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  • C++ Singleton design pattern.

    - by Artem Barger
    Recently I've bumped into realization/implementation of Singleton design pattern for C++. It has looked in the following way (I have adopted it from real life example): // a lot of methods is omitted here class Singleton { public: static Singleton* getInstance( ); ~Singleton( ); private: Singleton( ); static Singleton* instance; }; From this declaration I can deduce that instance field is initiated on the heap, that means there is a memory allocation. That is completely unclear for me is when does exactly memory is going to be deallocated? Or there is a bug and memory leak? It seems like there is a problem in implementation. PS. And main question how to implement it in the right way?

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  • Question about a possible design pattern...

    - by Aftershock
    I have such a design in my mind.... My aim is to reuse the program with some features included and without some features. What is it called in the literature? class feature1 { void feature1function1(); void feature1function2(); } class feature2 { void feature2function1(); void feature2function2(); } class program: feature1, feature2 { void function1() { feature2function1(); } void function2() { feature1function1(); feature2function1(); } void execute() { function1(); function2(); } }

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  • How to expose a control collection to a property grid at design time

    - by Stefano Delendati
    I have a custom control that with a property that is a collection of custom object. This custom object hava a reference to some component/controls. When at design time I tray to add an item to the collection and select the object, VS tells me that the control is not serializable. This is the code (simplified version - but not to much): public class ViewRefObj { public control view { get; set; } public ViewRefObj() { } } private List<ViewRefObj> _controls=new List<ViewRefObj>(); public List<ViewRefObj> Views { get { return _controls; } }

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  • What elegant method callback design should be used ?

    - by ereOn
    Hi, I'm surprised this question wasn't asked before on SO (well, at least I couldn't find it). Have you ever designed a method-callback pattern (something like a "pointer" to a class method) in C++ and, if so, how did you do it ? I know a method is just a regular function with some hidden this parameter to serve as a context and I have a pretty simple design in mind. However, since things are often more complex than they seem to, I wonder how our C++ gurus would implement this, preferably in an elegant and standard way. All suggestions are welcome !

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  • command design pattern usage

    - by sagie
    Hi. I've read 3 descriptions of the command design pattern: wikipedia, dofactory and source making. In all of them, the UML shows a relation between the client to the receiver & the concrete command, but no relation to the invoker. But in all 3 examples the client is the one that initiates the invoker and call its Execute method. I think that should be a relation to the invoker as well. Am I missing somthing in here? Maybe even a basic UML knowladge?

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  • Design patter for extending Android's activities?

    - by Carl
    While programming on Android, I end up writing a parent activity which is extended by several others. A bit like ListActivity. My parent activity extends Activity. if I intend to use a Map or a List, I can't use my parent activity as superclass - the child activity can only extend one activity obviously. As such I end up writing my parent activities with the same logic for Activity, ListActivity, MapActivity and so forth. What am I looking for is some sort of trait functionality/design pattern which would help in this case. Any suggestions?

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  • commad design pattern usage

    - by sagie
    Hi. I've read 3 descriptions of the command design pattern: wikipedia, dofactory and source making. In all of them, the UML shows a relation between the client to the receiver & the concrete command, but no relation to the invoker. But in all 3 examples the client is the one that initiates the invoker and call its Execute method. I think that should be a relation to the invoker as well. Am I missing somthing in here? Maybe even a basic UML knowladge?

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  • Design pattern for data entry forms with LINQ2SQL

    - by petebob796
    I am about to start a new winforms data entry application, it already has the database designed which I am comfortable with. I was going to use LINQ2SQL to access the tables to keep things type safe but am now wondering about design patterns, something I am just getting into. Since LINQ is giving me objects to use should I still create classes in between to hold the validation code and helper methods or should these just go in with the UI? It just seems I will end up with classes sat in between with little code which will cause the UI classes to have code just getting and setting values in the intermediate class and returning from validation to flag errors... Any good reading on this? Should I consider the entity framework (or similar) instead?

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  • tsql source control help please

    - by rod
    Hi All, According to the following section of BOL: How to: Use Source Control with SQL Server Management Studio If you have a source control client installed you should be able to choose it in the plug-in selection. I have both source control clients for Visual Studio 2005 and 2008 (tfs2005) installed and there's no plug-in to choose in the list for me.

