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  • Pattern for managing reference count and object life

    - by Gopalakrishnan Subramani
    We have a serial port which is connected to hundreds of physical devices on the same wire. We have protocols like Modbus and Hart to handle the request and response between the application and devices. The question is related to managing the reference count of the channel. When no device is using the channel, the channel should be closed. public class SerialPortChannel { int refCount = 0; public void AddReference() { refCount++; } public void ReleaseReference() { refCount--; if (refCount <= 0) this.ReleasePort(); //This close the serial port } } For each device connected, we create a object for the device like device = new Device(); device.Attach(channel); //this calls channel.AddReference() When the device disconnect, device.Detach(channel); //this calls channel.ReleaseReference() I am not convinced by the reference count model. Are there any better way to handle this problem in .NET World?

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  • How can i return IEnumarable data from function in GridView with Entity FrameWork?

    - by programmerist
    protected IEnumerable GetPersonalsData() { // List personel; using (FirmaEntities firmactx = new FirmaEntities()) { var personeldata = (from p in firmactx.Personals select new { p.ID, p.Name, p.SurName }); return personeldata.AsEnumerable(); } } i wan to send GetPersonelData() into GridView DataSource. Like That: gwPersonel.DataSource = GetPersonelData(); gwPersonel.DataBind(); it monitored to me on : gwPersonel.DataBind(); this error: "The ObjectContext instance has been disposed and can no longer be used for operations that require a connection."

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  • Python: Recursively access dict via attributes as well as index access?

    - by Luke Stanley
    I'd like to be able to do something like this: from dotDict import dotdictify life = {'bigBang': {'stars': {'planets': [] } } } dotdictify(life) #this would be the regular way: life['bigBang']['stars']['planets'] = {'earth': {'singleCellLife': {} }} #But how can we make this work? life.bigBang.stars.planets.earth = {'singleCellLife': {} } #Also creating new child objects if none exist, using the following syntax life.bigBang.stars.planets.earth.multiCellLife = {'reptiles':{},'mammals':{}} My motivations are to improve the succinctness of the code, and if possible use similar syntax to Javascript for accessing JSON objects for efficient cross platform development.(I also use Py2JS and similar.)

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  • What do you call functions which get and set?

    - by nickf
    The jQuery framework has a lot of functions which will either retrieve or mutate values depending on the parameters passed: $(this).html(); // get the html $(this).html('blah'); // set the html Is there a standard name for functions which behave like this?

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  • How can i return abstract class from any factory?

    - by programmerist
    using System; using System.Collections.Generic; using System.Linq; using System.Web; namespace EfTestFactory { public abstract class _Company { public abstract List<Personel> GetPersonel(); public abstract List<Prim> GetPrim(); public abstract List<Finans> GetFinans(); } public abstract class _Radyoloji { public abstract List<string> GetRadyoloji(); } public abstract class _Satis { public abstract List<string> GetSatis(); } public abstract class _Muayene { public abstract List<string> GetMuayene(); } public class Company : _Company { public override List<Personel> GetPersonel() { throw new NotImplementedException(); } public override List<Prim> GetPrim() { throw new NotImplementedException(); } public override List<Finans> GetFinans() { throw new NotImplementedException(); } } public class Radyoloji : _Radyoloji { public override List<string> GetRadyoloji() { throw new NotImplementedException(); } } public class Satis : _Satis { public override List<string> GetSatis() { throw new NotImplementedException(); } } public class Muayene : _Muayene { public override List<string> GetMuayene() { throw new NotImplementedException(); } } public class GenoTipController { public object CreateByEnum(DataModelType modeltype) { string enumText = modeltype.ToString(); // will return for example "Company" Type classType = Type.GetType(enumText); // the Type for Company class object t = Activator.CreateInstance(classType); // create an instance of Company class return t; } } public class AntsController { static Dictionary<DataModelType, Func<object>> s_creators = new Dictionary<DataModelType, Func<object>>() { { DataModelType.Radyoloji, () => new _Radyoloji() }, { DataModelType.Company, () => new _Company() }, { DataModelType.Muayene, () => new _Muayene() }, { DataModelType.Satis, () => new _Satis() }, }; public object CreateByEnum(DataModelType modeltype) { return s_creators[modeltype](); } } public class CompanyView { public static List<Personel> GetPersonel() { GenoTipController controller = new GenoTipController(); _Company company = controller.CreateByEnum(DataModelType.Company) as _Company; return company.GetPersonel(); } } public enum DataModelType { Radyoloji, Satis, Muayene, Company } } if i write above codes i see some error: Cannot create an instance of abstract class or interface 'EfTestFactory_Company'How can i solve it? Look please below pic.

