Search Results

Search found 45436 results on 1818 pages for 'singleton class'.

Page 12/1818 | < Previous Page | 8 9 10 11 12 13 14 15 16 17 18 19  | Next Page >

• How to bind a control to a singleton in Cocoa?

  - by SphereCat1

  I have a singleton in my FTP app designed to store all of the types of servers that the app can handle, such as FTP or Amazon S3. These types are plugins which are located in the app bundle. Their path is located by applicationWillFinishLoading: and sent to the addServerType: method inside the singleton to be loaded and stored in an NSMutableDictionary. My question is this: How do I bind an NSDictionaryController to the dictionary inside the singleton instance? Can it be done in IB, or do I have to do it in code? I need to be able to display the dictionary's keys in an NSPopupButton so the user can select a server type. Thanks in advance! SphereCat1

  Read the article

• Do I still have to implement a singleton class by hand in .net, even when using .Net4.0?

  - by Hamish Grubijan

  Once the singleton pattern is understood, writing subsequent singleton classes in C# is a brainless exercise. I would hope that the framework would help you by providing an interface or a base class to do that. Here is how I envision it: public sealed class Schablone : ISingleton<Schablone> { // Stuff forced by the interface goes here // Extra logic goes here } Does what I am looking for exist? Is there some syntactic sugar for constructing a singleton class - whether with an interface, a class attribute, etc.? Can one write a useful and bullet-proof ISingleton themselves? Care to try? Thanks!

  Read the article

• Is this a valid, lazy, thread-safe Singleton implementation for C#?

  - by Matthew

  I implemented a Singleton pattern like this: public sealed class MyClass { ... public static MyClass Instance { get { return SingletonHolder.instance; } } ... static class SingletonHolder { public static MyClass instance = new MyClass (); } } From Googling around for C# Singleton implementations, it doesn't seem like this is a common way to do things in C#. I found one similar implementation, but the SingletonHolder class wasn't static, and included an explicit (empty) static constructor. Is this a valid, lazy, thread-safe way to implement the Singleton pattern? Or is there something I'm missing?

  Read the article

• Foolishness Check: PHP Class finds Class file but not Class in the file.

  - by Daniel Bingham

  I'm at a loss here. I've defined an abstract superclass in one file and a subclass in another. I have required the super-classes file and the stack trace reports to find an include it. However, it then returns an error when it hits the 'extends' line: Fatal error: Class 'HTMLBuilder' not found in View/Markup/HTML/HTML4.01/HTML4_01Builder.php on line 7. I had this working with another class tree that uses factories a moment ago. I just added the builder layer in between the factories and the consumer. The factory layer looked almost exactly the same in terms of includes and dependencies. So that makes me think I must have done something silly that's causes the HTMLBuilder.php file to not be included correctly or interpreted correctly or some such. Here's the full stack trace (paths slightly altered): # Time Memory Function Location 1 0.0001 53904 {main}( ) ../index.php:0 2 0.0002 67600 require_once( 'View/Page.php' ) ../index.php:3 3 0.0003 75444 require_once( 'View/Sections/SectionFactory.php' ) ../Page.php:4 4 0.0003 81152 require_once( 'View/Sections/HTML/HTMLSectionFactory.php' ) ../SectionFactory.php:3 5 0.0004 92108 require_once( 'View/Sections/HTML/HTMLTitlebarSection.php' ) ../HTMLSectionFactory.php:5 6 0.0005 99716 require_once( 'View/Markup/HTML/HTMLBuilder.php' ) ../HTMLTitlebarSection.php:3 7 0.0005 103580 require_once( 'View/Markup/MarkupBuilder.php' ) ../HTMLBuilder.php:3 8 0.0006 124120 require_once( 'View/Markup/HTML/HTML4.01/HTML4_01Builder.php' ) ../MarkupBuilder.php:3 Here's the code in question: Parent class (View/Markup/HTML/HTMLBuilder.php): <?php require_once('View/Markup/MarkupBuilder.php'); abstract class HTMLBuilder extends MarkupBuilder { public abstract function getLink($text, $href); public abstract function getImage($src, $alt); public abstract function getDivision($id, array $classes=NULL, array $children=NULL); public abstract function getParagraph($text, array $classes=NULL, $id=NULL); } ?> Child Class, (View/Markup/HTML/HTML4.01/HTML4_01Builder.php): <?php require_once('HTML4_01Factory.php'); require_once('View/Markup/HTML/HTMLBuilder.php'); class HTML4_01Builder extends HTMLBuilder { private $factory; public function __construct() { $this->factory = new HTML4_01Factory(); } public function getLink($href, $text) { $link = $this->factory->getA(); $link->addAttribute('href', $href); $link->addChild($this->factory->getText($text)); return $link; } public function getImage($src, $alt) { $image = $this->factory->getImg(); $image->addAttribute('src', $src); $image->addAttribute('alt', $alt); return $image; } public function getDivision($id, array $classes=NULL, array $children=NULL) { $div = $this->factory->getDiv(); $div->setID($id); if(!empty($classes)) { $div->addClasses($classes); } if(!empty($children)) { $div->addChildren($children); } return $div; } public function getParagraph($text, array $classes=NULL, $id=NULL) { $p = $this->factory->getP(); $p->addChild($this->factory->getText($text)); if(!empty($classes)) { $p->addClasses($classes); } if(!empty($id)) { $p->setID($id); } return $p; } } ?> I would appreciate any and all ideas. I'm at a complete loss here as to what is going wrong. I'm sure it's something stupid I just can't see...

