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  • general learning methodology

    - by momo
    just wanted to hear on the different general learning paths people embark on when learning a new language/framework. the one i currently use, which is how i learned bash and am currently learning python, is: instant hacking tutorial (very short tutorial introducing the basic syntax, variable declaration, loops, data types, etc. and how they are generally used) in depth tutorial with good programming style and slightly topic-specific (e.g. Mark Pilgrim's Dive into Python), important topics for me personally are regex methods, file IO, and ways the different data types are utilized best (i wrote a very primitive bayesian spam filter using python's dictionaries to keep track of word occurrences) spaced-repition of syntax or short recipes (i use anki, with questions like 'create dictionary with filename and filesize metadata, human-readable' or simpler ones like 'match 0 - 3 occurences of the letter M in a string', or 'return/create an iterator from two sequences') the use of spaced-repitition has been invaluable, and i credit it with the ease that i can recall/create python algorithms. however, i've recently started looking into django, and i've found that spaced-repitition, at least in my case, doesn't work very well for learning a framework, it works best with short code recipes (either that or i should start looking into more basic django framework tutorials). the problem i'm encountering is that since framework programming is not only algorithms, but actually learning the API, which can be quite complex since you have to learn all the methods, modules, the places where they are stored, and the sequence of which things have to be done. for ex. in django to start a project that deals with polls (from the django tutorial), one has to create the project, edit the settings.py file, create the polls app, edit the models.py file (which requires knowing the classes that are present in the module models), edit the urls.py file, etc. i found that my spaced-repition method didn't work very well for this type of learning, so i wanted to ask you guys what method(s) you use for learning the different frameworks/APIs.

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  • ASP.NET MVC Newbie: why isn't my model available when creating a strongly-typed view?

    - by Rax Olgud
    I'm starting with ASP.NET MVC, and working with NerdDinner as reference. I did the following: Created a new project Added a couple of tables Created LINQ to SQL for them Created a new controller My Models directory now contains MyModel.dbml, under which I have MyModel.designer.cs, that contains classes for models relating to both of my tables (let's call them Categories and Products). Now, under my new controller, I would like to create a strongly typed view. So for example I have the following code in my controller (for my application I must work by name, and the "Name" field is unique): public ActionResult Details(string name) { MyModelDataContext db = new MyModelDataContext(); Product user = db.Products.Single(t => t.Name == name); return View(user); } I would like to create a strongly-typed view. So I right-click the line "return View(user)", and choose "Add View...". I click "Create a strongly-typed view". When I click the dropdown of "View data class", I don't see my models, but only: MyProject.Controllers.AccountMembershipService MyProject.Controllers.FormsAuthenticationService What am I missing?

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  • Classloader issue (GWT)

    - by Banang
    I'm currently working on a gwt app, where the server uses a few third party libs. recently I discovered that one of these libs isn't being properly loaded when running my app in deployed mode, and I just can't seem to figure out what out is I'm doing wrong. In my build script I have the following classpath declaration: <path id="project.class.path"> <pathelement location="${war.dir}/WEB-INF/classes"/> <fileset dir="${war.dir}/WEB-INF/lib" includes="**/*.jar"/> </path> and in a later target I copy the jar I need to the right location: <copy todir="${war.dir}/WEB-INF/lib" file="someJar.jar" /> The project builds as it should, without any errors. The jars are copied to where the should be, and are included in the resulting war file. In development mode everything is working as it should, everything gets loaded properly and I hear no complaints. However, in the deployed version I get this thrown at me: java.lang.NoClassDefFoundError: org/apache/commons/lang/exception/NestableRuntimeException java.lang.ClassLoader.defineClass1(Native Method) java.lang.ClassLoader.defineClass(ClassLoader.java:621) java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124) org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:2331) org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:976) org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1451) org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1329) java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) my.package.server.util.SomeUtils.doSomethingFantastic(SomeUtils.java:84) Line 84 in SomeUtils is trying to instantiate a class from someJar.jar. I know very little about how the class loader for gwt works, and I sure could use a hand. Anyone got any ideas on how to solve this?

