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  • Copying a Polymorphic object in C++

    - by doron
    I have base-class Base from which is derived Derived1, Derived2 and Derived3. I have constructed an instance for one of the the derived classes which I store as Base* a. I now need to make a deep copy of the object which I will store as Base* b. As far as I know, the normal way of copying a class is to use copy constructors and to overload operator=. However since I don't know whether a is of type Derived1, Derived2 or Derived3, I cannot think of a way of using either the copy constructor or operator=. The only way I can think of to cleanly make this work is to implement something like: class Base { public: virtual Base* Clone() = 0; }; and the implement Clone in in the derived class as in: class Derivedn : public Base { public: Base* Clone() { Derived1* ret = new Derived1; copy all the data members } }; Java tends to use Clone quite a bit is there more of a C++ way of doing this?

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  • A c# Generics question involving Controllers and Repositories

    - by UpTheCreek
    I have a base repository class which contains all the common repository methods (as generic): public abstract class BaseRepository<T, IdType> : IBaseRepository<T, IdType> My repositories from this base e.g.: public class UserRepository : BaseRepository<User, int>, IUserRepository I also have a base controller class containing common actions, and inherit from this in controllers. The repository is injected into this by DI. E.g. public class UserController : BaseController<User> { private readonly IUserRepository userRepository; public UserController (IUserRepository userRepository) { this.userRepository= userRepository; } My question is this: The base controller needs to be able to access the repository methods that are defined in the base repository. However I'm passing in via DI a different repository type for each controller (even though they all inherrit from the base repository). How can the base controller somehow access the repository that is passed in (regardless of what type it is), so that it can access the common base methods?

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  • Base SDK Missing? No, I fixed that. Still?!

    - by Moshe
    XCode 3.2.3 Beta does not allow building for below 3.2. I opened a project that was made in an earlier XCode. For some reason, the base SDK is reported as missing even after changing it to 4.0. Other projects from earlier XCode do not have this issue. What can I do?

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  • How to handle building and parsing HTTP URL's / URI's / paths in Perl

    - by Robert S. Barnes
    I have a wget like script which downloads a page and then retrieves all the files linked in img tags on that page. Given the URL of the original page and the the link extracted from the img tag in that page I need to build the URL for the image file I want to retrieve. Currently I use a function I wrote: sub build_url { my ( $base, $path ) = @_; # if the path is absolute just prepend the domain to it if ($path =~ /^\//) { ($base) = $base =~ /^(?:http:\/\/)?(\w+(?:\.\w+)+)/; return "$base$path"; } my @base = split '/', $base; my @path = split '/', $path; # remove a trailing filename pop @base if $base =~ /[[:alnum:]]+\/[\w\d]+\.[\w]+$/; # check for relative paths my $relcount = $path =~ /(\.\.\/)/g; while ( $relcount-- ) { pop @base; shift @path; } return join '/', @base, @path; } The thing is, I'm surely not the first person solving this problem, and in fact it's such a general problem that I assume there must be some better, more standard way of dealing with it, using either a core module or something from CPAN - although via a core module is preferable. I was thinking about File::Spec but wasn't sure if it has all the functionality I would need.

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  • Does dynamic_cast work inside overloaded operator delete ?

    - by iammilind
    I came across this: struct Base { void* operator new (size_t); void operator delete (void*); virtual ~Base () {} // <--- polymorphic }; struct Derived : Base {}; void Base::operator delete (void *p) { Base *pB = static_cast<Base*>(p); if(dynamic_cast<Derived*>(pB) != 0) { /* ... NOT reaching here ? ... */ } free(p); } Now if we do, Base *p = new Derived; delete p; Surprisingly, the condition inside the Base::delete is not satisfied Am I doing anything wrong ? Or casting from void* looses the information of Derived* ?

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  • How to approach huge code base of undocumented code?

    - by nimo9367
    I have recently been assigned a project to further develop an existing code base. The code doesn't contain any tests and not even one single line of comments. The whole "thing" is written in a really obfuscating manner so it takes a lot of time to figure out what happens. How do you usually approach this kind of problem? Tips and trix on how to handle this situation?

