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• Getting up to speed on modern architecture

  - by Matt Thrower

  Hi, I don't have any formal qualifications in computer science, rather I taught myself classic ASP back in the days of the dotcom boom and managed to get myself a job and my career developed from there. I was a confident and, I think, pretty good programmer in ASP 3 but as others have observed one of the problems with classic ASP was that it did a very good job of hiding the nitty-gritty of http so you could become quite competent as a programmer on the basis of relatively poor understanding of the technology you were working with. When I changed on to .NET at first I treated it like classic ASP, developing stand-alone applications as individual websites simply because I didn't know any better at the time. I moved jobs at this point and spent the next several years working on a single site whose architecture relied heavily on custom objects: in other words I gained a lot of experience working with .NET as a middle-tier development tool using a quite old-fashioned approach to OO design along the lines of the classic "car" class example that's so often used to teach OO. Breaking down programs into blocks of functionality and basing your classes and methods around that. Although we worked under an Agile approach to manage the work the whole setup was classic client/server stuff. That suited me and I gradually got to grips with .NET and started using it far more in the manner that it should be, and I began to see the power inherent in the technology and precisely why it was so much better than good old ASP 3. In my latest job I have found myself suddenly dropped in at the deep end with two quite young, skilled and very cutting-edge programmers. They've built a site architecture which is modelling along a lot of stuff which is new to me and which, in truth I'm having a lot of trouble understanding. The application is built on a cloud computing model with multi-tenancy and the architecture is all loosely coupled using a lot of interfaces, factories and the like. They use nHibernate a lot too. Shortly after I joined, both these guys left and I'm now supposedly the senior developer on a system whose technology and architecture I don't really understand and I have no-one to ask questions of. Except you, the internet. Frankly I feel like I've been pitched in at the deep end and I'm sinking. I'm not sure if this is because I lack the educational background to understand this stuff, if I'm simply not mathematically minded enough for modern computing (my maths was never great - my approach to design is often to simply debug until it works, then refactor until it looks neat), or whether I've simply been presented with too much of too radical a nature at once. But the only way to find out which it is is to try and learn it. So can anyone suggest some good places to start? Good books, tutorials or blogs? I've found a lot of internet material simply presupposes a level of understanding that I just don't have. Your advice is much appreciated. Help a middle-aged, stuck in the mud developer get enthusastic again! Please!

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• Technical non-terminating condition in a loop

  - by Snarfblam

  Most of us know that a loop should not have a non-terminating condition. For example, this C# loop has a non-terminating condition: any even value of i. This is an obvious logic error. void CountByTwosStartingAt(byte i) { // If i is even, it never exceeds 254 for(; i < 255; i += 2) { Console.WriteLine(i); } } Sometimes there are edge cases that are extremely unlikeley, but technically constitute non-exiting conditions (stack overflows and out-of-memory errors aside). Suppose you have a function that counts the number of sequential zeros in a stream: int CountZeros(Stream s) { int total = 0; while(s.ReadByte() == 0) total++; return total; } Now, suppose you feed it this thing: class InfiniteEmptyStream:Stream { // ... Other members ... public override int Read(byte[] buffer, int offset, int count) { Array.Clear(buffer, offset, count); // Output zeros return count; // Never returns -1 (end of stream) } } Or more realistically, maybe a stream that returns data from external hardware, which in certain cases might return lots of zeros (such as a game controller sitting on your desk). Either way we have an infinite loop. This particular non-terminating condition stands out, but sometimes they don't. A completely real-world example as in an app I'm writing. An endless stream of zeros will be deserialized into infinite "empty" objects (until the collection class or GC throws an exception because I've exceeded two billion items). But this would be a completely unexpected circumstance (considering my data source). How important is it to have absolutely no non-terminating conditions? How much does this affect "robustness?" Does it matter if they are only "theoretically" non-terminating (is it okay if an exception represents an implicit terminating condition)? Does it matter whether the app is commercial? If it is publicly distributed? Does it matter if the problematic code is in no way accessible through a public interface/API? Edit: One of the primary concerns I have is unforseen logic errors that can create the non-terminating condition. If, as a rule, you ensure there are no non-terminating conditions, you can identify or handle these logic errors more gracefully, but is it worth it? And when? This is a concern orthogonal to trust.

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• Visual Studio 2010 and Test Driven Development

  - by devoured elysium

  I'm making my first steps in Test Driven Development with Visual Studio. I have some questions regarding how to implement generic classes with VS 2010. First, let's say I want to implement my own version of an ArrayList. I start by creating the following test (I'm using in this case MSTest): [TestMethod] public void Add_10_Items_Remove_10_Items_Check_Size_Is_Zero() { var myArrayList = new MyArrayList<int>(); for (int i = 0; i < 10; ++i) { myArrayList.Add(i); } for (int i = 0; i < 10; ++i) { myArrayList.RemoveAt(0); } int expected = 0; int actual = myArrayList.Size; Assert.AreEqual(expected, actual); } I'm using VS 2010 ability to hit ctrl + . and have it implement classes/methods on the go. I have been getting some trouble when implementing generic classes. For example, when I define an .Add(10) method, VS doesn't know if I intend a generic method(as the class is generic) or an Add(int number) method. Is there any way to differentiate this? The same can happen with return types. Let's assume I'm implementing a MyStack stack and I want to test if after I push and element and pop it, the stack is still empty. We all know pop should return something, but usually, the code of this test shouldn't care for it. Visual Studio would then think that pop is a void method, which in fact is not what one would want. How to deal with this? For each method, should I start by making tests that are "very specific" such as is obvious the method should return something so I don't get this kind of ambiguity? Even if not using the result, should I have something like int popValue = myStack.Pop() ? How should I do tests to generic classes? Only test with one generic kind of type? I have been using ints, as they are easy to use, but should I also test with different kinds of objects? How do you usually approach this? I see there is a popular tool called TestDriven for .NET. With VS 2010 release, is it still useful, or a lot of its features are now part of VS 2010, rendering it kinda useless? Thanks

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• Web Services, Memory Leaks and CRM

