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• How do I change the class of an object to a subclass of its current class in C++?

  - by Jared P

  I have an array of pointers to a base class, so that I can make those pointers point to (different) subclasses of the base class, but still interact with them. (really only a couple of methods which I made virtual and overloaded) I'm wondering if I can avoid using the pointers, and instead just make an array of the base class, but have some way to set the class to the subclass of my choosing. I know there must be something there specifying the class, as it needs to use that to look up the function pointer for virtual methods. By the way, the subclasses all have the same ivars and layout. Note: the design is actually based on using a template argument instead of a variable, due to performance increases, so really the abstract base class is just the interface for the subclasses, which are all the same except for their compiled code. Thanks

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• c++ when to put method out side the class

  - by user63898

  i saw that some times in c++ applications using only namespace declarations with header and source file like this : #ifndef _UT_ #define _UT_ #include <string> #include <windows.h> namespace UT { void setRootPath(char* program_path, char* file_path); char * ConvertStringToCharP(std::string str); }; #endif //and then in UT.cpp #include "UT.h" namespace UT { char * ConvertStringToCharP(std::string str) { char * writable = new char[str.size() + 1]; std::copy(str.begin(), str.end(), writable); writable[str.size()] = '\0'; return writable; } void setRootPath(char* program_path, char* file_path) { //... } } is it better then defining classic class with static methods? or just simple class ? dose this method has something better for the compiler linker ? the methods in this namespace are called allot of times .

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• ConcurentModificationException in Java HashMap

  - by Bear

  Suppose I have two methods in my classes, writeToMap() and processKey() and both methods are called by multiple threads. writeToMap is a method to write something in hashmap and processKey() is used to do sth based on the keySet of HashMap. Inside processKey, I first copy the originalMap before getting the key set. new HashMap<String, Map<String,String>(originalMap).get("xx").keySet(); But I am still getting ConcurrentModificationException even though I always copy the hashmap. Whats the problem?

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• How can unit testing make parameter validation redundant?

  - by Johann Gerell

  We have a convention to validate all parameters of constructors and public functions/methods. For mandatory parameters of reference type, we mainly check for non-null and that's the chief validation in constructors, where we set up mandatory dependencies of the type. The number one reason why we do this is to catch that error early and not get a null reference exception a few hours down the line without knowing where or when the faulty parameter was introduced. As we start transitioning to more and more TDD, some team members feel the validation is redundant. Uncle Bob, who is a vocal advocate of TDD, strongly advices against doing parameter validation. His main argument seems to be "I have a suite of unit tests that makes sure everything works". But I can for the life of it just not see in what way unit tests can prevent our developers from calling these methods with bad parameters in production code. Please, unit testers out there, if you could explain this to me in a rational way with concrete examples, I'd be more than happy to seize this parameter validation!

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• naming a method - using set() when *not* setting a property?

  - by user151841

  Is setX() method name appropriate for only for setting class property X? For instance, I have a class where the output is a string of an html table. Before you can you can call getTable, you have to call setTable(), which just looks at a other properties and decides how to construct the table. It doesn't actually directly set any class property -- only causes the property to be set. When it's called, the class will construct strHtmlTable, but you can't specify it. So, calling it setTable breaks the convention of get and set being interfaces for class properties. Is there another naming convention for this kind of method? Edit: in this particular class, there are at least two ( and in total 8 optional ) other methods that must be called before the class knows everything it needs to to construct the table. I chose to have the data set as separate methods rather than clutter up the __construct() with 8 optional parameters which I'll never remember the order of.

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• Playing a .wav sound file in JPanel/JFrame using javax (Swing)

  - by JavaIceCream

  I need some code example on how I would use a filepath from a harddrive location to then play a .wav sound file when opened in swing GUI. I don't need it to show a play button, or pause or stop. I just want it to play when I select the 'Sound' option from my 'Files' in my window (I know how to do that already, no need to explain that). So basically, just how to play a .wav sound file from a filepath (i.e. c:/cake/thereisnone.wav) inside of a JFrame. And how can I easily apply methods to that sound file afterwards. Also, if anyone knows how to apply methods on a BufferedImage in a JFrame, that would be helpful too. Thank you very much everyone!

