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  • C++ static virtual members?

    - by cvb
    Is it possible in C++ to have a member function that is both static and virtual? Apperantly, there isn't a straight-forward way to do it (static virtual member(); is a complie error), but at least a way to acheive the same effect? I.E: struct Object { struct TypeInformation; static virtual const TypeInformation &GetTypeInformation() const; }; struct SomeObject : public Object { static virtual const TypeInformation &GetTypeInformation() const; }; It makes sence to use GetTypeInformation() both on an instance (object->GetTypeInformation()) and on a class (SomeObject::GetTypeInformation()), which can be useful for comparsions and vital for templates. The only ways I can think of involves writing two functions / a function and a constant, per class, or use macros. Any other solutions?

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  • Make methods that do not depend on instance fields, static?

    - by m3th0dman
    Recently I started programming in Groovy for a integration testing framework, for a Java project. I use Intellij IDEA with Groovy plug-in and I am surprised to see as a warning for all the methods that are non-static and do not depend on any instance fields. In Java, however, this is not an issue (at least from IDE's point of view). Should all methods that do not depend onto any instance fields be transformed into static functions? If true, is this specific to Groovy or it is available for OOP in general? And why?

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  • What is the difference between all-static-methods and applying a singleton pattern?

    - by shahensha
    I am making a database to store information about the users of my website (I am using stuts2 and hence Java EE technology). For the database I'll be making a DBManager. Should I apply singleton pattern here or rather make all it's methods static? I will be using this DBManager for basic things like adding, deleting and updating User profiles. Along with it, I'll use for all other querying purposes, for instance to find out whether a username already exists and to get all users for administrative purposes and stuff like that. My questions What is the benefit of singleton pattern? Which thing is most apt here? All static methods or a singleton pattern? Please compare both of them. regards shahensha P.S. The database is bigger than this. Here I am talking only about the tables which I'll be using for storing User Information.

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  • Requriing static class setter to be called before Constructor, bad design?

    - by roverred
    I have a class, say Foo, and every instance of Foo will need and contain the same List object, myList. Since every class instance will share the same List Object, I thought it would be good to make myList static and use a static function to set myList before the constructor is called. I was wondering if this was bad, because this requires the setter to be called before the constructor. If the person doesn't, the program will crash. Alternative way would be passing myList every time. Thanks.

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  • What is the difference between all-static-methods and applying a singleton pattern?

    - by shahensha
    I am making a database to store information about the users of my website (I am using stuts2 and hence Java EE technology). For the database I'll be making a DBManager. Should I apply singleton pattern here or rather make all it's methods static? I will be using this DBManager for basic things like adding, deleting and updating User profiles. Along with it, I'll use for all other querying purposes, for instance to find out whether a username already exists and to get all users for administrative purposes and stuff like that. My questions What is the benefit of singleton pattern? Which thing is most apt here? All static methods or a singleton pattern? Please compare both of them. P.S. The database is bigger than this. Here I am talking only about the tables which I'll be using for storing User Information.

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  • Apache - Serving static files from different subdomain + machine

    - by rubayeet
    Here's the scenario A site is running on this domain - www.someserver.com I'm going to host subdomain.someserver.com on my machine. Let's say all the image files are under the directory 'img'. I don't want to copy all their images to my machine. So what should be the Apache directive(s) that'll map the request for an image, like http://subdomain.someserver.com/img/image.png to http://www.someserver.com/img/image.png

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  • Static Routes and the Routing Table

    - by TheD
    This is very much a learning question if someone would be happy to explain a couple of concepts. My question is - the default routing table that exists in, in my case, a default Windows 7 install, what do each of the routes in the table do? Here is a screenshot: The 10.128.4.0 is just a route I've added while messing. I understand from a question I posted on Superuser the first route is just a default route that will route all traffic for any IP to my default gateway on my Interface in use. But what about the others? And how would the routing table handle a machine with multiple NIC's, perhaps connected to two different networks, or maybe even two NIC's on the same network so a VM can have a physical Network card instead of each VM sharing the hosts. Thanks!