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  • Weird bug with C++ lambda expressions in VS2010

    - by Andrei Tita
    In a couple of my projects, the following code: class SmallClass { public: int x1, y1; void TestFunc() { auto BadLambda = [&]() { int g = x1 + 1; //ok int h = y1 + 1; //c2296 int l = static_cast<int>(y1); //c2440 }; int y1_copy = y1; //it works if you create a local copy auto GoodLambda = [&]() { int h = y1_copy + 1; //ok int l = this->y1 + 1; //ok }; } }; generates error C2296: '+' : illegal, left operand has type 'double (__cdecl *)(double)' or alternatively error C2440: 'static_cast' : cannot convert from 'double (__cdecl *)(double)' to 'int' You get the picture. It also happens if catching by value. The error seems to be tied to the member name "y1". It happened in different classes, different projects and with (seemingly) any type for y1; for example, this code: [...] MyClass y1; void TestFunc() { auto BadLambda = [&]()->void { int l = static_cast<int>(y1); //c2440 }; } generates both these errors: error C2440: 'static_cast' : cannot convert from 'MyClass' to 'int' No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called error C2440: 'static_cast' : cannot convert from 'double (__cdecl *)(double)' to 'int' There is no context in which this conversion is possible It didn't, however, happen in a completely new project. I thought maybe it was related to Lua (the projects where I managed to reproduce this bug both used Lua), but I did not manage to reproduce it in a new project linking Lua. It doesn't seem to be a known bug, and I'm at a loss. Any ideas as to why this happens? (I don't need a workaround; there are a few in the code already). Using Visual Studio 2010 Express version 10.0.40219.1 Sp1Rel.

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  • Resolve php "deadlock"

    - by Matt
    Hey all, I'm currently running into a situation that I guess would be called deadlock. I'm implementing a message service that calls various object methods.. it's quite similar to observer pattern.. Here's whats going on: Dispatcher.php Dispatcher.php <? class Dispatcher { ... public function message($name, $method) { // Find the object based on the name $object = $this->findObjectByName($name); // Slight psuedocode.. for ease of example if($this->not_initialized($object)) $object = new $object(); // This is where it locks up. } return $object->$method(); ... } class A { function __construct() { $Dispatcher->message("B", "getName"); } public function getName() { return "Class A"; } } class B { function __construct() { // Assume $Dispatcher is the classes $Dispatcher->message("A", "getName"); } public function getName() { return "Class B"; } } ?> It locks up when neither object is initialized. It just goes back and forth from message each other and no one can be initialized. Any help would be immensely helpful.. Thanks! Matt Mueller

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  • What is the way to go to fake my database layer in a unit test?

    - by Michel
    Hi, i have a question about unit testing. say i have a controller with one create method which puts a new customer in the database: //code a bit shortened public actionresult Create(Formcollection formcollection){ client c = nwe client(); c.Name = formcollection["name"]; ClientService.Save(c); { Clientservice would call a datalayer object and save it in the database. What i do now is create a database testscript and set my database in a know condition before testing. So when i test this method in the unit test, i know that there must be one more client in the database, and what it's name is. In short: ClientController cc = new ClientController(); cc.Create(new FormCollection (){name="John"}); //i know i had 10 clients before assert.areEqual(11, ClientService.GetNumberOfClients()); //the last inserted one is John assert.areEqual("John", ClientService.GetAllClients()[10].Name); So i've read that unit testing should not be hitting the database, i've setup an IOC for the database classes, but then what? I can create a fake database class, and make it do nothing. But then ofcourse my assertions will not work because if i say GetNumberOfClients() it will alwasy return X because it has no interaction with the fake database class used in the Create Method. I can also create a List of Clients in the fake database class, but as there will be two different instance created (one in the controller action and one in the unit test), they will have no interaction. What is the way to make this unit test work without a database?