  Read the article

• Prefer class members or passing arguments between internal methods?

  - by geoffjentry

  Suppose within the private portion of a class there is a value which is utilized by multiple private methods. Do people prefer having this defined as a member variable for the class or passing it as an argument to each of the methods - and why? On one hand I could see an argument to be made that reducing state (ie member variables) in a class is generally a good thing, although if the same value is being repeatedly used throughout a class' methods it seems like that would be an ideal candidate for representation as state for the class to make the code visibly cleaner if nothing else. Edit: To clarify some of the comments/questions that were raised, I'm not talking about constants and this isn't relating to any particular case rather just a hypothetical that I was talking to some other people about. Ignoring the OOP angle for a moment, the particular use case that I had in mind was the following (assume pass by reference just to make the pseudocode cleaner) int x doSomething(x) doAnotherThing(x) doYetAnotherThing(x) doSomethingElse(x) So what I mean is that there's some variable that is common between multiple functions - in the case I had in mind it was due to chaining of smaller functions. In an OOP system, if these were all methods of a class (say due to refactoring via extracting methods from a large method), that variable could be passed around them all or it could be a class member.

  Read the article

• ctags doesn't work when class is defined like "class Gem::SystemExitException"

  - by dan

  You can define a class in a namespace like this class Gem class SystemExitException end end or class Gem::SystemExitException end When code uses first method of class definition, ctags indexes the class definition like this: SystemExitException test_class.rb /^ class SystemExitException$/;" c class:Gem With the second way, ctags indexes it like this: Gem rubygems/exceptions.rb /^class Gem::SystemExitException < SystemExit$/;" c The problem with the second way is that you can't put your cursor (in vim) over a reference to "Gem::SystemExitException" and have that jump straight to the class definition. Your only recourse is to page through all the (110!) class definitions that start with "Gem::" and find the one you're looking for. Does anyone know of a workaround? Maybe I should report this to the maintainer of ctags?