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  • Static Route Qestion

    - by mrlayance
    I have a Wan simulator between 2 networks. I can ping both networks from the wan simulator, but I can not ping from one network to the other. testr01 Fa0/0 10.0.0.1/24 FA0/1 192.168.0.1/30 | | Wan Sim 2 nics Eth0 192.168.0.2/30 | Eth1 192.168.1.2/30 | | testr02 Fa0/1 192.168.1.1/30 Fa0/0 10.1.0.2/24 I can not figure out what type of routes I need. On the route? On the Server? I guess all 10. traffic to the Fa0/0 ports? Thanks

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  • Generate static gallery

    - by theomega
    Hy, I need a (linux/shell) script which does the following: It takes a folder full of jpg-files, generates thumbnails and previews (maybe using imagemagik's convert) and creates a html-page which includes all the thumbnails, opens a preview using something like LightBox and links to the original size. Does somebody know a script which does this? I could write one on my own, but it would save me some time.

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  • Static initialization of a struct with class members

    - by JS Bangs
    I have a struct that's defined with a large number of vanilla char* pointers, but also an object member. When I try to statically initialize such a struct, I get a compiler error. typedef struct { const char* pszA; // ... snip ... const char* pszZ; SomeObject obj; } example_struct; // I only want to assign the first few members, the rest should be default example_struct ex = { "a", "b" }; SomeObject has a public default constructor with no arguments, so I didn't think this would be a problem. But when I try to compile this (using VS), I get the following error: error C2248: 'SomeObject::SomeObject' : cannot access private member declared in class 'SomeObject' Any idea why?

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  • Why are static classes considered “classes” and “reference types”?

    - by Timwi
    I’ve been pondering about the C# and CIL type system today and I’ve started to wonder why static classes are considered classes. There are many ways in which they are not really classes: A “normal” class can contain non-static members, a static class can’t. In this respect, a class is more similar to a struct than it is to a static class, and yet structs have a separate name. You can have a reference to an instance of a “normal” class, but not a static class (despite it being considered a “reference type”). In this respect, a class is more similar to an interface than it is to a static class, and yet interfaces have a separate name. The name of a static class can never be used in any place where a type name would normally fit: you can’t declare a variable of this type, you can’t use it as a base type, and you can’t use it as a generic type parameter. In this respect, static classes are somewhat more like namespaces. A “normal” class can implement interfaces. Once again, that makes classes more similar to structs than to static classes. A “normal” class can inherit from another class. It is also bizarre that static classes are considered to derive from System.Object. Although this allows them to “inherit” the static methods Equals and ReferenceEquals, the purpose of that inheritance is questionable as you would call those methods on object anyway. C# even allows you to specify that useless inheritance explicitly on static classes, but not on interfaces or structs, where the implicit derivation from object and System.ValueType, respectively, actually has a purpose. Regarding the subset-of-features argument: Static classes have a subset of the features of classes, but they also have a subset of the features of structs. All of the things that make a class distinct from the other kinds of type, do not seem to apply to static classes. Regarding the typeof argument: Making a static class into a new and different kind of type does not preclude it from being used in typeof. Given the sheer oddity of static classes, and the scarcity of similarities between them and “normal” classes, shouldn’t they have been made into a separate kind of type instead of a special kind of class?

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  • Variables in static library are never initialized. Why?

    - by Coyote
    I have a bunch of variables that should be initialized then my game launches, but must of them are never initialized. Here is an example of the code: MyClass.h class MyClass : public BaseObject { DECLARE_CLASS_RTTI(MyClass, BaseObject); ... }; MyClass.cpp REGISTER_CLASS(MyClass) Where REGISTER_CLASS is a macro defined as follow #define REGISTER_CLASS(className)\ class __registryItem##className : public __registryItemBase {\ virtual className* Alloc(){ return NEW className(); }\ virtual BaseObject::RTTI& GetRTTI(){ return className::RTTI; }\ }\ \ const __registryItem##className __registeredItem##className(#className); and __registryItemBase looks like this: class __registryItemBase { __registryItemBase(const _string name):mName(name){ ClassRegistry::Register(this); } const _string mName; virtual BaseObject* Alloc() = 0; virtual BaseObject::RTTI& GetRTTI() = 0; } Now the code is similar to what I currently have and what I have works flawlessly, all the registered classes are registered to a ClassManager before main(...) is called. I'm able to instantiate and configure components from scripts and auto-register them to the right system etc... The problem arrises when I create a static library (currently for the iPhone, but I fear it will happen with android as well). In that case the code in the .cpp files is never registered. Why is the resulting code not executed when it is in the library while the same code in the program's binary is always executed? Bonus questions: For this to work in the static library, what should I do? Is there something I am missing? Do I need to pass a flag when building the lib? Should I create another structure and init all the __registeredItem##className using that structure?