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  • EF 6 Code First Many to many With Payload and self referencing many to many

    - by lesley86
    I Have the problem where i have a many to many relationship and on one of the tables there will be a self referencing many to many. So basically a school have zero or many groups and many groups can have 0 or many schools. The groups table will contain a parent child many to many with itself because a group can be a child of another group or it can have no children and that child can have a child, one child can also have many parents or a entity can have no parents. I created a mapping table with Payload to solvethe first many to many problem. code snippet public class School { public virtual ICollection<SchoolGroupMap> SchoolGroupMaps } public class SchoolGroup { public virtual ICollection<SchoolGroupMap> SchoolGroupMaps } public class SchoolGroupMap { public virtual School School public virtual SchoolGroup SchoolGroup } i Then tried modifying the code the following way for the the self referencing many to many public class SchoolGroup { public virtual ICollection<SchoolGroupMap> SchoolGroupMaps public virtual ICollection<SchoolGroup> Parents public virtual ICollection<SchoolGroup> Children } I changed the context with has many and an auto mapping table (forgive me i have been trying so many things today i do not have the exact code). I received an error the properties on the classes must match. Can anyone help please. I want to do create navigation properties on the self referencing many to many. Also a seed example would be appreciated regards

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  • How to get a Class literal from a generically specific Class

    - by h2g2java
    There are methods like these which require Class literals as argument. Collection<EmpInfo> emps = SomeSqlUtil.select( EmpInfo.class, "select * from emps"); or GWT.create(Razmataz.class); The problem presents itself when I need to supply generic specific classes like EmpInfo<String> Razmataz<Integer> The following would be wrong syntax Collection<EmpInfo<String>> emps = SomeSqlUtil.select( EmpInfo<String>.class, "select * from emps"); or GWT.create(Razmataz<Integer>.class); Because you cannot do syntax like Razmataz<Integer>.class So, how would I be able to squeeze a class literal out of EmpInfo<String> Razmataz<Integer> so that I could feed them as arguments to methods requiring Class literals? Further info Okay, I confess that I am asking this primarily for GWT. I have a pair of GWT RPC interface Razmataz. (FYI, GWT RPC interface has to be defined in server-client pairs). I plan to use the same interface pair for communicating whether it be String, Integer, Boolean, etc. GWT.create(Razmataz) for Razmataz<T> complains that, since I did not specify T, GWT compiler treated it as Object. Then GWT compiler would not accept Object class. It needs to be more specific than being an Object. So, it seems there is no way for me to tell GWT.create what T is because a Class literal is a runtime concept while generics is a compile time concept, Right?

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  • Write a program which works out which is the lowest priced computer in an ArrayList of computer obje

    - by Eoin
    Hello everybody! I am trying to study some java and cannot get my head around this question! Any help would be really appreciated and would help me in further studies! Thank you so much in advance! Eoin from Dublin, Ireland. ArrayList of Objects Write a program which works out which is the lowest priced computer in an ArrayList of computer objects. You should have two classes, one called ComputerTest, and the other called Computer. In the ComputerTest class you should: Have a main method which declares an ArrayList of type Computer called computerList, each element of which represents a computer. Initialise the first three entries of the ArrayList Call a static method which prints out the lowest price computer, called lowestPrice The parameter of this method is (i) an ArrayList of type Computer i.e. ArrayList data Sample output: The lowest priced computer is the Cheapo400 at 399 euro. The Computer class should have: Private instance variables: manufacturer, model, price and quality. Quality is a rating from 1 to 10. public get and set methods to retrieve and set/change the value of the four instance variables a default constructor a constructor that takes four parameters

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  • Objective-C and NSURL: where am I supposed to declare receivedData?

    - by jthomas
    I have a two classes, a controller called "AppController" and a class called "URLDelegate" that encapsulates the sample NSURL code from Apple's URL Loading System Programming Guide. The guide repeatedly mentions declaring the receivedData instance variable "elsewhere." I assume this means outside of the URLDelagate class, because if I declare it in the URLDelegate class, my controller class can't "see" the data that has been downloaded. I know that data is received, because in my connectionDidFinishLoading function, I have NSLog display the results: NSLog(@"Succeeded! Received %d bytes of data",[receivedData length]); receivedText=[[NSString alloc] initWithData:receivedData encoding: NSASCIIStringEncoding]; NSLog(@"receivedText=%@",receivedText); So I'm a bit stumped with the following questions: Where should I declare receivedData? My controller class? A third class? Can I just declare it like any normal NSMutableData variable? How do I give my URLDelegate class "access" to this variable? E.g., if I declare receivedData in my AppController class, wouldn't I have to instantiate AppController within URLDelegate? But how would this possible if it's the AppController class which is instantiating the URLDelegate class in the first place? Especially with regard to the last question, I feel like I must be overlooking something blindingly obvious and fundamental. If anyone could point me in the right direction, I would really appreciate it. Thank you!