  Read the article

• Singleton code linker errors in vc 9.0. Runs fine in linux compiled with gcc

  - by user306560

  I have a simple logger that is implemented as a singleton. It works like i want when I compile and run it with g++ in linux but when I compile in Visual Studio 9.0 with vc++ I get the following errors. Is there a way to fix this? I don't mind changing the logger class around, but I would like to avoid changing how it is called. 1>Linking... 1>loggerTest.obj : error LNK2005: "public: static class Logger * __cdecl Logger::getInstance(void)" (?getInstance@Logger@@SAPAV1@XZ) already defined in Logger.obj 1>loggerTest.obj : error LNK2005: "public: void __thiscall Logger::log(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)" (?log@Logger@@QAEXABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z) already defined in Logger.obj 1>loggerTest.obj : error LNK2005: "public: void __thiscall Logger::closeLog(void)" (?closeLog@Logger@@QAEXXZ) already defined in Logger.obj 1>loggerTest.obj : error LNK2005: "private: static class Logger * Logger::_instance" (?_instance@Logger@@0PAV1@A) already defined in Logger.obj 1>Logger.obj : error LNK2001: unresolved external symbol "private: static class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > Logger::_path" (?_path@Logger@@0V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@A) 1>loggerTest.obj : error LNK2001: unresolved external symbol "private: static class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > Logger::_path" (?_path@Logger@@0V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@A) 1>Logger.obj : error LNK2001: unresolved external symbol "private: static class boost::mutex Logger::_mutex" (?_mutex@Logger@@0Vmutex@boost@@A) 1>loggerTest.obj : error LNK2001: unresolved external symbol "private: static class boost::mutex Logger::_mutex" (?_mutex@Logger@@0Vmutex@boost@@A) 1>Logger.obj : error LNK2001: unresolved external symbol "private: static class std::basic_ofstream<char,struct std::char_traits<char> > Logger::_log" (?_log@Logger@@0V?$basic_ofstream@DU?$char_traits@D@std@@@std@@A) 1>loggerTest.obj : error LNK2001: unresolved external symbol "private: static class std::basic_ofstream<char,struct std::char_traits<char> > Logger::_log" (?_log@Logger@@0V?$basic_ofstream@DU?$char_traits@D@std@@@std@@A) The code, three files Logger.h Logger.cpp test.cpp #ifndef __LOGGER_CPP__ #define __LOGGER_CPP__ #include "Logger.h" Logger* Logger::_instance = 0; //string Logger::_path = "log"; //ofstream Logger::_log; //boost::mutex Logger::_mutex; Logger* Logger::getInstance(){ { boost::mutex::scoped_lock lock(_mutex); if(_instance == 0) { _instance = new Logger; _path = "log"; } } //mutex return _instance; } void Logger::log(const std::string& msg){ { boost::mutex::scoped_lock lock(_mutex); if(!_log.is_open()){ _log.open(_path.c_str()); } if(_log.is_open()){ _log << msg.c_str() << std::endl; } } } void Logger::closeLog(){ Logger::_log.close(); } #endif ` ... #ifndef __LOGGER_H__ #define __LOGGER_H__ #include <iostream> #include <string> #include <fstream> #include <boost/thread/mutex.hpp> #include <boost/thread.hpp> using namespace std; class Logger { public: static Logger* getInstance(); void log(const std::string& msg); void closeLog(); protected: Logger(){} private: static Logger* _instance; static string _path; static bool _logOpen; static ofstream _log; static boost::mutex _mutex; //check mutable }; #endif test.cpp ` #include <iostream> #include "Logger.cpp" using namespace std; int main(int argc, char *argv[]) { Logger* log = Logger::getInstance(); log->log("hello world\n"); return 0; }

  Read the article

• Why do pure virtual base classes get direct access to static data members while derived instances do

  - by Shamster

  I've created a simple pair of classes. One is pure virtual with a static data member, and the other is derived from the base, as follows: #include <iostream> template <class T> class Base { public: Base (const T _member) { member = _member; } static T member; virtual void Print () const = 0; }; template <class T> T Base<T>::member; template <class T> void Base<T>::Print () const { std::cout << "Base: " << member << std::endl; } template <class T> class Derived : public Base<T> { public: Derived (const T _member) : Base<T>(_member) { } virtual void Print () const { std::cout << "Derived: " << this->member << std::endl; } }; I've found from this relationship that when I need access to the static data member in the base class, I can call it with direct access as if it were a regular, non-static class member. i.e. - the Base::Print() method does not require a this- modifier. However, the derived class does require the this-member indirect access syntax. I don't understand why this is. Both class methods are accessing the same static data, so why does the derived class need further specification? A simple call to test it is: int main () { Derived<double> dd (7.0); dd.Print(); return 0; } which prints the expected "Derived: 7"

  Read the article

• Is there any reason for an object pool to not be treated as a singleton?