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  • Comparing Design Patterns

    - by Lijo
    Hi, I am learning design patterns using C#. One of the challenges that I am facing is that they look similar. Could you please help me to distinguish them – basically when to use them? - Why not the other? Bridge and Strategy State and Strategy Façade and Strategy Composite and Strategy I understand that there are lots of resources available in the web. However they does not treat this special question. [Note: I am looking for implementation examples and rationale behind the selection; not mere explanations] It would be great if you are taking examples from any of the following 1) E-Commerce 2) Payroll system 3) Banking 4) Retailing Thanks for your understanding.. Thanks Lijo

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  • How to design model for multi-tiered data?

    - by Chris
    Say I have three types of object: Area, Subarea and Topic. I want to be able to display an Area, which is just a list of Subareas and the Topics contained in those Subareas. I never want to be able to display Subareas separately - they're just for breaking up the Topics. Topics can, however, appear in multiple Areas (but probably under the same Subarea). How would I design a model for this? I could use ForeignKey from Topic to Subarea and from Subarea to Area, but it seems unnecessarily complex given that I never want to interact with subareas themselves. Also, none of these objects are ever altered or added to by the user. They're just for me to represent information. Maybe there is a better way to represent it all?

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  • which design choose? - pros and cons

    - by Guarava Makanili
    Which of these 3 approches would choose and why? // This is the one I would choose class Car { } class FeeCalculator { public double calculateFee(Car car) { return 0; } } // in that case the problem might be when we use ORM framework and we try to invoke save with parameter Car class Car { private FeeCalculator calculator; public double calculateFee() { return calculator.calculateFee(this); } } class FeeCalculator { public double calculateFee(Car car) { return 0; } } // in that case the problem mentioned above is solved, but I don't like this design class Car { public double calculateFee(FeeCalculator calculator) { return calculator.calculateFee(this); } } class FeeCalculator { public double calculateFee(Car car) { return 0; } }

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  • Generic Database table design

    - by Gazeth
    Just trying to figure out the best way to design my table for the following scenario: I have several areas in my system (documents, projects, groups and clients) and each of these can have comments logged against them. My question is should I have one table like this: CommentID DocumentID ProjectID GroupID ClientID etc Where only one of the ids will have data and the rest will be NULL or should I have a seperate CommentType table and have my comments table like this: CommentID CommentTypeID ResourceID (this being the id of the project/doc/client) etc My thoughts are that option 2 would be more efficient from an indexing point of view?

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  • related categories - database design

    - by mike
    Hello! I'm looking for a little database design advice... I have a spreadsheet with a few columns in it. Column 1 being a list of categories and the rest being related categories(to the category in column 1). I'm trying to figure out what the best way to setup the tables would be... My thought so far is to have a table that just lists the categories then have a table with 2 columns that holds the id of the category and the id of a related category.... Would this be the best way to do this? Any better ideas?

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  • Class design question (Disposable and singleton behavior)

    - by user137348
    The Repository class has singleton behavior and the _db implements the disposable pattern. As excepted the _db object gets disposed after the first call and because of the singleton behavior any other call of _db will crash. [ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)] public class Repository : IRepository { private readonly DataBase _db; public Repository(DataBase db) { _db = db; } public int GetCount() { using(_db) { return _db.Menus.Count(); } } public Item GetItem(int id) { using(_db) { return _db.Menus.FirstOrDefault(x=>x.Id == id); } } } My question is, is there any way to design this class to work properly without removing the singleton behavior? The Repositoryclass will be serving big amount of requests.

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  • Customers and suppliers database design issue

    - by hectorsq
    I am developing a web application in which I will have customers and suppliers. Initially I thought on using a Customers table and a Suppliers table. Then when I was thinking on bank transactions, I noticed that each transaction needs to refer to a customer or a supplier, so I thought on using a single table named Business in which I will save both customers and suppliers. If I use Customers and Suppliers tables when I want to list the bank transactions I will have to search in both tables to get the company name. If I use a Businesses table I will have to use a business type column, and have the union of possible fields for all businesses types. Any suggestions on the design?

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  • C++ Singleton design pattern

    - by Artem Barger
    Recently I've bumped into a realization/implementation of the Singleton design pattern for C++. It has looked like this (I have adopted it from the real life example): // a lot of methods are omitted here class Singleton { public: static Singleton* getInstance( ); ~Singleton( ); private: Singleton( ); static Singleton* instance; }; From this declaration I can deduce that the instance field is initiated on the heap. That means there is a memory allocation. What is completely unclear for me is when exactly the memory is going to be deallocated? Or is there a bug and memory leak? It seems like there is a problem in the implementation. My main question is, how do I implement it in the right way?

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  • Does the following indicate a bad design?

