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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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  • ignore this test

    - by Name
    http://markitup.jaysalvat.com/downloads/markupsets/wiki/set.js Here is a useful construct when trying to hide variables from the parent namespace. All the code within the function is contained in the private scope of the function, meaning it is allowed. So you've become comfortable with jQuery and would like to learn how to write your own plugins. Great! You're in the right spot. Extending jQuery with plugins and methods is very powerful and can save you and your peers a lot of development time by abstracting your most clever functions into plugins. This post will outline the basics, best practices, and common pitfalls to watch out for as you begin writing your plugin.

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  • Java: Superclass to construct a subclass on certain conditions, possible?

    - by ramihope
    I have this condition public class A { public action() { System.out.println("Action done in A"); } } public class B extends A { public action() { System.out.println("Action done in B"); } } when I create an instance of B, the action will do just actions in B, as it overrides the action of the superclass. the problem is that in my project, the super class A is already used too many times, and I am looking for a way that under certain conditions, when i create an instance of A it makes a check and if it is true, replace itself with B. public class A { public A() { if ([condition]) { this = new B(); } } public action() { System.out.println("Action done in A"); } } A a = new A(); a.action(); // expect to see "Action done in B"... is this possible in some way?

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  • How to elegantly work with a lot of print functions?

    - by user1824372
    I'm working on a Python project that is executed on a terminal (or console) for which I am planning to implement a GUI. I did not major in CS so I really have no idea how to effectively design a terminal GUI such that: the user interface looks good in GUI, it is directed to a certain widget, let's say, a text label, or a bottom bar, or a hide-able frame. Do you have any suggestions? Currently, I am using the print function to provide essential information on STDOUT during execution, so a lot of print calls are distributed here and there in the code. I'm thinking of using macro-like variables such as 'FILE_NOT_EXISTS_MESSAGE' for printing, and all of them and their values would be defined in one file. Is that a standard way to do this? Should I introduce a logging system? In summary, I'm looking for a pattern for handling console output that is effective and adaptable.

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  • No mapping for LONGVARCHAR in Hibernate 3.2

    - by jimbokun
    I am running Hibernate 3.2.0 with MySQL 5.1. After updating the group_concat_max_len in MySQL (because of a group_concat query that was exceeding the default value), I got the following exception when executing a SQLQuery with a group_concat clause: "No Dialect mapping for JDBC type: -1" -1 is the java.sql.Types value for LONGVARCHAR. Evidently, increasing the group_concat_max_len value causes calls to group_concat to return a LONGVARCHAR value. This appears to be an instance of this bug: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3892 I guess there is a fix for this issue in Hibernate 3.5, but that is still a development version, so I am hesitant to put it into production, and don't know if it would cause issues for other parts of my code base. I could also just use JDBC queries, but then I have to replace every instance of a SQLQuery with a group_concat clause. Any other suggestions?

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  • Random List of numbers in C

    - by Ant
    I have just started a C programming course and so far have only done the basics like printf, read a little on variables etc on the course book. The teacher has tasked us with writing a program that will take a value entered by the user, this will be the number of students in the class (25 at the moment but can be variable). It will then list the number of students randomly and place them in 3 columns. The purpose is to sort students into groups of 3 randomly, then display on the screen in columns. Now my question is not for the code that defeats the object of me attempting the exercise, but how to structure it. I can see that using an array can be used to display the list, but really after some pointers on how best to approach the problem in blocks, then I can attempt to program each block.

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  • Analytics - Total events divided by number of unique pages?

    - by GeekyAndUnique
    I am using Google Analytics events to track keywords on my articles - not necessarily the best system I know but there are too many for variables I can't easily change it right now - and I would like to be able to see how popular each keyword is by dividing the number of page views with a keyword by the number of unique pages. Is there a/what is the best way of doing this? EDIT FOR CLARITY I currently have a system set up where every time somebody loads an article an event is fired for each of the tags/keywords used, with the keyword being the label. I can currently view my view count for each of the keywords by looking at the total events for each label, however I would like to be able to see which keywords are the most popular by dividing the number of times the event has been fired by the the number of different pages it has been fired from.

