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• How to force VS 2010 to skip "builds" of projects which haven't changed?

  - by Ladislav Mrnka

  Our product's solution has more than 100+ projects (500+ksloc of production code). Most of them are C# projects but we also have few using C++/CLI to bridge communication with native code. Rebuilding the whole solution takes several minutes. That's fine. If I want to rebuilt the solution I expect that it will really take some time. What is not fine is time needed to build solution after full rebuild. Imagine I used full rebuild and know without doing any changes to to the solution I press Build (F6 or Ctrl+Shift+B). Why it takes 35s if there was no change? In output I see that it started "building" of each project - it doesn't perform real build but it does something which consumes significant amount of time. That 35s delay is pain in the ass. Yes I can improve the time by not using build solution but only build project (Shift+F6). If I run build project on particular test project I'm currently working on it will take "only" 8+s. It requires me to run project build on correct project (the test project to ensure dependent tested code is build as well). At least ReSharper test runner correctly recognizes that only this single project must be build and rerunning test usually contains only 8+s compilation. My current coding Kata is: don't touch Ctrl+Shift+B. The test project build will take 8s even if I don't do any changes. The reason why it takes 8s is because it also "builds" dependencies = in my case it "builds" more than 20 projects but I made changes only to unit test or single dependency! I don't want it to touch other projects. Is there a way to simply tell VS to build only projects where some changes were done and projects which are dependent on changed ones (preferably this part as another build option)? I worry you will tell me that it is exactly what VS is doing but in MS way ... I want to improve my TDD experience and reduce the time of compilation (in TDD the compilation can happen twice per minute). To make this even more frustrated I'm working in a team where most of developers used to work on Java projects prior to joining this one. So you can imagine how they are pissed off when they must use VS in contrast to full incremental compilation in Java. I don't require incremental compilation of classes. I expect working incremental compilation of solutions. Especially in product like VS 2010 Ultimate which costs several thousands dollars. I really don't want to get answers like: Make a separate solution Unload projects you don't need etc. I can read those answers here. Those are not acceptable solutions. We're not paying for VS to do such compromises.

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• G++, compiler warnings, c++ templates

  - by Ian

  During the compilatiion of the C++ program those warnings appeared: c:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bc:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bits/stl_algo.h:2317: instantiated from `void std::partial_sort(_RandomAccessIterator, _RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Object<double>**, std::vector<Object<double>*, std::allocator<Object<double>*> > >, _Compare = sortObjects<double>]' c:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bits/stl_algo.h:2506: instantiated from `void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Object<double>**, std::vector<Object<double>*, std::allocator<Object<double>*> > >, _Size = int, _Compare = sortObjects<double>]' c:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bits/stl_algo.h:2589: instantiated from `void std::sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Object<double>**, std::vector<Object<double>*, std::allocator<Object<double>*> > >, _Compare = sortObjects<double>]' io/../structures/objects/../../algorithm/analysis/../../structures/list/ObjectsList.hpp:141: instantiated from `void ObjectsList <T>::sortObjects(unsigned int, T, T, T, T, unsigned int) [with T = double]' I do not why, because all objects have only template parameter T, their local variables are also T. The only place, where I am using double is main. There are objects of type double creating and adding into the ObjectsList... Object <double> o1; ObjectsList <double> olist; olist.push_back(o1); .... T xmin = ..., ymin = ..., xmax = ..., ymax = ...; unsigned int n = ...; olist.sortAllObjects(xmin, ymin, xmax, ymax, n); and comparator template <class T> class sortObjects { private: unsigned int n; T xmin, ymin, xmax, ymax; public: sortObjects ( const T xmin_, const T ymin_, const T xmax_, const T ymax_, const int n_ ) : xmin ( xmin_ ), ymin ( ymin_ ), xmax ( xmax_ ), ymax ( ymax_ ), n ( n_ ) {} bool operator() ( const Object <T> *o1, const Object <T> *o2 ) const { T dmax = (std::max) ( xmax - xmin, ymax - ymin ); T x_max = ( xmax - xmin ) / dmax; T y_max = ( ymax - ymin ) / dmax; ... return ....; } representing ObjectsList method: template <class T> void ObjectsList <T> ::sortAllObjects ( const T xmin, const T ymin, const T xmax, const T ymax, const unsigned int n ) { std::sort ( objects.begin(), objects.end(), sortObjects <T> ( xmin, ymin, xmax, ymax, n ) ); }

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• How to measure a canvas that has auto height and with

  - by Wymmeroo

  Hi Folks, I'm a beginner in silverlight so i hope i can get an answer that brings me some more light in the measure process of silverlight. I found an interessting flap out control from silverlight slide control and now I try to use it in my project. So that the slide out is working proper, I have to place the user control on a canvas. The user control then uses for itself the height of its content. I just wanna change that behavior so that the height is set to the available space from the parent canvas. You see the uxBorder where the height is set. How can I measure the actual height and set it to the border? I tried it with Height={Binding ElementName=notificationCanvas, Path=ActualHeight} but this dependency property has no callback, so the actualHeight is never set. What I want to achieve is a usercontrol like the tweetboard per example on Jesse Liberty's blog Sorry for my English writing, I hope you understand my question. <Canvas x:Name="notificationCanvas" Background="Red"> <SlideEffectEx:SimpleSlideControl GripWidth="20" GripTitle="Task" GripHeight="100"> <Border x:Name="uxBorder" BorderThickness="2" CornerRadius="5" BorderBrush="DarkGray" Background="DarkGray" Padding="5" Width="300" Height="700" > <StackPanel> <TextBlock Text="Tasks"></TextBlock> <Button x:Name="btn1" Margin="5" Content="{Binding ElementName=MainBorder, Path=Height}"></Button> <Button x:Name="btn2" Margin="5" Content="Second Button"></Button> <Button x:Name="btn3" Margin="5" Content="Third Button"></Button> <Button x:Name="btn1_Copy" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy1" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy2" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy3" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy4" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy5" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy6" Margin="5" Content="First Button"/> </StackPanel> </Border> </SlideEffectEx:SimpleSlideControl>

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• Checking if an int is prime more efficiently