  - by Neil

  Hi, I have a website that allows users to upload a csv file. This calls a service that reads the information from the csv, puts it into DynamicEntity objects and calls the CRM service to Create/Update entities in CRM. When this service creates/updates an entity this kicks off other plugins to apply certain business rules. These rules can also Create or Update entites in CRM. The issue here is that the handle count of the w3wp.exe process that the website is calling increases every time the an entity is created or updated and it never comes back down. I tried putting Garbage Collection code in the business rules and this reduces the handle count of the CRM w3wp process (run by the Network Service), but not the other w3wp process. Should I have Dispose methods on the Web Service that calls the CRM service? I hope that makes sense. I'm not overly familiar with memory management issues so any help is appreciated. Can anybody give me some tips on how to stop this from occurring? Thanks, Neil -- EDIT Okay well the handle count goes up when I call the Service.Create(DynamicEntity) method. I don't think placing any code here would be beneficial. When I exit the method/class/service that contains this call the handle count stays as it is. What I need to know is whether this is something I should be managing or is it something CRM takes care of (or doesn't take care of but I can't do anything about it) -- Another Edit Right this is how it works. 1) We have CRM and its related services 2) We have another service independent of CRM that uses the CRM services (number 1 above) to create entities based on csv info passed into it 3) We have a website that allows a user to upload a csv, and calls service no 2 above to Create/Update entities in CRM 4) We have plugins fired by CRM which use Service 1 above to create/update entities So the user uploads a csv to the website (3), this fires a service(2). When service 2 creates an entity using service 1, Service 4 fires. Service 4 calls also uses service 1 to Create entities, and when these services are called (using the Service.Create() method) the handle count of the process increases. When the method/class/services finish the handle count remains the same, and so when the whole process occurs again the handle count will increased again.

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• how to set footer image in this video screen?

  - by bala

  hi my problem is how to create footer image in this video screen while playing.... how to create this format. now i am give my description: • 1) Header image, a stretched background image. The location of this external image comes from the application xml; • 2) Footer image, a stretched background image. The location of this external image comes from the application xml; 2.a) the copyright, disclaimer and buy block, this block contains links to popup windows that contain a copyright and or disclaimer. And an option to buy the application for the advertisement less version. The content of this block is fed trough the application XML feed. The color of the text is fed by the application xml plus the popup links and texts itself; • 3) Carousel image, a stretched background image. The location of this external image comes from the application xml; 3.a) the carousel contains objects that can flow from right to left, possibly trough a animation (a soft break of the slide). The first object is centered in the middle of the carousel. This is the first element in the video feed. All the subsequent video object are added to the right of the centered object; 4) Total Video object, this object links to window two with the corresponding video of this object. This object is visually build out of the following sub parts:o 4.a) Thumb object (possible playing video thumb); 4.b) Reflection of the Thumb; 4.c) Textual Explanation of Thumb. 1) Video stream, this is the video stream coming from a external server streamed to the television (maybe up scaled) as 720p stream; 2) Advertisement, the type of advertisement shown overlaid on the video is based on previous settings in the video feed. This could mean that Admob, Adsense or a third party image plus URL could be shown. When the advertisement is selected trough navigation (it will highlight in a different color as a border around the advertisement. The color an thickness can be managed trough the application xml), when clicked a browser will open with the associated site (the application will be pushed to the background process, when the user is finished it will return to the app); 3) A back button, an image and navigational element. The location of the image comes from the application xml. The button is only shown when a cursor is moved (a button is pressed on the remote) it will highlight when selected and when pressed will forward the screen to the main window. When the main window is opened the video will be removed from cache and memory and cannot be start from the point it was exited. please give me your idea....

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• Where are the function literals c++?

  - by academicRobot

  First of all, maybe literals is not the right term for this concept, but its the closest I could think of (not literals in the sense of functions as first class citizens). The idea is that when you make a conventional function call, it compiles to something like this: callq <immediate address> But if you make a function call using a function pointer, it compiles to something like this: mov <memory location>,%rax callq *%rax Which is all well and good. However, what if I'm writing a template library that requires a callback of some sort with a specified argument list and the user of the library is expected to know what function they want to call at compile time? Then I would like to write my template to accept a function literal as a template parameter. So, similar to template <int int_literal> struct my_template {...};` I'd like to write template <func_literal_t func_literal> struct my_template {...}; and have calls to func_literal within my_template compile to callq <immediate address>. Is there a facility in C++ for this, or a work around to achieve the same effect? If not, why not (e.g. some cataclysmic side effects)? How about C++0x or another language? Solutions that are not portable are fine. Solutions that include the use of member function pointers would be ideal. I'm not particularly interested in being told "You are a <socially unacceptable term for a person of low IQ>, just use function pointers/functors." This is a curiosity based question, and it seems that it might be useful in some (albeit limited) applications. It seems like this should be possible since function names are just placeholders for a (relative) memory address, so why not allow more liberal use (e.g. aliasing) of this placeholder. p.s. I use function pointers and functions objects all the the time and they are great. But this post got me thinking about the don't pay for what you don't use principle in relation to function calls, and it seems like forcing the use of function pointers or similar facility when the function is known at compile time is a violation of this principle, though a small one.

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• Help with code optimization