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  • how to implement a sparse_vector class

    - by Neil G
    I am implementing a templated sparse_vector class. It's like a vector, but it only stores elements that are different from their default constructed value. So, sparse_vector would store the index-value pairs for all indices whose value is not T(). I am basing my implementation on existing sparse vectors in numeric libraries-- though mine will handle non-numeric types T as well. I looked at boost::numeric::ublas::coordinate_vector and eigen::SparseVector. Both store: size_t* indices_; // a dynamic array T* values_; // a dynamic array int size_; int capacity_; Why don't they simply use vector<pair<size_t, T>> data_; My main question is what are the pros and cons of both systems, and which is ultimately better? The vector of pairs manages size_ and capacity_ for you, and simplifies the accompanying iterator classes; it also has one memory block instead of two, so it incurs half the reallocations, and might have better locality of reference. The other solution might search more quickly since the cache lines fill up with only index data during a search. There might also be some alignment advantages if T is an 8-byte type? It seems to me that vector of pairs is the better solution, yet both containers chose the other solution. Why?

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  • Change classloader

    - by Chris
    I'm trying to switch the class loader at runtime: public class Test { public static void main(String[] args) throws Exception { final InjectingClassLoader classLoader = new InjectingClassLoader(); Thread.currentThread().setContextClassLoader(classLoader); Thread thread = new Thread("test") { public void run() { System.out.println("running..."); // approach 1 ClassLoader cl = TestProxy.class.getClassLoader(); try { Class c = classLoader.loadClass("classloader.TestProxy"); Object o = c.newInstance(); c.getMethod("test", new Class[] {}).invoke(o); } catch (Exception e) { e.printStackTrace(); } // approach 2 new TestProxy().test(); }; }; thread.setContextClassLoader(classLoader); thread.start(); } } and: public class TestProxy { public void test() { ClassLoader tcl = Thread.currentThread().getContextClassLoader(); ClassLoader ccl = ClassToLoad.class.getClassLoader(); ClassToLoad classToLoad = new ClassToLoad(); } } (it is not relevant what the InjectingClassLoader is) I'd like to make the result of "approach 1" and "approach 2" exactly same, but it looks like thread.setContextClassLoader(classLoader) does nothing and the "approach 2" always uses the system classloader (can be determined by comparing tcl and ccl variables while debugging). Is it possible to make all classes loaded by new thread use given classloader?

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  • Can i use microsoft ajax tab controls SKIN only ?

    - by Anil Namde
    I like YUI's Tab, to use its look and feel for own tab like implementation we just have to include yui tabs CSS and use markups and css classes and done. example below, <link rel="stylesheet" type="text/css" href="http://yui.yahooapis.com/2.8.0r4/build/tabview/assets/skins/sam/tabview.css" /> <ul class="yui-nav"> <li><a href="#tab1"><em>Tab One Label</em></a></li> <li class="selected"><a href="#tab2"><em>Tab Two Label</em></a></li> <li><a href="#tab3"><em>Tab Three Label</em></a></li> </ul> Now i have a site where Microsort's tab tab controls are used and there are some which are old simple tabs. Now i would like to change these old tabs to Microsoft tab structures just by using CSS if possible as we have done above for YUI. Is that possible to do that using CSS/file? How it can be done for Microsofts tab?

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  • Returning the same type the function was passed

    - by Ken Bloom
    I have the following code implementation of Breadth-First search. trait State{ def successors:Seq[State] def isSuccess:Boolean = false def admissableHeuristic:Double } def breadthFirstSearch(initial:State):Option[List[State]] = { val open= new scala.collection.mutable.Queue[List[State]] val closed = new scala.collection.mutable.HashSet[State] open.enqueue(initial::Nil) while (!open.isEmpty){ val path:List[State]=open.dequeue() if(path.head.isSuccess) return Some(path.reverse) closed += path.head for (x <- path.head.successors) if (!closed.contains(x)) open.enqueue(x::path) } return None } If I define a subtype of State for my particular problem class CannibalsState extends State { //... } What's the best way to make breadthFirstSearch return the same subtype as it was passed? Supposing I change this so that there are 3 different state classes for my particular problem and they share a common supertype: abstract class CannibalsState extends State { //... } class LeftSideOfRiver extends CannibalsState { //... } class InTransit extends CannibalsState { //... } class RightSideOfRiver extends CannibalsState { //... } How can I make the types work out so that breadthFirstSearch infers that the correct return type is CannibalsState when it's passed an instance of LeftSideOfRiver? Can this be done with an abstract type member, or must it be done with generics?

