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  • In Ruby, how can I initialize instance variables in new objects of core classes created from literal

    - by Ollie Saunders
    class Object attr_reader :foo def initialize @foo = 'bar' end end Object.new.foo # => 'bar' ''.foo # => nil //.foo # => nil [].foo # => nil I want them all to return 'bar' Am aware that you can do this already: class Object def foo 'bar' end end But I specifically want to initialize a state variable. Also note that this doesn't work. class String alias_method :old_init, :initialize def initialize(*args) super old_init(*args) end end class Object attr_reader :foo def initialize @foo = 'bar' super end end ''.foo # => nil Nor does this: class String attr_reader :foo def initialize @foo = 'bar' end end ''.instance_variables # => [] I'm beginning to think that this isn't actually possible.

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  • Safe to pass objects to C functions when working in JNI Invocation API?

    - by bubbadoughball
    I am coding up something using the JNI Invocation API. A C program starts up a JVM and makes calls into it. The JNIenv pointer is global to the C file. I have numerous C functions which need to perform the same operation on a given class of jobject. So I wrote helper functions which take a jobject and process it, returning the needed data (a C data type...for example, an int status value). Is it safe to write C helper functions and pass jobjects to them as arguments? i.e. (a simple example - designed to illustrate the question): int getStatusValue(jobject jStatus) { return (*jenv)->CallIntMethod(jenv,jStatus,statusMethod); } int function1() { int status; jobject aObj = (*jenv)->NewObject (jenv, aDefinedClass, aDefinedCtor); jobject j = (*jenv)->CallObjectMethod (jenv, aObj, aDefinedObjGetMethod) status = getStatusValue(j); (*jenv)->DeleteLocalRef(jenv,aObj); (*jenv)->DeleteLocalRef(jenv,j); return status; } Thanks.

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  • How to include all objects of an archive in a shared object?

    - by Didier Trosset
    When compiling our project, we create several archives (static libraries), say liby.a and libz.a that each contains an object file defining a function y_function() and z_function(). Then, these archives are joined in a shared object, say libyz.so, that is one of our main distributable target. g++ -fPIC -c -o y.o y.cpp ar cr liby.a y.o g++ -fPIC -c -o z.o z.cpp ar cr libz.a z.o g++ -shared -L. -ly -lz -o libyz.so When using this shared object into the example program, say x.c, the link fails because of an undefined references to functions y_function() and z_function(). g++ x.o -L. -lyz -o xyz It works however when I link the final executable directly with the archives (static libraries). g++ x.o -L. -ly -lz -o xyz My guess is that the object files contained in the archives are not linked into the shared library because they are not used in it. How to force inclusion? Edit: Inclusion can be forced using --whole-archive ld option. But if results in compilation errors: g++ -shared '-Wl,--whole-archive' -L. -ly -lz -o libyz.so /usr/lib/libc_nonshared.a(elf-init.oS): In function `__libc_csu_init': (.text+0x1d): undefined reference to `__init_array_end' /usr/bin/ld: /usr/lib/libc_nonshared.a(elf-init.oS): relocation R_X86_64_PC32 against undefined hidden symbol `__init_array_end' can not be used when making a shared object /usr/bin/ld: final link failed: Bad value Any idea where this comes from?

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  • How do I initialize attributes when I instantiate objects in Rails?

    - by nfm
    Clients have many Invoices. Invoices have a number attribute that I want to initialize by incrementing the client's previous invoice number. For example: @client = Client.find(1) @client.last_invoice_number > 14 @invoice = @client.invoices.build @invoice.number > 15 I want to get this functionality into my Invoice model, but I'm not sure how to. Here's what I'm imagining the code to be like: class Invoice < ActiveRecord::Base ... def initialize(attributes = {}) client = Client.find(attributes[:client_id]) attributes[:number] = client.last_invoice_number + 1 client.update_attributes(:last_invoice_number => client.last_invoice_number + 1) end end However, attributes[:client_id] isn't set when I call @client.invoices.build. How and when is the invoice's client_id initialized, and when can I use it to initialize the invoice's number? Can I get this logic into the model, or will I have to put it in the controller?

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  • Why do bind1st and bind2nd require constant function objects?