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• [iOS] How to catch cancallation of UIScrollView or others?

  - by kyu

  Sometimes, interruptions such as phone call occur and disturb a regular behavior of an app in iPhone or iPad. For example, I created one UIScrollView instance and implemented UIScrollView delegate methods: scrollViewWillBeginDragging and scrollViewDidEndDragging(and scrollViewDidEndDecelerating). A scrollViewWillBeginDragging method deactivated all custom buttons in my app. Then scrollViewDidEndDragging and scrollViewDidEndDecelerating methods activated these custom buttons. That is, while the user scrolled, all custom buttons became deactivated for a while. The problem was that while the user started to drag and just held an UIScrollView instance, if I took a screenshot by pressing a home button and a power button, then any of scrollViewDidEndDragging and scrollViewDidEndDecelerating didn't get called. So the app became messed up. I implemented a UIApplicationWillResignActiveNotification method in my UIViewController, but it didn't get called after taking a screenshot. How can I catch any kind of interruption that disturbs a regular flow of events? Sometimes, touchesEnd and touchesCanceled didn't get called too due to an interruption. Thank you.

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• Backward compatibility in dlls

  - by michaelleuzinger

  Hi I do have three dlls. a.dll - released many years ago b.dll - released not so many years c.dll - released shortly Each one contains the same function - unfortunatelly with different parameters. so I do have the following Methods aMethod(param1) aMethod(param1, param2) aMethod(param1, param2, param3) My Task is to make a new dll (or new dlls) wich is backward compatible. But as far as I've learned from Google there is no possibility to overload methods in a dll. Does any one have a tip how I can solve this problem elegantly? -- Michael

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• Is it bad practice to use Reflection in Unit testing?

  - by Sebi

  During the last years I always thought that in Java, Reflection is widely used during Unit testing. Since some of the variables/methods which have to be checked are private, it is somehow necessary to read the values of them. I always thought that the Reflection API is also used for this purpose. Last week i had to test some packages and therefore write some JUnit tests. As always i used Reflection to access private fields and methods. But my supervisor who checked the code wasn't really happy with that and told me that the Reflection API wasn't meant to use for such "hacking". Instead he suggested to modifiy the visibility in the production code. Is it really bad practice to use Reflection? I can't really believe that

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• Why would I want to have a non-standard attribute?

  - by dontWatchMyProfile

  The documentation on Core Data entities says: You might implement a custom class, for example, to provide custom accessor or validation methods, to use non-standard attributes, to specify dependent keys, to calculate derived values, or to implement any other custom logic. I stumbled over the non-standard attributes claim. It's just a guess: If my attribute is anything other than NSString, NSNumber or NSDate I will want to have a non-standard Attribute with special setter and getter methods? So, for example, if I wanted to store an image, this would be a non-standard Attribute with type NSData and a special method, say -(void)setImageWithFileURL:(NSURL*)url which then pulls the image data from the file, puts in in an NSData and assigns it to core data? Or did I get that wrong?

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• Unit testing with Data Access Layer

  - by chobo

  Hi, what is a good way to write unit tests with a LINQ to SQL DAL? Currently I am doing some database testing and need to create helper methods that access the database, but I don't want those methods in my main repo's. So what I have is two copies of the DAL, one in my main project and one in the Test project. Is it easier to manage these things if I create a separate project for the data layer? I'm not sure which way is a better way to approach this. If I do create a data layer project would I move all my repo's to that project as well? I'm not sure how to properly setup the layers. Thanks

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• How can I print a text in two columns using Java Swing?

  - by Jonas

  I have a longer text saved in a String. I would like to print the text in two columns on a single page. How can I do this using Java Swing? I don't understand how I can wrap the text when it's time to use a new line. I have read Lesson: Printing in the Java tutorial, but I haven't found any useful methods for working with text or Strings except FontMetrics. Is there any good methods in the Java API for this or is there any good library I can use for this?