  - by SipSop

  I recently was part of a small java programming competition at my school. My partner and I have just finished our first pure oop class and most of the questions were out of our league so we settled on this one (and I am paraphrasing somewhat): "given an input integer n return the next int that is prime and its reverse is also prime for example if n = 18 your program should print 31" because 31 and 13 are both prime. Your .class file would then have a test case of all the possible numbers from 1-2,000,000,000 passed to it and it had to return the correct answer within 10 seconds to be considered valid. We found a solution but with larger test cases it would take longer than 10 seconds. I am fairly certain there is a way to move the range of looping from n,..2,000,000,000 down as the likely hood of needing to loop that far when n is a low number is small, but either way we broke the loop when a number is prime under both conditions is found. At first we were looping from 2,..n no matter how large it was then i remembered the rule about only looping to the square root of n. Any suggestions on how to make my program more efficient? I have had no classes dealing with complexity analysis of algorithms. Here is our attempt. public class P3 { public static void main(String[] args){ long loop = 2000000000; long n = Integer.parseInt(args[0]); for(long i = n; i<loop; i++) { String s = i +""; String r = ""; for(int j = s.length()-1; j>=0; j--) r = r + s.charAt(j); if(prime(i) && prime(Long.parseLong(r))) { System.out.println(i); break; } } System.out.println("#"); } public static boolean prime(long p){ for(int i = 2; i<(int)Math.sqrt(p); i++) { if(p%i==0) return false; } return true; } } ps sorry if i did the formatting for code wrong this is my first time posting here. Also the output had to have a '#' after each line thats what the line after the loop is about Thanks for any help you guys offer!!!

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• Why does my ko computed observable not update bound UI elements when its value changes?

  - by Allen

  I'm trying to wrap a cookie in a computed observable (which I'll later turn into a protectedObservable) and I'm having some problems with the computed observable. I was under the opinion that changes to the computed observable would be broadcast to any UI elements that have been bound to it. I've created the following fiddle JavaScript: var viewModel = {}; // simulating a cookie store, this part isnt as important var cookie = function () { // simulating a value stored in cookies var privateZipcode = "12345"; return { 'write' : function (val) { privateZipcode = val; }, 'read': function () { return privateZipcode; } } }(); viewModel.zipcode = ko.computed({ read: function () { return cookie.read(); }, write: function (value) { cookie.write(value); }, owner: viewModel }); ko.applyBindings(viewModel);? HTML: zipcode: <input type='text' data-bind="value: zipcode"> <br /> zipcode: <span data-bind="text: zipcode"></span>? I'm not using an observable to store privateZipcode since that's really just going to be in a cookie. I'm hoping that the ko.computed will provide the notifications and binding functionality that I need, though most of the examples I've seen with ko.computed end up using a ko.observable underneath the covers. Shouldn't the act of writing the value to my computed observable signal the UI elements that are bound to its value? Shouldn't these just update? Workaround I've got a simple workaround where I just use a ko.observable along side of my cookie store and using that will trigger the required updates to my DOM elements but this seems completely unnecessary, unless ko.computed lacks the signaling / dependency type functionality that ko.observable has. My workaround fiddle, you'll notice that the only thing that changes is that I added a seperateObservable that isn't used as a store, its only purpose is to signal to the UI that the underlying data has changed. // simulating a cookie store, this part isnt as important var cookie = function () { // simulating a value stored in cookies var privateZipcode = "12345"; // extra observable that isnt really used as a store, just to trigger updates to the UI var seperateObservable = ko.observable(privateZipcode); return { 'write' : function (val) { privateZipcode = val; seperateObservable(val); }, 'read': function () { seperateObservable(); return privateZipcode; } } }(); This makes sense and works as I'd expect because viewModel.zipcode depends on seperateObservable and updates to that should (and does) signal the UI to update. What I don't understand, is why doesn't a call to the write function on my ko.computed signal the UI to update, since that element is bound to that ko.computed? I suspected that I might have to use something in knockout to manually signal that my ko.computed has been updated, and I'm fine with that, that makes sense. I just haven't been able to find a way to accomplish that.

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• Rails. Putting update logic in your migrations

  - by Daniel Abrahamsson

  A couple of times I've been in the situation where I've wanted to refactor the design of some model and have ended up putting update logic in migrations. However, as far as I've understood, this is not good practice (especially since you are encouraged to use your schema file for deployment, and not your migrations). How do you deal with these kind of problems? To clearify what I mean, say I have a User model. Since I thought there would only be two kinds of users, namely a "normal" user and an administrator, I chose to use a simple boolean field telling whether the user was an adminstrator or not. However, after I while I figured I needed some third kind of user, perhaps a moderator or something similar. In this case I add a UserType model (and the corresponding migration), and a second migration for removing the "admin" flag from the user table. And here comes the problem. In the "add_user_type_to_users" migration I have to map the admin flag value to a user type. Additionally, in order to do this, the user types have to exist, meaning I can not use the seeds file, but rather create the user types in the migration (also considered bad practice). Here comes some fictional code representing the situation: class CreateUserTypes < ActiveRecord::Migration def self.up create_table :user_types do |t| t.string :name, :nil => false, :unique => true end #Create basic types (can not put in seed, because of future migration dependency) UserType.create!(:name => "BASIC") UserType.create!(:name => "MODERATOR") UserType.create!(:name => "ADMINISTRATOR") end def self.down drop_table :user_types end end class AddTypeIdToUsers < ActiveRecord::Migration def self.up add_column :users, :type_id, :integer #Determine type via the admin flag basic = UserType.find_by_name("BASIC") admin = UserType.find_by_name("ADMINISTRATOR") User.all.each {|u| u.update_attribute(:type_id, (u.admin?) ? admin.id : basic.id)} #Remove the admin flag remove_column :users, :admin #Add foreign key execute "alter table users add constraint fk_user_type_id foreign key (type_id) references user_types (id)" end def self.down #Re-add the admin flag add_column :users, :admin, :boolean, :default => false #Reset the admin flag (this is the problematic update code) admin = UserType.find_by_name("ADMINISTRATOR") execute "update users set admin=true where type_id=#{admin.id}" #Remove foreign key constraint execute "alter table users drop foreign key fk_user_type_id" #Drop the type_id column remove_column :users, :type_id end end As you can see there are two problematic parts. First the row creation part in the first model, which is necessary if I would like to run all migrations in a row, then the "update" part in the second migration that maps the "admin" column to the "type_id" column. Any advice?

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• Isn't the C++ standard library backward-compatible?

