sacrifice this for the privilege of doing research. I enjoy programming, but don't just want to hack some web-based system for the rest of my life. That is, working in IT for a bank is not a future I see myself enjoying. I want to work on interesting problms (that's difficult to define clearly): things where you don't know how to start, that take some time to figure out and attack, that require a rigorous approach to demonstrate that the problem has been solved, and problems that need a solution in the real world. Give the experience of people on stackoverflow, what do you think suitable options are and why (or alternatively, what gaps in my thinking does the above reveal)? Is industrial research (aka IBM Research, Microsoft Research) the only alternative avenue to a career in academia? What other areas, companies, occupations, etc. could provide me with stimulating, inspiring work? Which regions, countries am I most likely to find such work? Please share your experience.

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• Catching an exception class within a template

  - by Todd Bauer

  I'm having a problem using the exception class Overflow() for a Stack template I'm creating. If I define the class regularly there is no problem. If I define the class as a template, I cannot make my call to catch() work properly. I have a feeling it's simply syntax, but I can't figure it out for the life of me. #include<iostream> #include<exception> using namespace std; template <class T> class Stack { private: T *stackArray; int size; int top; public: Stack(int size) { this->size = size; stackArray = new T[size]; top = 0; } ~Stack() { delete[] stackArray; } void push(T value) { if (isFull()) throw Overflow(); stackArray[top] = value; top++; } bool isFull() { if (top == size) return true; else return false; } class Overflow {}; }; int main() { try { Stack<double> Stack(5); Stack.push( 5.0); Stack.push(10.1); Stack.push(15.2); Stack.push(20.3); Stack.push(25.4); Stack.push(30.5); } catch (Stack::Overflow) { cout << "ERROR! The stack is full.\n"; } return 0; } The problem is in the catch (Stack::Overflow) statement. As I said, if the class is not a template, this works just fine. However, once I define it as a template, this ceases to work. I've tried all sorts of syntaxes, but I always get one of two sets of error messages from the compiler. If I use catch(Stack::Overflow): ch18pr01.cpp(89) : error C2955: 'Stack' : use of class template requires template argument list ch18pr01.cpp(13) : see declaration of 'Stack' ch18pr01.cpp(89) : error C2955: 'Stack' : use of class template requires template argument list ch18pr01.cpp(13) : see declaration of 'Stack' ch18pr01.cpp(89) : error C2316: 'Stack::Overflow' : cannot be caught as the destructor and/or copy constructor are inaccessible EDIT: I meant If I use catch(Stack<double>::Overflow) or any variety thereof: ch18pr01.cpp(89) : error C2061: syntax error : identifier 'Stack' ch18pr01.cpp(89) : error C2310: catch handlers must specify one type ch18pr01.cpp(95) : error C2317: 'try' block starting on line '75' has no catch handlers I simply can not figure this out. Does anyone have any idea?

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• How do you unit test a unit test?

  - by FlySwat

  I was watching Rob Connerys webcasts on the MVCStoreFront App, and I noticed he was unit testing even the most mundane things, things like: public Decimal DiscountPrice { get { return this.Price - this.Discount; } } Would have a test like: [TestMethod] public void Test_DiscountPrice { Product p = new Product(); p.Price = 100; p.Discount = 20; Assert.IsEqual(p.DiscountPrice,80); } While, I am all for unit testing, I sometimes wonder if this form of test first development is really beneficial, for example, in a real process, you have 3-4 layers above your code (Business Request, Requirements Document, Architecture Document), where the actual defined business rule (Discount Price is Price - Discount) could be misdefined. If that's the situation, your unit test means nothing to you. Additionally, your unit test is another point of failure: [TestMethod] public void Test_DiscountPrice { Product p = new Product(); p.Price = 100; p.Discount = 20; Assert.IsEqual(p.DiscountPrice,90); } Now the test is flawed. Obviously in a simple test, it's no big deal, but say we were testing a complicated business rule. What do we gain here? Fast forward two years into the application's life, when maintenance developers are maintaining it. Now the business changes its rule, and the test breaks again, some rookie developer then fixes the test incorrectly...we now have another point of failure. All I see is more possible points of failure, with no real beneficial return, if the discount price is wrong, the test team will still find the issue, how did unit testing save any work? What am I missing here? Please teach me to love TDD, as I'm having a hard time accepting it as useful so far. I want too, because I want to stay progressive, but it just doesn't make sense to me. EDIT: A couple people keep mentioned that testing helps enforce the spec. It has been my experience that the spec has been wrong as well, more often than not, but maybe I'm doomed to work in an organization where the specs are written by people who shouldn't be writing specs.

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• Stata - Multiple rotated plots on graph (including distributions on sides of axes)

  - by meerak

  I would like to produce a single graph containing both: (1) a scatter plot (2) either histograms or kernel density functions of the Y and X variables to the left of the Y axis and below the X axis. I found a graph that does this in MATLAB -- I would just like to produce something similar in Stata: That graph was produced using the following MATLAB code: n = 1000; rho = .7; Z = mvnrnd([0 0], [1 rho; rho 1], n); U = normcdf(Z); X = [gaminv(U(:,1),2,1) tinv(U(:,2),5)]; [n1,ctr1] = hist(X(:,1),20); [n2,ctr2] = hist(X(:,2),20); subplot(2,2,2); plot(X(:,1),X(:,2),'.'); axis([0 12 -8 8]); h1 = gca; title('1000 Simulated Dependent t and Gamma Values'); xlabel('X1 ~ Gamma(2,1)'); ylabel('X2 ~ t(5)'); subplot(2,2,4); bar(ctr1,-n1,1); axis([0 12 -max(n1)*1.1 0]); axis('off'); h2 = gca; subplot(2,2,1); barh(ctr2,-n2,1); axis([-max(n2)*1.1 0 -8 8]); axis('off'); h3 = gca; set(h1,'Position',[0.35 0.35 0.55 0.55]); set(h2,'Position',[.35 .1 .55 .15]); set(h3,'Position',[.1 .35 .15 .55]); colormap([.8 .8 1]); UPDATE: The Stata13 manual entry for "graph combine" has precisely this example (http://www.stata.com/manuals13/g-2graphcombine.pdf). Here is the code: use http://www.stata-press.com/data/r13/lifeexp, clear generate loggnp = log10(gnppc) label var loggnp "Log base 10 of GNP per capita" scatter lexp loggnp, ysca(alt) xsca(alt) xlabel(, grid gmax) fysize(25) saving(yx) twoway histogram lexp, fraction xsca(alt reverse) horiz fxsize(25) saving(hy) twoway histogram loggnp, fraction ysca(alt reverse) ylabel(,nogrid) xlabel(,grid gmax) saving(hx) graph combine hy.gph yx.gph hx.gph, hole(3) imargin(0 0 0 0) graphregion(margin(l=22 r=22)) title("Life expectancy at birth vs. GNP per capita") note("Source: 1998 data from The World Bank Group")

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• Which mobile operating system should I code for?