  - by Ockonal

  Hello, I've written a little particle system for my 2d-application. Here is raining code: // HPP ----------------------------------- struct Data { float x, y, x_speed, y_speed; int timeout; Data(); }; std::vector<Data> mData; bool mFirstTime; void processDrops(float windPower, int i); // CPP ----------------------------------- Data::Data() : x(rand()%ScreenResolutionX), y(0) , x_speed(0), y_speed(0), timeout(rand()%130) { } void Rain::processDrops(float windPower, int i) { int posX = rand() % mWindowWidth; mData[i].x = posX; mData[i].x_speed = WindPower*0.1; // WindPower is float mData[i].y_speed = Gravity*0.1; // Gravity is 9.8 * 19.2 // If that is first time, process drops randomly with window height if (mFirstTime) { mData[i].timeout = 0; mData[i].y = rand() % mWindowHeight; } else { mData[i].timeout = rand() % 130; mData[i].y = 0; } } void update(float windPower, float elapsed) { // If this is first time - create array with new Data structure objects if (mFirstTime) { for (int i=0; i < mMaxObjects; ++i) { mData.push_back(Data()); processDrops(windPower, i); } mFirstTime = false; } for (int i=0; i < mMaxObjects; i++) { // Sleep until uptime > 0 (To make drops fall with randomly timeout) if (mData[i].timeout > 0) { mData[i].timeout--; } else { // Find new x/y positions mData[i].x += mData[i].x_speed * elapsed; mData[i].y += mData[i].y_speed * elapsed; // Find new speeds mData[i].x_speed += windPower * elapsed; mData[i].y_speed += Gravity * elapsed; // Drawing here ... // If drop has been falled out of the screen if (mData[i].y > mWindowHeight) processDrops(windPower, i); } } } So the main idea is: I have some structure which consist of drop position, speed. I have a function for processing drops at some index in the vector-array. Now if that's first time of running I'm making array with max size and process it in cycle. But this code works slower that all another I have. Please, help me to optimize it. I tried to replace all int with uint16_t but I think it doesn't matter.

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• WPF PathGeometry/RotateTransform optimization

  - by devinb

  I am having performance issues when rendering/rotating WPF triangles If I had a WPF triangle being displayed and it will be rotated to some degree around a centrepoint, I can do it one of two ways: Programatically determine the points and their offset in the backend, use XAML to simply place them on the canvas where they belong, it would look like this: <Path Stroke="Black"> <Path.Data> <PathGeometry> <PathFigure StartPoint ="{Binding CalculatedPointA, Mode=OneWay}"> <LineSegment Point="{Binding CalculatedPointB, Mode=OneWay}" /> <LineSegment Point="{Binding CalculatedPointC, Mode=OneWay}" /> <LineSegment Point="{Binding CalculatedPointA, Mode=OneWay}" /> </PathFigure> </PathGeometry> </Path.Data> </Path> Generate the 'same' triangle every time, and then use a RenderTransform (Rotate) to put it where it belongs. In this case, the rotation calculations are being obfuscated, because I don't have any access to how they are being done. <Path Stroke="Black"> <Path.Data> <PathGeometry> <PathFigure StartPoint ="{Binding TriPointA, Mode=OneWay}"> <LineSegment Point="{Binding TriPointB, Mode=OneWay}" /> <LineSegment Point="{Binding TriPointC, Mode=OneWay}" /> <LineSegment Point="{Binding TriPointA, Mode=OneWay}" /> </PathFigure> </PathGeometry> </Path.Data> <Path.RenderTransform> <RotateTransform CenterX="{Binding Centre.X, Mode=OneWay}" CenterY="{Binding Centre.Y, Mode=OneWay}" Angle="{Binding Orientation, Mode=OneWay}" /> </Path.RenderTransform> </Path> My question is which one is faster? I know I should test it myself but how do I measure the render time of objects with such granularity. I would need to be able to time how long the actual rendering time is for the form, but since I'm not the one that's kicking off the redraw, I don't know how to capture the start time.

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• Architecture Suggestions/Recommendations for a Web Application with Sub-Apps

  - by user579218

  Hello. I’m starting to plan an architecture for a big web application, and I wanted to get suggestions and/or recommendations on where to begin and which technologies and/or frameworks to use. The application will be an Intranet-based web site using Windows authentication, running on IIS and using SQL Server and ASP.NET. It’ll need to be structured as a main/shell application with sub-applications that are “pluggable” based on some configuration settings. The main or shell application is to provide the overall user interface structure – header/footer, dynamically built tabs for each available sub-app, and a content area in which the sub-application will be loaded when the user clicks on the sub-application’s tab. So, on start-up of the main/shell application, configuration information will be queried from a database, and, based on the user and which of the sub-apps are available, the main or shell app would dynamically build tabs (or buttons or something) as a way to access each individual application. On start-up, the content area will be populated with the “home” sub-app. But, clicking on an sub-app tab will cause the content area to be populated with the sub-app corresponding to the tab. For example, we’re going to have a reports application, a display application, and probably a couple other distinct applications. On startup of the main/shell application, after determining who the user is, the main app will query the database to determine which sub-apps the user can use and build out the UI. Then the user can navigate between available sub-apps and do their work in each. Finally, the entire app and all sub-apps need to be a layered design with presentation, service, business, and data access layers, as well as cross-cutting objects for things such as logging, exception handling, etc. Anyway, my questions revolve around where to begin to plan something like this application. What technologies/frameworks would work best in developing a solution for this application? MVC? MVP? WCSF? EF? NHibernate? Enterprise Library? Repository Pattern? Others???? I know all these technologies/frameworks are not used for the same purpose, but knowing which ones to focus on is a little overwhelming. Which ones would be the best choice(s) for a solution? Which ones work well together for an end-to-end design? How would one structure the VS project for something like this? Thanks!

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• What is GC holes?

  - by tianyi

  I wrote a long TCP connection socket server in C#. Spike in memory in my server happens. I used dotNet Memory Profiler(a tool) to detect where the memory leaks. Memory Profiler indicates the private heap is huge, and the memory is something like below(the number is not real,what I want to show is the GC0 and GC2's Holes are very very huge, the data size is normal): Managed heaps - 1,500,000KB Normal heap - 1400,000KB Generation #0 - 600,000KB Data - 100,000KB "Holes" - 500,000KB Generation #1 - xxKB Data - 0KB "Holes" - xKB Generation #2 - xxxxxxxxxxxxxKB Data - 100,000KB "Holes" - 700,000KB Large heap - 131072KB Large heap - 83KB Overhead/unused - 130989KB Overhead - 0KB Howerver, what is GC hole? I read an article about the hole: http://kaushalp.blogspot.com/2007/04/what-is-gc-hole-and-how-to-create-gc.html The author said : The code snippet below is the simplest way to introduce a GC hole into the system. //OBJECTREF is a typedef for Object*. { PointerTable *pTBL = o_pObjectClass->GetPointerTable(); OBJECTREF aObj = AllocateObjectMemory(pTBL); OBJECTREF bObj = AllocateObjectMemory(pTBL); //WRONG!!! “aObj” may point to garbage if the second //“AllocateObjectMemory” triggered a GC. DoSomething (aOb, bObj); } All it does is allocate two managed objects, and then does something with them both. This code compiles fine, and if you run simple pre-checkin tests, it will probably “work.” But this code will crash eventually. Why? If the second call to “AllocateObjectMemory” triggers a GC, that GC discards the object instance you just assigned to “aObj”. This code, like all C++ code inside the CLR, is compiled by a non-managed compiler and the GC cannot know that “aObj” holds a root reference to an object you want kept live. ======================================================================== I can't understand what he explained. Does the sample mean aObj becomes a wild pointer after GC? Is it mean { aObj = (*aObj)malloc(sizeof(object)); free(aObj); function(aObj);? } ? I hope somebody can explain it.