  - by Chris Charabaruk

  I don't necessarily mean implemented using the singleton pattern, but rather, only having and using one instance of a pool. I don't like the idea of having just one pool (or one per pooled type). However, I can't really come up with any concrete situations where there's an advantage to multiple pools for mutable types, at least not any where a single pool can function just as well. What advantages are there to having multiple pools over a singleton pool?

  Read the article

• Singleton Objects, C#

  In this article I will explain you about Singleton Objects using C#.

  Read the article

• Could a singleton type replace static methods and classes?

  - by MKO

  In C# Static methods has long served a purpose allowing us to call them without instantiating classes. Only in later year have we became more aware of the problems of using static methods and classes. They can’t use interfaces They can’t use inheritance They are hard to test because you can’t make mocks and stubs Is there a better way ? Obviously we need to be able to access library methods without instantiated classes all the time otherwise our code would become pretty cluttered One possibly solution is to use a new keyword for an old concept: the singleton. Singleton’s are global instances of a class, since they are instances we can use them as we would normal classes. In order to make their use nice and practical we'd need some syntactic sugar however Say that the Math class would be of type singleton instead of an actual class. The actual class containing all the default methods for the Math singleton is DefaultMath, which implements the interface IMath. The singleton would be declared as singleton Math : IMath { public Math { this = new DefaultMath(); } } If we wanted to substitute our own class for all math operations we could make a new class MyMath that inherits DefaultMath, or we could just inherit from the interface IMath and create a whole new Class. To make our class the active Math class, you'd do a simple assignment Math = new MyMath(); and voilá! the next time we call Math.Floor it will call your method. Note that for a normal singleton we'd have to write something like Math.Instance.Floor but the compiler eliminates the need for the Instance property Another idea would be to be able to define a singletons as Lazy so they get instantiated only when they're first called, like lazy singleton Math : IMath What do you think, would it have been a better solution that static methods and classes? Is there any problems with this approach?

  Read the article

• Class Plugins in PHP?

  - by YuriKolovsky

  i just got some more questions while learning PHP, does php implement any built in plugin system? so the plugin would be able to change the behavior of the core component. for example something like this works: include 'core.class.php'; include 'plugin1.class.php'; include 'plugin2.class.php'; new plugin2; where core.class.php contains class core { public function coremethod1(){ echo 'coremethod1'; } public function coremethod2(){ echo 'coremethod2'; } } plugin1.class.php contains class plugin1 extends core { public function coremethod1(){ echo 'plugin1method1'; } } plugin2.class.php contains class plugin2 extends plugin1 { public function coremethod2(){ echo 'plugin2method2'; } } This would be ideal, if not for the problem that now the plugins are dependable on each other, and removing one of the plugins: include 'core.class.php'; //include 'plugin1.class.php'; include 'plugin2.class.php'; new plugin2; breaks the whole thing... are there any proper methods to doing this? if there are not, them i might consider moving to a different langauge that supports this... thanks for any help.

  Read the article

• Interface vs Abstract Class (general OO)

  - by Kave

  Hi, I have had recently two telephone interviews where I've been asked about the differences between an Interface and an Abstract class. I have explained every aspect of them I could think of, but it seems they are waiting for me to mention something specific, and I dont know what it is. From my experience I think the following is true, if i am missing a major point please let me know: Interface: Every single Method declared in an Interface will have to be implemented in the subclass. Only Events, Delegates, Properties (C#) and Methods can exist in a Interface. A class can implement multiple Interfaces. Abstract Class Only Abstract methods have to be implemented by the subclass. An Abstract class can have normal methods with implementations. Abstract class can also have class variables beside Events, Delegates, Properties and Methods. A class can only implement one abstract class only due non-existence of Multi-inheritance in C#. 1) After all that the interviewer came up with the question What if you had an Abstract class with only abstract methods, how would that be different from an interface? I didnt know the answer but I think its the inheritance as mentioned above right? 2) An another interviewer asked me what if you had a Public variable inside the interface, how would that be different than in Abstract Class? I insisted you can't have a public variable inside an interface. I didn't know what he wanted to hear but he wasn't satisfied either. Many Thanks for clarification, Kave See Also: When to use an interface instead of an abstract class and vice versa Interfaces vs. Abstract Classes How do you decide between using an Abstract Class and an Interface?