  - by samgoody

  It seems as though mobile computing has fully arrived. I would like to rewrite two of our programs for mobile devices, but am a bit lost as to which platform to target. Complicating this decision: I would need to learn the relevant languages and IDEs - my coding to date has been almost all web based (PHP, JS, Actionscript, etc. Some ASPX). Most users seem to be religious about their mobile decision, so oral conversations leave me more confused then enlightened. I do not yet own a smartphone - will have to buy one once I know which platform to be aiming for. Both of my programs are more for business users, (one is only useful for C.P.A.s). I am a single developer, and cannot develop for more than one platform at a time. Getting it right is important. Based on what I've found on the web, I would've expected RIM to be a shoo-in, and the general order to be as follows: RIM Blackberry - More of them than any other brand. Despite naysayers, they've had double the sales (or perhaps 5X the sales) of any other smartphone, and have continued to grow. And, they have business users. Android - According to Schmidt, they have outsold everyone else except RIM (though I can't find where I read that now), and they are just getting started. According to Comscore, they are already at 8% of the market and expected to hit Shcmidt's claims within six months. Nokia - The largest worldwide. If they would just make up between Maemo or Symbian, I would be far less confused. iPhone - Much more competition by other apps, fewer sales to be had, and a overlord that can delay or cancel my app at any time. Is Cocoa hard to learn? Windows Mobile - Word is that version 7 will not be backwards compatible and losing market share. Palm WebOS - Perhaps this should go first, as it is the only one that offers tools to make my life easy as a web application developer. No competition in marketplace. But not very many users either. However, a search on StackOverflow shows a hugely disproportionate number of iPhone questions versus Blackberry. Likewise, there are clearly more apps on iPhone, so it must be getting developer love. What is the one platform I should develop for? Please back up your answer with the logic.

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• iPhone SDK / Core Data usage scenario, similar to GAE data store?

  - by boliva

  Hi all, I am currently rewriting a map based App which I wrote in the past, specifically for 2.2.1 devices. Originally I wrote it to make use of SQLite databases but I would like to try and migrate it over Core Data, now that it's available on 3.X (for which I am rewriting to). I am fairly experienced in iPhone/Obj-C development, SQL and server backend technologies, but I have never had the chance to work with Core Data so IDK really if it's the appropiate tool for what I am trying to accomplish. The App works on a limited area in a map over which there are about 4000 placemarks, with different kinds of icons and sizes. Of course not all 4000 placemarks are shown at once but only those currently visible in the map viewport, and depending on the zoom level. What I am doing right now is, after the user moves the map in any way (panning or zooming) I am requesting from the backend server the required information for the placemarks that would be visible given the viewport coordinates boundaries and zoom level, however the process isn't as smooth as I'd like (the backend is sending its response in XML and I am compressing it using gzip), it takes anywhere from 1 to 3 seconds to update the display of the placemarks after the user ends moving the map. What I would like to do is to prefetch all the placemarks data at the App launch and use it all through the app life time - I don't mind storing it for later use because the data should be dynamic. The way I would do it right now is, after retrieving all the data, to store it on an SQLite db which I would query later, whenever the user moves the map, to return only the placemarks inside the viewport coordinate boundaries and specific to a given zoom level. Now, the question itself is, if is it possible to use some more 'native', object driven way to carry this queries process, which got me thinking about Core Data and if it is in any way similar to what Google App Engine offers through its datastore where you can fetch a number of objects from the backend given a certain query or criteria, without resorting to an SQL query itself. Like I said before I don't have any experience on Core Data but I have a pretty deep understanding of Obj-C and iPhone development, as well as SQL databases. Any guides on how to achieve what I'm trying (if possible at all) would be greatly appreciated.

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• Creating a variable list Pashua, OS X & Bash.

  - by S1syphus

  First of all, for those that don't know pashua is a tool for creating native Aqua dialog windows. An example of what a window config looks like is # pashua_run() # Define what the dialog should be like # Take a look at Pashua's Readme file for more info on the syntax conf=" # Set transparency: 0 is transparent, 1 is opaque *.transparency=0.95 # Set window title *.title = Introducing Pashua # Introductory text tb.type = text tb.default = "HELLO WORLD" tb.height = 276 tb.width = 310 tb.x = 340 tb.y = 44 if [ -e "$icon" ] then # Display Pashua's icon conf="$conf img.type = image img.x = 530 img.y = 255 img.path = $icon" fi if [ -e "$bgimg" ] then # Display background image conf="$conf bg.type = image bg.x = 30 bg.y = 2 bg.path = $bgimg" fi pashua_run "$conf" echo " tb = $tb" The problem is, Pashua can't really get output from stdout, but it can get arguments. Following on from what Dennis Williamson posted here. What ideally it should do is generate an output file based on information from a text file, To executed in pashua_run ore add the pashua_run around the window argument: count=1 while read -r i do echo "AB${count}.type = openbrowser" echo "AB${count}.label = Choose a master playlist file" echo "AB${count}.width=310" echo "AB${count}.tooltip = Blabla filesystem browser" echo "some text with a line from the file: $i" (( count++ )) done < TEST.txt >> long.txt SO the output is AB1.type = openbrowser AB1.label = Choose a master playlist file AB1.width=310 AB1.tooltip = Blabla filesystem browser some text with a line from the file: foo AB2.type = openbrowser AB2.label = Choose a master playlist file AB2.width=310 AB2.tooltip = Blabla filesystem browser some text with a line from the file: bar AB3.type = openbrowser AB3.label = Choose a master playlist file AB3.width=310 AB3.tooltip = Blabla filesystem browser some text with a line from the file: dev AB4.type = openbrowser AB4.label = Choose a master playlist file AB4.width=310 AB4.tooltip = Blabla filesystem random So if there is a clever way to get the output of that and place it into pashua run would be cool, on the fly: I.E load te contents of TEST.txt and generate the place it into pashua_run, I've tried using cat and opening the file... but because it's in Pashua_run it doesn't work, is there a smart way to break out then back in? Or the second way which I was thinking, was create get the output then append it into the middle text file containing the pashua runtime, then execute it, maybe slightly hacky, but I would imagine it will do the job. Any ideas? ++ I know I probably could make my life a lot easier, by doing this in actionscript and cocoa, although at present don't have time for such a learning curve, although I do plan to get round to it.