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  • strange chi-square result using scikit_learn with feature matrix

    - by user963386
    I am using scikit learn to calculate the basic chi-square statistics(sklearn.feature_selection.chi2(X, y)): def chi_square(feat,target): """ """ from sklearn.feature_selection import chi2 ch,pval = chi2(feat,target) return ch,pval chisq,p = chi_square(feat_mat,target_sc) print(chisq) print("**********************") print(p) I have 1500 samples,45 features,4 classes. The input is a feature matrix with 1500x45 and a target array with 1500 components. The feature matrix is not sparse. When I run the program and I print the arrray "chisq" with 45 components, I can see that the component 13 has a negative value and p = 1. How is it possible? Or what does it mean or what is the big mistake that I am doing? I am attaching the printouts of chisq and p: [ 9.17099260e-01 3.77439701e+00 5.35004211e+01 2.17843312e+03 4.27047184e+04 2.23204883e+01 6.49985540e-01 2.02132664e-01 1.57324454e-03 2.16322638e-01 1.85592258e+00 5.70455805e+00 1.34911126e-02 -1.71834753e+01 1.05112366e+00 3.07383691e-01 5.55694752e-02 7.52801686e-01 9.74807972e-01 9.30619466e-02 4.52669897e-02 1.08348058e-01 9.88146259e-03 2.26292358e-01 5.08579194e-02 4.46232554e-02 1.22740419e-02 6.84545170e-02 6.71339545e-03 1.33252061e-02 1.69296016e-02 3.81318236e-02 4.74945604e-02 1.59313146e-01 9.73037448e-03 9.95771327e-03 6.93777954e-02 3.87738690e-02 1.53693158e-01 9.24603716e-04 1.22473138e-01 2.73347277e-01 1.69060817e-02 1.10868365e-02 8.62029628e+00] ********************** [ 8.21299526e-01 2.86878266e-01 1.43400668e-11 0.00000000e+00 0.00000000e+00 5.59436980e-05 8.84899894e-01 9.77244281e-01 9.99983411e-01 9.74912223e-01 6.02841813e-01 1.26903019e-01 9.99584918e-01 1.00000000e+00 7.88884155e-01 9.58633878e-01 9.96573548e-01 8.60719653e-01 8.07347364e-01 9.92656816e-01 9.97473024e-01 9.90817144e-01 9.99739526e-01 9.73237195e-01 9.96995722e-01 9.97526259e-01 9.99639669e-01 9.95333185e-01 9.99853998e-01 9.99592531e-01 9.99417113e-01 9.98042114e-01 9.97286030e-01 9.83873717e-01 9.99745466e-01 9.99736512e-01 9.95239765e-01 9.97992843e-01 9.84693908e-01 9.99992525e-01 9.89010468e-01 9.64960636e-01 9.99418323e-01 9.99690553e-01 3.47893682e-02]

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  • Java swing app can't find image

    - by KáGé
    Hello, I'm making a torpedo game for school in java with swing gui, please see the zipped source HERE. I use custom button icons and mouse cursors of images stored in the /bin/resource/graphics/default folder's subfolders, where the root folder is the program's root folder (it will be the root in the final .jar as well I suppose) which apart from "bin" contains a "main" folder with all the classes. The relative path of the resources is stored in MapStruct.java's shipPath and mapPath variables. Now Battlefield.java's PutPanel class finds them all right and sets up its buttons' icons fine, but every other class fail to get their icons, e.g. Table.java's setCursor, which should set the mouse cursor for all its elements for the selected ship's image or Field.java's this.button.setIcon(icon); in the constructor, which should set the icon for the buttons of the "water". I watched with debug what happens, and the images stay null after loading, though the paths seem to be correct. I've also tried to write a test file in the image folder but the method returns a filenotfound exception. I've tried to get the path of the class to see if it runs from the supposed place and it seems it does, so I really can't find the problem now. Could anyone please help me? Thank you.