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• How do I properly register the Type Library of A VB.NET COM+ Component?

  - by k_Dank

  I am looking to upgrade legacy VB6 COM+ components to VB.NET components. I have seemingly upgraded one already, called EventPackage, which has one class, IEventListener. Another, TradeOrders, Implements EventPackage.IEventListener. When attempting to build TradeOrders, I get the following Errors/Warnings; Cannot load type library for reference "EventPackage". Library not registered. (Exception from HRESULT: 0x8002801D (TYPE_E_LIBNOTREGISTERED)) The referenced component 'EventPackage' could not be found. Type 'EventPackage.IEventListener' is not defined. In the .vbproj, I notice this reference <COMReference Include="EventPackage"> <Guid>{0D76C094-21A6-4E04-802B-6E539F7102D7}</Guid> <Lcid>0</Lcid> <VersionMajor>2</VersionMajor> <VersionMinor>0</VersionMinor> <WrapperTool>tlbimp</WrapperTool> </COMReference> When I search the registry for this Guid, I find nothing. When using GUIDs for similar COM+ objects, I find them in HKEY_CLASSES_ROOT\CLSID\{...}\TypeLib ("..." being the GUID of the other component). When I go to the registry key name corresponding to EventPackage.IEventListener, I find that there is no \TypeLib subkey. As you might suspect, searching the reg for "0D76C094-21A6-4E04-802B-6E539F7102D7" yields no results. So I know this must be a registry problem, But I have tried seemingly every google result I have found. I have tried Regasm and regsvcs .exe's to no avail. Many pages just tell me that dragging the dll to the COM+ manager should automatically register the component. So how do I register the Type library? Details on how I made EventPackage COM+ component Ran the VB6-VB.NET wizard Then I added some lines to the assemblyinfo.vb file added Imports System.EnterpriseServices added Imports System.EnterpriseServices Imports System.Data.SqlClient <Assembly: CLSCompliant(True)> <Assembly: AssemblyKeyFileAttribute("...")> for a strong name <Assembly: Guid("...")> (Where "..." is the COM+ CLSID of the old component) I added the following to the class file IEventListener.VB Imports System.EnterpriseServices <ComClass("...")> _ (Where ... is the proper COM+ CLSID, that is the only argument) Inherits ServicedComponent changed the ID made by the Conversion wizard to the proper value (from <System.Runtime.InteropServices.ProgId("IEventListener_NET.IEventListener)> to <System.Runtime.InteropServices.ProgId("EventPackage.IEventListener")> _ Then I dragged the DLL into the COM+ manager in the proper COM+ application (although, the "Path" is not specified and only says mscoree.dll)

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• Converting this code from ASP to PHP

  - by jethomas

  I'll admit I'm a novice programmer and really the only experience I have is in classic ASP. I'm looking for a way to convert this asp code to PHP. For a customer who only has access to a linux box but also as a learning tool for me. Thanks in advance for the help: Recordset and Function: Function pd(n, totalDigits) if totalDigits > len(n) then pd = String(totalDigits-len(n),"0") & n else pd = n end if End Function 'declare the variables Dim Connection Dim Recordset Dim SQL Dim SQLDate SQLDate = Year(Date)& "-" & pd(Month(Date()),2)& "-" & pd(Day(Date()),2) 'declare the SQL statement that will query the database SQL = "SELECT * FROM tblXYZ WHERE element_8 = 2 AND element_9 > '" & SQLDate &"'" 'create an instance of the ADO connection and recordset objects Set Connection = Server.CreateObject("ADODB.Connection") Set Recordset = Server.CreateObject("ADODB.Recordset") 'open the connection to the database Connection.Open "PROVIDER=MSDASQL;DRIVER={MySQL ODBC 5.1 Driver};SERVER=localhost;UID=xxxxx;PWD=xxxxx;database=xxxxx;Option=3;" 'Open the recordset object executing the SQL statement and return records Recordset.Open SQL,Connection Display page/loop: Dim counter counter = 0 While Not Recordset.EOF counter = counter + 1 response.write("<div><td width='200' valign='top' align='center'><a href='" & Recordset("element_6") & "' style='text-decoration: none;'><div id='ad_header'>" & Recordset("element_3") & "</div><div id='store_name' valign='bottom'>" & Recordset("element_5") & "</div><img id='photo-small-img' src='http://xyz.com/files/" & Recordset("element_7") & "' /><br /><div id='ad_details'>"& Recordset("element_4") & "</div></a></td></div>") Recordset.MoveNext If counter = 3 Then Response.Write("</tr><tr>") counter = 0 End If Wend

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• exclude private property from print_r or object?