  - by Chris Metzler

  Hi. I'm working on a 64-bit Linux system, trying to build some code that depends on third-party libraries for which I have binaries. During linking, I get a stream of undefined reference errors for one of the libraries, indicating that the linker couldn't resolve references to standard C++ functions/classes, e.g.: librxio.a(EphReader.o): In function `gpstk::EphReader::read_fic_data(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)': EphReader.cpp:(.text+0x27c): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, long)' EphReader.cpp:(.text+0x4e8): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, long)' I'm not really a C++ programmer, but this looks to me like it can't find the standard library. Doing some more research, I got the following when I looked at librxio's dependency for the standard library: $ ldd librxio.so.16.0 ./librxio.so.16.0: /usr/lib64/libstdc++.so.6: version `GLIBCXX_3.4.9' not found (required by ./librxio.so.16.0) libm.so.6 => /lib64/libm.so.6 (0x00002aaaaad45000) libstdc++.so.6 => /usr/lib64/libstdc++.so.6 (0x00002aaaaafc8000) libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00002aaaab2c8000) libc.so.6 => /lib64/libc.so.6 (0x00002aaaab4d7000) /lib64/ld-linux-x86-64.so.2 (0x0000555555554000) So I read that as saying that librxio (one of the third-party libraries) requires at least v3.4.9 of the standard library. But the version I have installed is 4.1.2: $ rpm -qa | grep libstdc compat-libstdc++-33-3.2.3-61.x86_64 libstdc++-devel-4.1.2-14.el5.i386 libstdc++-devel-4.1.2-14.el5.x86_64 libstdc++-4.1.2-14.el5.x86_64 libstdc++-4.1.2-14.el5.i386 Shouldn't this work? The shared object major number is 6, same as for v3.4.9. At this level, shouldn't this be backward compatible? It seems like the third-party library is looking for an earlier version of the standard library than what I have installed; but isn't there backward compatibility between versions with the same major number for the shared library? Again, I'm not really a C++ programmer; but I don't see what the problem is. Any advice greatly appreciated. Thanks.

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• Consolidating coding styles: Funcs, private method, single method classes

  - by jdoig

  Hi all, We currently have 3 devs with, some, conflicting styles and I'm looking for a way to bring peace to the kingdom... The Coders: Foo 1: Likes to use Func's & Action's inside public methods. He uses actions to alias off lengthy method calls and Func's to perform simple tasks that can be expressed in 1 or 2 lines and will be used frequently through out the code Pros: The main body of his code is succinct and very readable, often with only one or 2 public methods per class and rarely any private methods. Cons: The start of methods contain blocks of lambda rich code that other developers don't enjoy reading; and, on occasion, can contain higher order functions that other dev's REALLY don't like reading. Foo 2: Likes to create a private method for (almost) everything the public method will have to do . Pros: Public methods remain small and readable (to all developers). Cons: Private methods are numerous. With private methods that call into other private methods, that call into... etc, etc. Making code hard to navigate. Foo 3: Likes to create a public class with a, single, public method for every, non-trivial, task that needs performing, then dependency inject them into other objects. Pros: Easily testable, easy to understand (one object, one responsibility). Cons: project gets littered by classes, opening multiple class files to understand what code does makes navigation awkward. It would be great to take the best of all these techniques... Foo-1 Has really nice, readable (almost dsl-like) code... for the most part, except for all the Action and Func lambda shenanigans bulked together at the start of a method. Foo-3 Has highly testable and extensible code that just feels a bit "belt-&-braces" for some solutions and has some code-navigation niggles (constantly hitting F12 in VS and opening 5 other .cs files to find out what a single method does). And Foo-2... Well I'm not sure I like anything about the one-huge .cs file with 2 public methods and 12 private ones, except for the fact it's easier for juniors to dig into. I admit I grossly over-simplified the explanations of those coding styles; but if any one knows of any patterns, practices or diplomatic-manoeuvres that can help unite our three developers (without just telling any of them to just "stop it!") that would be great. From a feasibility standpoint : Foo-1's style meets with the most resistance due to some developers finding lambda and/or Func's hard to read. Foo-2's style meets with a less resistance as it's just so easy to fall into. Foo-3's style requires the most forward thinking and is difficult to enforce when time is short. Any ideas on some coding styles or conventions that can make this work?

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• Bracketing algorithm when root finding. Single root in "quadratic" function

  - by Ander Biguri

  I am trying to implement a root finding algorithm. I am using the hybrid Newton-Raphson algorithm found in numerical recipes that works pretty nicely. But I have a problem in bracketing the root. While implementing the root finding algorithm I realised that in several cases my functions have 1 real root and all the other imaginary (several of them, usually 6 or 9). The only root I am interested is in the real one so the problem is not there. The thing is that the function approaches the root like a cubic function, touching with the point the y=0 axis... Newton-Rapson method needs some brackets of different sign and all the bracketing methods I found don't work for this specific case. What can I do? It is pretty important to find that root in my program... EDIT: more problems: sometimes due to reaaaaaally small numerical errors, say a variation of 1e-6 in some value the "cubic" function does NOT have that real root, it is just imaginary with a neglectable imaginary part... (checked with matlab) EDIT 2: Much more information about the problem. Ok, I need root finding algorithm. Info I have: The root I need to find is between [0-1] , if there are more roots outside that part I am not interested in them. The root is real, there may be imaginary roots, but I don't want them. Probably all the rest of the roots will be imaginary The root may be double in that point, but I think that actually doesn't mater in numerical analysis problems I need to use the root finding algorithm several times during the overall calculations, but the function will always be a polynomial In one of the particular cases of the root finding, my polynomial will be similar to a quadratic function that touches Y=0 with the point. Example of a real case: The coefficient may not be 100% precise and that really slight imprecision may make the function not to touch the Y=0 axis. I cannot solve for this specific case because in other cases it may be that the polynomial is pretty normal and doesn't make any "strange" thing. The method I am actually using is NewtonRaphson hybrid, where if the derivative is really small it makes a bisection instead of NewRaph (found in numerical recipes). Matlab's answer to the function on the image: roots: 0.853553390593276 + 0.353553390593278i 0.853553390593276 - 0.353553390593278i 0.146446609406726 + 0.353553390593273i 0.146446609406726 - 0.353553390593273i 0.499999999999996 + 0.000000040142134i 0.499999999999996 - 0.000000040142134i The function is a real example I prepared where I know that the answer I want is 0.5 Note: I still haven't check completely some of the answers I you people have give me (Thank you!), I am just trying to give al the information I already have to complete the question.

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• How can I structure and recode messy categorical data in R?