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  • Specialization hierarchy in a domain-model

    - by devoured elysium
    I'm trying to make the domain model of a management system. I have the following kinds of persons in this system: employee manager top mananger I decided to define a User, from where employee, manager and top manager will specialize from. What I don't know is what kind of specialization hierarchy I should choose from. I thought of two ways: or Which might be preferable and why? As a long time coder, every time I try to do a domain-model, I have to fight against the idea of trying to think in how I'm going to code this. From what I've understood, I should not think about those matters in the domain-model, only in object relationships. I don't have to think of code duplication or any of these kind of details here, so I can't really pick any of the options over the other. Thanks

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  • property not updating in object when page is posted

    - by Jared
    Hi I have set a property in a constructor like so function __construct() { $this->count = count(@$_SESSION['filearray']); //count how many files in array } and using it in condition statements if($this->count > 10) //then do something but it appears the count isn't being updated when I use another method of injecting values into this 'filearray' until I refresh the page. am I doing something wrong? I thought that my constructor would detect a change had been made in the session and whenever I call $this-count I would get the current count value but it seems to be 1 step behind until I refresh the page. If this is all vague I can include my form page that has all the method calls, but this is the jist of my question, why is my property not updating and how do I fix it :) TIA

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  • How do I improve the efficiency of the queries executed by this generic Linq-to-SQL data access clas

    - by Lee D
    Hi all, I have a class which provides generic access to LINQ to SQL entities, for example: class LinqProvider<T> //where T is a L2S entity class { DataContext context; public virtual IEnumerable<T> GetAll() { return context.GetTable<T>(); } public virtual T Single(Func<T, bool> condition) { return context.GetTable<T>().SingleOrDefault(condition); } } From the front end, both of these methods appear to work as you would expect. However, when I run a trace in SQL profiler, the Single method is executing what amounts to a SELECT * FROM [Table], and then returning the single entity that meets the given condition. Obviously this is inefficient, and is being caused by GetTable() returning all rows. My question is, how do I get the query executed by the Single() method to take the form SELECT * FROM [Table] WHERE [condition], rather than selecting all rows then filtering out all but one? Is it possible in this context? Any help appreciated, Lee

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  • Cpp some basic problems

    - by DevAno1
    Hello. My task was as follows : Create class Person with char*name and int age. Implement contructor using dynamic allocation of memory for variables, destructor, function init and friend function show. Then transform this class to header and cpp file and implement in other program. Ok so I've almost finished my Person class, but I get error after destructor. First question is how to write this properly ? #include <iostream> using namespace std; class Person { char* name; int age; public: int * take_age(); Person(){ int size=0; cout << "Give length of char*" << endl; cin >> size; name = new char[size]; age = 0; } ~Person(){ cout << "Destroying resources" << endl; delete *[] name; delete * take_age(); } friend void(Person &p); int * Person::take_age(){ return age; } void init(char* n, int a) { name = n; age = a; } void show(Person &p){ cout << "Name: " << p.name << "," << "age: " << p.age << endl; } }; int main(void) { Person *p = new Person; p->init("Mary", 25); p.show(); system("PAUSE"); return 0; } And now with header/implementation part : - do I need to introduce constructor in header/implementation files ? If yes - how? - my show() function is a friendly function. Should I take it into account somehow ? I already failed to return this task on my exam, but still I'd like to know how to implement it.

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  • Policy-based template design: How to access certain policies of the class?