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  • Static method not called

    - by Smile
    I'm trying to call a static method (printABC()) in this class but it's not working. If I uncomment both of the lines marked T_T (1 and 2), it works! Why does it fail with only one of the lines? import java.util.Scanner; class pro0009 { static Scanner in = new Scanner(System.in); static int A,B,C; static void printABC(){ String ABC = in.nextLine(); ABC=ABC.replace("A"," "+A+" "); ABC=ABC.replace("B"," "+B+" "); ABC=ABC.replace("C"," "+C+" "); //System.out.print(ABC.substring(1)); System.out.print(ABC); } public static void main(String[] args){ int x = in.nextInt(); //1 int y = in.nextInt(); //2 int z = in.nextInt(); //3 if(x<y){//1<2 if(x<z){ //1<3 if(y<z){//x<y<z 2<3 //1<2<3 A=x; B=y; C=z; printABC();//T_T 1 System.out.println("Here"); //pro0009.printABC();//T_T 2 //System.out.println("Here2"); }else{ //x<z<y A=x; B=z; C=y; } }else{//z<x<y A=z; B=x; C=y; } }else{//y<x if(y<z){ if(x<z){//y<x<z A=y; B=x; C=z; }else{//y<z<x A=y; B=z; C=x; } }else{//z<y<x A=z; B=y; C=x; } } } }

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  • Accessing Static Methods on a Generic class in c#

    - by mrlane
    Hello, I have the following situation in code, which I suspect may be a bit dodgey: I have a class: abstract class DataAccessBase<T> : IDataAccess where T : AnotherAbstractClass This class DataAccessBase also has a static factory method which creates instances of derived classes of itself using an enum value in a which statement to decide which derived type to create: static IDataAccess CreateInstance(TypeToCreateEnum) Now, the types derived from DataAccessBase<T> are themselves NOT generic, they specify a type for T: class PoLcZoneData : DataAccessBase<PoLcZone> // PoLcZone is derived from AnotherAbstractClass So far I am not sure if this is pushing the limits of good use of generics, but what I am really concerned about is how to access the static CreateInstance() method in the first place: The way I am doing this at the moment is to simply pass any type T where T : AnotherAbstractClass. In particular I am passing AnotherAbstractClass itself. This allows compilation just fine, but it does seem to me that passing any type to a generic class just to get at the statics is a bit dodgey. I have actually simplified the situation somewhat as DataAccessBase<T> is the lower level in the inheritance chain, but the static factory methods exists in a middle tier with classes such as PoLcZoneData being the most derived on the only level that is not generic. What are peoples thoughts on this arrangement?

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  • Thread-safe initialization of function-local static const objects

    - by sbi
    This question made me question a practice I had been following for years. For thread-safe initialization of function-local static const objects I protect the actual construction of the object, but not the initialization of the function-local reference referring to it. Something like this: namspace { const some_type& create_const_thingy() { lock my_lock(some_mutex); static const some_type the_const_thingy; return the_const_thingy; } } void use_const_thingy() { static const some_type& the_const_thingy = create_const_thingy(); // use the_const_thingy } The idea is that locking takes time, and if the reference is overwritten by several threads, it won't matter. I'd be interested if this is safe enough in practice? safe according to The Rules? (I know, the current standard doesn't even know what "concurrency" is, but what about trampling over an already initialized reference? And do other standards, like POSIX, have something to say that's relevant to this?) For the inquiring minds: Many such function-local static const objects I used are maps which are initialized from const arrays upon first use and used for lookup. For example, I have a few XML parsers where tag name strings are mapped to enum values, so I could later switch over the tags enum values.

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  • Categories in static library for iPhone device 3.0

    - by Nick
    I have categories in my static library. Any application developer should set -ObjC flag to "Other Linker Flags" to use my static library properly. It works fine for iPhone device/iPhone Simulator 2.x and iPhone Simulator 3.0. But it crashes for iPhone device 3.0. As written in this article it is new linker bug. They suggest to use one more linker flag: -all_load. But when I add this flag, build fails too, because there are duplicate symbols. How to use categories in static libraries for iPhone device 3.0? Any suggestions?