    - by Mewzer
    Hello, I was wondering whether you think the following code usually indicates a bad design ... class X { public: ... private: Y y; }; Class Y { public: Y( X& value ){ x = value; }; private: X& x; } (i.e. there is some sort of cyclic dependency between the classes X and Y).

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  • Visual Studio Little Wonders: Quick Launch / Quick Access

    - by James Michael Hare
    Once again, in this series of posts I look at features of Visual Studio that may seem trivial, but can help improve your efficiency as a developer. The index of all my past little wonders posts can be found here. Well, my friends, this post will be a bit short because I’m in the middle of a bit of a move at the moment.  But, that said, I didn’t want to let the blog go completely silent this week, so I decided to add another Little Wonder to the list for the Visual Studio IDE. How often have you wanted to change an option or execute a command in Visual Studio, but can’t remember where the darn thing is in the menu, settings, etc.?  If so, Quick Launch in VS2012 (or Quick Access in VS2010 with the Productivity Power Tools extension) is just for you! Quick Launch / Quick Access – find a command or option quickly For those of you using Visual Studio 2012, Quick Launch is built right into the IDE at the top of the title bar, near the minimize, maximize, and close buttons: But do not despair if you are using Visual Studio 2010, you can get Quick Access from the Productivity Power Tools extension.  To do this, you can go to the extension manager: And then go to the gallery and search for Productivity Power Tools and install it.  If you don’t have VS2012 yet, then the Productivity Power Tools is the next best thing.  This extension updates VS2010 with features such as Quick Access, the Solution Navigator, searchable Add Reference Dialog, better tab wells, etc.  I highly recommend it! But back to the topic at hand!  In VS2012 Quick Launch is built into the IDE and can be accessed by clicking in the Quick Launch area of the title bar, or by pressing CTRL+Q.  If you have VS2010 with the PPT installed, though, it is called Quick Access and is accessible through View –> Quick Access: Regardless of which IDE you are using, the feature behaves mostly the same.  It allows you to search all of Visual Studio’s commands and options for a particular topic.  For example, let’s say you want to change from tabs to tabs expanded to spaces, but don’t remember where that option is buried.  You can bring up Quick Launch / Quick Access and type in “tabs”: And it brings up a list of all options on tabs, you can then choose the one appropriate to you and click on it and it will take you right there! A lot easier than diving through the options tree to find what you are looking for!  It also works on menu commands, for example if you can’t remember how to open the Output window: It shows you the menu items that will get you to the Output window, and (if applicable) the keyboard shortcuts.  Again, clicking on one of these will perform the action for you as well. There are also some tasks you can perform directly from Quick Launch / Quick Access.  For example, perhaps you are one of those people who like to have the line numbers in your editor (I do), so let’s bring up Quick Launch / Quick Access and type “line numbers”: And let’s select Turn Line Numbers On, and now our editor looks like: And Voila!  We have line numbers in VS2010.  You can do this in VS2012 too, but it takes you to the option settings instead of directly turning them off and on.  There are bound to be differences between the way the two editors organize settings and commands, but you get the point. So, as you can see, the Quick Launch / Quick Access feature in Visual Studio makes it easy to jump right to the options, commands, or tasks you are interested in without all the digging. Summary An IDE as powerful as Visual Studio has so many options and commands that it can be confusing to remember how to find and invoke them.  Quick Launch (Quick Access in VS2010 with Productivity Power Tools extension) is a quick and handy way to jump to any of these options, commands, or tasks quickly without having to remember in what menu or screen they are buried!  Technorati Tags: C#,CSharp,.NET,Little Wonders,Visual Studio,Quick Access,Quick Launch

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  • SQL SERVER – Fix Visual Studio Error : Connections to SQL Server files (.mdf) require SQL Server Express 2005 to function properly. Please verify the installation of the component or download from the URL

    - by pinaldave
    In one of the virtual environment while I was trying to add SQL Server Database (.mdf) file to asp.net project I encountered following error: Connections to SQL Server files (.mdf) require SQL Server Express 2005 to function properly. Please verify the installation of the component or download from the URL:  For a long time I am using SQL Server 2012 but this error was a bit interesting to me. I realize that there should not be any need of the SQL Server 2005 installation. I quickly figured out that I can remove this error if I do as mentioned below: Open Microsoft Visual Studio Select Tools >> Options >> Database Tools >> Data Connections Enter the name of an installed instance in “SQL Server Instance Name” field. Click OK If you do not know the instance name, you can follow either of the options. 1) Use the command line sqlcmd utility 2) Using SQL Server Management Studio Is there any other way to resolve this error? Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Error Messages, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: sqlcmd, Visual Studio

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  • Is there a cheaper non-express non-student, non-msdn version of Visual Studio 2010 that supports plugins in the US than the $710 Professional Edition?