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• SQL CLR Stored Procedure and Web Service

  - by Nathan

  I am current working on a task in which I am needing to call a method in a web service from a CLR stored procedure. A bit of background: Basically, I have a task that requires ALOT of crunching. If done strictly in SQL, it takes somewhere around 30-45 mins to process. If I pull the same process into code, I can get it complete in seconds due to being able to optimize the processing so much more efficiently. The only problem is that I have to have this process set as an automated task in SQL Server. In that vein, I have exposed the process as a web service (I use it for other things as well) and want the SQL CLR sproc to consume the service and execute the code. This allows me to have my automated task. The problem: I have read quite a few different topics regarding how to consume a web service in a CLR Sproc and have done so effectivly. Here is an example of what I have followed. http://blog.hoegaerden.be/2008/11/11/calling-a-web-service-from-sql-server-2005/ I can get this example working without any issues. However, whenever I pair this process w/ a Web Service method that involves a database call, I get the following exceptions (depending upon whether or not I wrap in a try / catch): Msg 10312, Level 16, State 49, Procedure usp_CLRRunDirectSimulationAndWriteResults, Line 0 .NET Framework execution was aborted. The UDP/UDF/UDT did not revert thread token. or Msg 6522, Level 16, State 1, Procedure MyStoredProc , Line 0 A .NET Framework error occurred during execution of user defined routine or aggregate 'MyStoredProc': System.Security.SecurityException: Request for the permission of type 'System.Security.Permissions.EnvironmentPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed. System.Security.SecurityException: at System.Security.CodeAccessSecurityEngine.Check(Object demand, StackCrawlMark& stackMark, Boolean isPermSet) at System.Security.CodeAccessPermission.Demand() at System.Net.CredentialCache.get_DefaultCredentials() at System.Web.Services.Protocols.WebClientProtocol.set_UseDefaultCredentials(Boolean value) at MyStoredProc.localhost.MPWebService.set_UseDefaultCredentials(Boolean Value) at MyStoredProclocalhost.MPWebService..ctor() at MyStoredProc.StoredProcedures.MyStoredProc(String FromPostCode, String ToPostCode) I am sure this is a permission issue, but I can't, for the life of me get it working. I have attempted using impersonation in the CLR sproc and a few other things. Any suggestions? What am I missing?

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• How to setup a webserver in common lisp?

  - by Serpico

  Several months ago, I was inspired by the magnificent book ANSI Common Lisp written by Paul Graham, and the statement that Lisp could be used as a secret weapon in your web development, published by the same author on his blog. Wow, that is amazing. That is something that I have been looking for long time. The author really developed a successful web applcation and sold it to Yahoo. With those encouraging images, I determined to spend some time (1 year or 2 year, who knows) on learning Common Lisp. Maybe someday I will development my web application and turn into a great Lisp expert. In fact, this is the second time for me to get to study Lisp. The first time was a couple of years ago when I was fascinated by the famous book SICP but found later Scheme was so unbelievably immature for real life application. After reading some chapters of ANSI Common Lisp, I was pretty sure that is a great book full of detailed exploration of Common Lisp. Then I began to set up a web server in Common Lisp. After all, this should be the best way if you want to learn something. Demonstrations are always better than definations. As suggested by the book Practical Common Lisp (by the way, this is also a great book), I chose to install AllegroServe on some Common Lisp implementation. Then, from somewhere else, I learned that Hunchentoot seems to be better than AllegroServe. (I don't remember where and whom this word is from. So don't argue with me.) Ironically, you know what, I never could installed the two packages on any Common Lisp implementation. More annoyingly, I even don't know why. The machine always spit up a lot of jargon and lead me into a chaos. I've tried searching the internet and have not found anything. Could anybody who has successfully installed these packages in Linux tell me how you did it? Have you run into any trouble? How did you figured out what is wrong and fixed it? The more detailed, the more helpful.

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• Making footer image stick to bottom of web browser or page

  - by Slyphee

  Hello, I know this has been asked alot of times in the past but for the life of me I can't seem to get any of the other solutions to work. What I'm trying to do is to get the footer (which is an image that repeats across the width of the page) to stick to the bottom of the browser when there isn't enough content to naturally push it to the bottom of the page and when there IS enough content to push it to the bottom it does just that. An example is the one at http://www.themaninblue.com/experiment/footerStickAlt/good_example_short.htm which does exactly what I want but I can't get to work either. The code that I've currently got implemented makes the footer stick to a certain section of the page with text going under it. You can see it at sourcectrl.co.uk but its not much to look at. Heres the code for your viewing pleasure. html, body { font: 100% Arial, Helvetica, sans-serif; height: 100%; color: #597347; margin: 0; padding: 0; background: #573909; } header { display: block; position: relative; top: 0; left: 0; width: 100%; height: 66px; background: url(../images/FillerPage_01.gif) repeat-x left bottom; } section { width: 940px; margin: 0 auto; font-size: 1.4em; overflow: auto; min-height: 100%; height: auto !important; height: 100%; margin-bottom: 87px; position: relative; padding-bottom: 90px; } footer { display:block; position: absolute; bottom: 0; width: 100%; height: 87px; background: url(../images/FillerPage_08.gif) repeat-x left bottom; } Sorry if it seems messy! I'd just like to know if I'm heading in the right direction or theres something I'm just not getting? Oh yeah I'm trying to do all of this with the html 5 markup which is why there is no #footer and the like (could this be why none of the solutions work?). If anyone could give me any help or guidance I'd be soooooo grateful.