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  • Inheriting XML files and modifying values

    - by Veehmot
    This is a question about concept. I have an XML file, let's call it base: <base id="default"> <tags> <tag>tag_one</tag> <tag>tag_two</tag> <tag>tag_three</tag> </tags> <data> <data_a>blue</data_a> <data_b>3</data_b> </data> </base> What I want to do is to be able to extend this XML in another file, modifying individual properties. For example, I want to inherit that file and make a new one with a different data/data_a node: <base id="green" import="default"> <data> <data_a>green</data_a> </data> </base> So far it's pretty simple, it replaces the old data/data_a with the new one. I even can add a new node: <base id="ext" import="default"> <moredata> <data>extended version</data> </moredata> </base> And still it's pretty simple. The problem comes when I want to delete a node or deal with XML Lists (like the tags node). How should I reference a particular index on a list? I was thinking doing something like: <base id="diffList" import="default"> <tags> <tag index="1">this is not anymore tag_two</tag> </tags> </base> And for deleting a node / array index: <base id="deleting" import="default"> <tags> <tag index="2"/> </tags> <data/> </base> <!-- This will result in an XML containing these values: --> <base> <tag>tag_one</tag> <tag>tag_two</tag> </base> But I'm not happy with my solutions. I don't know anything about XSLT or other XML transformation tools, but I think someone must have done this before. The key goal I'm looking for is ease to write the XML by hand (both the base and the "extended"). I'm open to new solutions besides XML, if they are easy to write manually. Thanks for reading.

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  • How well does knowledge of J2ME generalize to other mobile platforms?

    - by dimatura
    I'm considering taking mobile phone software development course at my university. The course uses J2ME with an emulator. I'm interested in software development for mobile phones, but I get the impression that J2ME is somewhat stale and limited in comparison to the newer platforms like the iPhone and Android. I'm most interested in Android, as I dislike the closed nature of the iPhone. So if I take the course, how well would the skills acquired transfer to a platform like Android? And I have a related question. I'm pretty comfortable with Java (and various other programming languages), but I haven't used J2ME. Is there anything that makes it particularly painful to program with? (Not that Java is that pleasant anyway :))

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  • Can JAXB store the class name in the XML so that the the deserialize code doesn't need knowledge of the class?

    - by Andrew
    It seems the standard approach for deserializing JAXB XML is to specify the package name when creating the context. Then, JAXB looks up the class based on the root element: JAXBContext jc = JAXBContext.newInstance("com.foo"); Unmarshaller u = jc.createUnmarshaller(); Object o = u.unmarshal(new StringReader("...")); I'm looking for a more flexible approach where I don't have to specify the package name and could still deserialize any object. This would be as simple as JAXB storing the package in the XML, but I can't seem to find out how to do this. I can write the code to do it myself but that would be unpleasant. It would like JAXB to do it, if possible. BTW, I am not using schemas, just Annotations and marshal/unmarshal. Any ideas?

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  • How can I build and parse HTTP URL's / URI's / paths in Perl?

    - by Robert S. Barnes
    I have a wget-like script which downloads a page and then retrieves all the files linked in IMG tags on that page. Given the URL of the original page and the the link extracted from the IMG tag in that page I need to build the URL for the image file I want to retrieve. Currently I use a function I wrote: sub build_url { my ( $base, $path ) = @_; # if the path is absolute just prepend the domain to it if ($path =~ /^\//) { ($base) = $base =~ /^(?:http:\/\/)?(\w+(?:\.\w+)+)/; return "$base$path"; } my @base = split '/', $base; my @path = split '/', $path; # remove a trailing filename pop @base if $base =~ /[[:alnum:]]+\/[\w\d]+\.[\w]+$/; # check for relative paths my $relcount = $path =~ /(\.\.\/)/g; while ( $relcount-- ) { pop @base; shift @path; } return join '/', @base, @path; } The thing is, I'm surely not the first person solving this problem, and in fact it's such a general problem that I assume there must be some better, more standard way of dealing with it, using either a core module or something from CPAN - although via a core module is preferable. I was thinking about File::Spec but wasn't sure if it has all the functionality I would need.