  - by briandk

  I'm struggling with how to best structure categorical data that's messy, and comes from a dataset I'll need to clean. The Coding Scheme I'm analyzing data from a university science course exam. We're looking at patterns in student responses, and we developed a coding scheme to represent the kinds of things students are doing in their answers. A subset of the coding scheme is shown below. Note that within each major code (1, 2, 3) are nested non-unique sub-codes (a, b, ...). What the Raw Data Looks Like I've created an anonymized, raw subset of my actual data which you can view here. Part of my problem is that those who coded the data noticed that some students displayed multiple patterns. The coders' solution was to create enough columns (reason1, reason2, ...) to hold students with multiple patterns. That becomes important because the order (reason1, reason2) is arbitrary--two students (like student 41 and student 42 in my dataset) who correctly applied "dependency" should both register in an analysis, regardless of whether 3a appears in the reason column or the reason2 column. How Can I Best Structure Student Data? Part of my problem is that in the raw data, not all students display the same patterns, or the same number of them, in the same order. Some students may do just one thing, others may do several. So, an abstracted representation of example students might look like this: Note in the example above that student002 and student003 both are coded as "1b", although I've deliberately shown the order as different to reflect the reality of my data. My (Practical) Questions Should I concatenate reason1, reason2, ... into one column? How can I (re)code the reasons in R to reflect the multiplicity for some students? Thanks I realize this question is as much about good data conceptualization as it is about specific features of R, but I thought it would be appropriate to ask it here. If you feel it's inappropriate for me to ask the question, please let me know in the comments, and stackoverflow will automatically flood my inbox with sadface emoticons. If I haven't been specific enough, please let me know and I'll do my best to be clearer.

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• Cached ObjectDataSource not firing Select Event even Cache Dependecy Removed

  - by John Polvora

  I have the following scenario. A Page with a DetailsView binded to an ObjectDatasource with cache-enabled. The SelectMethod is assigned at Page_Load event, depending on my User Level Logic. After assigned the selectMethod and Parameters for the ODS, if Cache not exists, then ODS will be cached the first time. The next time, the cache will be applied to the ODS and the select event don't need to be fired since the dataresult is cached. The problem is, the ODS Cache works fine, but I have a Refresh button to clear the cache and rebind the DetailsView. Am I doing correctly ? Below is my code. <asp:DetailsView ID="DetailsView1" runat="server" DataSourceID="ObjectDataSource_Summary" EnableModelValidation="True" EnableViewState="False" ForeColor="#333333" GridLines="None"> </asp:DetailsView> <asp:ObjectDataSource ID="ObjectDataSource_Summary" runat="server" SelectMethod="" TypeName="BL.BusinessLogic" EnableCaching="true"> <SelectParameters> <asp:Parameter Name="idCompany" Type="String" /> <SelectParameters> </asp:ObjectDataSource> <asp:ImageButton ID="ImageButton_Refresh" runat="server" OnClick="RefreshClick" ImageUrl="~/img/refresh.png" /> And here is the code behind public partial class Index : Page { protected void Page_Load(object sender, EventArgs e) { ObjectDataSource_Summary.SelectMethod = ""; ObjectDataSource_Summary.SelectParameters[0].DefaultValue = ""; switch (this._loginData.UserLevel) //this is a struct I use for control permissions e pages behaviour { case OperNivel.SysAdmin: case OperNivel.SysOperator: { ObjectDataSource_Summary.SelectMethod = "SystemSummary"; ObjectDataSource_Summary.SelectParameters[0].DefaultValue = "0"; break; } case OperNivel.CompanyAdmin: case OperNivel.CompanyOperator: { ObjectDataSource_Summary.SelectMethod = "CompanySummary"; ObjectDataSource_Summary.SelectParameters[0].DefaultValue = this._loginData.UserLevel.ToString(); break; } default: break; } } protected void Page_LoadComplete(object sender, EventArgs e) { if (Cache[ObjectDataSource_Summary.CacheKeyDependency] == null) { this._loginData.LoginDatetime = DateTime.Now; Session["loginData"] = _loginData; Cache[ObjectDataSource_Summary.CacheKeyDependency] = _loginData; DetailsView1.DataBind(); } } protected void RefreshClick(object sender, ImageClickEventArgs e) { Cache.Remove(ObjectDataSource_Summary.CacheKeyDependency); } } Can anyone help me? The Select() Event of the ObjectDasource is not firing even I Remove the CacheKey Dependency

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• translating specifications into query predicates

  - by Jeroen

  I'm trying to find a nice and elegant way to query database content based on DDD "specifications". In domain driven design, a specification is used to check if some object, also known as the candidate, is compliant to a (domain specific) requirement. For example, the specification 'IsTaskDone' goes like: class IsTaskDone extends Specification<Task> { boolean isSatisfiedBy(Task candidate) { return candidate.isDone(); } } The above specification can be used for many purposes, e.g. it can be used to validate if a task has been completed, or to filter all completed tasks from a collection. However, I want to re-use this, nice, domain related specification to query on the database. Of course, the easiest solution would be to retrieve all entities of our desired type from the database, and filter that list in-memory by looping and removing non-matching entities. But clearly that would not be optimal for performance, especially when the entity count in our db increases. Proposal So my idea is to create a 'ConversionManager' that translates my specification into a persistence technique specific criteria, think of the JPA predicate class. The services looks as follows: public interface JpaSpecificationConversionManager { <T> Predicate getPredicateFor(Specification<T> specification, Root<T> root, CriteriaQuery<?> cq, CriteriaBuilder cb); JpaSpecificationConversionManager registerConverter(JpaSpecificationConverter<?, ?> converter); } By using our manager, the users can register their own conversion logic, isolating the domain related specification from persistence specific logic. To minimize the configuration of our manager, I want to use annotations on my converter classes, allowing the manager to automatically register those converters. JPA repository implementations could then use my manager, via dependency injection, to offer a find by specification method. Providing a find by specification should drastically reduce the number of methods on our repository interface. In theory, this all sounds decent, but I feel like I'm missing something critical. What do you guys think of my proposal, does it comply to the DDD way of thinking? Or is there already a framework that does something identical to what I just described?