    - by dehmann
    I have a class that uses several policies that are templated. It is called Dish in the following example. I store many of these Dishes in a vector (using a pointer to simple base class), but then I'd like to extract and use them. But I don't know their exact types. Here is the code; it's a bit long, but really simple: #include <iostream> #include <vector> struct DishBase { int id; DishBase(int i) : id(i) {} }; std::ostream& operator<<(std::ostream& out, const DishBase& d) { out << d.id; return out; } // Policy-based class: template<class Appetizer, class Main, class Dessert> class Dish : public DishBase { Appetizer appetizer_; Main main_; Dessert dessert_; public: Dish(int id) : DishBase(id) {} const Appetizer& get_appetizer() { return appetizer_; } const Main& get_main() { return main_; } const Dessert& get_dessert() { return dessert_; } }; struct Storage { typedef DishBase* value_type; typedef std::vector<value_type> Container; typedef Container::const_iterator const_iterator; Container container; Storage() { container.push_back(new Dish<int,double,float>(0)); container.push_back(new Dish<double,int,double>(1)); container.push_back(new Dish<int,int,int>(2)); } ~Storage() { // delete objects } const_iterator begin() { return container.begin(); } const_iterator end() { return container.end(); } }; int main() { Storage s; for(Storage::const_iterator it = s.begin(); it != s.end(); ++it){ std::cout << **it << std::endl; std::cout << "Dessert: " << *it->get_dessert() << std::endl; // ?? } return 0; } The tricky part is here, in the main() function: std::cout << "Dessert: " << *it->get_dessert() << std::endl; // ?? How can I access the dessert? I don't even know the Dessert type (it is templated), let alone the complete type of the object that I'm getting from the storage. This is just a toy example, but I think my code reduces to this. I'd just like to pass those Dish classes around, and different parts of the code will access different parts of it (in the example: its appetizer, main dish, or dessert).

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  • RijndaelManaged Padding when data matches block size

    - by trampster
    If I use PKCS7 padding in RijndaelManaged with 16 bytes of data then I get 32 bytes of data output. It appears that for PKCS7 when the data size matches the block size it adds a whole extra block of data. If I use Zeros padding for 16 bytes of data I get out 16 bytes of data. So for Zeros padding if the data matches the block size then it doesn't pad. I have searched through the documentation and it says nothing about this difference in padding behavior. Can someone please point me to some kind of documentation which specifies what the padding behavior should be for the different padding modes when the data size matches the block size.

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  • constructor function's object literal returns toString() method but no other method

    - by JohnMerlino
    I'm very confused with javascript methods defined in objects and the "this" keyword. In the below example, the toString() method is invoked when Mammal object instantiated: function Mammal(name){ this.name=name; this.toString = function(){ return '[Mammal "'+this.name+'"]'; } } var someAnimal = new Mammal('Mr. Biggles'); alert('someAnimal is '+someAnimal); Despite the fact that the toString() method is not invoked on the object someAnimal like this: alert('someAnimal is '+someAnimal.toString()); It still returns 'someAnimal is [Mammal "Mr. Biggles"]' . That doesn't make sense to me because the toString() function is not being called anywhere. Then to add even more confusion, if I change the toString() method to a method I make up such as random(): function Mammal(name){ this.name=name; this.random = function(){ return Math.floor(Math.random() * 15); } } var someAnimal = new Mammal('Mr. Biggles'); alert(someAnimal); It completely ignores the random method (despite the fact that it is defined the same way was the toString() method was) and returns: [object object] Another issue I'm having trouble understanding with inheritance is the value of "this". For example, in the below example function person(w,h){ width.width = w; width.height = h; } function man(w,h,s) { person.call(this, w, h); this.sex = s; } "this" keyword is being send to the person object clearly. However, does "this" refer to the subclass (man) or the super class (person) when the person object receives it? Thanks for clearing up any of the confusion I have with inheritance and object literals in javascript.