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• If 'Architect' is a dirty word - what's the alternative; when not everyone can actually design a goo

  - by Andras Zoltan

  Now - I'm a developer first and foremost; but whenever I sit down to work on a big project with lots of interlinking components and areas, I will forward-plan my interfaces, base classes etc as best I can - putting on my Architect hat. For a few weeks I've been doing this for a huge project - designing whole swathes of interfaces etc for a business-wide platform that we're developing. The basic structure is a couple of big projects that consists of service and data interfaces, with some basic implementations of all of these. On their own, these assemblies are useless though, as they are simply intended intended as a scaffold on which to build a business-specific implementation (we have a lot of businesses). Therefore, the design of the core platform is absolutely crucial, since consumers of the system are not intended to know which implementation they are actually using. In the past it's not worked so well, but after a few proof-of-concepts and R&D projects this new platform is now growing nicely and is already proving itself. Then somebody else gets involved in the project - he's a TDD man who sees code-level architecture as an irrelevance and is definitely from the camp that 'architect' is a dirty word - I should add that our working relationship is very good despite this :) He's open about the fact that he can't architect in advance and obviously TDD really helps him because it allows him to evolve his systems over time. That I get, and totally understand; but it means that his coding style, basically, doesn't seem to be able to honour the architecture that I've been putting in place. Now don't get me wrong - he's an awesome coder; but the other day he needed to extend one of his components (an implementation of a core interface) to bring in an extra implementation-specific dependency; and in doing so he extended the core interface as well as his implementation (he uses ReSharper), thus breaking the independence of the whole interface. When I pointed out his error to him, he was dismayed. Being test-first, all that mattered to him was that he'd made his tests pass, and just said 'well, I need that dependency, so can't we put it in?'. Of course we could put it in, but I was frustrated that he couldn't see that refactoring the generic interface to incorporate an implementation-specific feature was just wrong! But it is all very Charlie Brown to him (you know the sound the adults make when they're talking to the children) - as far as he's concerned we don't need to worry about it because we can always refactor. The problem is, the culture of test-write-refactor is all very well and good - but not when you're dealing with a platform that is going to be shared out among so many projects that you could never get them all in one place to make the refactorings work. In my opinion, sometimes you actually have to think about what you're doing, and not just let nature take its course. Am I simply fulfilling the role of Architect as a dirty word here? I believe that architecture is important and should be thought about before code gets written; unless it's a particularly small project. But when you're working in a team of people who don't think that way, or even can't think that way how can you actually get this across? Is it a case of simply making the architecture off-limits to changes by other people? I don't want to start having bloody committees just to be able to grow the system; but equally I don't want to be the only one responsible for it all. Do you think the architect role is a waste of time? Is it at odds with TDD and other practises? Can this mix of different practises be made to work, or should I just be a lot less precious (and in so doing allow a generic platform become useless!)? Or do I just lay down the law? Any ideas/experiences/views gratefully received.

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• POD global object initialization

  - by paercebal

  I've got bitten today by a bug. The following source can be copy/pasted (and then compiled) into a main.cpp file #include <iostream> // The point of SomeGlobalObject is for its // constructor to be launched before the main // ... struct SomeGlobalObject { SomeGlobalObject() ; } ; // ... // Which explains the global object SomeGlobalObject oSomeGlobalObject ; // A POD... I was hoping it would be constructed at // compile time when using an argument list struct MyPod { short m_short ; const char * const m_string ; } ; // declaration/Initialization of a MyPod array MyPod myArrayOfPod[] = { { 1, "Hello" }, { 2, "World" }, { 3, " !" } } ; // declaration/Initialization of an array of array of void * void * myArrayOfVoid[][2] = { { (void *)1, "Hello" }, { (void *)2, "World" }, { (void *)3, " !" } } ; // constructor of the global object... Launched BEFORE main SomeGlobalObject::SomeGlobalObject() { std::cout << "myArrayOfPod[0].m_short : " << myArrayOfPod[0].m_short << std::endl ; std::cout << "myArrayOfVoid[0][0] : " << myArrayOfVoid[0][0] << std::endl ; } // main... What else ? int main(int argc, char* argv[]) { return 0 ; } MyPod being a POD, I believed there would be no constructors. Only initialization at compile time. Thus, the global object SomeGlobalObject would have no problem to use the global array of PODs upon its construction. The problem is that in real life, nothing is so simple. On Visual C++ 2008 (I did not test on other compilers), upon execution myArrayOfPodis not initialized, even ifmyArrayOfVoid` is initialized. So my questions is: Are C++ compilers not supposed to initialize global PODs (including POD structures) at compilation time ? Note that I know global variable are evil, and I know that one can't be sure of the order of creation of global variables declared in different compilation units. The problem here is really the POD C-like initialization which seems to call a constructor (the default, compiler-generated one?). And to make everyone happy: This is on debug. On release, the global array of PODs is correctly initialized.

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• Computation on db data then list them using either SimpleCursorAdapter or ArrayAdapter

  - by kc2uno

  Hi all, I juststarted programming in android a few weeks ago, so I am not entirely sure how to deal with listing values. Please help me out! I have some questions regarding displaying data sets from db in a list. Currently I have a cursor returned by my db points to a list of rows and I want display 2 columns values in a single row of the list. The row xml looks like this: <TextView android:id="@+id/text1" android:textSize="16sp" android:textStyle="bold" android:layout_width="fill_parent" android:layout_height="wrap_content"/> <TextView android:id="@+id/text2" android:textSize="14sp" android:layout_width="fill_parent" android:layout_height="wrap_content"/> so I was thinking using simplecursoradapter which supposedly makes my life easier by displaying the data in a list. However that is only true if I want to display the raw data. For the purpose of my program I need to do some computations on the raw data sets, then display them. I am not sure how to do that using SimpleCursorAdapter. Here's how I display the raw data: String[] from = new String[]{BtDbAdapter.KEY_EX_TYPE,BtDbAdapter.KEY_EX_TIMESTAMP}; int[] to = new int[]{R.id.text1, R.id.text2}; // Now create a simple cursor adapter and set it to display SimpleCursorAdapter records = new SimpleCursorAdapter(this, R.layout.exset_row, mExsetCursor, from, to); setListAdapter(records); Is there a way to do computation on the data in those rows before I bind it with the SimpleCursorAdapter? I was trying to use an alternative way of doing this by using arraylist and arrayadapter, but that way I dont know to how achieve displaying 2 items in a single row. This is my code for using arrayadapter which only display 1 text in a row instead of 2 textviews in a row: //fill in the array timestamp_arr = new ArrayList<String>(); type_arr = new ArrayList<String>(); fillRecord(); Log.d(TAG,"setting now in recordlist"); setListAdapter(new ArrayAdapter<String>(this, R.layout.list_item,timestamp_arr)); setListAdapter(new ArrayAdapter<String>(this, R.layout.list_item2,type_arr)); It's very obvious that it only displays one textview in a row because I set the second arrayadapter overwrites the first one! I was trying to use R.id.text1 and R.id.text2 for them, but it gave me some errors saying 04-23 01:40:58.658: ERROR/AndroidRuntime(3309): android.content.res.Resources$NotFoundException: Resource ID #0x7f070008 type #0x12 is not valid I believe the second method can achieve this, but I'm not sure how do deal with the layout problems, so if you any suggestions, please post them out. Thank you!!