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  • Is MSDN referencing a system.thread, a worker thread, an io thread or all three?

    - by w0051977
    Please see the warning below taken from the StreamWriter class specification (http://msdn.microsoft.com/en-us/library/system.io.streamwriter.aspx): "Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe." I understand that a W3WC process contains two thread pools i.e. worker threads and I/O threads. A worker thread could contain many threads of its own (if the application creates its own System.Thread instances). Does the warning only relate to System.Threads or does it relate to worker threads and I/O threads as well I.e. as the instance variables of the streamwriter class are not thread safe then does this mean that there would be problems if multiple worker threads access it eg if two users on two different web clients attempt to write to the log file at the same time, then could one lock out the other?

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  • NSInvalidArgumentException – App terminates while i'm trying to copy a captured video to documents f

    - by ChrNis
    I'd like to try the wisdom of the crowds..because i'm frustrated right now. Thanks in advance. So here is my code: - (void)imagePickerController:(UIImagePickerController *)ipc didFinishPickingMediaWithInfo:(NSDictionary *)info{ NSLog(@"info: %@",info); NSString *newFilename = [NSString stringWithFormat:@"%@/%@.mov", [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"], [NSString stringWithFormat:@"%d", (long)[[NSDate date] timeIntervalSince1970]]]; NSLog(@"newFilename: %@",newFilename); NSFileManager *filemgr = [NSFileManager defaultManager]; NSError *err; if ([filemgr copyItemAtPath:[info objectForKey:@"UIImagePickerControllerMediaURL"] toPath:newFilename error:&err] == YES) NSLog (@"Move successful"); else NSLog (@"Move failed"); and this is the log: 2010-05-16 18:19:01.975 erlkoenig[7099:307] info: { UIImagePickerControllerMediaType = "public.movie"; UIImagePickerControllerMediaURL = "file://localhost/private/var/mobile/Applications/BE25F9B5-2D08-4B59-8B62-D04DF7BB7E5B/tmp/-Tmp-/capture-T0x108cb0.tmp.8M81HU/capturedvideo.MOV"; } newFilename: /var/mobile/Applications/BE25F9B5-2D08-4B59-8B62-D04DF7BB7E5B/Documents/1274026741.mov [NSURL fileSystemRepresentation]: unrecognized selector sent to instance 0x1c1f90 *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSURL fileSystemRepresentation]: unrecognized selector sent to instance 0x1c1f90

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  • Generating CMakeLists.txt

    - by vanna
    I got a bunch of C++ sources files and headers. They may use external libraries such as Boost e.g. I am interested in the process of building binaries for Windows and *nix. Makefiles (*nix) and .vcproj (Windows) call compilers with some specifications such as the order of compilation, compilation options and stuff. CMakeLists.txt can be used by CMake to build either makefiles or .vcproj and use very helpful commands such as recursive search of files, automatic linkage with known libraries, installers, variables that can be used in source files... Is there any existing tool that would generate a CMakeLists.txt from specified options ? Options could be like : scan this folder and make a library out of it, then scan this other folder and make an executable and automatically link both with Boost as well along with a user friendly installer with generated INSTALL.txt and README.txt. Something very powerful like that.

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  • How to retrieve base class only (entity framework)?

    - by Juvaly
    Hi All, I've been scratching my head here for a while now... I have a Consumer class and a BillableConsumer class that inherits Consumer. They are both a part of the Consumers set. The problem is that this following query: Consumer consumer = (from c in _ctx.Consumers where c.ID = id select c).First(); returns a BillableConsumer instance! Just the same as this query: BillableConsumer bconsumer = (from c in _ctx.Consumers.OfType<BillableConsumer>() where c.ID = id select c).First(); How can I return an instance of just the base class? (these are separate tables in the data store).

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  • Is LocalDB supported by Visual Studio 2010 in Entity Framework 5?