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  • How to easily substitute a Base class

    - by JTom
    Hi, I have the following hierarchy of classes class classOne { virtual void abstractMethod() = 0; }; class classTwo : public classOne { }; class classThree : public classTwo { }; All classOne, classTwo and classThree are abstract classes, and I have another class that is defining the pure virtual methods class classNonAbstract : public classThree { void abstractMethod(); // Couple of new methods void doIt(); void doItToo(); }; And right now I need it differently...I need it like class classNonAbstractOne : public classOne { void abstractMethod(); // Couple of new methods void doIt(); void doItToo(); }; class classNonAbstractTwo : public classTwo { void abstractMethod(); // Couple of new methods void doIt(); void doItToo(); }; and class classNonAbstractThree : public classThree { void abstractMethod(); // Couple of new methods void doIt(); void doItToo(); }; But all the nonAbstract classes have the same new methods, with the same code...and I would like to avoid copying all the methods and it's code to every nonAbstract class. How could I accomplish that? Hopefully it's understandable...

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  • PHP MVC Framework Structure

    - by bigstylee
    I am sorry about the amount of code here. I have tried to show enough for understanding while avoiding confusion (I hope). I have included a second copy of the code at Pastebin. (The code does execute without error/notice/warning.) I am currently creating a Content Management System while trying to implement the idea of Model View Controller. I have only recently come across the concept of MVC (within the last week) and trying to implement this into my current project. One of the features of the CMS is dynamic/customisable menu areas and each feature will be represented by a controller. Therefore there will be multiple versions of the Controller Class, each with specific extended functionality. I have looked at a number of tutorials and read some open source solutions to the MVC Framework. I am now trying to create a lightweight solution for my specific requirements. I am not interested in backwards compatibility, I am using PHP 5.3. An advantage of the Base class is not having to use global and can directly access any loaded class using $this->Obj['ClassName']->property/function();. Hoping to get some feedback using the basic structure outlined (with performance in mind). Specifically; a) Have I understood/implemented the concept of MVC correctly? b) Have I understood/implemented Object Orientated techniques with PHP 5 correctly? c) Should the class propertise of Base be static? d) Improvements? Thank you very much in advance! <?php /* A "Super Class" that creates/stores all object instances */ class Base { public static $Obj = array(); // Not sure this is the correct use of the "static" keyword? public static $var; static public function load_class($directory, $class) { echo count(self::$Obj)."\n"; // This does show the array is getting updated and not creating a new array :) if (!isset(self::$Obj[$class]) && !is_object(self::$Obj[$class])) //dont want to load it twice { /* Locate and include the class file based upon name ($class) */ return self::$Obj[$class] = new $class(); } return TRUE; } } /* Loads general configuration objects into the "Super Class" */ class Libraries extends Base { public function __construct(){ $this->load_class('library', 'Database'); $this->load_class('library', 'Session'); self::$var = 'Hello World!'; //testing visibility /* Other general funciton classes */ } } class Database extends Base { /* Connects to the the database and executes all queries */ public function query(){} } class Session extends Base { /* Implements Sessions in database (read/write) */ } /* General functionality of controllers */ abstract class Controller extends Base { protected function load_model($class, $method) { /* Locate and include the model file */ $this->load_class('model', $class); call_user_func(array(self::$Obj[$class], $method)); } protected function load_view($name) { /* Locate and include the view file */ #include('views/'.$name.'.php'); } } abstract class View extends Base { /* ... */ } abstract class Model extends Base { /* ... */ } class News extends Controller { public function index() { /* Displays the 5 most recent News articles and displays with Content Area */ $this->load_model('NewsModel', 'index'); $this->load_view('news', 'index'); echo $this->var; } public function menu() { /* Displays the News Title of the 5 most recent News articles and displays within the Menu Area */ $this->load_model('news/index'); $this->load_view('news/index'); } } class ChatBox extends Controller { /* ... */ } /* Lots of different features extending the controller/view/model class depending upon request and layout */ class NewsModel extends Model { public function index() { echo $this->var; self::$Obj['Database']->query(/*SELECT 5 most recent news articles*/); } public function menu() { /* ... */ } } $Libraries = new Libraries; $controller = 'News'; // Would be determined from Query String $method = 'index'; // Would be determined from Query String $Content = $Libraries->load_class('controller', $controller); //create the controller for the specific page if (in_array($method, get_class_methods($Content))) { call_user_func(array($Content, $method)); } else { die('Bad Request'. $method); } $Content::$var = 'Goodbye World'; echo $Libraries::$var . ' - ' . $Content::$var; ?> /* Ouput */ 0 1 2 3 Goodbye World! - Goodbye World