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• Translating itunes affiliate rss via xslt

  - by jd

  I can't get this working for the life of me. Here is a snippet of the xml I get from an RSS feed from itunes affiliate. I want top print the values within tags but I cannot for some reason: <?xml version="1.0" encoding="utf-8"?> <feed xmlns:im="http://itunes.apple.com/rss" xmlns="http://www.w3.org/2005/Atom" xml:lang="en"> <id>http://ax.itunes.apple.com/WebObjects/MZStoreServices.woa/ws/RSS/toppaidapplications/sf=143441/limit=100/genre=6014/xml</id><title>iTunes Store: Top Paid Applications</title><updated>2010-03-24T15:36:42-07:00</updated><link rel="alternate" type="text/html" href="http://itunes.apple.com/WebObjects/MZStore.woa/wa/viewTop?id=25180&amp;popId=30"/><link rel="self" href="http://ax.itunes.apple.com/WebObjects/MZStoreServices.woa/ws/RSS/toppaidapplications/sf=143441/limit=100/genre=6014/xml"/><icon>http://phobos.apple.com/favicon.ico</icon><author><name>iTunes Store</name><uri>http://www.apple.com/itunes/</uri></author><rights>Copyright 2008 Apple Inc.</rights> <entry> <updated>date</updated> <id>someID</id> <title>a</title> <im:name>b</im:name> </entry> <entry> <updated>date2/updated> <id>someID2</id> <title>a2</title> <im:name>b2</im:name> </entry> </feed> If I try <xsl:apply-templates match="entry"/> it spits out the entire contents of file. If I use <xsl:call-template name="entry"> it will show only one entry and I have to use <xsl:value-of select="//*[local-name(.)='name']"/> to get name but that's a hack. I've used xslt before for xml without namespaces and xml that has proper parent child relationships but not like this RSS feed. Notice entry is not wrapped in entries or anything. Any help is appreciated. I want to use xslt because I want to alter the itunes link to go through my affiliate account - so something automated wouldn't work for me.

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• A methology that allows for a single Java code base covering many different versions?

  - by Thorbjørn Ravn Andersen

  I work in a small shop where we have a LOT of legacy Cobol code and where a methology has been adopted to allow us to minimize forking and branching as much as possible. For a given release we have three levels: CORE - bottom layer, this code is common to all releases GROUP - optional code common to several customers. CUSTOMER - optional code specific for a single customer. When a program is needed, it is first searched for in CUSTOMER, then in GROUP and finally in CORE. A given application for us invokes many programs which all are looked for in this sequence (think exe files and PATH under Windows). We also have Java programs interacting with this legacy code, and as the core-group-customer lookup mehchanism does not lend it self easily to Java it has tended to grow in a CVS branch for each customer, requiring much too much maintainance. The Java part and the backend part tend to be developed in parallel. I have been assigned to figure out a way to make the two worlds meet. Essentially we want a Java enviornment which allows us to have a single code base with sources for each release, where we easily can select a group and a customer and work with the application as it goes for that customer, and then easily switch to another codeset and THAT customer. I was thinking of perhaps a scenario with an Eclipse project for each core, customer, and group and then use Project Sets to select those we need for a given scenario. The problem I cannot get my head about, is how we would create robust code in the CORE projects which will work regardless of which group and customer is selected. A Factory class which knows which sub class of a passed Class object to invoke instead of each and every new? Others must have had similar code base management problems. Anybody with experiences to share? EDIT: The conclusion to this problem above has been that CVS needs to be replaced with a source code management system better suited for dealing with many branches concurrently and the migration of source from one component to the other while keeping history. Inspired by the recent migration by slf4j and logback we are currently looking at git as it handles branches very well. We've considered subversion and mercurial too but git appears to be better for single location, multibranched projects. I've asked about Perforce in another question, but my personal inclination is towards open source solutions for something as crucial as this. EDIT: After some more pondering, we've found that our actual pain point is that we use branches in CVS, and that branches in CVS are the easiest to work with if you branch ALL files! The revised conclusion is that we can do this with CVS alone, by switching to a forest of java projects, each corresponding to one of the levels above, and use the Eclipse build paths to tie them together so each CUSTOMER version pulls in the appropriate GROUP and CORE project. We still want to switch to a better versioning system but this is so important a decision so we want to delay it as much as possible. EDIT: I now have a proof-of-concept implementation of the CORE-GROUP-CUSTOMER concept using Google Guice 2.0 - the @ImplementedBy tag is just what we need. I wonder what everybody else does? Using if's all over the place? EDIT: Now I also need this functionality for web applications. Guice was until the JSR-330 is in place. Anybody with versioning experience? EDIT: JSR-330/299 is now in place with the JEE6 reference implementation Weld based on JBoss Seam and I have reimplemented the proof-of-concept with Weld and can see that if we use @Alternative along with ... in beans.xml we can get the behaviour we desire. I.e. provide a new implementation for a given functionality in CORE without changing a bit in the CORE jars. Initial reading up on the Servlet 3.0 specification indicates that it may support the same functionality for web application resources (not code). We will now do initial testing on the real application.

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• How do you attract programmers in rural areas?

  - by Reed Copsey

  I run a software development group for a very small, but stable and established company in a small town, somewhat outside of the "big city". Unfortunately, the "programmer" labor pool is much smaller due to the size of the city. There are many positives to working in this area, especially in terms of quality of life (particularly for people interested in outdoor activities), lower cost of living, great schools and neighborhoods, etc. However, I've always had difficulty attracting high-qualtiy, experienced developers. For those of you who hire developers outside of large cities: Where do you advertise to find good developers? Many of the large sites are very focused in certain metropolitan areas, and seem inappropriate places to advertise if you're outside of that main region. How do you attract quality developers to rural (or at least less metropolitan) locations? Do you find that you make more sacrifices in your hiring due to a smaller labor pool? Or do you just wait, and take extra time to attract people? What sacrifices do you expect to make if you are outside of the main developer-rich cities? For all of the developers out there... What would entice you to working in a smaller town? Are there things that would stand out and make you willing to relocate or at least apply to a position that was not nearby? What specific qualities would help you want to move outside of the city? In the past, I've had difficulty with finding good people. Most of the people who've applied and been willing to move out to a more rural location seem like the types that can't keep a quality job elsewhere. I'd like to know what advice people have to attracting quality technical staff. I don't believe its the work itself that's been the problem - The work is both interesting and challenging, and nearly 100% new development. The developers I have seem very happy with their situation - they love the work, the atmosphere, etc. It's more a matter of finding willing, able developers. Edit: More info after the first couple of answers: Right now, some of my best developers telecommute (some work from overseas); however, for this question, I'm trying to figure out how to get people who want to live and work full time locally. I need some people with whom I interact every day.