    - by Mathias Lykkegaard Lorenzen
    Is LocalDB supported by Visual Studio 2010 in Entity Framework 5, on .NET 4.0? Or am I doing it wrong? I'm getting a "The network path can't be found" issue when instantiating my model container with a connection string for LocalDB. Here's the connection string: var connectionString = "metadata=res://*/Model.csdl|res://*/Model.ssdl|res://*/Model.msl;provider=System.Data.SqlClient;provider connection string=\"data source=(localdb)\v11.0;initial catalog=fablelane_com_db;integrated security=SSPI;multipleactiveresultsets=True;App=EntityFramework\""; Edit 1 I'm receiving the following error when connecting, more specifically: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server). Edit 2 I just figured out that changing to Visual Studio 11 beta doesn't work either. Still receiving the same error-message.

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  • Spring MVC managing multiple views with single controller

    - by Sudhir
    I am trying to implement order management module. There are different order types (approximately about 15). Each order has a seperate view. But the actions performed on UI are same irrespective of order type. Below is the structure of my DTO abstract class Order abstract class SecurityOrder extends Order abstract class TermDepositOrder extends Order ..... ..... ..... I am trying to implement a single controller capable of managing all views. Something similar to the one below: @Controller public class OrderController<F extends Order> { public F validate(F order) { } public F insert(F order) { } } I am not sure how spring mvc would be able to map request parameters properly to the order instance as it doesn't know which order instance to populate. Is it possible to achieve this with single controller or should I go with a controller for each order type and duplicate same code across all controllers?

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  • How do I reference a pointer from a different class?

    - by Justagruvn
    First off, I despise singletons with a passion. Though I should probably be trying to use one, I just don't want to. I want to create a data class (that is instantiated only once by a view controller on loading), and then using a different class, message the crap out of that data instance until it is brimming with so much data, it smiles. So, how do I do that? I made a pointer to the instance of the data class when I instantiated it. I'm now over in a separate view controller, action occurs, and I want to update the initial data object. I think I need to reference that object by way of pointer, but I have no idea how to do that. Yes, I've set properties and getters and setters, which seem to work, but only in the initial view controller class. Peace Love applesauce.

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  • Ruby forwarding method calls

    - by JP
    I have an instance of a master class which generates instances of a subclass, these subclasses need to forward some method calls back to the master instance. At the moment I have code looking something like this, but it feels like I should be able to do the same thing more efficiently (maybe with method_missing?) class Master def initalize(mynum) @mynum = mynum end def one_thing(subinstance) "One thing with #{subinstance.var} from #{@mynum}" end def four_things(subinstance) "Four things with #{subinstance.var} from #{@mynum}" end def many_things(times,subinstance) "#{times} things with #{subinstance.var} from #{@mynum}" end def make_a_sub(uniqueness) Subthing.new(uniqueness,self) end class Subthing def initialize(uniqueness,master) @u = uniqueness @master = master end # Here I'm forwarding method calls def one_thing master.one_thing(self) end def four_things master.four_things(self) end def many_things(times) master.many_things(times,self) end end end m = Master.new(42) s = m.make_a_sub("very") s.one_thing === m.one_thing(s) s.many_things(8) === m.many_things(8,s) I hope you can see what's going on here. I would use method_missing, but I'm not sure how to cope with the possibility of some calls having arguments and some not (I can't really rearrange the order of the arguments to the Master methods either) Thanks for reading!

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  • Multiple inclusion of header file c++

    - by iSight
    Hi, I have a problem regarding multiple inclusion of header file in C++ code. say for example, i have three class X,Y,Z. X and Y are derived from Base class Z. And i want to create an instance of X in Y. The code will go like this. class Z{some code} class X:public Z{some code};//here #include header of class Z added class Y:public Z //here #include header of class Z added as well as of X class {private: X* mX;//instance of X some code}; So in this multiple definition of all methods of base class arises. how can i cope with this problem

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  • In Django, using __init__() method of non-abstract parent model to record class name of child model