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  • OO Objective-C design with XML parsing

    - by brainfsck
    Hi, I need to parse an XML record that represents a QuizQuestion. The "type" attribute tells the type of question. I then need to create an appropriate subclass of QuizQuestion based on the question type. The following code works ([auto]release statements omitted for clarity): QuizQuestion *question = [[QuizQuestion alloc] initWithXMLString:xml]; if( [ [question type] isEqualToString:@"multipleChoiceQuestion"] ) { [myQuestions addObject:[[MultipleChoiceQuizQuestion alloc] initWithXMLString:xml]; } //QuizQuestion.m -(id)initWithXMLString:(NSString*)xml { self.type = ...// parse "type" attribute from xml // parse the rest of the xml } //MultipleChoiceQuizQuestion.m -(id)initWithXMLString:(NSString*)xml { if( self= [super initWithXMLString:xml] ) { // multiple-choice stuff } } Of course, this means that the XML is parsed twice: once to find out the type of QuizQuestion, and once when the appropriate QuizQuestion is initialized. To prevent parsing the XML twice, I tried the following approach: // MultipleChoiceQuizQuestion.m -(id)initWithQuizRecord:(QuizQuestion*)record { self=record; // record has already parsed the "type" and other parameters // multiple-choice stuff } However, this fails due to the "self=record" assignment; whenever the MultipleChoiceQuizQuestion tries to call an instance-method, it tries to call the method on the QuizQuestion class instead. Can someone tell me the correct approach for parsing XML into the appropriate subclass when the parent class needs to be initialized to know which subclass is appropriate?

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  • Bad method names and what it says about code structure.

    - by maxfridbe
    (Apologies in advance if this is a re-post but I didn't find similar posts) What bad method name patterns have you seen in code and what did it tell you about the code. For instance, I keep seeing: public void preform___X___IfNecessary(...); I believe that this is bad because the operation X has an inversion of conditions. Note that this is a public method because classes methods might legitimately require private helpers like this

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  • Can can I reference extended methods/params without having to cast from the base class object return

    - by Greg
    Hi, Is there away to not have a "cast" the top.First().Value() return to "Node", but rather have it automatically assume this (as opposed to NodeBase), so I then see extended attributes for the class I define in Node? That is is there a way to say: top.Nodes.First().Value.Path; as opposed to now having to go: ((Node)top.Nodes.First().Value).Path) thanks [TestMethod()] public void CreateNoteTest() { var top = new Topology(); Node node = top.CreateNode("a"); node.Path = "testpath"; Assert.AreEqual("testpath", ((Node)top.Nodes.First().Value).Path); // *** HERE *** } class Topology : TopologyBase<string, Node, Relationship> { } class Node : NodeBase<string> { public string Path { get; set; } } public class NodeBase<T> { public T Key { get; set; } public NodeBase() { } public NodeBase(T key) { Key = key; } } public class TopologyBase<TKey, TNode, TRelationship> where TNode : NodeBase<TKey>, new() where TRelationship : RelationshipBase<TKey>, new() { // Properties public Dictionary<TKey, NodeBase<TKey>> Nodes { get; private set; } public List<RelationshipBase<TKey>> Relationships { get; private set; } }

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  • What's the standard way to organize the contents of Java packages -- specifically the location of in

    - by RenderIn
    I suppose this could go for many OO languages. I'm building my domain objects and am not sure where the best place is for the interfaces & abstract classes. If I have a pets package with various implementations of the APet abstract class: should it live side-by-side with them or in the parent package? How about interfaces? It seems like they almost have to live above the implementations in the parent package, since there could potentially be other subpackages which implement it, while there seems to be a stronger correlation between one abstract class and a subpackage. e.g. com.foo com.foo.IConsumer (interface) com.foo.APet (abstract) com.foo.pets.Dog extends APet implements IConsumer OR com.foo com.foo.IConsumer (interface) com.foo.pets.APet (abstract) com.foo.pets.Dog extends APet implements IConsumer or something else?

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