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  • What to do to improve my skill and knowledge on javascript??

    - by caramel1991
    Currently I've finish studying the book name "beginning javascript 3rd edition",so i just wonder what should be my next step in order to strengthen myself on using and manipulating this language?Besides,how to improve myself in programming in javascript??Is it by thinking something cool myself,and start coding it??Or googling around the internet to find some task and question offered??Besides,is there any book that teaches the correct method of coding?? Thanks you

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  • Sql Alchemy Duplicated Commit

    - by PythonWolf
    Good Morning i'm currently facing a problem in my Cherrypy application. Im my own custom session module , anyway when performing session.add() The exact same object gets updated Twice. cherrypy.request.SessionManager.user_data = user try: db_session.add(cherrypy.request.SessionManager) db_session.commit() Will Return 2011-06-21 09:16:48,991 INFO sqlalchemy.engine.base.Engine.0x...04cL BEGIN (implicit) 2011-06-21 09:16:49,015 INFO sqlalchemy.engine.base.Engine.0x...04cL SELECT ..... FROM "Clients_Users" WHERE "Clients_Users".username = %(username_1)s AND "Clients_Users".password = %(password_1)s LIMIT 1 OFFSET 0 2011-06-21 09:16:49,015 INFO sqlalchemy.engine.base.Engine.0x...04cL {'password_1': '123', 'username_1': u'1'} 2011-06-21 09:16:49,047 INFO sqlalchemy.engine.base.Engine.0x...04cL UPDATE "SYS_Sessions" SET user_data=%(user_data)s WHERE "SYS_Sessions".id = %(SYS_Sessions_id)s 2011-06-21 09:16:49,067 INFO sqlalchemy.engine.base.Engine.0x...04cL {'SYS_Sessions_id': 92L, 'user_data': } 2011-06-21 09:16:49,071 INFO sqlalchemy.engine.base.Engine.0x...04cL COMMIT 2011-06-21 09:16:49,093 INFO sqlalchemy.engine.base.Engine.0x...04cL BEGIN (implicit) 2011-06-21 09:16:49,095 INFO sqlalchemy.engine.base.Engine.0x...04cL UPDATE "SYS_Sessions" SET user_data=%(user_data)s WHERE "SYS_Sessions".id = %(SYS_Sessions_id)s 2011-06-21 09:16:49,095 INFO sqlalchemy.engine.base.Engine.0x...04cL {'SYS_Sessions_id': 92L, 'user_data': } 2011-06-21 09:16:49,108 INFO sqlalchemy.engine.base.Engine.0x...04cL COMMIT As Anyone seen this before ? P.S This doesn't happen in the rest of the modules i have made.

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  • Are programming languages and methods ineffective? (assembler and C knowledge needed)

    - by b-gen-jack-o-neill
    Hi, for a long time, I am thinking and studying output of C language compiler in asemlber form, as well as CPU architecture. I know this may be silly to you, but it seems to me that something is very ineffective. Please, don´t be angry if I am wrong, and there is some reason I do not see for all these principles. I will be very glad if you tell me why is it designed this way. I actually trully believe I am wrong, I know the genius minds of people which get PCs together knew a reason to do so. What exactly, do you ask? I´ll tell you right away, I use C as a example: 1, Stack local scope memory allocation: So, typical local memory allocation uses stack. Just copy esp to ebp and than allocate all the memory via ebp. OK, I would understand this if you explicitly need allocate RAM by default stack values, but if I do understand it correctly, modern OS use paging as a translation layer between application and physical RAM, when adress you desire is further translated before reaching actuall RAM byte. So why don´t just say 0x00000000 is int a,0x00000004 is int b and so? And access them just by mov 0x00000000,#10? Becouse you wont actually access memory blocks 0x00000000 and 0x00000004 but those your OS set the paging tables to. Actually, since memory allocation by ebp and esp use indirect adressing, "my" way would be even faster. 2, Variable allocation duplicitly: When you run aaplication, Loader load its code into RAM. When you create variable, or string, compiler generates code that pushes these values on the top o stack when created in main. So there is actuall instruction for do so, and that actuall number in memory. So, there are 2 entries of the same value in RAM. One in fomr of instruction, second in form of actuall bytes in the RAM. But why? Why not to just when declaring variable count at which memory block it would be, than when used, just insert this memory location?

