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  • Buffering db inserts in multithreaded program

    - by Winter
    I have a system which breaks a large taks into small tasks using about 30 threads as a time. As each individual thread finishes it persists its calculated results to the database. What I want to achieve is to have each thread pass its results to a new persisance class that will perform a type of double buffering and data persistance while running in its own thread. For example, after 100 threads have moved their data to the buffer the persistance class then the persistance class swaps the buffers and persists all 100 entries to the database. This would allow utilization of prepared statements and thus cut way down on the I/O between the program and the database. Is there a pattern or good example of this type of multithreading double buffering?

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  • AppFabric serialization problem.

    - by jandark
    I am trying cache a class instance with AppFabric but it return class instance with empty members. The reason is DataContract Attribute. My class is marked with [Serializable] and [DataContract(Name = "TestClass", Namespace = "CustomNameSpace.TestClass")] attributes. Problem solving if I mark all properties with DataMember or remove DataContract attribute. But I do not want to remove DataContract attributte because of other serialization needs (such as json or something else) Or I do not want to add DataMember attribute to other classes. (a lot of) Do you have any idea to solve that problem ? Thanks.

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  • static const double in c++

    - by Crystal
    Is this the proper way to use a static const variable? In my top level class (Shape) #ifndef SHAPE_H #define SHAPE_H class Shape { public: static const double pi; private: double originX; double originY; }; const double Shape::pi = 3.14159265; #endif And then later in a class that extends Shape, I use Shape::pi. I get a linker error. I moved the const double Shape::pi = 3.14... to the Shape.cpp file and my program then compiles. Why does that happen? thanks.

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  • C# - Why can't I enforce derived classes to have parameterless constructors?

    - by FrisbeeBen
    I am trying to do the following: public class foo<T> where T : bar, new { _t = new T(); private T _t; } public abstract class bar { public abstract void someMethod(); // Some implementation } public class baz : bar { public overide someMethod(){//Implementation} } And I am attempting to use it as follows: foo<baz> fooObject = new foo<baz>(); And I get an error explaining that 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. I fully understand why this must be, and also understand that I could pass a pre-initialized object of type 'T' in as a constructor argument to avoid having to 'new' it, but is there any way around this? any way to enforce classes that derive from 'bar' to supply parameterless constructors?

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  • Custom Sorting (IComparer on three fields)

    - by Kave
    I have a person class with three fields, Title, Name, Gender and I would like to create a Custom Sort for it to sort it first by Title, then by Name and then by Gender ascending: public class SortPerson : IComparer { public int Compare(object x, object y) { (…) } } I know how to do this for only one variable to compare against: But How would I have to proceed with three? public class SortPerson : IComparer { int IComparer.Compare(object a, object b) { Person p1=(Person)a; Person p2=(Person)b; if (p1.Title > p2.Title) return 1; if (p1.Title < p2.Title) return -1; else return 0; } } Many Thanks,

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  • Serializing System.Drawing.Color in .NET

    - by alankdkd
    Hi all, I've used the default .NET serialization for a class with a System.Drawing.Color member. The code is now in use by people, and I need to add an extra member to the class, but still deserialize older versions. So I tried the standard way of doing this: The ISerializable interface, using SerializationInfo methods to get the int and string members. The problem: My class also has a System.Drawing.Color member, but SerializationInfo doesn't provide a "GetColor" method read this data type. I've tried getting it as an int and as a string, and casting it to System.Drawing.Color, but no luck. Does anyone know how to deserialize a System.Drawing.Color from SerializationInfo? Thanx! Alan

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  • Fastest/One-liner way to list attr_accessors in Ruby?

    - by viatropos
    What's the shortest, one-liner way to list all methods defined with attr_accessor? I would like to make it so, if I have a class MyBaseClass, anything that extends that, I can get the attr_accessor's defined in the subclasses. Something like this: class MyBaseClass < Hash def attributes # ?? end end class SubClass < MyBaseClass attr_accessor :id, :title, :body end puts SubClass.new.attributes.inspect #=> [id, title, body] What about to display just the attr_reader and attr_writer definitions?

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  • Can C++ Constructors be templates?

    - by Gokul
    Hi, I have non-template class with a templatized constructor. This code compiles for me. But i remember that somewhere i have referred that constructors cannot be templates. Can someone explain whether this is a valid usage? typedef double Vector; //enum Method {A, B, C, D, E, F}; struct A {}; class Butcher { public: template <class Method> Butcher(Method); private: Vector a, b, c; }; template <> Butcher::Butcher(struct A) : a(2), b(4), c(2) { // a = 0.5, 1; // b = -1, 1, 3, 2; // c = 0, 1; } Thanks, Gokul.

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  • jQuery .parent() does not work

    - by Misha Moroshko
    Why the following code fails with: Error: class_a_jquery_objects[0].parent is not a function ? HTML: <div> <div class='a b'></div> <div class='b c'></div> <div class='c a'></div> </div> <div id='log'></div> JS: $(function() { var class_a_jquery_objects = $(".a"); $("#log").append(class_a_jquery_objects.length + "<br />"); $("#log").append(class_a_jquery_objects[0] + "<br />"); $("#log").append(class_a_jquery_objects[0].parent() + "<br />"); });

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  • Should we avoid to use Object as the input parameter/ output value of a method?