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  • DLL export of a static function

    - by Begbie00
    Hi all - I have the following static function: static inline HandVal StdDeck_StdRules_EVAL_N( StdDeck_CardMask cards, int n_cards ) Can I export this function in a DLL? If so, how? Thanks, Mike Background information: I'm doing this because the original source code came with a VS project designed to compile as a static (.lib) library. In order to use ctypes/Python, I'm converting the project to a DLL. I started a VS project as a DLL and imported the original source code. The project builds into a DLL, but none of the functions (including functions such as the one listed above) are exported (as confirmed by both the absence of dllexport in the source code and tools such as DLL Export Viewer). I tried to follow the general advice here (create an exportable wrapper function within the header) to no avail...functions still don't appear to be exported.

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  • accessing a static property via COM

    - by joreg
    is it possible to access a static property of a COM object without creating an instance of the object? my situation is this: i have an unmanaged application (written in delphi). this application exposes a COM-based plugininterface. until now i only wrote managed plugins in c#. plugins provide their info (name, author, ..) via a static property that returns an instance of PluginInfo (which implements IPluginInfo). this static property i can access on the managed plugins using http://managedvcl.com. now i want to write unmanaged plugins on the same interface. i can load them using: plug := CreateComObject(TGuid) as IMyPlugInterface; and they run, but i don't know how to read out their PluginInfo. so the question again is: is there another way than implementing IPluginInfo in the plugin-class and only accessing the info after i have created an instance of the plugin?

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  • .NET: will Random.Random operate differently inside a static method

    - by Craig Johnston
    I am having difficulty with the following code which is inside a static method of a non-static class. int iRand; int rand; rand = new Random((int)DateTime.Now.Ticks); iRand = rand.Next(50000); The iRand number, along with some other values, are being inserted into a new row of an Access MDB table via OLEDB. The iRand number is being inserted into a field that is part of the primary key, and the insert attempt is throwing the following exception even though the iRand number is supposed to be random: System.Data.OleDb.OleDbException: The changes you requested to the table were not successful because they would create duplicate values in the index, primary key, or relationship. Change the data in the field or fields that contain duplicate data, remove the index, or redefine the index to permit duplicate entries and try again. Could the fact the method is static be making the iRand number stay the same, for some reason?

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  • Java: startingPath as "public static final" exception

    - by HH
    [Updated] Thanks to polygenelubricants's reply, the real problem is the exception from the method getCanonicalPath() because I cannot include try-catch-loop there. $ cat StartingPath.java import java.util.*; import java.io.*; public class StartingPath { public static final String startingPath = (new File(".")).getCanonicalPath(); public static void main(String[] args){ System.out.println(startingPath); } } $ javac StartingPath.java StartingPath.java:5: unreported exception java.io.IOException; must be caught or declared to be thrown public static final String startingPath = (new File(".")).getCanonicalPath(); ^ 1 error

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  • Finding C++ static initialization order problems

    - by Fred Larson
    We've run into some problems with the static initialization order fiasco, and I'm looking for ways to comb through a whole lot of code to find possible occurrences. Any suggestions on how to do this efficiently? Edit: I'm getting some good answers on how to SOLVE the static initialization order problem, but that's not really my question. I'd like to know how to FIND objects that are subject to this problem. Evan's answer seems to be the best so far in this regard; I don't think we can use valgrind, but we may have memory analysis tools that could perform a similar function. That would catch problems only where the initialization order is wrong for a given build, and the order can change with each build. Perhaps there's a static analysis tool that would catch this. Our platform is IBM XLC/C++ compiler running on AIX.

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  • Returning in a static class constructor

    - by Martijn Courteaux
    Hello, This isn't valid code: public class MyClass { private static boolean yesNo = false; static { if (yesNo) { System.out.println("Yes"); return; // The return statement is the problem } System.exit(0); } } This is a stupid example, but in a static class constructor we can't return;. Why? Are there good reasons for this? Does someone know something more about this? So the reason why I should do return is to end constructing there. Thanks

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  • Why is this static routing not working ?

    - by geeko
    Greeting gurus, I'm trying to develop a DHCP enforcement extension like Microsoft NAP. My trick to block dynamic-IP requesting machines (that don't meet certain policy) is to strip the default gateway (no default gateway) stated in the IP lease and set the lease subnet mask to 255.255.255.255. Now I need the blocked machines to be able to reach some specific locations (IPs) on the network. To allow for this, I'm including some static routes in the lease. For example, I'm including 10.10.10.11 via router 10.10.10.254 (the one to which the blocked machine that needs to access 10.10.10.11 is connected). Unfortunately, as soon as I set the default gateway to nothing, blocked machines cannot reach any of the added static routes. I also tried classless static routes. Any ideas ? any one knows how MS NAP actually do it ? Geeko

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