    - by rlbond
    So, I was writing a C++ program which would allow me to take control of the entire world. I was all done writing the final translation unit, but I got an error: error C3848: expression having type 'const `anonymous-namespace'::ElementAccumulator<T,BinaryFunction>' would lose some const-volatile qualifiers in order to call 'void `anonymous-namespace'::ElementAccumulator<T,BinaryFunction>::operator ()(const point::Point &,const int &)' with [ T=SideCounter, BinaryFunction=std::plus<int> ] c:\program files (x86)\microsoft visual studio 9.0\vc\include\functional(324) : while compiling class template member function 'void std::binder2nd<_Fn2>::operator ()(point::Point &) const' with [ _Fn2=`anonymous-namespace'::ElementAccumulator<SideCounter,std::plus<int>> ] c:\users\****\documents\visual studio 2008\projects\TAKE_OVER_THE_WORLD\grid_divider.cpp(361) : see reference to class template instantiation 'std::binder2nd<_Fn2>' being compiled with [ _Fn2=`anonymous-namespace'::ElementAccumulator<SideCounter,std::plus<int>> ] I looked in the specifications of binder2nd and there it was: it took a const AdaptibleBinaryFunction. So, not a big deal, I thought. I just used boost::bind instead, right? Wrong! Now my take-over-the-world program takes too long to compile (bind is used inside a template which is instantiated quite a lot)! At this rate, my nemesis is going to take over the world first! I can't let that happen -- he uses Java! So can someone tell me why this design decision was made? It seems like an odd decision. I guess I'll have to make some of the elements of my class mutable for now...

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  • How can I save and read to XML the new C++ style matrix objects in OpenCV?

    - by neuviemeporte
    The old, C style cvMat matrices could be passed to the cvSave() function for easy writing to an XML file. The new C++ style cv::Mat and cv::Mat_ matrices are not accepted by this function. The OpenCV reference has a section on XML persistence, but the three classes (FileStorage, FileNode and FileNodeIterator) lack any description or example and I can't figure out how to use them from the interface. Thanks.

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  • [Python] How can I speed up unpickling large objects if I have plenty of RAM?

    - by conradlee
    It's taking me up to an hour to read a 1-gigabyte NetworkX graph data structure using cPickle (its 1-GB when stored on disk as a binary pickle file). Note that the file quickly loads into memory. In other words, if I run: import cPickle as pickle f = open("bigNetworkXGraph.pickle","rb") binary_data = f.read() # This part doesn't take long graph = pickle.loads(binary_data) # This takes ages How can I speed this last operation up? Note that I have tried pickling the data both in using both binary protocols (1 and 2), and it doesn't seem to make much difference which protocol I use. Also note that although I am using the "loads" (meaning "load string") function above, it is loading binary data, not ascii-data. I have 128gb of RAM on the system I'm using, so I'm hoping that somebody will tell me how to increase some read buffer buried in the pickle implementation.

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  • WPF: Turning off animations, data binding temporarly for invisible objects?;)

    - by TomTom
    I have a window that contains a tab control - basically multiple sheets with visualizations on them. The visualtizations are: possible very resource intensive during rendering relying on constant data updates to update their underlying models Obviously only one sheet can be visible every time ;) Anyone knows of a good way to turn off all visualization, animations, data binding for a control / panel and it's contained controls? If I would find a way to do that, I could simply turn off all the invisible sheets and reactivate them as needed. The models must be kept running - some of the visual stuff is pretty complex and really relies on constant data updates, and recalculating it when someone switches tabs would be too hard.

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  • Keep a reference to an NSThread around and message its objects?

    - by RickiG
    Hi I am a bit uncertain on how to do this: I start a "worker-thread" that runs for the duration of my apps "life". [NSThread detachNewThreadSelector:@selector(updateModel) toTarget:self withObject:nil]; then - (void) updateModel { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; BackgroundUpdate *update = [[BackgroundUpdate alloc] initWithTimerInterval:5]; [[NSRunLoop currentRunLoop] run]; //keeps it going 'forever' [update release]; [pool release]; } Now the thread "wakes" up every 5 seconds(initWithTimerInterval) to see if there are any tasks it can do. All the tasks in the BackGroundUpdate Class are only time dependent for now. I would like to have a few that were "event dependent". e.g. I would like to call the Background Object from my main thread and tell it to "speedUp", "slowDown", "reset" or any method on the object. To do this I guess I need something like performSelectorOnThread but how to get a reference to the NSthread and the Background Object?

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  • C# / XNA - Load objects to the memory - how it works?

    - by carl
    Hello I'm starting with C# and XNA. In the "Update" method of the "Game" class I have this code: t = Texture2D.FromFile( [...] ); //t is a 'Texture2D t;' which loads small image. "Update" method is working like a loop, so this code is called many times in a second. Now, when I run my game, it takes 95MB of RAM and it goes slowly to about 130MB (due to the code I've posted, without this code it remains at 95MB), then goes immediately to about 100MB (garbare colletion?) and again goes slowly to 130MB, then immediately to 100MB and so on. So my first question: Can You explain why (how) it works like that? I've found, that if I change the code to: t.Dispose() t = Texture2D.FromFile( [...] ); it works like that: first it takes 95MB and then goes slowly to about 101MB (due to the code) and remains at this level. I don't understand why it takes this 6MB (101-95)... ? I want to make it works like that: load image, release from memory, load image, release from memory and so on, so the program should always takes 95MB (it takes 95MB when image is loaded only once in previous method). Whats instructions should I use? If it is important, the size of the image is about 10KB. Thank You!