    - by developer.cyrus
    Take Java syntax as an example, though the question itself is language independent. If the following snippet takes an object MyAbstractEmailTemplate as input argument in the method setTemplate, the class MyGateway will then become tightly-coupled with the object MyAbstractEmailTemplate, which lessens the re-usability of the class MyGateway. A compromise is to use dependency-injection to ease the instantiation of MyAbstractEmailTemplate. This might solve the coupling problem to some extent, but the interface is still rigid, hardly providing enough ?exibility to other developers/ applications. So if we only use primitive data type (or even plain XML in web service) as the input/ output of a method, it seems the coupling problem no longer exists. So what do you think? public class MyGateway { protected MyAbstractEmailTemplate template; publoc void setTemplate(MyAbstractEmailTemplate template) { this.template = template; } }

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  • Check if a variable is empty

    - by Thomas
    I have some user-submitted variables that I want to display in a different part of my site like this: <div class="pre_box">Term: </div> <div class="entry"><?php $key='term'; echo get_post_meta($post->ID, $key, true); ?></div> Occasionally, these variables might be empty in which case I don't want to display the label for the empty variable. In the example above I would want to hide the <div class="pre_box">Term: </div> part. Is there some simple way to check if a php variable like the one above is empty and prevent the label from being displayed?

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  • IRepository with Inherited Classes

    - by Stacey
    In keeping with the Repository pattern of data input, I've a question in regards to using inherited classes. For instance, suppose I would have the class... class Employee IEmployeeRepository { Add(Employee employee); } This works fine, nothing wrong with it so far... but now let's say I continue on.. class Manager : Employee Okay, now let's assume that I never need to enter a manager different than an Employee? What's the best approach here? Would a scenario such as .. IEmployeeRepository { Add<T>(T employee) where T : Employee } Be the best approach, or do I need to abstract a different repository for each type?

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  • Push html attribute to array onClick

    - by Hunkeone
    I'm trying to push number attribute of the element to the array onclick with a simple function, but array contains only empty values separated with commas. Here's html code. <button type="button" class="btn btn-success btn-lg" number="12" onclick="basket.push(this.number)">toBakset</button> <button type="button" class="btn btn-success btn-lg" number="15" onclick="basket.push(this.number)">toBakset</button> <button type="button" class="btn btn-success btn-lg" number="18" onclick="basket.push(this.number)">toBakset</button> from the start "basket" array is empty. Seems this question is so dumb but I can't find a solution :(

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  • Possible for C++ template to check for a function's existence?

    - by andy
    Is it possible to write a C++ template that changes behavior depending on if a certain member function is defined on a class? Here's a simple example of what I would want to write: template<class T> std::string optionalToString(T* obj) { if (FUNCTION_EXISTS(T->toString)) return obj->toString(); else return "toString not defined"; } So if class T has "toString" defined then it uses it, otherwise it doesn't. The magical part that I don't know how to do is the "FUNCTION_EXISTS" part.

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  • [PHP] Processing custom XML namespace within XSL

    - by sander
    I'm using the php class XSLTProcessor to generate HTML from a xsl. Within the xsl, I'd like all my custom namespace elements to be processed by my own processor class. So for example: <xsl:for-each select="doc/elements/*"> <doc:renderElement element="." /> </xsl:for-each> This should call the method renderElement of an instance of my custom processor class. I know I can enable calling php functions by using the registerPHPFunctions function. However, this only seems to support calling static methods.

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  • How to Dispose myClass with Garbage Collecter C#

    - by Ibrahim AKGUN
    Hi, I have a class and got a method that doin so many things in memory and need to be disposed when its jobs done.But i have looked for MSDN for solution.There is an example thats not solved my problem.When my Class is instanced and run this method my memory is getting bigger and bigger.How can i Dispose it when its job done ? Here is my CODES ; class Deneme { public Deneme() { } ~Deneme() { GC.Collect(); GC.SuppressFinalize(this); } public void TestMetodu() { System.Windows.Forms.MessageBox.Show("Test"); // This is my method that doing big jobs :) } } Deneme CCCX = new Deneme(); CCCX.TestMetodu(); CCCX = null; So i cant dispose it with this.

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  • non-scalar type requested

    - by lego69
    can somebody please help me with an error conversion from `A' to non-scalar type `B' requested I have class A and derived from it B, but I have problems with these rows: A a(1); A *pb = new B(a); B b = *pb; //here I have an error thanks in advance for any help class A { protected: int player; public: A(int initPlayer = 0); A(const A&); A& operator=(const A&); virtual ~A(){}; virtual void foo(); void foo() const; operator int(); }; class B: public A { public: B(int initPlayer): A(initPlayer){}; ~B(){}; virtual void foo(); };

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  • What is the use of reflection in Java/C# etc

    - by zengr
    I was just curious, why should we use reflection in the first place? // Without reflection Foo foo = new Foo(); foo.hello(); // With reflection Class cls = Class.forName("Foo"); Object foo = cls.newInstance(); Method method = cls.getMethod("hello", null); method.invoke(foo, null); We can simply create an object and call the class's method, but why do the same using forName, newInstance and getMthod functions? To make everything dynamic?