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• Objective-c design advice for use of different data sources, swapping between test and live

  - by user200341

  I'm in the process of designing an application that is part of a larger piece of work, depending on other people to build an API that the app can make use of to retrieve data. While I was thinking about how to setup this project and design the architecture around it, something occurred to me, and I'm sure many people have been in similar situations. Since my work is depending on other people to complete their tasks, and a test server, this slows work down at my end. So the question is: What's the best practice for creating test repositories and classes, implementing them, and not having to depend on altering several places in the code to swap between the test classes and the actual repositories / proper api calls. Contemplate the following scenario: GetDataFromApiCommand *getDataCommand = [[GetDataFromApiCommand alloc]init]; getDataCommand.delegate = self; [getDataCommand getData]; Once the data is available via the API, "GetDataFromApiCommand" could use the actual API, but until then a set of mock data could be returned upon the call of [getDataCommand getData] There might be multiple instances of this, in various places in the code, so replacing all of them wherever they are, is a slow and painful process which inevitably leads to one or two being overlooked. In strongly typed languages we could use dependency injection and just alter one place. In objective-c a factory pattern could be implemented, but is that the best route to go for this? GetDataFromApiCommand *getDataCommand = [GetDataFromApiCommandFactory buildGetDataFromApiCommand]; getDataCommand.delegate = self; [getDataCommand getData]; What is the best practices to achieve this result? Since this would be most useful, even if you have the actual API available, to run tests, or work off-line, the ApiCommands would not necessarily have to be replaced permanently, but the option to select "Do I want to use TestApiCommand or ApiCommand". It is more interesting to have the option to switch between: All commands are test and All command use the live API, rather than selecting them one by one, however that would also be useful to do for testing one or two actual API commands, mixing them with test data. EDIT The way I have chosen to go with this is to use the factory pattern. I set up the factory as follows: @implementation ApiCommandFactory + (ApiCommand *)newApiCommand { // return [[ApiCommand alloc]init]; return [[ApiCommandMock alloc]init]; } @end And anywhere I want to use the ApiCommand class: GetDataFromApiCommand *getDataCommand = [ApiCommandFactory newApiCommand]; When the actual API call is required, the comments can be removed and the mock can be commented out. Using new in the message name implies that who ever uses the factory to get an object, is responsible for releasing it (since we want to avoid autorelease on the iPhone). If additional parameters are required, the factory needs to take these into consideration i.e: [ApiCommandFactory newSecondApiCommand:@"param1"]; This will work quite well with repositories as well.

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• PDF Report generation

  - by IniTech

  EDIT : I completed this project using ABCpdf. For anyone interested, I love this product and their support is A+. Everything I listed as a 'Con' for the HTML - PDF solution was easily doable in ABCpdf. I've been charged with creating a data driven pdf report. After reviewing the plethora of options, I have narrowed it down to 2. I need you all to to help me decide, or offer alternatives I haven't considered. Here are the requirements: 100% Data driven Eventually PDF (a stop in HTML is fine, so long as it is converted) Can be run with multiple sets of data (the layout is always the same, the data is variable) Contains normal analysis-style copy (saved in DB with html markup) Contains tables (data for tables is generated at run-time) Header/Page # on each page Table of Contents .NET (VB or C#) Done quickly Now, because of the fact that the report is going to be generated with multiple sets of data, I don't think a stamped pdf template will work since I won't know how long or how many pages a certain piece of the report could require. So, I think my best options are: Programmatic creation using an iText-like solution. Generate in HTML and convert to PDF using a third-party application (ABCPdf is the tool I have played with so far) Both solutions have their pro's and con's. Programmatic solution: Pros: Flexible Easy page numbering/page header/table of contents Free Cons: Time consuming (to write a layer on top of iText to do what I need and keep maintainable) Since the copy is already stored in the db with html markup, I would have to parse through the data before I place it into the pdf, ensuring I don't have to break the paragraph into chunks so I can apply bold, italic, underline, etc. to specific phrases. This seems like a huge PITA, and I hope I am wrong about that assumption. HTML - PDF Pros: Easy to generate from db (no parsing necessary) Many tools for conversion Uses technology I am already familiar with Built-in "Print Preview" - not a req, but nice Cons: (Edited after project completion. All of my assumptions were incorrect and ABCpdf is awesome) 1. Almost impossible to generate page headers - Not True 2. Very difficult to generate page numbers Not True 3. Nearly impossible to generate table of contents Not True 4. (Cross-browser support isn't a con; Since its internal, I can dictate what browser to use) 5. Conversion tool quirks - may not convert exactly as rendered in browser Not True 6. Overall, I think it would be very hard to format the HTML exactly as I would want it to appear/convert to PDF. Not True That's it - I need the communitys help in deciding which way I should go. I might be wrong about some of my Pro/Con assumptions. If I am, please tell me. All thoughts and suggestions are welcome and appreciated. Thanks

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• Is "Systems Designer" the job title that best describes what I do? [closed]

  - by ivo-rossi

  After having worked as Java developer for almost 3 years in the same company that I currently work at, I moved to a new position associated with the development of the same application. I’m in this new position for more than 1 year now. My official job title is Systems Designer, but I’m not sure this is a title that expresses well what I do. So my question here is what would be the most appropriate job title for me? I see this question as important for my career development. After all, I should be able to explain in one word what I do. And it’s no longer “Java Developer”. Well, in more than one word, this is what I do: The business analysts gather requirements / business problems to be solved with the clients and then discuss these requirements with me. Given the requirements, I design the high level solutions to be implemented in our system (e.g. a new screen on the client application, modifications to existing reports, extension to the XML export format of some objects, etc). I base my decision on the current capabilities of the system, the overall impact that the solutions would have on the system and the estimated effort to implement them (as I was a developer of this same application for almost 3 years before I moved to this position, I’m confident in my estimates). The solutions are discussed iteratively with the business analysts until we agree that they are good. The outcome of this analysis is what we call the “requirements design” document, which is written by me, shared with clients for approval and then also with the team that is going to implement the solutions and test them. Note that there are a few problems that I need to find a solution for that are non-functional. If the users are unhappy with the performance of a certain tool, I will investigate what can be done to speed it up. I will do some research – often based in the Java code itself - to identify possibilities of optimizations. But in this new position I no longer code, the main outcome of my work is really the “requirements design”. Is “Systems Designer” really the most appropriate job title?

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• Memory Leak with Swing Drag and Drop

  - by tom

  I have a JFrame that accepts top-level drops of files. However after a drop has occurred, references to the frame are held indefinitely inside some Swing internal classes. I believe that disposing of the frame should release all of its resources, so what am I doing wrong? Example import java.awt.datatransfer.DataFlavor; import java.io.File; import java.util.List; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.TransferHandler; public class DnDLeakTester extends JFrame { public static void main(String[] args) { new DnDLeakTester(); //Prevent main from returning or the jvm will exit while (true) { try { Thread.sleep(10000); } catch (InterruptedException e) { } } } public DnDLeakTester() { super("I'm leaky"); add(new JLabel("Drop stuff here")); setTransferHandler(new TransferHandler() { @Override public boolean canImport(final TransferSupport support) { return (support.isDrop() && support .isDataFlavorSupported(DataFlavor.javaFileListFlavor)); } @Override public boolean importData(final TransferSupport support) { if (!canImport(support)) { return false; } try { final List<File> files = (List<File>) support.getTransferable().getTransferData(DataFlavor.javaFileListFlavor); for (final File f : files) { System.out.println(f.getName()); } } catch (Exception e) { e.printStackTrace(); } return true; } }); setDefaultCloseOperation(DISPOSE_ON_CLOSE); pack(); setVisible(true); } } To reproduce, run the code and drop some files on the frame. Close the frame so it's disposed of. To verify the leak I take a heap dump using JConsole and analyse it with the Eclipse Memory Analysis tool. It shows that sun.awt.AppContext is holding a reference to the frame through its hashmap. It looks like TransferSupport is at fault. What am I doing wrong? Should I be asking the DnD support code to clean itself up somehow? I'm running JDK 1.6 update 19.