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  • New Rails deployment half working...not sure why?

    - by Meltemi
    I'm in the final stages of going round trip through the entire Rails cycle: development - test - production (on an external server). I'm very close...but seeing some errors with the production version and don't know enough about Rails' "magic" to troubleshoot it yet... all seems well and I can load my app by going to www.mydomain.com/rails and it seems to work...I can interact with my app and create new objects in my database. However, when I go to www.mydomain.com/rails/ (difference is the trailing slash) i get a webpage that just says "Index from public" on it?!? I don't know where that's coming from? index.html is long removed from public. this may or may not be related to why I can't access, say, the first record in one of my classes by calling its controller like so: www.mydomain.com/rails/mycontroller/1 . and yes, there are records in the database. anyway, something's askew. it works fine on development box. but, only half working on production server. anyone know what might be causing this? this app is running on the server box (not development) Installed Passenger on server to serve app via Apache modified my httpd.conf with Passenger's stuff (headache but finally got it to respond) loaded schema into the production database: rake db:schema:load RAILS_ENV=production

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  • Is my objective possible using WCF (and is it the right way to do things?)

    - by David
    I'm writing some software that modifies a Windows Server's configuration (things like MS-DNS, IIS, parts of the filesystem). My design has a server process that builds an in-memory object graph of the server configuration state and a client which requests this object graph. The server would then serialize the graph, send it to the client (presumably using WCF), the server then makes changes to this graph and sends it back to the server. The server receives the graph and proceeds to make modifications to the server. However I've learned that object-graph serialisation in WCF isn't as simple as I first thought. My objects have a hierarchy and many have parametrised-constructors and immutable properties/fields. There are also numerous collections, arrays, and dictionaries. My understanding of WCF serialisation is that it requires use of either the XmlSerializer or DataContractSerializer, but DCS places restrictions on the design of my object-graph (immutable data seems right-out, it also requires parameter-less constructors). I understand XmlSerializer lets me use my own classes provided they implement ISerializable and have the de-serializer constructor. That is fine by me. I spoke to a friend of mine about this, and he advocates going for a Data Transport Object-only route, where I'd have to maintain a separate DataContract object-graph for the transport of data and re-implement my server objects on the client. Another friend of mine said that because my service only has two operations ("GetServerConfiguration" and "PutServerConfiguration") it might be worthwhile just skipping WCF entirely and implementing my own server that uses Sockets. So my questions are: Has anyone faced a similar problem before and if so, are there better approaches? Is it wise to send an entire object graph to the client for processing? Should I instead break it down so that the client requests a part of the object graph as it needs it and sends only bits that have changed (thus reducing concurrency-related risks?)? If sending the object-graph down is the right way, is WCF the right tool? And if WCF is right, what's the best way to get WCF to serialise my object graph?

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  • How to store some of the entity's values in another table using hibernate?

    - by nimcap
    Hi guys, is there a simple way to persist some of the fields in another class and table using hibernate. For example, I have a Person class with name, surname, email, address1, address2, city, country fields. I want my classes to be: public class Person { private String name; private String surname; private String email; private Address address; // .. } public class Address { private Person person; // to whom this belongs private String address1; private String address2; private String city; private Address country; // .. } and I want to store Address in another table. What is the best way to achieve this? Edit: I am using annotations. It does not have to be the way I described, I am looking for best practices. PS. If there is a way to make Address immutable (to use as a value object) that is even better, or maybe not because I thought everything from wrong perspective :)

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  • NullPointerException with static variables