    - by k-g-f
    In my Django project, I have a non-abstract parent model defined as follows: class Parent(models.Model): classType = models.CharField(editable=False,max_length=50) and, say, two children models defined as follows: class ChildA(Parent): parent = models.OneToOneField(Parent,parent_link=True) class ChildB(Parent): parent = models.OneToOneField(Parent,parent_link=True) Each time I create an instance of ChildA or of ChildB, I'd like the classType attribute to be set to the strings "ChildA" or "ChildB" respectively. What I have done is added an _ _ init_ _() method to Parent as follows: class Parent(models.Model): classType = models.CharField(editable=False,max_length=50) def __init__(self,*args,**kwargs): super(Parent,self).__init__(*args,**kwargs) self.classType = self.__class__.__name__ Is there a better way to implement and achieve my desired result? One downside of this implementation is that when I have an instance of the Parent, say "parent", and I want to get the type of the child object linked with "parent", calling "parent.classType" gives me "Parent". In order to get the appropriate "ChildA" or "ChildB" value, I need to write a "_getClassType()" method to wrap a custom sql query.

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  • Loading multiple embedded flash apps onto an HTML page- problem with ordering

    - by shudson250
    We need to load an embedded version of a site written in Flash, and not originally designed to load multiple instances of itself, on a HTML page. The specific issue is how to get them to load in order when embedded, given that they are all being opened by the same instance of the flash player. It's a complicated mapping application, and at the moment, the maps and data get intermixed as the session variables are overwritten by another instance starting to load before the previous one has finished. We need a way to have them load sequentially, one finishing before another starts to load. The most we can specify in the URL is an &order=1 or similar. We have PHP and SQL on the backend. Edit: The embedded versions are being loaded in an iFrame of a parent site. One php file loads one swf, as many times as the parent site desires.

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  • Reading in multiple words for prolog

    - by prolog123456789
    Im running prolog via poplog on unix and was wondering if there was a way to read in multiple words (such as encase it into a string). For instance, read(X) will only allow X to be 1 term. However, if I encase the user input with "", it will return a list of character codes, is this the correct method as I can not find a way to convert it back to a readable string. I would also like to be able to see if the multiworded string contains a set value (for instance, if it contains "i have been") and am unsure of how i will be able to do this as well.

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  • Django GenericRelation doesn't save related object's id - is this a bug or am I doing it wrong?

    - by pinkeen
    I have a model with a generic relation (call it A), when creating an instance of this object I pass an instance of another model (call it B) as the initializer of the content_object field (via kwargs of the constructor). If I don't save B before creating A then when saving A the content_object_id is saved to the db as NULL. If I save B before passing it to the constructor of A then everything's allright. It's not logical. I assumed that the ID of the related object (B) is fetched when doing A.save() and it should throw some kind of an exception if B isn't saved yet but it just fails silently. I don't like the current solution (saving B beforhand) because we don't know yet if I will be always willing to keep the object, not just scrap it, and there are performance considerations - what if I will add some another data and save it once more shortly after. class BaseNodeData(models.Model): ... extnodedata_content_type = models.ForeignKey(ContentType, null=True) extnodedata_object_id = models.PositiveIntegerField(null=True) extnodedata = generic.GenericForeignKey(ct_field='extnodedata_content_type', fk_field='extnodedata_object_id') class MarkupNodeData(models.Model): raw_content = models.TextField() Suppose we do: markup = MarkupNodeData(raw_content='...') base = BaseNodeData(..., extnodedata=markup) markup.save() base.save() # both records are inserted to the DB but base is stored with extnodedata_object_id=NULL markup = MarkupNodeData(raw_content='...') base = BaseNodeData(..., extnodedata=markup) base.save() markup.save() # no exception is thrown and everything is the same as above markup = MarkupNodeData(raw_content='...') markup.save() base = BaseNodeData(..., extnodedata=markup) base.save() # this works as expected Of course I can do it this way, but it doesn't change anything: base = BaseNodeData(...) base.extnodedata = markup My question is - is this a bug in django which I should report or maybe I'm doing something wrong. Docs on GenericRelations aren't exactly verbose.