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• CDI SessionScoped Bean instance remains unchanged when login with different user

  - by Jason Yang

  I've been looking for the workaround of this problem for rather plenty of time and no result, so I ask question here. Simply speaking, I'm using a CDI SessionScoped Bean User in my project to manage user information and display them on jsf pages. Also container-managed j_security_check is used to resolve authentication issue. Everything is fine if first logout with session.invalidate() and then login in the same browser tab with a different user. But when I tried to directly login (through login.jsf) with a new user without logout beforehand, I found the user information remaining unchanged. I debugged and found the User bean, as well as the HttpSession instance, always remaining the same if login with different users in the same browser, as long as session.invalidate() not invoked. But oddly, the session id did modified, and I've both checked in Java code and Firebug. org.apache.catalina.session.StandardSessionFacade@5d7b4092 StandardSession[c69a71d19f369d08b5dddbea2ef0] attrName = org.jboss.weld.context.conversation.ConversationIdGenerator : attrValue=org.jboss.weld.context.conversation.ConversationIdGenerator@583c9dd8 attrName = org.jboss.weld.context.ConversationContext.conversations : attrValue = {} attrName = org.jboss.weld.context.http.HttpSessionContext#org.jboss.weld.bean-Discipline-ManagedBean-class com.netease.qa.discipline.profile.User : attrValue = Bean: Managed Bean [class com.netease.qa.discipline.profile.User] with qualifiers [@Any @Default @Named]; Instance: com.netease.qa.discipline.profile.User@c497c7c; CreationalContext: org.jboss.weld.context.CreationalContextImpl@739efd29 attrName = javax.faces.request.charset : attrValue = UTF-8 org.apache.catalina.session.StandardSessionFacade@5d7b4092 StandardSession[c6ab4b0c51ee0a649ef696faef75] attrName = org.jboss.weld.context.conversation.ConversationIdGenerator : attrValue = org.jboss.weld.context.conversation.ConversationIdGenerator@583c9dd8 attrName = com.sun.faces.renderkit.ServerSideStateHelper.LogicalViewMap : attrValue = {-4968076393130137442={-7694826198761889564=[Ljava.lang.Object;@43ff5d6c}} attrName = org.jboss.weld.context.ConversationContext.conversations : attrValue = {} attrName = org.jboss.weld.context.http.HttpSessionContext#org.jboss.weld.bean-Discipline-ManagedBean-class com.netease.qa.discipline.profile.User : attrValue = Bean: Managed Bean [class com.netease.qa.discipline.profile.User] with qualifiers [@Any @Default @Named]; Instance: com.netease.qa.discipline.profile.User@c497c7c; CreationalContext: org.jboss.weld.context.CreationalContextImpl@739efd29 attrName = javax.faces.request.charset : attrValue = UTF-8 Above block contains two successive logins and their Session info. We can see that the instance(1st row) the same while session id(2nd row) different. Seems that session object is reused to contain different session id and CDI framework manages session bean life cycle in accordance with the session object only(?). I'm wondering whether there could be only one server-side session object within the same browser unless invalidated? Since I'm adopting j_security_check I fancy intercepting it and invalidating old session is not so easy. So is it possible to accomplish the goal without altering the CDI+JSF+j_security_check design that one can relogin with different account in the same or different tab within the same browser? Really look forward for your response. More info: Glassfish v3.1 is my appserver.

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• Technology to communicate with someone with expressive aphasia?

  - by rascher

  A family member had a stroke a few years back and now has expressive aphasia. She understands what is said to her, is cognitive of what is going on, but cannot express herself. She is able to respond to yes/no questions (do you want to go shopping? are you looking for your earrings?) She is not, however, able to read (English is not her native language and she hasn't read Hindi for decades.) I am the technologist in the family, and I intend to come up with something to help us communicate. The idea is to have some sort of picture book where she can point to what she wants. My first question: does some sort of assistive technology for people with expressive aphasia already exist? These can be hardware or software devices? If not, then such a software doesn't seem difficult to write. My initial thought is to have an interface with pictures - maybe separated by category (food, shopping) - where she can point to an individual picture to indicate what she needs. We could easily add more items with such a software, and we could have an interface where she (or we) could "flip pages". Which suggests that the best solution would use a touch screen rather than a mouse. It would be really difficult to train her to aim a mouse or find keys on a keyboard. We're thinking of maybe getting a tablet and writing some basic software. But tablets computers are expensive and fragile - I'm not sure if it would be able to stand spills or being knocked about in a nursing home. So my next question: what kind of tablet-like devices are out there which I can program on? I don't know anything about hardware, but if there is something then we could special-order it. What would be safe and durable for such a project? We could do something on an iPod or cell phone, but I feel like that interface would be too small. Finally, does anyone here have experience with this kind of assistive technology? Things I might not anticipate when designing such a system? edit I've added a (pretty hefty!) bounty. I'd kinda like to open this question up to any suggestions, comments, and experiences that people might have. This is a pretty real and important project, so while we will (are working on) a solution, any insights would be particularly helpful. Right now the plan is to mount a screen in her room. We'll either teach her to use a trackball or use a touch-screen panel, after seeing what she is able to use with a simple prototype. Then software akin to an old "hypercard" deck: ---------------------------------------------------------------- | -------------- -------------- | | | Clothes | | Food | ... | | -------------- -------------- | | | | Pic of item 1 Pic of item 2 Pic of item 3 | | | | | | | | | | Pic of item 4 Pic of item 5 Pic of item 6 | | | | | | | | | | <-Back Next-> | ---------------------------------------------------------------- commentcommentcomment!