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  • Getting all objects with a certain element inside a collection of strings with criteria API.

    - by Jens Jansson
    Hey. I'm trying to build a Hibernate Criteria query to find entities that have a specific element inside a collection. We can take as an example a Book -object that looks like this: public class Book { private Long id; private String title; private Set<String> authors = new HashSet<String>(); } The entity is mapped like this: <class name="Book" table="Book"> <id name="id" column="BOOK_ID"> <generator class="native"/> </id> <property name="title"/> <set name="authors" table="Book_Authors"> <key column="BOOK_ID"/> <element type="string" column="AUTHORS"/> </set> </class> Now I would like to find out which books are written by Matt. With pure SQL I can do a query like this: String author = "Matt"; String query = "SELECT * FROM Book " + "WHERE BOOK_ID IN " + "(SELECT BOOK_ID FROM Book_Authors " + "WHERE authors = :author )"; List<Book> result = session.createSQLQuery(query) .addEntity(Book.class) .setParameter("author", author) .list(); This works all good and well, and I get out all books that Matt has been a part of writing. The project I work in, however, uses the Criteria API instead of raw SQL, and I haven't found a way to express the same query in that form. I've taken a look on the Restrictions API and the closest I've found is Restions.in(propertyName, collection) but that works the other way around (one value in object, many values to match against). Any ideas?

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  • Trying to put a generic MyObj<T, U> into an IList where U can be different between objects

    - by Sergio Romero
    I have the following class definition: public interface IItem{} public class FirstObject<T, U> : IItem { public U SomeProperty { get; private set; } } IList<IItem> myList = new List<IItem>(); I did it like this because U can be of different types. Now I want to iterate the list and get my items back, the problem is that I do not know how to cast them back to their original type so I can read the value of SomeProperty. Thanks for your help.

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  • What is the best way to implement multilingual domain objects using NHibernate?

    - by Amitabh
    I have found few links but could not decide which one is the best way. http://fabiomaulo.blogspot.com/2009/06/localized-property-with-nhibernate.html (This stores all localised language data in one field. Can be a problem if we query from Sql) http://ayende.com/Blog/archive/2006/12/26/LocalizingNHibernateContextualParameters.aspx (This one has a warning at the beginning that it is a hack and no longer supported) http://www.webdevbros.net/2009/06/24/create-a-multi-languaged-domain-model-with-nhibernate-and-c/ (This does not describe how multilingual data will be structured in the database.)

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  • Why "Finalize method should not reference any other objects" ?

    - by mishal153
    I have been pondering why it is recommended that we should not release managed resources inside finalize. If you see the code example at http://msdn.microsoft.com/en-us/library/system.gc.suppressfinalize.aspx , and search for string "Dispose(bool disposing) executes in two distinct scenarios" and read that comment, you will understand what I mean. Only possibility I can think of is that it probably has something to do with the fact that it is not possible to predict when finalizer will get called. Does anyone know the right answer ? thanks, mishal

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  • How can i filter a list of objects using lamda expression?

    - by Colour Blend
    I know i shouldn't have id's with the same value. This is just fictitious, so overlook that. I have: List<Car> carList = new List<Car>(); carList.Add(new Car() { id = 1, name = "Honda" }); carList.Add(new Car() { id = 2, name = "Toyota" }); carList.Add(new Car() { id = 1, name = "Nissan" }); I want to use Lamda Expression to retreive all cars that have an id of 1. Anticipated Result: -- Id: 1, Name: Honda -- Id: 1, Name: Nissan The problem is more filtering an object list based on a foriegn key. Please help me.

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  • How to save objects using Multi-Threading in Core Data?

    - by Konstantin
    I'm getting some data from the web service and saving it in the core data. This workflow looks like this: get xml feed go over every item in that feed, create a new ManagedObject for every feed item download some big binary data for every item and save it into ManagedObject call [managedObjectContext save:] Now, the problem is of course the performance - everything runs on the main thread. I'd like to re-factor as much as possible to another thread, but I'm not sure where I should start. Is it OK to put everything (1-4) to the separate thread?

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  • List<> of objects, different types, sort and pull out types individually?