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• Limiting what a .net plugin can access

  - by David Hogue

  I have a web application that can load plugins through reflection. It currently uses Assembly.LoadFrom() and Activator.CreateInstance() to get this done. Right now plugins are loaded into the same AppDomain and have access to anything in my app and anything my app could access. What I'm looking for is a way to limit what classes and methods the plugin can access for security purposes. I want to have all of my classes and methods throw an exception when called unless they are whitelisted. I'd be whitelisting basically all the functions in an API class and a few data transfer objects. I also don't want the plugin to be able to access the filesystem or the database on it's own. I think I can do that with trust levels in a separate AppDomain though. Does anyone out there have any good ideas or resources? Is this something that could be done with Code Access Security or the new Security-Transparent Code features in .net 4?

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• SSIS Script Component + Helper Assemblies (.dll's)

  - by Nev_Rahd

  I got a script component which does Transformation / DataType conversions / Creating some calculated columns. All the transform validations / datatype conversion methods and for new column generation is put into custom .dll. As this script component would be same for all other tables, only thing is to define input / ouput columns and apply validation methods on required columns. This all works fine. On production server where do I need to deploy my .dll. Would just putting it into GAC will be enough or need to do something else. Regards

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• Using iPhone Core Data to many Relationship

  - by BLeB

  When I define a to many relationship between entities in Xcode and then generate the data class from the entity I get a header with the following methods defined: @interface PriceList (CoreDataGeneratedAccessors) - (void)addItemsObject:(PriceListItem *)value; - (void)removeItemsObject:(PriceListItem *)value; - (void)addItems:(NSSet *)value; - (void)removeItems:(NSSet *)value; @end When I attempt to call addItemsObject with the following code a doesNotRecognizeSelector exception is thrown. PriceListItem *item = [NSEntityDescription insertNewObjectForEntityForName:@"PriceListItem" inManagedObjectContext:managedObjectContext]; item.cat = [attributeDict valueForKey:@"c"]; item.sel = [attributeDict valueForKey:@"s"]; [self addItemsObject:item]; From what I have read I do not have to implement these methods and that they are generated at runtime. Any ideas?

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• SWIG interface file questions

  - by morpheous

  I am writing a C/C++ extension module for other languages and I am using SWIG to generate the bindings. I have two questions Can I include more than 1 header file in the declaration part of the interface file e.g.: /* Declarations exposed to wrapper: */ > %{ > #define SWIG_FILE_WITH_INIT > #include "a.h" > #include "b.h" > #include "c.h" %} In all of the examples I have seen so far, after the header include declaration (as shown above), the functions declared in the header are then declared again in the interface file. Is this really necessary, as it means there are two copies of the function declarations that need to be maintained. Note: I can appreciate that some functions/methods declaration may need to be 'decorated' with the 'newobject' declaration so these obviously need to be in the interface file, to avoid memory leaks - however, I would have though that it would be sufficient to include the headers and then ONLY the declarations of the functions/methods that need to be declared with 'newobject' - is this recommended way of doing things?

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• Can I add a custom method to Core Data-generated classes?

  - by Andy

  I've got a couple of Core Data-generated class files that I'd like to add custom methods to. I don't need to add any instance variables. How can I do this? I tried adding a category of methods: // ContactMethods.h (my category on Core Data-generated "Contact" class) #import "Contact.h" @interface Contact (ContactMethods) -(NSString*)displayName; @end ... // ContactMethods.m #import "ContactMethods.h" @implementation Contact (ContactMethods) -(NSString*)displayName { return @"Some Name"; // this is test code } @end This doesn't work, though. I get a compiler message that "-NSManagedObject may not respond to 'displayName' " and sure enough, when I run the app, I don't get "Some Name" where I should be seeing it.

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• R: Change the fields' (slots') values of the class assigning a value to some other field

  - by Max Li

  Assgning a value to one field, how can I make the other fields changing. Consider the following R5 class C<-setRefClass("C", fields=list(a="numeric",b="numeric") , methods=list( seta = function(x){ a<<-x b<<-x+10 cat("The change took place!") } ) # end of the methods list ) # end of the class Now create the instance of the class c<-C$new() This command c$seta(10) will result in that c$a is 10 and c$b is 20. So it actually works, however, I want to achieve this result by the command c$a<-10 (i.e. after that I want c$b to be equal to 20 as defined in the class in the logic of seta() function) How can I do it?