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• Reading Source Code Aloud

  - by Jon Purdy

  After seeing this question, I got to thinking about the various challenges that blind programmers face, and how some of them are applicable even to sighted programmers. Particularly, the problem of reading source code aloud gives me pause. I have been programming for most of my life, and I frequently tutor fellow students in programming, most often in C++ or Java. It is uniquely aggravating to try to verbally convey the essential syntax of a C++ expression. The speaker must give either an idiomatic translation into English, or a full specification of the code in verbal longhand, using explicit yet slow terms such as "opening parenthesis", "bitwise and", et cetera. Neither of these solutions is optimal. On the one hand, an idiomatic translation is only useful to a programmer who can de-translate back into the relevant programming code—which is not usually the case when tutoring a student. In turn, education (or simply getting someone up to speed on a project) is the most common situation in which source is read aloud, and there is a very small margin for error. On the other hand, a literal specification is aggravatingly slow. It takes far far longer to say "pound, include, left angle bracket, iostream, right angle bracket, newline" than it does to simply type #include <iostream>. Indeed, most experienced C++ programmers would read this merely as "include iostream", but again, inexperienced programmers abound and literal specifications are sometimes necessary. So I've had an idea for a potential solution to this problem. In C++, there is a finite set of keywords—63—and operators—54, discounting named operators and treating compound assignment operators and prefix versus postfix auto-increment and decrement as distinct. There are just a few types of literal, a similar number of grouping symbols, and the semicolon. Unless I'm utterly mistaken, that's about it. So would it not then be feasible to simply ascribe a concise, unique pronunciation to each of these distinct concepts (including one for whitespace, where it is required) and go from there? Programming languages are far more regular than natural languages, so the pronunciation could be standardised. Speakers of any language would be able to verbally convey C++ code, and due to the regularity and fixity of the language, speech-to-text software could be optimised to accept C++ speech with a high degree of accuracy. So my question is twofold: first, is my solution feasible; and second, does anyone else have other potential solutions? I intend to take suggestions from here and use them to produce a formal paper with an example implementation of my solution.

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• Writing a code example

  - by Stefano Borini

  I would like to have your feedback regarding code examples. One of the most frustrating experiences I sometimes have when learning a new technology is finding useless examples. I think an example as the most precious thing that comes with a new library, language, or technology. It must be a starting point, a wise and unadulterated explanation on how to achieve a given result. A perfect example must have the following characteristics: Self contained: it should be small enough to be compiled or executed as a single program, without dependencies or complex makefiles. An example is also a strong functional test if you correctly installed the new technology. The more issues could arise, the more likely is that something goes wrong, and the more difficult is to debug and solve the situation. Pertinent: it should demonstrate one, and only one, specific feature of your software/library, involving the minimal additional behavior from external libraries. Helpful: the code should bring you forward, step by step, using comments or self-documenting code. Extensible: the example code should be a small “framework” or blueprint for additional tinkering. A learner can start by adding features to this blueprint. Recyclable: it should be possible to extract parts of the example to use in your own code Easy: An example code is not the place to show your code-fu skillz. Keep it easy. helpful acronym: SPHERE. Prototypical examples of violations of those rules are the following: Violation of self-containedness: an example spanning multiple files without any real need for it. If your example is a python program, keep everything into a single module file. Don’t sub-modularize it. In Java, try to keep everything into a single class, unless you really must partition some entity into a meaningful object you need to pass around (and java mandates one class per file, if I remember correctly). Violation of Pertinency: When showing how many different shapes you can draw, adding radio buttons and complex controls with all the possible choices for point shapes is a bad idea. You de-focalize your example code, introducing code for event handling, controls initialization etc., and this is not part the feature you want to demonstrate, they are unnecessary noise in the understanding of the crucial mechanisms providing the feature. Violation of Helpfulness: code containing dubious naming, wrong comments, hacks, and functions longer than one page of code. Violation of Extensibility: badly factored code that have everything into a single function, with potentially swappable entities embedded within the code. Example: if an example reads data from a file and displays it, create a method getData() returning a useful entity, instead of opening the file raw and plotting the stuff. This way, if the user of the library needs to read data from a HTTP server instead, he just has to modify the getData() module and use the example almost as-is. Another violation of Extensibility comes if the example code is not under a fully liberal (e.g. MIT or BSD) license. Violation of Recyclability: when the code layout is so intermingled that is difficult to easily copy and paste parts of it and recycle them into another program. Again, licensing is also a factor. Violation of Easiness: Yes, you are a functional-programming nerd and want to show how cool you are by doing everything on a single line of map, filter and so on, but that could not be helpful to someone else, who is already under pressure to understand your library, and now has to understand your code as well. And in general, the final rule: if it takes more than 10 minutes to do the following: compile the code, run it, read the source, and understand it fully, it means that the example is not a good one. Please let me know your opinion, either positive or negative, or experience on this regard.

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• Stack Overflow Exploit in C

  - by Fernando Gonzalez

  Hey there guys, the question is actually about stack overflows in C. I have an assigment that I can not get done for the life of me, i've looked at everything in the gdb and I just cant figure it. The question is the following: int i,n; void confused() { printf("who called me"); exit(0); } void shell_call(char *c) { printf(" ***Now calling \"%s\" shell command *** \n",c); system(c); exit(0); } void victim_func() { int a[4]; printf("[8]:%x\n", &a[8]); printf("Enter n: "); scanf("%d",&n); printf("Enter %d HEX Values \n",n); for(i=0;i<n;i++) scanf("%x",&a[i]); printf("Done reading junk numbers\n"); } int main() { printf("ls=736c --- ps = 7370 --- cal = 6c6163\n"); printf("location of confused %x \n", confused); printf("location of shell_call %x \n", shell_call); victim_func(); printf("Done, thank you\n"); } Ok, so I managed to get the first question correctly, which is to arbitrarily call one of the two functions not explicitly called in the main path. By the way, this has to be done while running the program without any modifications. I did this by running the program, setting N to 7, which gets me to the Function Pointer of the victim_func frame, I write a[7] with the memory address of confused or shell_call, and it works. (I have a 64 bit machine, thats why I have to get it to 7, since the EBI pointer is 2 ints wide, instead of 1) My question is the following, how could I control which argument gets passed to the shell_code funcion? ie. how do i write a string to char* c. The whole point is executing unix commands like "ps" etc, by running only the program. I figured writing the EBI pointer with the hex representation of "ps" and setting the arg list of shell_call to that, but that didn't work. I also tried inputing argsv arguments and setting the arg list of shell_call to the arg_list of main, but didnt work either. I think the second version should work, but i believe im not setting the arg list of the new stack frame correctly ( I did it by writing a[8] to 0, since its the first part of the functin pointer, and writing a[9]=736c and a[10]=0000, but its probably not right since those are the parameters of victim_func. So how do i access the parameters of shell_call?

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• Rendering javascript at the server side level. A good or bad idea?