  - by Hailwood

  Basically I am using Code Igniter, and the Code Igniter base class is huge, when I print_r some of my objects they have the base class embedded inside them. this makes it a pain to get the information I actually wanted (the rest of the properties). So, I am wondering if there is a way I can hide, or remove the base class object? I have tried clone $object; unset($object->ci); print_r($object); but of course the ci property is private. the actual function I am using for dumping is: /** * Outputs the given variables with formatting and location. Huge props * out to Phil Sturgeon for this one (http://philsturgeon.co.uk/blog/2010/09/power-dump-php-applications). * To use, pass in any number of variables as arguments. * Optional pass in "true" as final argument to kill script after dump * * @return void */ function dump() { list($callee) = debug_backtrace(); $arguments = func_get_args(); $total_arguments = count($arguments); if (end($arguments) === true) $total_arguments--; echo '<fieldset style="background: #fefefe !important; border:2px red solid; padding:5px">'; echo '<legend style="background:lightgrey; padding:5px;">' . $callee['file'] . ' @ line: ' . $callee['line'] . '</legend><pre>'; $i = 0; foreach ($arguments as $argument) { //if the last argument is true we don't want to display it. if ($i == ($total_arguments) && $argument === true) break; echo '<br/><strong>Debug #' . (++$i) . ' of ' . $total_arguments . '</strong>: '; if ((is_array($argument) || is_object($argument)) && count($argument)) { print_r($argument); } else { var_dump($argument); } } echo '</pre>' . PHP_EOL; echo '</fieldset>' . PHP_EOL; //if the very last argument is "true" then die if (end($arguments) === true) die('Killing Script'); }

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• Force deletion of slot in boost::signals2

  - by villintehaspam

  Hi! I have found that boost::signals2 uses sort of a lazy deletion of connected slots, which makes it difficult to use connections as something that manages lifetimes of objects. I am looking for a way to force slots to be deleted directly when disconnected. Any ideas on how to work around the problem by designing my code differently are also appreciated! This is my scenario: I have a Command class responsible for doing something that takes time asynchronously, looking something like this (simplified): class ActualWorker { public: boost::signals2<void ()> OnWorkComplete; }; class Command : boost::enable_shared_from_this<Command> { public: ... void Execute() { m_WorkerConnection = m_MyWorker.OnWorkDone.connect(boost::bind(&Command::Handle_OnWorkComplete, shared_from_this()); // launch asynchronous work here and return } boost::signals2<void ()> OnComplete; private: void Handle_OnWorkComplete() { // get a shared_ptr to ourselves to make sure that we live through // this function but don't keep ourselves alive if an exception occurs. shared_ptr<Command> me = shared_from_this(); // Disconnect from the signal, ideally deleting the slot object m_WorkerConnection.disconnect(); OnComplete(); // the shared_ptr now goes out of scope, ideally deleting this } ActualWorker m_MyWorker; boost::signals2::connection m_WorkerConnection; }; The class is invoked about like this: ... boost::shared_ptr<Command> cmd(new Command); cmd->OnComplete.connect( foo ); cmd->Execute(); // now go do something else, forget all about the cmd variable etcetera. the Command class keeps itself alive by getting a shared_ptr to itself which is bound to the ActualWorker signal using boost::bind. When the worker completes, the handler in Command is invoked. Now, since I would like the Command object to be destroyed, I disconnect from the signal as can be seen in the code above. The problem is that the actual slot object is not deleted when disconnected, it is only marked as invalid and then deleted at a later time. This in turn appears to depend on the signal to fire again, which it doesn't do in my case, leading to the slot never expiring. The boost::bind object thus never goes out of scope, holding a shared_ptr to my object that will never get deleted. I can work around this by binding using the this pointer instead of a shared_ptr and then keeping my object alive using a member shared_ptr which I then release in the handler function, but it kind of makes the design feel a bit overcomplicated. Is there a way to force signals2 to delete the slot when disconnecting? Or is there something else I could do to simplify the design? Any comments are appreciated!

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• how to create text file in window service

  - by angel ansari

  Hi, I have an XML file <config> <ServiceName>autorunquery</ServiceName> <DBConnection> <server>servername</server> <user>xyz</user> <password>klM#2bs</password> <initialcatelog>TEST</initialcatelog> </DBConnection> <Log> <logfilename>d:\testlogfile.txt</logfilename> </Log> <Frequency> <value>10</value> <unit>minute</unit> </Frequency> <CheckQuery>select * from credit_debit1 where station='Corporate'</CheckQuery> <Queries total="3"> <Query id="1">Update credit_debit1 set station='xxx' where id=2</Query> <Query id="2">Update credit_debit1 set station='xxx' where id=4</Query> <Query id="3">Update credit_debit1 set station='xxx' where id=9</Query> </Queries> </config> using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Diagnostics; using System.Linq; using System.ServiceProcess; using System.Text; using System.IO; using System.Xml; namespace Service1 { public partial class Service1 : ServiceBase { XmlTextReader reader = null; string path = null; FileStream fs = null; StreamWriter sw = null; public Service1() { InitializeComponent(); } protected override void OnStart(string[] args) { timer1.Enabled = true; timer1.Interval = 10000; timer1.Start(); logfile("start service"); } protected override void OnStop() { timer1.Enabled = false; timer1.Stop(); logfile("stop service"); } private void logfile(string content) { try { reader = new XmlTextReader("queryconfig.xml");//xml file name which is in current directory if (reader.ReadToFollowing("logfilename")) { path = reader.ReadElementContentAsString(); } fs = new FileStream(path, FileMode.Append, FileAccess.Write); sw = new StreamWriter(fs); sw.Write(content); sw.WriteLine(DateTime.Now.ToString()); } catch (Exception ex) { sw.Write(ex.ToString()); throw; } finally { if (reader != null) reader.Close(); if (sw != null) sw.Close(); if (fs != null) fs.Close(); } } } } My problem is that the file is not created.