  Read the article

• PHP Access property of a class from within a class instantiated in the original class.

  - by Iain

  I'm not certain how to explain this with the correct terms so maybe an example is the best method... $master = new MasterClass(); $master->doStuff(); class MasterClass { var $a; var $b; var $c; var $eventProccer; function MasterClass() { $this->a = 1; $this->eventProccer = new EventProcess(); } function printCurrent() { echo '<br>'.$this->a.'<br>'; } function doStuff() { $this->printCurrent(); $this->eventProccer->DoSomething(); $this->printCurrent(); } } class EventProcess { function EventProcess() {} function DoSomething() { // trying to access and change the parent class' a,b,c properties } } My problem is i'm not certain how to access the properties of the MasterClass from within the EventProcess-DoSomething() method? I would need to access, perform operations on and update the properties. The a,b,c properties will be quite large arrays and the DoSomething() method would be called many times during the execuction of the script. Any help or pointers would be much appreciated :)

  Read the article

• DataAnnotation attributes buddy class strangeness - ASP.NET MVC

  - by JK

  Given this POCO class that was automatically generated by an EntityFramework T4 template (has not and can not be manually edited in any way): public partial class Customer { [Required] [StringLength(20, ErrorMessage = "Customer Number - Please enter no more than 20 characters.")] [DisplayName("Customer Number")] public virtual string CustomerNumber { get;set; } [Required] [StringLength(10, ErrorMessage = "ACNumber - Please enter no more than 10 characters.")] [DisplayName("ACNumber")] public virtual string ACNumber{ get;set; } } Note that "ACNumber" is a badly named database field, so the autogenerator is unable to generate the correct display name and error message which should be "Account Number". So we manually create this buddy class to add custom attributes that could not be automatically generated: [MetadataType(typeof(CustomerAnnotations))] public partial class Customer { } public class CustomerAnnotations { [NumberCode] // This line does not work public virtual string CustomerNumber { get;set; } [StringLength(10, ErrorMessage = "Account Number - Please enter no more than 10 characters.")] [DisplayName("Account Number")] public virtual string ACNumber { get;set; } } Where [NumberCode] is a simple regex based attribute that allows only digits and hyphens: [AttributeUsage(AttributeTargets.Property)] public class NumberCodeAttribute: RegularExpressionAttribute { private const string REGX = @"^[0-9-]+$"; public NumberCodeAttribute() : base(REGX) { } } NOW, when I load the page, the DisplayName attribute works correctly - it shows the display name from the buddy class not the generated class. The StringLength attribute does not work correctly - it shows the error message from the generated class ("ACNumber" instead of "Account Number"). BUT the [NumberCode] attribute in the buddy class does not even get applied to the AccountNumber property: foreach (ValidationAttribute attrib in prop.Attributes.OfType<ValidationAttribute>()) { // This collection correctly contains all the [Required], [StringLength] attributes // BUT does not contain the [NumberCode] attribute ApplyValidation(generator, attrib); } Why does the prop.Attributes.OfType<ValidationAttribute>() collection not contain the [NumberCode] attribute? NumberCode inherits RegularExpressionAttribute which inherits ValidationAttribute so it should be there. If I manually move the [NumberCode] attribute to the autogenerated class, then it is included in the prop.Attributes.OfType<ValidationAttribute>() collection. So what I don't understand is why this particular attribute does not work in when in the buddy class, when other attributes in the buddy class do work. And why this attribute works in the autogenerated class, but not in the buddy. Any ideas? Also why does DisplayName get overriden by the buddy, when StringLength does not?

  Read the article

• What all does a compiler add to an empty class declaration?

  - by cambr

  Suppose, I write class A { }; compiler should provide (as and when needed) a constructor a destructor a copy constructor = operator Is this all what the compiler provides? Are there any additions or deletions to this list?

  Read the article

• Why and when should I make a class 'static'? What is the purpose of 'static' keyword on classes?