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• Spring constructor injection error

  - by Jeune

  I am getting the following error for a bean in my application context: Related cause: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'businessLogicContext' d efined in class path resource [activemq-jms-consumer.xml]: Unsatisfied dependency expressed through constructor argument with index 0 of type [java.lang.String]: Could not convert constructor argument value of type [java.util.ArrayList] to required type [java.lang.String]: Failed to convert value of type [java.util.ArrayList] to required type [java.lang.Stri ng]; nested exception is java.lang.IllegalArgumentException: Cannot convert value of type [java.util.ArrayList] to requi red type [java.lang.String]: no matching editors or conversion strategy found at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:53 4) at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:18 6) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAuto wireCapableBeanFactory.java:855) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutow ireCapableBeanFactory.java:765) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCap ableBeanFactory.java:412) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBea nFactory.java:383) at java.security.AccessController.doPrivileged(Native Method) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapab leBeanFactory.java:353) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:245) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegis try.java:169) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:242) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListable BeanFactory.java:400) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplic ationContext.java:736) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:369) at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java :123) at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java :66) Here is my bean: <bean id="businessLogicContext" class="org.springframework.context.support.ClassPathXmlApplicationContext" depends-on="resolveProperty"> <constructor-arg index="0"> <list> <value>jms-applicationContext.xml</value> <value>jms-managerBeanContext.xml</value> <value>jms-daoContext.xml</value> <value>jms-serviceContext.xml</value> </list> </constructor-arg> </bean> I don't know what's wrong, I have googled how to inject a string array via constructor injection and the way I do it above seems okay.

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• How can I prevent external MSBuild files from being cached (by Visual Studio) during a project build

  - by Damian Powell

  I have a project in my solution which started life as a C# library project. It's got nothing of any interest in it in terms of code, it is merely used as a dependency in the other projects in my solution in order to ensure that it is built first. One of the side-effects of building this project is that a shared AssemblyInfo.cs is created which contains the version number in use by the other projects. I have done this by adding the following to the .csproj file: <ItemGroup> <None Include="Properties\AssemblyInfo.Shared.cs.in" /> <Compile Include="Properties\AssemblyInfo.Shared.cs" /> <None Include="VersionInfo.targets" /> </ItemGroup> <Import Project="$(ProjectDir)VersionInfo.targets" /> <Target Name="BeforeBuild" DependsOnTargets="UpdateSharedAssemblyInfo" /> The referenced file, VersionInfo.targets, contains the following: <Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003"> <PropertyGroup> <!-- Some properties defining tool locations and the name of the AssemblyInfo.Shared.cs.in file etc. --> </PropertyGroup> <Target Name="UpdateSharedAssemblyInfo"> <!-- Uses the Exec task to run one of the tools to generate AssemblyInfo.Shared.cs based on the location of AssemblyInfo.Shared.cs.in and some of the other properties. --> </Target> </Project> The contents of the VersionInfo.targets file could simply be embedded within the .csproj file but it is external because I am trying to turn all of this into a project template. I want the users of the template to be able to add the new project to the solution, edit the VersionInfo.targets file, and run the build. The problem is that modifying and saving the VersionInfo.targets file and rebuilding the solution has no effect - the project file uses the values from the .targets file as they were when the project was opened. Even unloading and reloading the project has no effect. In order to get the new values, I need to close Visual Studio and reopen it (or reload the solution). How can I set this up so that the configuration is external to the .csproj file and not cached between builds?

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• How to measure a canvas that has auto height and width

  - by Wymmeroo

  Hi Folks, I'm a beginner in silverlight so i hope i can get an answer that brings me some more light in the measure process of silverlight. I found an interessting flap out control from silverlight slide control and now I try to use it in my project. So that the slide out is working proper, I have to place the user control on a canvas. The user control then uses for itself the height of its content. I just wanna change that behavior so that the height is set to the available space from the parent canvas. You see the uxBorder where the height is set. How can I measure the actual height and set it to the border? I tried it with Height={Binding ElementName=notificationCanvas, Path=ActualHeight} but this dependency property has no callback, so the actualHeight is never set. What I want to achieve is a usercontrol like the tweetboard per example on Jesse Liberty's blog Sorry for my English writing, I hope you understand my question. <Canvas x:Name="notificationCanvas" Background="Red"> <SlideEffectEx:SimpleSlideControl GripWidth="20" GripTitle="Task" GripHeight="100"> <Border x:Name="uxBorder" BorderThickness="2" CornerRadius="5" BorderBrush="DarkGray" Background="DarkGray" Padding="5" Width="300" Height="700" > <StackPanel> <TextBlock Text="Tasks"></TextBlock> <Button x:Name="btn1" Margin="5" Content="{Binding ElementName=MainBorder, Path=Height}"></Button> <Button x:Name="btn2" Margin="5" Content="Second Button"></Button> <Button x:Name="btn3" Margin="5" Content="Third Button"></Button> <Button x:Name="btn1_Copy" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy1" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy2" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy3" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy4" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy5" Margin="5" Content="First Button"/> <Button x:Name="btn1_Copy6" Margin="5" Content="First Button"/> </StackPanel> </Border> </SlideEffectEx:SimpleSlideControl>

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• How to Load Dependent Files on Demand + Check if They're Loaded or Not?