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• AngularJS recursive directive with a dynamic HTML template (bounty)

  - by Nazar Sobchuk

  I have a realy hard task here. I am working on an AngularJS web app, which is capable of sending different HTTP methods to our project's Restful Web Service and receiving responses in JSON. Basicaly it looks like this: You can create some REST resource from this application. Let's say an exam. To create an exam - you pick a resource from a list of available resources. This triggers a function, that sends a request to localhost:8080/STEP/api/explain/resorceName and gets a description for this resource. Description looks like this: http://jsonblob.com/534fc022e4b0bb44248d6460 After receiving a response - I start building input fields like follows (allFields - array of field objects for this resource, enumValues - enum values for resource's field if it's property isEnum = true): <div ng-repeat="field in allFields"> <div ng-show={{!field.isEnum}}> <p ng-show={{field.isRequired}}>{{field.name}}*: </p> <p ng-show={{!field.isRequired}}>{{field.name}}: </p> <input type="text" ng-model="updateEntityResource[field.name]" ng-change="getUpdateEntityAsText()" class="form-control" placeholder="{{parseClassName(field.type)}}"> </div> <div ng-show={{field.isEnum}}> <p ng-show={{field.isRequired}}>{{field.name}}*: </p> <p ng-show={{!field.isRequired}}>{{field.name}}: </p> <select ng-model="updateEntityResource[field.name]" ng-change="getUpdateEntityAsText()" class="form-control"> <option></option> <option ng-repeat="enumValue in field.enumValues" label={{enumValue.name}}>{{enumValue.ordinal}}</option> </select> </div> </div> Now, the problem. I need to create a recursive directive, which would be capable of generating fields in such maner as described above for every resource's field that has "restResourceName" not null. To get all it's fields you just send a request to localhost:8080/STEP/api/explain/restResourceName and get similar JSON response as shown above, which is then used to build HTML elements for inputing values into model. Does anyone know how this can be achieved using angular recursive directive? Every useful answer is highly appreciated and evaluated. The correct answer will get +50 or I will start a bounty, because I'm realy stuck with this for 2 days. If you need any additional info - let me know. Thank you.

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• How to close all, or only some, tabs in Safari using AppleScript?

  - by Form

  I have made a very simple AppleScript to close all tabs in Safari. The problem is, it works, but not completely. The problem is that only a couple of tabs are closed. Here's the code: tell application "Safari" repeat with aWindow in windows repeat with aTab in tabs of aWindow if [some condition is encountered] then aTab close end if end repeat end repeat end tell I've also tried this script: tell application "Safari" repeat with i from 0 to the number of items in windows set aWindow to item i of windows repeat with j from 0 to the number of tabs in aWindow set aTab to item j of tabs of aWindow if [some condition is encountered] then aTab close end if end repeat end repeat end tell ... but it does not work either (same behavior). I tried that on my system (MacBook Pro jan 2008), as well as on a Mac Pro G5 under Tiger and the script fails on both, albeit with a much less descriptive error on Tiger. Running the script a few times closes a few tab each time until none is left, but always fails with the same error after closing a few tabs. Under Leopard I get an out of bounds error. Since I am using fast enumeration (not using "repeat from 0 to number of items in windows") I don't see how I can get an out of bounds error with this... My goal is to use the Cocoa Scripting Bridge to close tabs in Safari from my Objective-C Cocoa application but the Scripting Bridge fails in the same manner. The non-deletable tabs show as NULL in the Xcode debugger, while the other tabs are valid objects from which I can get values back (such as their title). In fact I tried with the Scripting Bridge first then told myself why not try this directly in AppleScript and I was surprised to see the same results. I must have a glaring omission or something in there... (seems like a bug in Safari AppleScript support to me... :S) I've used repeat loops and Obj-C 2.0 fast enumeration to iterate through collections before with zero problems, so I really don't see what's wrong here. Anyone can help? Thanks in advance!

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• c++ std::ostringstream vs std::string::append

  - by NickSoft

  In all examples that use some kind of buffering I see they use stream instead of string. How is std::ostringstream and << operator different than using string.append. Which one is faster and which one uses less resourses (memory). One difference I know is that you can output different types into output stream (like integer) rather than the limited types that string::append accepts. Here is an example: std::ostringstream os; os << "Content-Type: " << contentType << ";charset=" << charset << "\r\n"; std::string header = os.str(); vs std::string header("Content-Type: "); header.append(contentType); header.append(";charset="); header.append(charset); header.append("\r\n"); Obviously using stream is shorter, but I think append returns reference to the string so it can be written like this: std::string header("Content-Type: "); header.append(contentType) .append(";charset=") .append(charset) .append("\r\n"); And with output stream you can do: std::string content; ... os << "Content-Length: " << content.length() << "\r\n"; But what about memory usage and speed? Especially when used in a big loop. Update: To be more clear the question is: Which one should I use and why? Is there situations when one is preferred or the other? For performance and memory ... well I think benchmark is the only way since every implementation could be different. Update 2: Well I don't get clear idea what should I use from the answers which means that any of them will do the job, plus vector. Cubbi did nice benchmark with the addition of Dietmar Kühl that the biggest difference is construction of those objects. If you are looking for an answer you should check that too. I'll wait a bit more for other answers (look previous update) and if I don't get one I think I'll accept Tolga's answer because his suggestion to use vector is already done before which means vector should be less resource hungry.

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• Graph Tour with Uniform Cost Search in Java

  - by user324817

  Hi. I'm new to this site, so hopefully you guys don't mind helping a nub. Anyway, I've been asked to write code to find the shortest cost of a graph tour on a particular graph, whose details are read in from file. The graph is shown below: http://img339.imageshack.us/img339/8907/graphr.jpg This is for an Artificial Intelligence class, so I'm expected to use a decent enough search method (brute force has been allowed, but not for full marks). I've been reading, and I think that what I'm looking for is an A* search with constant heuristic value, which I believe is a uniform cost search. I'm having trouble wrapping my head around how to apply this in Java. Basically, here's what I have: Vertex class - ArrayList<Edge> adjacencies; String name; int costToThis; Edge class - final Vertex target; public final int weight; Now at the moment, I'm struggling to work out how to apply the uniform cost notion to my desired goal path. Basically I have to start on a particular node, visit all other nodes, and end on that same node, with the lowest cost. As I understand it, I could use a PriorityQueue to store all of my travelled paths, but I can't wrap my head around how I show the goal state as the starting node with all other nodes visited. Here's what I have so far, which is pretty far off the mark: public static void visitNode(Vertex vertex) { ArrayList<Edge> firstEdges = vertex.getAdjacencies(); for(Edge e : firstEdges) { e.target.costToThis = e.weight + vertex.costToThis; queue.add(e.target); } Vertex next = queue.remove(); visitNode(next); } Initially this takes the starting node, then recursively visits the first node in the PriorityQueue (the path with the next lowest cost). My problem is basically, how do I stop my program from following a path specified in the queue if that path is at the goal state? The queue currently stores Vertex objects, but in my mind this isn't going to work as I can't store whether other vertices have been visited inside a Vertex object. Help is much appreciated! Josh