    - by tomekK
    I just hit very strange (to me) behaviour of java. I have following classes: public abstract class Unit { public static final Unit KM = KMUnit.INSTANCE; public static final Unit METERS = MeterUnit.INSTANCE; protected Unit() { } public abstract double getValueInUnit(double value, Unit unit); protected abstract double getValueInMeters(double value); } And: public class KMUnit extends Unit { public static final Unit INSTANCE = new KMUnit(); private KMUnit() { } //here are abstract methods overriden } public class MeterUnit extends Unit { public static final Unit INSTANCE = new MeterUnit(); private MeterUnit() { } ///abstract methods overriden } And my test case: public class TestMetricUnits extends TestCase { @Test public void testConversion() { System.out.println("Unit.METERS: " + Unit.METERS); System.out.println("Unit.KM: " + Unit.KM); double meters = Unit.KM.getValueInUnit(102.11, Unit.METERS); assertEquals(0.10211, meters, 0.00001); } } 1) MKUnit and MeterUnit are both singletons initialized statically, so during class loading. Constructors are private, so they can't be initialized anywhere else. 2) Unit class contains static final references to MKUnit.INSTANCE and MeterUnit.INSTANCE I would expect that: KMUnit class is loaded and instance is created. MeterUnit class is loaded and instance is created. Unit class is loaded and both KM and METERS variable are initialized, they are final so they cant be changed. But when I run my test case in console with maven my result is: T E S T S Running de.audi.echargingstations.tests.TestMetricUnits Unit.METERS: m Unit.KM: null Tests run: 3, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.089 sec <<< FAILURE! - in de.audi.echargingstations.tests.TestMetricUnits testConversion(de.audi.echargingstations.tests.TestMetricUnits) Time elapsed: 0.011 sec <<< ERROR! java.lang.NullPointerException: null at de.audi.echargingstations.tests.TestMetricUnits.testConversion(TestMetricUnits.java:29) Results : Tests in error: TestMetricUnits.testConversion:29 NullPointer And the funny part is that, when I run this test from eclipse via JUnit runner everything is fine, I have no NullPointerException and in console I have: Unit.METERS: m Unit.KM: km So the question is: what can be the reason that KM variable in Unit is null (and in the same time METERS is not null)

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  • What scenarios are possible where the VS C# compiler would not compile a reference of a reference?

    - by SuperKing
    Hello, I'm probably asking this question wrong (and that may be why Google isn't helping), but here goes: In Visual Studio I am compiling a C# project (let's call it Project A, the startup project) which has a reference to Project B. Project B has a reference to a Project C, so when A gets built, the dlls for B gets placed in the bin directory of A, as does the dll for C (because B requires C, and A requires B). However, I have apparently made some change recently so that the dll for Project C does not go into the bin directory of Project A when rebuilding the solution. I have no idea what I've done to make this happen. I have not modified the setup of the solution itself, and I have only added additional references to the project files. Code wise, I have commented out most of the actual code in Project B that references classes in Project C, but did not remove the reference from the project itself (I don't think this matters). I was told that perhaps the C# compiler was optimizing somehow so that it was not building Project C, but really I'm out of ideas. I would think someone has run into something similar before Any thoughts? Thanks!

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  • Coding the Python way

    - by Aaron Moodie
    I've just spent the last half semester at Uni learning python. I've really enjoyed it, and was hoping for a few tips on how to write more 'pythonic' code. This is the __init__ class from a recent assignment I did. At the time I wrote it, I was trying to work out how I could re-write this using lambdas, or in a neater, more efficient way, but ran out of time. def __init__(self, dir): def _read_files(_, dir, files): for file in files: if file == "classes.txt": class_list = readtable(dir+"/"+file) for item in class_list: Enrol.class_info_dict[item[0]] = item[1:] if item[1] in Enrol.classes_dict: Enrol.classes_dict[item[1]].append(item[0]) else: Enrol.classes_dict[item[1]] = [item[0]] elif file == "subjects.txt": subject_list = readtable(dir+"/"+file) for item in subject_list: Enrol.subjects_dict[item[0]] = item[1] elif file == "venues.txt": venue_list = readtable(dir+"/"+file) for item in venue_list: Enrol.venues_dict[item[0]] = item[1:] elif file.endswith('.roll'): roll_list = readlines(dir+"/"+file) file = os.path.splitext(file)[0] Enrol.class_roll_dict[file] = roll_list for item in roll_list: if item in Enrol.enrolled_dict: Enrol.enrolled_dict[item].append(file) else: Enrol.enrolled_dict[item] = [file] try: os.path.walk(dir, _read_files, None) except: print "There was a problem reading the directory" As you can see, it's a little bulky. If anyone has the time or inclination, I'd really appreciate a few tips on some python best-practices. Thanks.