    - by Justin Dearing
    I've never actually purchased a copy of Visual Studio myself. SharpDevelop and Express edition have always been good enough for my personal use, and my employers always furnished me with the IDEs I needed to serve them. However, I'm thinking of actually paying for a copy for my personal laptop. I need this mainly so I can open solutions that contain web projects. So my question is: Is there an edition cheaper than the $710 Pro edition on Amazon that will do what I need: http://www.amazon.com/Microsoft-C5E-00521-Visual-Studio-Professional/dp/B0038KTO8S/ref=sr_1_2?ie=UTF8&qid=1287456230&sr=8-2 ? What I need is defined as: Open up a solution with C#, Web App, VB.NET, and Web Projects. Install addins like resharper, testdriven.net, etc, SCM plugins, etc. Some level of db project support. At least to be able to open a dbproj. I only need that for SCM hooks. SSMS and SQLCMD are good enough for actually editing databases. Ability to install F#, IronPython, IronRuby etc. Now naturally I'm a fairly intelligent resourceful person so I realize I can get Visual Studio in a questionable manner. Thats not what I'm looking to do. I want a legal copy, I don't want a student copy, or an MSDN copy. I want a real copy, I just want to make sure I get the cheapest edition that serves my needs.

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  • Installing Visual Studio 2010 SP1 or Windows Phone tools in your VM (danger!)

    - by Jeff
    If you've read my blog for any amount of time, you probably know that I tend to develop stuff in a Parallels VM on a Mac. It's how I roll. I like VM's because I can trash them and do really stupid things with beta software. That said, there is a pain point that doesn't seem that well documented when it comes to installing stuff in this scenario.The WP7 tools, and SP1 for Visual Studio 2010 (perhaps only if you already have the WP7 tools installed, I'm not sure), do something strange on install. As if it weren't already a long and slow installation, for reasons I don't understand, the installer fires up an instance of Windows Phone Emulator. As you may already know, the emulator doesn't run in a VM, because it is itself a VM, apparently. What it will do is fire up your CPU, make your comprooder hot and make the fans blow harder.I found this out accidentally, as I started the (slow) phone tool installation once, and walked away. An hour and a half later, I came back to find it hadn't finished. But it was hot and the CPU was pegged, so I fired up the task manager to find XDE.exe, the phone emulator, cranking away. I had to kill it several times, and eventually the install finished. It fired up just once in the SP1 install, but it still had the same hanging effect.I can't for the life of me figure out why it does this. In a VM, I can connect the phone to it and use that, so I don't need the emulator. But this install, firing up the emulator, will make it choke until you kill the XDE.exe process. Watch out!

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  • Const references when dereferencing iterator on set, starting from Visual Studio 2010

    - by Patrick
    Starting from Visual Studio 2010, iterating over a set seems to return an iterator that dereferences the data as 'const data' instead of non-const. The following code is an example of something that does compile on Visual Studio 2005, but not on 2010 (this is an artificial example, but clearly illustrates the problem we found on our own code). In this example, I have a class that stores a position together with a temperature. I define comparison operators (not all them, just enough to illustrate the problem) that only use the position, not the temperature. The point is that for me two instances are identical if the position is identical; I don't care about the temperature. #include <set> class DataPoint { public: DataPoint (int x, int y) : m_x(x), m_y(y), m_temperature(0) {} void setTemperature(double t) {m_temperature = t;} bool operator<(const DataPoint& rhs) const { if (m_x==rhs.m_x) return m_y<rhs.m_y; else return m_x<rhs.m_x; } bool operator==(const DataPoint& rhs) const { if (m_x!=rhs.m_x) return false; if (m_y!=rhs.m_y) return false; return true; } private: int m_x; int m_y; double m_temperature; }; typedef std::set<DataPoint> DataPointCollection; void main(void) { DataPointCollection points; points.insert (DataPoint(1,1)); points.insert (DataPoint(1,1)); points.insert (DataPoint(1,2)); points.insert (DataPoint(1,3)); points.insert (DataPoint(1,1)); for (DataPointCollection::iterator it=points.begin();it!=points.end();++it) { DataPoint &point = *it; point.setTemperature(10); } } In the main routine I have a set to which I add some points. To check the correctness of the comparison operator, I add data points with the same position multiple times. When writing the contents of the set, I can clearly see there are only 3 points in the set. The for-loop loops over the set, and sets the temperature. Logically this is allowed, since the temperature is not used in the comparison operators. This code compiles correctly in Visual Studio 2005, but gives compilation errors in Visual Studio 2010 on the following line (in the for-loop): DataPoint &point = *it; The error given is that it can't assign a "const DataPoint" to a [non-const] "DataPoint &". It seems that you have no decent (= non-dirty) way of writing this code in VS2010 if you have a comparison operator that only compares parts of the data members. Possible solutions are: Adding a const-cast to the line where it gives an error Making temperature mutable and making setTemperature a const method But to me both solutions seem rather 'dirty'. It looks like the C++ standards committee overlooked this situation. Or not? What are clean solutions to solve this problem? Did some of you encounter this same problem and how did you solve it? Patrick