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• How to store array of NSManagedObjects in an NSManagedObject

  - by David Tay

  I am loading my app with a property list of data from a web site. This property list file contains an NSArray of NSDictionaries which itself contains an NSArray of NSDictionaries. Basically, I'm trying to load a tableView of restaurant menu categories each of which contains menu items. My property list file is fine. I am able to load the file and loop through the nodes structure creating NSEntityDescriptions and am able to save to Core Data. Everything works fine and expectedly except that in my menu category managed object, I have an NSArray of menu items for that category. Later on, when I fetch the categories, the pointers to the menu items in a category is lost and I get all the menu items. Am I suppose to be using predicates or does Core Data keep track of my object graph for me? Can anyone look at how I am loading Core Data and point out the flaw in my logic? I'm pretty good with either SQL and OOP by themselves, but am a little bewildered by ORM. I thought that I should just be able to use aggregation in my managed objects and that the framework would keep track of the pointers for me, but apparently not. NSError *error; NSURL *url = [NSURL URLWithString:@"http://foo.com"]; NSArray *categories = [[NSArray alloc] initWithContentsOfURL:url]; NSMutableArray *menuCategories = [[NSMutableArray alloc] init]; for (int i=0; i<[categories count]; i++){ MenuCategory *menuCategory = [NSEntityDescription insertNewObjectForEntityForName:@"MenuCategory" inManagedObjectContext:[self managedObjectContext]]; NSDictionary *category = [categories objectAtIndex:i]; menuCategory.name = [category objectForKey:@"name"]; NSArray *items = [category objectForKey:@"items"]; NSMutableArray *menuItems = [[NSMutableArray alloc] init]; for (int j=0; j<[items count]; j++){ MenuItem *menuItem = [NSEntityDescription insertNewObjectForEntityForName:@"MenuItem" inManagedObjectContext:[self managedObjectContext]]; NSDictionary *item = [items objectAtIndex:j]; menuItem.name = [item objectForKey:@"name"]; menuItem.price = [item objectForKey:@"price"]; menuItem.image = [item objectForKey:@"image"]; menuItem.details = [item objectForKey:@"details"]; [menuItems addObject:menuItem]; } [menuCategory setValue:menuItems forKey:@"menuItems"]; [menuCategories addObject:menuCategory]; [menuItems release]; } if (![[self managedObjectContext] save:&error]) { NSLog(@"An error occurred: %@", [error localizedDescription]); }

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• Hibernate Persistence problems with Bean Mapping (Dozer)

  - by BuffaloBuffalo

  I am using Hibernate 3, and having a particular issue when persisting a new Entity which has an association with an existing detached entity. Easiest way to explain this is via code samples. I have two entities, FooEntity and BarEntity, of which a BarEntity can be associated with many FooEntity: @Entity public class FooEntity implements Foo{ @Id private Long id; @ManyToOne(targetEntity = BarEntity.class) @JoinColumn(name = "bar_id", referencedColumnName = "id") @Cascade(value={CascadeType.ALL}) private Bar bar; } @Entity public class BarEntity implements Bar{ @Id private Long id; @OneToMany(mappedBy = "bar", targetEntity = FooEntity.class) private Set<Foo> foos; } Foo and Bar are interfaces that loosely define getters for the various fields. There are corresponding FooImpl and BarImpl classes that are essentially just the entity objects without the annotations. What I am trying to do is construct a new instance of FooImpl, and persist it after setting a number of fields. The new Foo instance will have its 'bar' member set to an existing Bar (runtime being a BarEntity) from the database (retrieved via session.get(..)). After the FooImpl has all of its properties set, Apache Dozer is used to map between the 'domain' object FooImpl and the Entity FooEntity. What Dozer is doing in the background is instantiating a new FooEntity and setting all of the matching fields. BarEntity is cloned as well via instantiation and set the FooEntity's 'bar' member. After this occurs, passing the new FooEntity object to persist. This throws the exception: org.hibernate.PersistentObjectException: detached entity passed to persist: com.company.entity.BarEntity Below is in code the steps that are occurring FooImpl foo = new FooImpl(); //returns at runtime a persistent BarEntity through session.get() Bar bar = BarService.getBar(1L); foo.setBar(bar); ... //This constructs a new instance of FooEntity, with a member 'bar' which itself is a new instance that is detached) FooEntity entityToPersist = dozerMapper.map(foo, FooEntity.class); ... session.persist(entityToPersist); I have been able to resolve this issue by either removing or changing the @Cascade annotation, but that limits future use for say adding a new Foo with a new Bar attached to it already. Is there some solution here I am missing? I would be surprised if this issue hasn't been solved somewhere before, either by altering how Dozer Maps the children of Foo or how Hibernate reacts to a detached Child Entity.

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• Using Entity Framework 4.0 with Code-First and POCO: How to Get Parent Object with All its Children

  - by SirEel

  I'm new to EF 4.0, so maybe this is an easy question. I've got VS2010 RC and the latest EF CTP. I'm trying to implement the "Foreign Keys" code-first example on the EF Team's Design Blog, http://blogs.msdn.com/efdesign/archive/2009/10/12/code-only-further-enhancements.aspx. public class Customer { public int Id { get; set; public string CustomerDescription { get; set; public IList<PurchaseOrder> PurchaseOrders { get; set; } } public class PurchaseOrder { public int Id { get; set; } public int CustomerId { get; set; } public Customer Customer { get; set; } public DateTime DateReceived { get; set; } } public class MyContext : ObjectContext { public RepositoryContext(EntityConnection connection) : base(connection){} public IObjectSet<Customer> Customers { get {return base.CreateObjectSet<Customer>();} } } I use a ContextBuilder to configure MyContext: { var builder = new ContextBuilder<MyContext>(); var customerConfig = _builder.Entity<Customer>(); customerConfig.Property(c => c.Id).IsIdentity(); var poConfig = _builder.Entity<PurchaseOrder>(); poConfig.Property(po => po.Id).IsIdentity(); poConfig.Relationship(po => po.Customer) .FromProperty(c => c.PurchaseOrders) .HasConstraint((po, c) => po.CustomerId == c.Id); ... } This works correctly when I'm adding new Customers, but not when I try to retrieve existing Customers. This code successfully saves a new Customer and all its child PurchaseOrders: using (var context = builder.Create(connection)) { context.Customers.AddObject(customer); context.SaveChanges(); } But this code only retrieves Customer objects; their PurchaseOrders lists are always empty. using (var context = _builder.Create(_conn)) { var customers = context.Customers.ToList(); } What else do I need to do to the ContextBuilder to make MyContext always retrieve all the PurchaseOrders with each Customer?