  - by Saeed Neamati

  The static keyword on a member in many languages mean that you shouldn't create an instance of that class to be able to have access to that member. However, I don't see any justification to make an entire class static. Why and when should I make a class static? What benefits do I get from making a class static? I mean, after declaring a static class, one should still declare all members which he/she wants to have access to without instantiation, as static too. This means that for example, Math class could be declared normal (not static), without affecting how developers code. In other words, making a class static or normal is kind of transparent to developers.

  Read the article

• Java Design Questions - Class, Function, Access Modifiers

  - by Ron

  I am newbie to Java. I have some design questions. Say I have a crawler application, that does the following: 1. Crawls a url and gets its content 2. Parses the contents 3. Displays the contents How do you decide between implementing a function or a class? -- Should the parser be a function of the crawler class, or should it be a class in itself, so it can be used by other applications as well? -- If it should be a class, should it be protected or public class? How do you decide between implementing a public or protected class? -- If I had to create a class to generate stats from the parsed contents for eg, should that class be protected (so only the crawler class can access it) or should it be public? Thanks Ron

  Read the article

• How can I load class's part using linq to sql without anonymous class or additional class?

  - by ais

  class Test { int Id{get;set;} string Name {get;set;} string Description {get;set;} } //1)ok context.Tests.Select(t => new {t.Id, t.Name}).ToList().Select(t => new Test{Id = t.Id, Name = t.Name}); //2)ok class TestPart{ int Id{get;set;} string Name {get;set;} } context.Tests.Select(t => new TestPart{Id = t.Id, Name = t.Name}).ToList().Select(t => new Test{Id = t.Id, Name = t.Name}); //3)error Explicit construction of entity type 'Test' in query is not allowed. context.Tests.Select(t => new Test{Id = t.Id, Name = t.Name}).ToList(); Is there any way to use third variant?

  Read the article

• question about class derivation in c++?

  - by jack22

  hi, i want to know some things about class derivation in c++ so i have super class x and an inherited class y and i did this class x{ public:a; private:b; protected:c; } class y:public x{ public:d; } in this case how y can access a,b,and c and by how i mean(public,protected,private) the second case: class x{ public:a; private:b; protected:c; } class y:private x{ public:d; } the same question? the third case: class x{ public:a; private:b; protected:c; } class y:private x{ public:d; } again the same question? sorry i think i wrote too much bye

  Read the article

• how can we call one class's method through another class's object in php

  - by hello

  I want to know that is there any method in PHP by which i can call one class's method from another class object. let me clear here is one class class A() { public function showData(){ //here is method of class A } } // here is another class class B(){ public function getData(){ //some method in class B } } //now i create two objects $objA= new class A(); $objB=new class B(); now i want to call this $objB->showData();<--- is that possible .. by any how method( using public, inheritence,child parent etc...) please help me

  Read the article

• JQuery: loop through elements with more than one css class name that share only the first class name

  - by omaether

  Hello, I'm trying to use JQuery to loop through several div's with more than one class name, that all have the same first css class name and each one has a different second class name, e.g. <div class="maintext blue"> </div> <div class="maintext purple"> </div> <div class="maintext chartreuse"> </div> <div class="maintext puce"> </div> <div class="maintext lime"> </div> In JQuery I have tried $(".mainText").each(function (i) $(".mainText.*").each(function (i) $(".mainText" *).each(function (i) $(".mainText .*").each(function (i) But it will not select any of the divs with class="mainText ..." thanks for considering the question.