  - by br4inwash3r

  I'm trying to implement an assets/dependency loader that i've found from an old article at 24Ways.org. most of you might be familiar with it. it's from this article by Christian Heilmann: http://24ways.org/2007/keeping-javascript-dependencies-at-bay i've modified the script to load CSS files as well. and it's now quite close to what i want. but i still need to do some checking to see wether an asset have been completely loaded or not. just wondering if you guys have any ideas :) here's what my script currently looked like: var assetLoader = { assets: { products: { js: 'products.js', css: 'products.css', loaded: false }, articles: { js: 'articles.js', css: 'articles.css', loaded: false }, [...] cycle: { js: 'jquery.cycle.min.js', loaded: false }, swfobject: { js: 'jquery.swfobject.min.js', loaded: false } }, add: function(asset) { var comp = assetLoader.assets[asset]; var path = '/path/to/assets/'; if (comp && comp.loaded == false) { if (comp.js) { // load js var js = document.createElement('script'); js.src = path + 'js/' + comp.js; js.type = 'text/javascript'; js.charset = 'utf-8'; // append to document document.getElementsByTagName('body')[0].appendChild(js); } if (comp.css) { // load css var css = document.createElement('link'); css.rel = 'stylesheet'; css.href = path + 'css/' + comp.css; css.type = 'text/css'; css.media = 'screen, projection'; css.charset = 'utf-8'; // append to document document.getElementsByTagName('head')[0].appendChild(css); } } }, check: function(asset) { assetLoader.assets[asset].loaded = true; } } Christian explains this method in his article in great detail. I don't want to confuse you guys anymore with my bad english :P and here's an example of how i run the script: ... // load jquery cycle plugin if (page=='tvc' || page=='products') { if (!assetLoader.assets.cycle.loaded) { assetLoader.add('cycle'); } } // load products page assets if (!assetLoader.assets.products.loaded) { assetLoader.add('products'); } ... this kind of approach is very problematic though. coz assets loads asynchronously, which means some of the code inside products.js that depends on jquery.cycle.js might continue running before jquery.cycle.js is even loaded resulting in errors. while i'm quite aware that scripts can be attached with an onload event, i'm just not really sure how to implement it to my script. anyone care to help me? please... :P

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• Persistent (purely functional) Red-Black trees on disk performance

  - by Waneck

  I'm studying the best data structures to implement a simple open-source object temporal database, and currently I'm very fond of using Persistent Red-Black trees to do it. My main reasons for using persistent data structures is first of all to minimize the use of locks, so the database can be as parallel as possible. Also it will be easier to implement ACID transactions and even being able to abstract the database to work in parallel on a cluster of some kind. The great thing of this approach is that it makes possible implementing temporal databases almost for free. And this is something quite nice to have, specially for web and for data analysis (e.g. trends). All of this is very cool, but I'm a little suspicious about the overall performance of using a persistent data structure on disk. Even though there are some very fast disks available today, and all writes can be done asynchronously, so a response is always immediate, I don't want to build all application under a false premise, only to realize it isn't really a good way to do it. Here's my line of thought: - Since all writes are done asynchronously, and using a persistent data structure will enable not to invalidate the previous - and currently valid - structure, the write time isn't really a bottleneck. - There are some literature on structures like this that are exactly for disk usage. But it seems to me that these techniques will add more read overhead to achieve faster writes. But I think that exactly the opposite is preferable. Also many of these techniques really do end up with a multi-versioned trees, but they aren't strictly immutable, which is something very crucial to justify the persistent overhead. - I know there still will have to be some kind of locking when appending values to the database, and I also know there should be a good garbage collecting logic if not all versions are to be maintained (otherwise the file size will surely rise dramatically). Also a delta compression system could be thought about. - Of all search trees structures, I really think Red-Blacks are the most close to what I need, since they offer the least number of rotations. But there are some possible pitfalls along the way: - Asynchronous writes -could- affect applications that need the data in real time. But I don't think that is the case with web applications, most of the time. Also when real-time data is needed, another solutions could be devised, like a check-in/check-out system of specific data that will need to be worked on a more real-time manner. - Also they could lead to some commit conflicts, though I fail to think of a good example of when it could happen. Also commit conflicts can occur in normal RDBMS, if two threads are working with the same data, right? - The overhead of having an immutable interface like this will grow exponentially and everything is doomed to fail soon, so this all is a bad idea. Any thoughts? Thanks! edit: There seems to be a misunderstanding of what a persistent data structure is: http://en.wikipedia.org/wiki/Persistent_data_structure

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• gcc optimization? bug? and its practial implication to project

  - by kumar_m_kiran

  Hi All, My questions are divided into three parts Question 1 Consider the below code, #include <iostream> using namespace std; int main( int argc, char *argv[]) { const int v = 50; int i = 0X7FFFFFFF; cout<<(i + v)<<endl; if ( i + v < i ) { cout<<"Number is negative"<<endl; } else { cout<<"Number is positive"<<endl; } return 0; } No specific compiler optimisation options are used or the O's flag is used. It is basic compilation command g++ -o test main.cpp is used to form the executable. The seemingly very simple code, has odd behaviour in SUSE 64 bit OS, gcc version 4.1.2. The expected output is "Number is negative", instead only in SUSE 64 bit OS, the output would be "Number is positive". After some amount of analysis and doing a 'disass' of the code, I find that the compiler optimises in the below format - Since i is same on both sides of comparison, it cannot be changed in the same expression, remove 'i' from the equation. Now, the comparison leads to if ( v < 0 ), where v is a constant positive, So during compilation itself, the else part cout function address is added to the register. No cmp/jmp instructions can be found. I see that the behaviour is only in gcc 4.1.2 SUSE 10. When tried in AIX 5.1/5.3 and HP IA64, the result is as expected. Is the above optimisation valid? Or, is using the overflow mechanism for int not a valid use case? Question 2 Now when I change the conditional statement from if (i + v < i) to if ( (i + v) < i ) even then, the behaviour is same, this atleast I would personally disagree, since additional braces are provided, I expect the compiler to create a temporary built-in type variable and them compare, thus nullify the optimisation. Question 3 Suppose I have a huge code base, an I migrate my compiler version, such bug/optimisation can cause havoc in my system behaviour. Ofcourse from business perspective, it is very ineffective to test all lines of code again just because of compiler upgradation. I think for all practical purpose, these kinds of error are very difficult to catch (during upgradation) and invariably will be leaked to production site. Can anyone suggest any possible way to ensure to ensure that these kind of bug/optimization does not have any impact on my existing system/code base? PS : When the const for v is removed from the code, then optimization is not done by the compiler. I believe, it is perfectly fine to use overflow mechanism to find if the variable is from MAX - 50 value (in my case).