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• synchronized in java - Proper use

  - by ZoharYosef

  I'm building a simple program to use in multi processes (Threads). My question is more to understand - when I have to use a reserved word synchronized? Do I need to use this word in any method that affects the bone variables? I know I can put it on any method that is not static, but I want to understand more. thank you! here is the code: public class Container { // *** data members *** public static final int INIT_SIZE=10; // the first (init) size of the set. public static final int RESCALE=10; // the re-scale factor of this set. private int _sp=0; public Object[] _data; /************ Constructors ************/ public Container(){ _sp=0; _data = new Object[INIT_SIZE]; } public Container(Container other) { // copy constructor this(); for(int i=0;i<other.size();i++) this.add(other.at(i)); } /** return true is this collection is empty, else return false. */ public synchronized boolean isEmpty() {return _sp==0;} /** add an Object to this set */ public synchronized void add (Object p){ if (_sp==_data.length) rescale(RESCALE); _data[_sp] = p; // shellow copy semantic. _sp++; } /** returns the actual amount of Objects contained in this collection */ public synchronized int size() {return _sp;} /** returns true if this container contains an element which is equals to ob */ public synchronized boolean isMember(Object ob) { return get(ob)!=-1; } /** return the index of the first object which equals ob, if none returns -1 */ public synchronized int get(Object ob) { int ans=-1; for(int i=0;i<size();i=i+1) if(at(i).equals(ob)) return i; return ans; } /** returns the element located at the ind place in this container (null if out of range) */ public synchronized Object at(int p){ if (p>=0 && p<size()) return _data[p]; else return null; }

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• Achieving C# "readonly" behavior in C++

  - by Tommy Fisk

  Hi guys, this is my first question on stack overflow, so be gentle. Let me first explain the exact behavior I would like to see. If you are familiar with C# then you know that declaring a variable as "readonly" allows a programmer to assign some value to that variable exactly once. Further attempts to modify the variable will result in an error. What I am after: I want to make sure that any and all single-ton classes I define can be predictably instantiated exactly once in my program (more details at the bottom). My approach to realizing my goal is to use extern to declare a global reference to the single-ton (which I will later instantiate at a time I choose. What I have sort of looks like this, namespace Global { extern Singleton& mainInstance; // not defined yet, but it will be later! } int main() { // now that the program has started, go ahead and create the singleton object Singleton& Global::mainInstance = Singleton::GetInstance(); // invalid use of qualified name Global::mainInstance = Singleton::GetInstance(); // doesn't work either :( } class Singleton { /* Some details ommited */ public: Singleton& GetInstance() { static Singleton instance; // exists once for the whole program return instance; } } However this does not really work, and I don't know where to go from here. Some details about what I'm up against: I'm concerned about threading as I am working on code that will deal with game logic while communicating with several third-party processes and other processes I will create. Eventually I would have to implement some kind of synchronization so multiple threads could access the information in the Singleton class without worry. Because I don't know what kinds of optimizations I might like to do, or exactly what threading entails (never done a real project using it), I was thinking that being able to predictably control when Singletons were instantiated would be a Good Thing. Imagine if Process A creates Process B, where B contains several Singletons distributed against multiple files and/or libraries. It could be a real nightmare if I can not reliably ensure the order these singleton objects are instantiated (because they could depend on each other, and calling methods on a NULL object is generally a Bad Thing). If I were in C# I would just use the readonly keyword, but is there any way I can implement this (compiler supported) behavior in C++? Is this even a good idea? Thanks for any feedback.

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• C++ abstract class template + type-specific subclass = trouble with linker

  - by user333279

  Hi there, The project in question is about different endpoints communicating with each other. An endpoint sends events (beyond the scope of the current problem) and can process incoming events. Each event is represented in a generic object as follows: #pragma interface ... // some includes template<typename T> class Event { public: Event(int senderId, Type type, T payload); // Type is an enum Event(int senderId, Type type, int priority, T payload); virtual ~Event(); virtual int getSenderId(); virtual int getPriority(); virtual T getPayload(); void setPriority(const int priority); protected: const int senderId; const Type type; const T payload; int priority; }; It has its implementing class with #pragma implementation tag. An endpoint is defined as follows: #pragma interface #include "Event.h" template<typename T> class AbstractEndPoint { public: AbstractEndPoint(int id); virtual ~AbstractEndPoint(); virtual int getId(); virtual void processEvent(Event<T> event) = 0; protected: const int id; }; It has its implementing class too, but only the constructor, destructor and getId() are defined. The idea is to create concrete endpoints for each different payload type. Therefore I have different payload objects and specific event classes for each type, e.g. Event<TelegramFormatA>, Event<TelegramFormatB> and ConcreteEndPoint for TelegramFormatA, ConcreteEndPoint for TelegramFormatB respectively. The latter classes are defined as class ConcreteEndPoint : AbstractEndPoint<TelegramFormatA> { ... } I'm using g++ 4.4.3 and ld 2.19. Everything compiles nicely, but the linker complaints about undefined references to type-specific event classes, like Event<TelegramFormatA>::Event(....) . I tried explicit instantiation using template class AbstractEndPoint<TelegramFormatA>; but couldn't get past the aforementioned linker errors. Any ideas would be appreciated.

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