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  • how can protected members of base class be accessed during unit test?

    - by amateur
    I am creating a unit test in mstest with rhino mocks. I have a class A that inherits class B. I am testing class A and create an instance of it for my test. The class it inherits, "B", has some protected methods and protected properties that I would like to access for the benefit of my tests. For example, validate that a protected property on my base class has the expected value. Any ideas how I might access these protected properties of class B during my test?

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  • Find all A^x in a given range

    - by Austin Henley
    I need to find all monomials in the form AX that when evaluated falls within a range from m to n. It is safe to say that the base A is greater than 1, the power X is greater than 2, and only integers need to be used. For example, in the range 50 to 100, the solutions would be: 2^6 3^4 4^3 My first attempt to solve this was to brute force all combinations of A and X that make "sense." However this becomes too slow when used for very large numbers in a big range since these solutions are used in part of much more intensive processing. Here is the code: def monoSearch(min, max): base = 2 power = 3 while 1: while base**power < max: if base**power > min: print "Found " + repr(base) + "^" + repr(power) + " = " + repr(base**power) power = power + 1 base = base + 1 power = 3 if base**power > max: break I could remove one base**power by saving the value in a temporary variable but I don't think that would make a drastic effect. I also wondered if using logarithms would be better or if there was a closed form expression for this. I am open to any optimizations or alternatives to finding the solutions.

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  • Custom base class for workflow activity , how to declare dependecy property ?

    - by Ajax2020
    Generally we derive custom activity from Activity or CompositeActivity class, i want to have my custom base class for all activities : like public class BusinessActivity : Activity { } then my custom activities will derive from BusinessActivity . The quetions is if i want ErrorMessageProperty and RetryCountProperty as dependency properties then in the BusinessActivity how to declare third param in Register method like public static DependencyProperty RetryCountProperty = DependencyProperty.Register("RetryCount", typeof(int), typeof(**BusinessActivity**)); What will happen if i derive from BusinessActivity class ?

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  • ASP.NET MVC: Converting business objects to select list items

    - by DigiMortal
    Some of our business classes are used to fill dropdown boxes or select lists. And often you have some base class for all your business classes. In this posting I will show you how to use base business class to write extension method that converts collection of business objects to ASP.NET MVC select list items without writing a lot of code. BusinessBase, BaseEntity and other base classes I prefer to have some base class for all my business classes so I can easily use them regardless of their type in contexts I need. NB! Some guys say that it is good idea to have base class for all your business classes and they also suggest you to have mappings done same way in database. Other guys say that it is good to have base class but you don’t have to have one master table in database that contains identities of all your business objects. It is up to you how and what you prefer to do but whatever you do – think and analyze first, please. :) To keep things maximally simple I will use very primitive base class in this example. This class has only Id property and that’s it. public class BaseEntity {     public virtual long Id { get; set; } } Now we have Id in base class and we have one more question to solve – how to better visualize our business objects? To users ID is not enough, they want something more informative. We can define some abstract property that all classes must implement. But there is also another option we can use – overriding ToString() method in our business classes. public class Product : BaseEntity {     public virtual string SKU { get; set; }     public virtual string Name { get; set; }       public override string ToString()     {         if (string.IsNullOrEmpty(Name))             return base.ToString();           return Name;     } } Although you can add more functionality and properties to your base class we are at point where we have what we needed: identity and human readable presentation of business objects. Writing list items converter Now we can write method that creates list items for us. public static class BaseEntityExtensions {            public static IEnumerable<SelectListItem> ToSelectListItems<T>         (this IList<T> baseEntities) where T : BaseEntity     {         return ToSelectListItems((IEnumerator<BaseEntity>)                    baseEntities.GetEnumerator());     }       public static IEnumerable<SelectListItem> ToSelectListItems         (this IEnumerator<BaseEntity> baseEntities)     {         var items = new HashSet<SelectListItem>();           while (baseEntities.MoveNext())         {             var item = new SelectListItem();             var entity = baseEntities.Current;               item.Value = entity.Id.ToString();             item.Text = entity.ToString();               items.Add(item);         }           return items;     } } You can see here to overloads of same method. One works with List<T> and the other with IEnumerator<BaseEntity>. Although mostly my repositories return IList<T> when querying data there are always situations where I can use more abstract types and interfaces. Using extension methods in code In your code you can use ToSelectListItems() extension methods like shown on following code fragment. ... var model = new MyFormModel(); model.Statuses = _myRepository.ListStatuses().ToSelectListItems(); ... You can call this method on all your business classes that extend your base entity. Wanna have some fun with this code? Write overload for extension method that accepts selected item ID.