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  • STL operator= behavior change with Visual Studio 2010?

    - by augnob
    Hi, I am attempting to compile QtScriptGenerator (gitorious) with Visual Studio 2010 (C++) and have run into a compile error. In searching for a solution, I have seen occasional references to compile breakages introduced since VS2008 due to changes in VS2010's implementation of STL and/or c++0x conformance changes. Any ideas what is happening below, or how I could go about fixing it? If the offending code appeared to be QtScriptGenerator's, I think I would have an easier time fixing it.. but it appears to me that the offending code may be in VS2010's STL implementation and I may be required to create a workaround? PS. I am pretty unfamiliar with templates and STL. I have a background in embedded and console projects where such things have until recently often been avoided to reduce memory consumption and cross-compiler risks. C:\Program Files\Microsoft Visual Studio 10.0\VC\INCLUDE\xutility(275) : error C2679: binary '=' : no operator found which takes a right-hand operand of type 'rpp::pp_output_iterator<_Container>' (or there is no acceptable conversion) with [ _Container=std::string ] c:\qt\qtscriptgenerator\generator\parser\rpp\pp-iterator.h(75): could be 'rpp::pp_output_iterator<_Container> &rpp::pp_output_iterator<_Container>::operator =(const char &)' with [ _Container=std::string ] while trying to match the argument list '(rpp::pp_output_iterator<_Container>, rpp::pp_output_iterator<_Container>)' with [ _Container=std::string ] C:\Program Files\Microsoft Visual Studio 10.0\VC\INCLUDE\xutility(2176) : see reference to function template instantiation '_Iter &std::_Rechecked<_OutIt,_OutIt>(_Iter &,_UIter)' being compiled with [ _Iter=rpp::pp_output_iterator<std::string>, _OutIt=rpp::pp_output_iterator<std::string>, _UIter=rpp::pp_output_iterator<std::string> ] c:\qt\qtscriptgenerator\generator\parser\rpp\pp-internal.h(83) : see reference to function template instantiation '_OutIt std::copy<std::_String_iterator<_Elem,_Traits,_Alloc>,_OutputIterator>(_InIt,_InIt,_OutIt)' being compiled with [ _OutIt=rpp::pp_output_iterator<std::string>, _Elem=char, _Traits=std::char_traits<char>, _Alloc=std::allocator<char>, _OutputIterator=rpp::pp_output_iterator<std::string>, _InIt=std::_String_iterator<char,std::char_traits<char>,std::allocator<char>> ] c:\qt\qtscriptgenerator\generator\parser\rpp\pp-engine-bits.h(500) : see reference to function template instantiation 'void rpp::_PP_internal::output_line<_OutputIterator>(const std::string &,int,_OutputIterator)' being compiled with [ _OutputIterator=rpp::pp_output_iterator<std::string> ] C:\Program Files\Microsoft Visual Studio 10.0\VC\INCLUDE\xutility(275) : error C2582: 'operator =' function is unavailable in 'rpp::pp_output_iterator<_Container>' with [ _Container=std::string ] Here's some context.. pp-internal.h-- #ifndef PP_INTERNAL_H #define PP_INTERNAL_H #include <algorithm> #include <stdio.h> namespace rpp { namespace _PP_internal { .. 68 template <typename _OutputIterator> 69 void output_line(const std::string &__filename, int __line, _OutputIterator __result) 70 { 71 std::string __msg; 72 73 __msg += "# "; 74 75 char __line_descr[16]; 76 pp_snprintf (__line_descr, 16, "%d", __line); 77 __msg += __line_descr; 78 79 __msg += " \""; 80 81 if (__filename.empty ()) 82 __msg += "<internal>"; 83 else 84 __msg += __filename; 85 86 __msg += "\"\n"; 87 std::copy (__msg.begin (), __msg.end (), __result); 88 }

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