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  • Google Spreadsheet API problem: memory exceeded

    - by Robbert
    Hi guys, Don't know if anyone has experience with the Google Spreadsheets API or the Zend_GData classes but it's worth a go: When I try to insert a value in a 750 row spreadsheet, it takes ages and then throws an error that my memory limit (which is 128 MB!) was exceeded. I also got this when querying all records of this spreadsheet but this I can imaging because it's quite a lot of data. But why does this happen when inserting a row? That's not too complex, is it? Here's the code I used: public function insertIntoSpreadsheet($username, $password, $spreadSheetId, $data = array()) { $service = Zend_Gdata_Spreadsheets::AUTH_SERVICE_NAME; $client = Zend_Gdata_ClientLogin::getHttpClient($username, $password, $service); $client->setConfig(array( 'timeout' => 240 )); $service = new Zend_Gdata_Spreadsheets($client); if (count($data) == 0) { die("No valid data"); } try { $newEntry = $service->insertRow($data, $spreadSheetId); return true; } catch (Exception $e) { return false; } }

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  • Strange behavior with complex Q object filter queries in Django

    - by HWM-Rocker
    Hi I am trying to write a tagging system for Django, but today I encountered a strange behavior in filter or the Q object (django.db.models.Q). I wrote a function, that converts a search string into a Q object. The next step would be to filter the TaggedObject with these query. But unfortunately I get a strange behavior. when I search (id=20) = Q: (AND: ('tags__tag__id', 20)) and it returns 2 Taged Objects with the ID 1127 and 132 when I search (id=4) = Q: (AND: ('tags__tag__id', 4)) and it returns also 2 Objects, but this time 1180 and 1127 until here is everything fine, but when i make a little bit more complex query like (id=4) or (id=20) = Q: (OR: ('tags__tag__id', 4), ('tags__tag__id', 20)) then it returns 4(!) Objects 1180, 1127, 1127, 132 But the object with the ID 1127 is returned twice, but thats not the behaviour I want. Do I have to live with it, and uniqify that list or can I do something different. The representation of the Q object looks fine for me. But the worst is now, when I search for (id=20) and (id=4) = Q: (AND: ('tags__tag__id', 20), ('tags__tag__id', 4)) then it returns no object at all. But why? The representation should be ok and the object with the id 1127 is tagged by both. What am I missing? Here are also the relevant parts of the classes, that are involved: class TaggedObject(models.Model): """ class that represent a tagged object """ tags = generic.GenericRelation('ObjectTagBridge', blank=True, null=True) class ObjectTagBridge(models.Model): """ Help to connect a generic object to a Tag. """ # pylint: disable-msg=W0232,R0903 content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey('content_type', 'object_id') tag = models.ForeignKey('Tag') class Tag(models.Model): ... Thanks for your help

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  • Adding web reference on client when using Net.TCP

    - by Marko
    Hi everyone... I am trying to using Net.TCP in my WCF Service, which is self hosted, when i try to add this service reference through web reference to my client, i am not able access the classes and methods of that service, can any have any idea to achieve this... How I can add web references in this case. My Service has one method (GetNumber) that returns int. WebService: public class WebService : IWebService { public int GetNumber(int num) { return num + 1; } } Service Contract code: [ServiceContract] public interface IWebService { [OperationContract] int GetNumber(int num); } WCF Service code: ServiceHost host = new ServiceHost(typeof(WebService)); host.AddServiceEndpoint(typeof(IWebService), new NetTcpBinding(), new Uri("net.tcp://" + Dns.GetHostName() + ":1255/WebService")); NetTcpBinding binding = new NetTcpBinding(); binding.TransferMode = TransferMode.Streamed; binding.ReceiveTimeout = TimeSpan.MaxValue; binding.MaxReceivedMessageSize = long.MaxValue; Console.WriteLine("{0}", Dns.GetHostName().ToString()); Console.WriteLine("Opening Web Service..."); host.Open(); Console.WriteLine("Web Service is running on port {0}",1255); Console.WriteLine("Press <ENTER> to EXIT"); Console.ReadLine(); This works fine. Only problem is how to add references of this service in my client application. I just want to send number and to receive an answer. Can anyone help me?

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