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  • A methology that allows for a single Java code base covering many different versions?

    - by Thorbjørn Ravn Andersen
    I work in a small shop where we have a LOT of legacy Cobol code and where a methology has been adopted to allow us to minimize forking and branching as much as possible. For a given release we have three levels: CORE - bottom layer, this code is common to all releases GROUP - optional code common to several customers. CUSTOMER - optional code specific for a single customer. When a program is needed, it is first searched for in CUSTOMER, then in GROUP and finally in CORE. A given application for us invokes many programs which all are looked for in this sequence (think exe files and PATH under Windows). We also have Java programs interacting with this legacy code, and as the core-group-customer lookup mehchanism does not lend it self easily to Java it has tended to grow in a CVS branch for each customer, requiring much too much maintainance. The Java part and the backend part tend to be developed in parallel. I have been assigned to figure out a way to make the two worlds meet. Essentially we want a Java enviornment which allows us to have a single code base with sources for each release, where we easily can select a group and a customer and work with the application as it goes for that customer, and then easily switch to another codeset and THAT customer. I was thinking of perhaps a scenario with an Eclipse project for each core, customer, and group and then use Project Sets to select those we need for a given scenario. The problem I cannot get my head about, is how we would create robust code in the CORE projects which will work regardless of which group and customer is selected. A Factory class which knows which sub class of a passed Class object to invoke instead of each and every new? Others must have had similar code base management problems. Anybody with experiences to share? EDIT: The conclusion to this problem above has been that CVS needs to be replaced with a source code management system better suited for dealing with many branches concurrently and the migration of source from one component to the other while keeping history. Inspired by the recent migration by slf4j and logback we are currently looking at git as it handles branches very well. We've considered subversion and mercurial too but git appears to be better for single location, multibranched projects. I've asked about Perforce in another question, but my personal inclination is towards open source solutions for something as crucial as this. EDIT: After some more pondering, we've found that our actual pain point is that we use branches in CVS, and that branches in CVS are the easiest to work with if you branch ALL files! The revised conclusion is that we can do this with CVS alone, by switching to a forest of java projects, each corresponding to one of the levels above, and use the Eclipse build paths to tie them together so each CUSTOMER version pulls in the appropriate GROUP and CORE project. We still want to switch to a better versioning system but this is so important a decision so we want to delay it as much as possible. EDIT: I now have a proof-of-concept implementation of the CORE-GROUP-CUSTOMER concept using Google Guice 2.0 - the @ImplementedBy tag is just what we need. I wonder what everybody else does? Using if's all over the place? EDIT: Now I also need this functionality for web applications. Guice was until the JSR-330 is in place. Anybody with versioning experience? EDIT: JSR-330/299 is now in place with the JEE6 reference implementation Weld based on JBoss Seam and I have reimplemented the proof-of-concept with Weld and can see that if we use @Alternative along with ... in beans.xml we can get the behaviour we desire. I.e. provide a new implementation for a given functionality in CORE without changing a bit in the CORE jars. Initial reading up on the Servlet 3.0 specification indicates that it may support the same functionality for web application resources (not code). We will now do initial testing on the real application.

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