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• Design patterns and interview question

  - by user160758

  When I was learning to code, I read up on the design patterns like a good boy. Long after this, I started to actually understand them. Design discussions such as those on this site constantly try to make the rules more and more general, which is good. But there is a line, over which it becomes over-analysis starts to feed off itself and as such I think begins to obfuscate the original point - for example the "What's Alternative to Singleton" post and the links contained therein. http://stackoverflow.com/questions/1300655/whats-alternative-to-singleton I say this having been asked in both interviews I’ve had over the last 2 weeks what a singleton is and what criticisms I have of it. I have used it a few times for items such as user data (simple key-value eg. last file opened by this user) and logging (very common i'm sure). I've never ever used it just to have what is essentially global application data, as this is clearly stupid. In the first interview, I reply that I have no criticisms of it. He seemed disappointed by this but as the job wasn’t really for me, I forgot about it. In the next one, I was asked again and, as I wanted this job, I thought about it on the spot and made some objections, similar to those contained in the post linked to above (I suggested use of a factory or dependency injection instead). He seemed happy with this. But my problem is that I have used the singleton without ever using it in this kind of stupid way, which I had to describe on the spot. Using it for global data and the like isn’t something I did then realised was stupid, or read was stupid so didn’t do, it was just something I knew was stupid from the start. Essentially I’m supposed to be able to think of ways of how to misuse a pattern in the interview? Which class of programmers can best answer this question? The best ones? The medium ones? I'm not sure.... And these were both bright guys. I read more than enough to get better at my job but had never actually bothered to seek out criticisms of the most simple of the design patterns like this one. Do people think such questions are valid and that I ought to know the objections off by heart? Or that it is reasonable to be able to work out what other people who are missing the point would do on the fly? Or do you think I’m at least partially right that the question is too unsubtle and that the questions ought to be better thought out in order to make sure only good candidates can answer. PS. Please don’t think I’m saying that I’m just so clever that I know everything automatically - I’ve learnt the hard way like everyone else. But avoiding global data is hardly revolutionary.

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• Asp.net Mvc - Kigg: Maintain User object in HttpContext.Items between requests.

  - by Pickels

  Hallo, first I want to say that I hope this doesn't look like I am lazy but I have some trouble understanding a piece of code from the following project. http://kigg.codeplex.com/ I was going through the source code and I noticed something that would be usefull for my own little project I am making. In their BaseController they have the following code: private static readonly Type CurrentUserKey = typeof(IUser); public IUser CurrentUser { get { if (!string.IsNullOrEmpty(CurrentUserName)) { IUser user = HttpContext.Items[CurrentUserKey] as IUser; if (user == null) { user = AccountRepository.FindByClaim(CurrentUserName); if (user != null) { HttpContext.Items[CurrentUserKey] = user; } } return user; } return null; } } This isn't an exact copy of the code I adjusted it a little to my needs. This part of the code I still understand. They store their IUser in HttpContext.Items. I guess they do it so that they don't have to call the database eachtime they need the User object. The part that I don't understand is how they maintain this object in between requests. If I understand correctly the HttpContext.Items is a per request cache storage. So after some more digging I found the following code. internal static IDictionary<UnityPerWebRequestLifetimeManager, object> GetInstances(HttpContextBase httpContext) { IDictionary<UnityPerWebRequestLifetimeManager, object> instances; if (httpContext.Items.Contains(Key)) { instances = (IDictionary<UnityPerWebRequestLifetimeManager, object>) httpContext.Items[Key]; } else { lock (httpContext.Items) { if (httpContext.Items.Contains(Key)) { instances = (IDictionary<UnityPerWebRequestLifetimeManager, object>) httpContext.Items[Key]; } else { instances = new Dictionary<UnityPerWebRequestLifetimeManager, object>(); httpContext.Items.Add(Key, instances); } } } return instances; } This is the part where some magic happens that I don't understand. I think they use Unity to do some dependency injection on each request? In my project I am using Ninject and I am wondering how I can get the same result. I guess InRequestScope in Ninject is the same as UnityPerWebRequestLifetimeManager? I am also wondering which class/method they are binding to which interface? Since the HttpContext.Items get destroyed each request how do they prevent losing their user object? Anyway it's kinda a long question so I am gradefull for any push in the right direction. Kind regards, Pickels

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• One Controller is Sometimes Bound Twice with Ninject

  - by Dusda

  I have the following NinjectModule, where we bind our repositories and business objects: /// <summary> /// Used by Ninject to bind interface contracts to concrete types. /// </summary> public class ServiceModule : NinjectModule { /// <summary> /// Loads this instance. /// </summary> public override void Load() { //bindings here. //Bind<IMyInterface>().To<MyImplementation>(); Bind<IUserRepository>().To<SqlUserRepository>(); Bind<IHomeRepository>().To<SqlHomeRepository>(); Bind<IPhotoRepository>().To<SqlPhotoRepository>(); //and so on //business objects Bind<IUser>().To<Data.User>(); Bind<IHome>().To<Data.Home>(); Bind<IPhoto>().To<Data.Photo>(); //and so on } } And here are the relevant overrides from our Global.asax, where we inherit from NinjectHttpApplication in order to integrate it with Asp.Net Mvc (The module lies in a separate dll called Thing.Web.Configuration): protected override void OnApplicationStarted() { base.OnApplicationStarted(); //routes and areas AreaRegistration.RegisterAllAreas(); RegisterRoutes(RouteTable.Routes); //Initializes a singleton that must reference this HttpApplication class, //in order to provide the Ninject Kernel to the rest of Thing.Web. This //is necessary because there are a few instances (currently Membership) //that require manual dependency injection. NinjectKernel.Instance = new NinjectKernel(this); //view model factory. NinjectKernel.Instance.Kernel.Bind<IModelFactory>().To<MasterModelFactory>(); } protected override NinjectControllerFactory CreateControllerFactory() { return base.CreateControllerFactory(); } protected override Ninject.IKernel CreateKernel() { var kernel = new StandardKernel(); kernel.Load("Thing.Web.Configuration.dll"); return kernel; } Now, everything works great, with one exception: For some reason, sometimes Ninject will bind the PhotoController twice. This leads to an ActivationException, because Ninject can't discern which PhotoController I want. This causes all requests for thumbnails and other user images on the site to fail. Here is the PhotoController in it's entirety: public class PhotoController : Controller { public PhotoController() { } public ActionResult Index(string id) { var dir = Server.MapPath("~/" + ConfigurationManager.AppSettings["UserPhotos"]); var path = Path.Combine(dir, id); return base.File(path, "image/jpeg"); } } Every controller works in exactly the same way, but for some reason the PhotoController gets double-bound. Even then, it only happens occasionally (either when re-building the solution, or on staging/production when the app pool kicks in). Once this happens, it continues to happen until I redeploy without changing anything. So...what's up with that?

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