  Read the article

• Give a reference to a python instance attribute at class definition

  - by Guenther Jehle

  I have a class with attributes which have a reference to another attribute of this class. See class Device, value1 and value2 holding a reference to interface: class Interface(object): def __init__(self): self.port=None class Value(object): def __init__(self, interface, name): self.interface=interface self.name=name def get(self): return "Getting Value \"%s\" with interface \"%s\""%(self.name, self.interface.port) class Device(object): interface=Interface() value1=Value(interface, name="value1") value2=Value(interface, name="value2") def __init__(self, port): self.interface.port=port if __name__=="__main__": d1=Device("Foo") print d1.value1.get() # >>> Getting Value "value1" with interface "Foo" d2=Device("Bar") print d2.value1.get() # >>> Getting Value "value1" with interface "Bar" print d1.value1.get() # >>> Getting Value "value1" with interface "Bar" The last print is wrong, cause d1 should have the interface "Foo". I know whats going wrong: The line interface=Interface() line is executed, when the class definition is parsed (once). So every Device class has the same instance of interface. I could change the Device class to: class Device(object): interface=Interface() value1=Value(interface, name="value1") value2=Value(interface, name="value2") def __init__(self, port): self.interface=Interface() self.interface.port=port So this is also not working: The values still have the reference to the original interface instance and the self.interface is just another instance... The output now is: >>> Getting Value "value1" with interface "None" >>> Getting Value "value1" with interface "None" >>> Getting Value "value1" with interface "None" So how could I solve this the pythonic way? I could setup a function in the Device class to look for attributes with type Value and reassign them the new interface. Isn't this a common problem with a typical solution for it? Thanks!

  Read the article

• Which is the better C# class design for dealing with read+write versus readonly

  - by DanM

  I'm contemplating two different class designs for handling a situation where some repositories are read-only while others are read-write. (I don't foresee any need to a write-only repository.) Class Design 1 -- provide all functionality in a base class, then expose applicable functionality publicly in sub classes public abstract class RepositoryBase { protected virtual void SelectBase() { // implementation... } protected virtual void InsertBase() { // implementation... } protected virtual void UpdateBase() { // implementation... } protected virtual void DeleteBase() { // implementation... } } public class ReadOnlyRepository : RepositoryBase { public void Select() { SelectBase(); } } public class ReadWriteRepository : RepositoryBase { public void Select() { SelectBase(); } public void Insert() { InsertBase(); } public void Update() { UpdateBase(); } public void Delete() { DeleteBase(); } } Class Design 2 - read-write class inherits from read-only class public class ReadOnlyRepository { public void Select() { // implementation... } } public class ReadWriteRepository : ReadOnlyRepository { public void Insert() { // implementation... } public void Update() { // implementation... } public void Delete() { // implementation... } } Is one of these designs clearly stronger than the other? If so, which one and why? P.S. If this sounds like a homework question, it's not, but feel free to use it as one if you want :)

  Read the article

• Request for advice about class design, inheritance/aggregation

  - by Lasse V. Karlsen

  I have started writing my own WebDAV server class in .NET, and the first class I'm starting with is a WebDAVListener class, modelled after how the HttpListener class works. Since I don't want to reimplement the core http protocol handling, I will use HttpListener for all its worth, and thus I have a question. What would the suggested way be to handle this: Implement all the methods and properties found inside HttpListener, just changing the class types where it matters (ie. the GetContext + EndGetContext methods would return a different class for WebDAV contexts), and storing and using a HttpListener object internally Construct WebDAVListener by passing it a HttpListener class to use? Create a wrapper for HttpListener with an interface, and constrct WebDAVListener by passing it an object implementing this interface? If going the route of passing a HttpListener (disguised or otherwise) to the WebDAVListener, would you expose the underlying listener object through a property, or would you expect the program that used the class to keep a reference to the underlying HttpListener? Also, in this case, would you expose some of the methods of HttpListener through the WebDAVListener, like Start and Stop, or would you again expect the program that used it to keep the HttpListener reference around for all those things? My initial reaction tells me that I want a combination. For one thing, I would like my WebDAVListener class to look like a complete implementation, hiding the fact that there is a HttpListener object beneath it. On the other hand, I would like to build unit-tests without actually spinning up a networked server, so some kind of mocking ability would be nice to have as well, which suggests I would like the interface-wrapper way. One way I could solve this would be this: public WebDAVListener() : WebDAVListener(new HttpListenerWrapper()) { } public WebDAVListener(IHttpListenerWrapper listener) { } And then I would implement all the methods of HttpListener (at least all those that makes sense) in my own class, by mostly just chaining the call to the underlying HttpListener object. What do you think? Final question: If I go the way of the interface, assuming the interface maps 1-to-1 onto the HttpListener class, and written just to add support for mocking, is such an interface called a wrapper or an adapter?

  Read the article

< Previous Page | 8 9 10 11 12 13 14 15 16 17 18 19  | Next Page >