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  • Copy one object to another

    - by developer
    Hi All, I have 2 tables, user and userprofile. The userprofile table has a lot of fields similar to the user table. What I need to do is, on click of a button I need to copy all the fields of user table to userprofile table. UserModel AttData = UserModel[0]; DataServices.Save((UserProfile)AttData.ProfileModel.Instance); UserModel[0] contains all the data in user table. I want to copy this data to AttData.ProfileModel.Instance. How can I do that?

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  • Starting a SKProductsRequest gives -[_NSCFArray length] invalid selector error a moment later. LoadMicroPaymentsProductsOperation error.

    - by quantumpotato
    I'm fetching a list of identifiers from my server, then passing them off in a products request to Apple. Here's my code, and below is the error I'm getting. The iPhone 4 is not crashing when this happens. -(void)didReceiveData:(NSArray *)data { NSLog(@"Received Identifiers: %@",data); NSSet *productIdentifiers = [NSSet setWithArray:data]; SKProductsRequest *productsRequest = [[SKProductsRequest alloc] initWithProductIdentifiers:productIdentifiers]; productsRequest.delegate = self; [productsRequest start]; NSLog(@"productsRequest should have started by now"); } Wed Dec 29 09:42:14 iPhone XXXX-iphone[6363] <Warning>: Received Identifiers: ( ( 1, 10, "com.XXXX.XXXX.10" ) ) Wed Dec 29 09:42:14 iPhone XXXX-iphone[6363] <Warning>: productsRequest should have started by now Wed Dec 29 09:42:18 iPhone itunesstored[6367] : -[__NSCFArray length]: unrecognized selector sent to instance 0x119070 Wed Dec 29 09:42:18 iPhone itunesstored[6367] : caught -[__NSCFArray length]: unrecognized selector sent to instance 0x119070 exception with stack trace: (0x33ac0975 0x3347b49d 0x33ac2133 0x33a69aa9 0x33a69860 0x2717b 0x27515 0x31469651 0x314693ed 0x31469e39 0x3362795f 0x336276c3 0x3363c4eb 0x33c32680 0x33c32ba0 0x33bd7251 0x33bcf978)

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  • How to choose programaticaly the column to be queried by Linq using PropertyInfo???

    - by Richard77
    Hello, I would like to control how linq querries my database programaticaly. For instance, I'd like to query the column X, column Y, or column Z, depending on some conditions. First of all, I've created an array of all the properties inside my class called myPropertyInfo. Type MyType = (typeOf(MyClass)); PropertyInfo[] myPropertyInfo = myType.GetProperties( BindingFlags.Public|BindingFlags.Instance); The myPropertyInfo array allows me to access each property details (Name, propertyType, etc) through the index*[i]* Now, how can I use the above information to control how linq queries my DB? Here's a sample of a querry I'd like to exploit. var myVar = from tp in db.MyClass select tp.{expression}; Expression using myPropertyInfo[i] to choose which property(column) to query. I'm not sure if that's the way of doing it, but if there's another way to do so, I'll be glad to learn. Thanks for helping.

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  • website inserting pics

    - by onfire4JesusCollins
    Hello i am getting this error message : Object reference not set to an instance of an object. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.NullReferenceException: Object reference not set to an instance of an object. Source Error: Line 7: Line 8: Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load Line 9: UserIdValue.Text = Membership.GetUser().ProviderUserKey.ToString() Line 10: cannotUploadImageMessage.Visible = False Line 11: End Sub can someone help me with this?

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  • Build git on embedded system

    - by naive231
    I want to build git on our embedded system and I got git's source code from here. I run ./configure tool with following arguments: ./configure --build=arm-eabi --host=`uname -p`-`uname -s`-`uname -o` Configure tool runs, and returns an error says: checking whether system succeeds to read fopen'ed directory...configure: error: in`/home/git-1.8.0.2`. I set necessary environment variables like CC and CXX to our tool chain already, so ./configure complains nothing about compilers. But I have no idea about that error message. It looks like some permission problem, but I have full permission of /home/git-1.8.0.2 for sure. Any idea ?

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