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  • How do I reference the other object in django models

    - by UserZero
    Hi, first post here.In Django, I want to have many files be associated with a particular model, so I'm doing a seperate model called files and have model 'A' 'have many' files. But I want my files to be saved in director named by model 'A'. So For example I want something like this: class Show(models.Model): name = models.CharField() showfolder = models.FilePathField() class Episode(models.Model): show = models.ForeignKey(Show) name = models.CharField() files = models.ManyToManyField(mp3) class Mp3(models.Model): file = FileField(upload_to=Episode.show.showfolder) So hopefully that last line expresses what I WANT it to do(get the folder name from Show object associated with the episode). The question is how would I really write that?(besides jumping through hoops in the controller.) Thanks.

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  • Which Java library lets me initialize an object's properties from a properties file?

    - by Kjetil Ødegaard
    Is there a Java library that lets you "deserialize" a properties file directly into an object instance? Example: say you have a file called init.properties: username=fisk password=frosk and a Java class with some properties: class Connection { private String username; private String password; public void setUsername(String username) { this.username = username; } public void setPassword(String password) { this.password = password; } } I want to do this: Connection c = MagicConfigurator.configure("init.properties", new Connection()) and have MagicConfigurator apply all the values from the properties file to the Connection instance. Is there a library with a class like this?

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  • App Engine: how would you... snapshotting entities

    - by Andrew B.
    Let's say you have two kinds, Message and Contact, related by a db.ListProperty of keys on Message. A user creates a message, adds some contacts as recipients, and emails the message. Later, the user deletes one of the contact entities that was a recipient of the message. Our application should delete the appropriate Contact entity, but we want to preserve the original recipient list for the message that was sent for the user's records. In essence, we want a snapshot of the message entity at the time it was sent. If we naively delete the contact entity, though, we lose snapshot integrity; if not, we are left with an invalid key. How would you handle this situation, either in controller logic or model changes? class User(db.Model): email = db.EmailProperty(required=True) class Contact(db.Model): email = db.EmailProperty(required=True) user = db.ReferenceProperty(User, collection_name='contacts') class Message(db.Model): recipients = db.ListProperty(db.Key) # contacts sender = db.ReferenceProperty(User, collection_name='messages') body = db.TextProperty() is_emailed = db.BooleanProperty(default=False)

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  • Sharing base object with inheritance

    - by max
    I have class Base. I'd like to extend its functionality in a class Derived. I was planning to write: class Derived(Base): def __init__(self, base_arg1, base_arg2, derived_arg1, derived_arg2): super().__init__(base_arg1, base_arg2) # ... def derived_method1(self): # ... Sometimes I already have a Base instance, and I want to create a Derived instance based on it, i.e., a Derived instance that shares the Base object (doesn't re-create it from scratch). I thought I could write a static method to do that: b = Base(arg1, arg2) # very large object, expensive to create or copy d = Derived.from_base(b, derived_arg1, derived_arg2) # reuses existing b object but it seems impossible. Either I'm missing a way to make this work, or (more likely) I'm missing a very big reason why it can't be allowed to work. Can someone explain which one it is? [Of course, if I used composition rather than inheritance, this would all be easy to do. But I was hoping to avoid the delegation of all the Base methods to Derived through __getattr__.]

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  • going to build a php MVC, what naming conventions do i need to be aware of?

    - by Haroldo
    I'm pretty new to OO PHP, however i get how it all works and am ready to start building an MVC for a big site i'm working on. I know it isnt necessary written that you must do it like this but there's gotta be some normal practises.... class names - camelcase? underscores? class files - same as class? url/post/get controll name - router.php? any other things i should be aware of before i embark?

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  • How are value types implemented in .NET

    - by Michael
    Been looking around the net and can't find any articles about how value types are actually implemented. For instance, an Int32 is a struct and it's direct parent is System.ValueType and that's ultimate parent is System.Object. Object is a class - I imagine ValueType is a class? What's the class hierarchy? What part does the CLR have to play? At what stage and how does the CLR know to allocate value types to the stack? (FYI, I am aware that value types are stored where they are declared).

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  • Hold border and Resize two or more DIV simultaneously in the same container

    - by Manu
    Code : <div id="widget1"> <div class="part blue">this is the part</div> <div class="part white">of the genial</div> <div class="part red">and good widget</div> </div> Let's say that div#widget1 is 99px width and div.part are 33px by default. How can I easily resize div.blue by increasing its width and deacreasing width of other div.part proportionnaly ? http://jqueryui.com/demos/resizable/#synchronous-resize : give an example which show element increase in the same time. Thanks,

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