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• Java Package, Project , NoSuchMethod error

  - by hamam

  I have 2 projects linked and these 2 projects each have a package under them. XProject - XPackage - XClass - X1Method(); X2Method(); YProject - YPackage - YClass - Y1Method(); I'm trying to call X1 and X2 methods from Y1 Method. I can call X1 Method but when I call X2 method I get a runtime error (java.lang.NoSuchMethodError:) All methods are public and there is nothing wrong with method names. It is just nonsense to have one of them working while other is giving runtime errors. Any help would be appreciated. Thanks.

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• What exactly does reloadData call?

  - by Sheehan Alam

  When calling reloadData on a UITableView what methods are actually invoked? [tableView reloadData];

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• Should properties in C# perform a lot of work?

  - by Hamish Grubijan

  When a property is read from or is assigned to, one would not expect it to perform a lot of work. When setSomeValue(...) and getSomeValue(...) methods are used instead, one should not be that surprised that something non-trivial might be going on under the hood. However, now that C# gave the world Properties, it seems silly to use getter and setter methods instead. What is your take on this? Should I mark this Q as a community wiki? Thanks.

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• Get machine name from Active Directory

  - by Stephen Murby

  I have performed an "LDAP://" query to get a list of computers within a specified OU, my issue is not being able to collect just the computer "name" or even "cn". DirectoryEntry toShutdown = new DirectoryEntry("LDAP://" + comboBox1.Text.ToString()); DirectorySearcher machineSearch = new DirectorySearcher(toShutdown); //machineSearch.Filter = "(objectCatergory=computer)"; machineSearch.Filter = "(objectClass=computer)"; machineSearch.SearchScope = SearchScope.Subtree; machineSearch.PropertiesToLoad.Add("name"); SearchResultCollection allMachinesCollected = machineSearch.FindAll(); Methods myMethods = new Methods(); string pcName; foreach (SearchResult oneMachine in allMachinesCollected) { //pcName = oneMachine.Properties.PropertyNames.ToString(); pcName = oneMachine.Properties["name"].ToString(); MessageBox.Show(pcName); } Help much appreciated.

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• Why Enumerable doesn't inherits from IEnumerable<T>

  - by sajjadlove

  Hi All I'm very confused about this issue and can't to underestand it.In the Enumerable Documentation, I readed this: that implement System.Collections.Generic.IEnumerable and some methods like Select() return IEnumerable that we can use from other methods like Where() after using that.for example: names.Select(name => name).Where(name => name.Length > 3 ); but Enumerable doesn't inherits from IEnumerable and IEnumerable doesn't contain Select(),Where() and etc too... have i wrong ? or exists any reason for this?

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• Why Controller doesn't recognize a public method which (yet) appears in the intellisense ?

  - by Richard77

  Hello, I'm using an helper class that I called CreateEditOrganizationService where I put all the helper methods. In my controller, I've createService as object of that class. So far, I've got 5 methods. Now, I've just defined a 6th method called Set_TypeOrganization. I'm getting the Set_TypeOrganization in the intellisense, but after I've chose it, I get the following error: *CreateEditOrganizationService does not contain a definition for Set_TypeOrganization are you missing a directive or a reference?* public List<TypeOrganization> Set_TypeOrganization(string choice) { //Definition goes here... } and in my Controller CreateEditOrganizationService createService = new CreateEditOrganizationService(); //... ViewData["TypeOrganizations"] = createService.Set_TypeOrganization(choice); Unfortunately, VS shows me the error? Yet, the method appear in the intellisense when I type a dot after the createService object. Thannks for helping

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• Is there a TextWriter interface to the System.Diagnostics.Debug class?

  - by John Källén

  I'm often frustrated by the System.Diagnostics.Debug.Write/WriteLine methods. I would like to use the Write/WriteLine methods familiar from the TextWriter class, so I often write Debug.WriteLine("# entries {0} for connection {1}", countOfEntries, connection); which causes a compiler error. I end up writing Debug.WriteLine(string.Format("# entries {0} for connection {1}", countOfEntries, connection)); which is really awkward. Does the CLR have a class deriving from TextWriter that "wraps" System.Debug, or should I roll my own?

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