    - by Brazos
    I've got a handful of products, any, all, or none of which may be associated with a specific submission. All 7 products are subclasses of the class Product. I need to store all the products associated with a submission, and then retrieve them and their field data on my presentation layer. I've been using a List, and List, but when I use the OfType, I throw an error saying that I can't implicitly convert systems.generic.IEnumerable to type 'Product'. I've tried to cast, but to no avail. When I use prodlist.OfType<EPL>(); there are no errors, but when I try and store that in an instance of EPL "tempEpl", I get the aforementioned cast-related error. What gives? Code below. ProductService pserv = new ProductService(); IList<object> prodlist = pserv.getProductById(x); EPL tempEpl = new EPL(); if ((prodlist.OfType<EPL>()) != null) { tempEpl = prodlist.OfType<EPL>(); // this throws a conversion error. } the Data layer List<object> TempProdList = new List<object>(); conn.Open(); SqlCommand EplCmd = new SqlCommand(EPLQuery, conn); SqlDataReader EplRead = null; EplRead = EplCmd.ExecuteReader(); EPL TempEpl = new EPL(); if (EplRead.Read()) { TempEpl.Entity1 = EplRead.GetString(0); TempEpl.Employees1 = EplRead.GetInt32(1); TempEpl.CA1 = EplRead.GetInt32(2); TempEpl.MI1 = EplRead.GetInt32(3); TempEpl.NY1 = EplRead.GetInt32(4); TempEpl.NJ1 = EplRead.GetInt32(5); TempEpl.PrimEx1 = EplRead.GetInt32(6); TempEpl.EplLim1 = EplRead.GetInt32(7); TempEpl.EplSir1 = EplRead.GetInt32(8); TempEpl.Premium1 = EplRead.GetInt32(9); TempEpl.Wage1 = EplRead.GetInt32(10); TempEpl.Sublim1 = EplRead.GetInt32(11); TempProdList.Add(TempEpl); }

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  • Is dependency injection only for service type objects and singletons? (and NOT for gui?)

    - by sensui
    I'm currently experimenting with the Google's guice inversion of control container. I previously had singletons for just about any service (database, active directory) my application used. Now I refactored the code: all the dependencies are given as parameters to constructors. So far, so good. Now the hardest part is with the graphical user interface. I face this problem: I have a table (JTable) of products wrapped in an ProductFrame. I give the dependencies as parameters (EditProductDialog). @Inject public ProductFrame(EditProductDialog editProductDialog) { // ... } // ... @Inject public EditProductDialog(DBProductController productController, Product product) { // ... } The problem is that guice can't know what Product I have selected in the table, so it can't know what to inject in the EditProductDialog. Dependency Injection is pretty viral (if I modify one class to use dependency injection I also need to modify all the other classes it interacts with) so my question is should I directly instantiate EditProductDialog? But then I would have to pass manually the DBProductController to the EditProductDialog and I will also need to pass it to the ProductFrame and all this boils down to not using dependency injection at all. Or is my design flawed and because of that I can't really adapt the project to dependecy injection? Give me some examples of how you used dependency injection with the graphical user interface. All the examples found on the Internet are really simple examples where you use some services (mostly databases) with dependency injection.

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  • deleting element objects of a std vector using erase : a) memory handling and b) better way?

    - by memC
    hi, I have a vec_A that stores instances of class A as: vec_A.push_back(A()); I want to remove some elements in the vector at a later stage and have two questions: a) The element is deleted as: vec_A.erase(iterator) Is there any additional code I need to add to make sure that there is no memory leak? . b) Assume that condition if(num <5) is if num is among a specific numberList. Given this, is there a better way to delete the elements of a vector than what I am illustrating below? #include<vector> #include<stdio.h> #include<iostream> class A { public: int getNumber(); A(int val); ~A(){}; private: int num; }; A::A(int val){ num = val; }; int A::getNumber(){ return num; }; int main(){ int i =0; int num; std::vector<A> vec_A; std::vector<A>::iterator iter; for ( i = 0; i < 10; i++){ vec_A.push_back(A(i)); } iter = vec_A.begin(); while(iter != vec_A.end()){ std::cout << "\n --------------------------"; std::cout << "\n Size before erase =" << vec_A.size(); num = iter->getNumber() ; std::cout << "\n num = "<<num; if (num < 5){ vec_A.erase(iter); } else{ iter++; } std::cout << "\n size after erase =" << vec_A.size(); } std::cout << "\nPress RETURN to continue..."; std::cin.get(); return 0; }

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  • How to (simply) create new service objects in java jax-ws webservices?

    - by cibercitizen1
    Is it possible in jax-ws to have a webmethod that creates a new object (of a service class) and returns a reference to it to the client caller (for the client, it's a remote reference) so that the client and this new service object maintain a session? (Therefore each client is served by a different instance). Schematically: client server o:Session -------- -------- ---------- s = server.access() ------------------> o = new Session() return o <--- o.doSomething() ----------------------------------------------> make it <--- o.doMore() --------------------------------------------------> make it <---

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