  - by davidhong

  I want to make it clear first: This isn't a question in relation to server-side Javascript or running Javascript server side. This is a question regarding rendering of Javascript code (which will be executed on the client-side) from server-side code. Having said that, take a look at below ASP.net code for example: hlRemoveCategory.Attributes.Add("onclick", "return confirm('Are you sure you want to delete this?');") This is prescribing the client-side onclick event on the server-side. As oppose to: $('a[rel=remove]').bind('click', function(event) { return confirm('Are you sure you want to delete this?'); } Now the question I want to ask is: What is the benefit of rendering javascript from the server-side code? Or the vice-versa? I personally prefer the second way of hooking up client-side UI/behaviour to HTML elements for the following reasons: Server-side does what ever it needs to already, including data-validation, event delegation and etc; and What server-side sees as an event is not necessarily the same process on the client-side. i.e., there are plenty more events on client-side (just look at custom events); and What happens on client-side and on server-side, during an event, could be completely irrelevant and decoupled; and What ever happens on client-side happens on client-side, there is no need for the server to know. Server should process and run what is given to them, how the process comes to life is not really up to them to decide in the event of the client-side events; and so and so forth. These are my thoughts obviously. I want to know what others think and if there has been any discussions on this topic. Topics branching from this argument can reach: Code management: is it easier to render everything from server-side? Separation of concern: is it easier if client-side logic is separated to server-side logic? Efficiency: which is more efficient both in terms of coding and running? At the end of the day, I am trying to move my team to go towards the second approach. There are lot of old guys in this team who are afraid of this change. I just wish to convince them with the right facts and stats. Let me know your thoughts.

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• Domain Validation in a CQRS architecture

  - by Jupaol

  Basically I want to know if there is a better way to validate my domain entities. This is how I am planning to do it but I would like your opinion The first approach I considered was: class Customer : EntityBase<Customer> { public void ChangeEmail(string email) { if(string.IsNullOrWhitespace(email)) throw new DomainException(“...”); if(!email.IsEmail()) throw new DomainException(); if(email.Contains(“@mailinator.com”)) throw new DomainException(); } } I actually do not like this validation because even when I am encapsulating the validation logic in the correct entity, this is violating the Open/Close principle (Open for extension but Close for modification) and I have found that violating this principle, code maintenance becomes a real pain when the application grows up in complexity. Why? Because domain rules change more often than we would like to admit, and if the rules are hidden and embedded in an entity like this, they are hard to test, hard to read, hard to maintain but the real reason why I do not like this approach is: if the validation rules change, I have to come and edit my domain entity. This has been a really simple example but in RL the validation could be more complex So following the philosophy of Udi Dahan, making roles explicit, and the recommendation from Eric Evans in the blue book, the next try was to implement the specification pattern, something like this class EmailDomainIsAllowedSpecification : IDomainSpecification<Customer> { private INotAllowedEmailDomainsResolver invalidEmailDomainsResolver; public bool IsSatisfiedBy(Customer customer) { return !this.invalidEmailDomainsResolver.GetInvalidEmailDomains().Contains(customer.Email); } } But then I realize that in order to follow this approach I had to mutate my entities first in order to pass the value being valdiated, in this case the email, but mutating them would cause my domain events being fired which I wouldn’t like to happen until the new email is valid So after considering these approaches, I came out with this one, since I am going to implement a CQRS architecture: class EmailDomainIsAllowedValidator : IDomainInvariantValidator<Customer, ChangeEmailCommand> { public void IsValid(Customer entity, ChangeEmailCommand command) { if(!command.Email.HasValidDomain()) throw new DomainException(“...”); } } Well that’s the main idea, the entity is passed to the validator in case we need some value from the entity to perform the validation, the command contains the data coming from the user and since the validators are considered injectable objects they could have external dependencies injected if the validation requires it. Now the dilemma, I am happy with a design like this because my validation is encapsulated in individual objects which brings many advantages: easy unit test, easy to maintain, domain invariants are explicitly expressed using the Ubiquitous Language, easy to extend, validation logic is centralized and validators can be used together to enforce complex domain rules. And even when I know I am placing the validation of my entities outside of them (You could argue a code smell - Anemic Domain) but I think the trade-off is acceptable But there is one thing that I have not figured out how to implement it in a clean way. How should I use this components... Since they will be injected, they won’t fit naturally inside my domain entities, so basically I see two options: Pass the validators to each method of my entity Validate my objects externally (from the command handler) I am not happy with the option 1 so I would explain how I would do it with the option 2 class ChangeEmailCommandHandler : ICommandHandler<ChangeEmailCommand> { public void Execute(ChangeEmailCommand command) { private IEnumerable<IDomainInvariantValidator> validators; // here I would get the validators required for this command injected, and in here I would validate them, something like this using (var t = this.unitOfWork.BeginTransaction()) { var customer = this.unitOfWork.Get<Customer>(command.CustomerId); this.validators.ForEach(x =. x.IsValid(customer, command)); // here I know the command is valid // the call to ChangeEmail will fire domain events as needed customer.ChangeEmail(command.Email); t.Commit(); } } } Well this is it. Can you give me your thoughts about this or share your experiences with Domain entities validation EDIT I think it is not clear from my question, but the real problem is: Hiding the domain rules has serious implications in the future maintainability of the application, and also domain rules change often during the life-cycle of the app. Hence implementing them with this in mind would let us extend them easily. Now imagine in the future a rules engine is implemented, if the rules are encapsulated outside of the domain entities, this change would be easier to implement

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• Writing reports with Perl

  - by georgemp

  Hi, I am trying to write out multiple report files using perl. Each file has the same structure, but with different data. So, my basic code looks something like #begin code our $log_fh; open %log_fh, ">" . $logfile our $rep; if (multipleReports) { while (@reports) { printReport($report[0]); } } sub printReports { open $rep, ">" . $[0]; printHeaders(); printBody(); close $rep; } sub printHeader() { format HDR = @>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> $generatedLine . format HDR_TOP = . $rep->format_name("HDR"); $rep->format_top_name("HDR_TOP"); $generatedLine = "test"; write($rep); $generatedLine = "next item"; write($rep); $generatedLine = "last header item"; write($rep); } sub printBody #There are multiple such sections in my code. For simplicity, I have just shown 1 here { #declare own header and header top. Set report to use these and print items to $rep } #end code The above is just a high level of the code I am using and I hope I have captured all the salient points. However, for some reason, I get the first report file output correctly. The second file instead of having in the first section test next item last item reads last item last item last item I have tried a whole lot of options primarily around autoflush, but, for the life of me can't figure out why it is doing this. I am using Perl 5.8.2. Any help/pointers much appreciated. Thanks George

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