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  • Java: Reflection against casting when you know superclass

    - by Ema
    I don't know exactly how to define my doubt so please be patient if the question has already been asked. Let's say I have to dinamically instantiate an object. This object will surely be instance of a subclass of a known, immutable class A. I can obtain dinamically the specific implementation class. Would it be better to use reflection exactly as if I didn't know anything about the target class, or would it be preferrable/possible to do something like: A obj = (Class.forName("com.package.Sub-A")) new A(); where Sub-A extends A ? The purpose would be to avoid reflection overhead times... Thank you in advance.

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  • [Using $this when not in object context in] php error

    - by JasonS
    I have solved this problem, I just need to know what to do. I get the above error because I just realised that the class is being run as class::function($values) instead of class-function($values). Does anyone know how to convert this function to instantiate the class then run the function with values? private function _load($values=null) { define('LOADED_CONTROLLER', $this->controller); define('LOADED_FUNCTION', $this->function); $function = $this->function; $controller = new $this->controller; ($values == null) ? $controller->$function() : call_user_func_array(array($this->controller, $function), $values); }

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  • jQuery dialog box not opening 2nd time

    - by Steven
    I found this thread which basically has the same issue I have. But their solution is not working for me. The dialog appears the first time I click the submit button, but not the 2nd time. I'm opening the dialog box after a form submission. UPDATE I finally got it working. Here is the correct code: if (jQuery('#registrationforms').length > 0) { //instantiate the dialog jQuery("#dialog").dialog({ modal:true, autoOpen:false }); //Some more code here to call processRegistration function. } function processRegistration(instanceID, formData) { jQuery.post("mypath/jquery_bll.php", { instance: 'processRegistration', formData : formData, instanceID : instanceID }, function(feedback) { jQuery('#dialog').text(feedback.message); jQuery('#dialog').parent().addClass(feedback.type); jQuery('#dialog').dialog('open'); },"json"); } Since I'm dynamically applying css class, I have to make sure to add it to the outer DIV which $.dialog creates to wrap my 'dialog' DIV.

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  • Figuring out what makes a C++ class abstract in VS2008

    - by suszterpatt
    I'm using VS2008 to build a plain old C++ program (not C++/CLI). I have an abstract base class and a non-abstract derived class, and building this: Base* obj; obj = new Derived(); fails with the error "'Derived': cannot instantiate abstract class". (It may be worth noting, however, that if I hover over Base with the cursor, VS will pop up a tooltip saying "class Base abstract", but hovering over Derived will only say "class Derived" (no "abstract")). The definitions of these classes are fairly large and I'd like to avoid manually checking if each method has been overridden. Can VS do this for me somehow? Any general tips on pinpointing the exact parts of the class' definition that make it abstract?

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  • Realtime processing and callbacks with Python and C++

    - by Doughy
    I need to write code to do some realtime processing that is fairly computationally complex. I would like to create some Python classes to manage all my scripting, and leave the intensive parts of the algorithm coded in C++ so that they can run as fast as possible. I would like to instantiate the objects in Python, and have the C++ algorithms chime back into the script with callbacks in python. Something like: myObject = MyObject() myObject.setCallback(myCallback) myObject.run() def myCallback(val): """Do something with the value passed back to the python script.""" pass Will this be possible? How can I run a callback in python from a loop that is running in a C++ module? Anyone have a link or a tutorial to help me do this correctly?

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  • Apache Axis web service clients vs plain SOAP requests.

    - by Andy Pryor
    I'm looking for the best way to consume a Java web service that returns rather large and complex objects. I am currently using Apache Axis clients generated from the wsdl, (using eclipse "generate web service client" tool). We have concerns about performance of this. The service proxy objects are not thread safe, and they are rather heavy to instantiate, 2-3 MB on the JVM. The other alternative is making HTTP connections and building a String SOAP requests. I would have to interpret the response, and build objects from the XML. Would this be a better alternative to the heavy axis objects? I searched for good reading on this, if any one had any links I would greatly appreciate it.

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  • PHP: Class extends problem "Call to private method ... from context ..."

    - by sombe
    I have 3 classes in WordPress (the question itself is unrelated to it): class WP_Widget class Theme_Widget extends WP_Widget class Specific_Widget extends Theme_Widget Essentially Theme_Widget contains some extension functions to the basic WP_Widget. Inside Specific_Widget I call one of Theme_Widget's methods: class Specific_Widget { function __construct() { $this->some_method_that_belongs_to_Theme_Widget(); } } When I instantiate Specific_Widget, PHP throws a fatal error as follows: Fatal error: Call to private method Theme_Widget::some_method_that_belongs_to_Theme_Widget() from context 'Specific_Widget' in ... Do you have an idea as to how I can resolve this? This is the first time I've received this error from PHP. Could it be derive from WordPress itself?

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  • List in a Python class shares the same object over 2 different instances?

    - by zfranciscus
    I created a class: class A: aList = [] now I have function that instantiate this class and add items into the aList. note: there are 2 items for item in items: a = A(); a.aList.append(item); I find that the first A and the second A object has the same number of items in their aList. I would expect that the first A object will have the first item in its list and the second A object will have the second item in its aList. Can anyone explain how this happens ? PS: I manage to solve this problem by moving the aList inside a constructor : def __init__(self): self.aList = []; but I am still curious about this behavior

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  • ASP.NET Server.Execute

    - by justin
    I'm having some problems with Server.Execute that I can't seem to find any details on. Page page = new WidgetProcessor(Widget); Server.Execute(page, htmlTextWriter, true); The Widget in the above code is a simple object that knows how to instantiate a usercontrol. The WidgetProcessor takes a Widget and adds the widgets control to the page. This works fine on the initial load, it doesn't seem to handle postbacks however; it never actually fires the user controls events, it just consistently returns the original page as if you had never posted back. I've found this article from 2003: http://support.microsoft.com/kb/817036, though I would think they would have fixed this by now. Any help would be appreciated.

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  • ViewState Vs Session ... maintaining object through page lifecycle

    - by Kyle
    Can someone please explain the difference between ViewState and Session? More specifically, I'd like to know the best way to keep an object available (continuously setting members through postbacks) throughout the lifecycle of my page. I currently use Sessions to do this, but I'm not sure if it's the best way. For example: SearchObject searchObject; protected void Page_Load(object sender, EventArgs e) { if(!IsPostBack) { searchObject = new SearchObject(); Session["searchObject"] = searchObject; } else { searchObject = (SearchObject)Session["searchObject"]; } } that allows me to use my searchObject anywhere else on my page but it's kind of cumbersome as I have to reset my session var if I change any properties etc. I'm thinking there must be a better way to do this so that .NET doesn't re-instantiate the object each time the page loads, but also puts it in the global scope of the Page class? Please advise. TIA

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  • What is the best design to this class?

    - by HPT
    assume this class: public class Logger { static TextWriter fs = null; public Logger(string path) { fs = File.CreateText(path); } public static void Log(Exception ex) { ///do logging } public static void Log(string text) { ///do logging } } and I have to use this like: Logger log = new Logger(path); and then use Logger.Log() to log what I want. the question is: is this a good design? to instantiate a class and then always call it's static method? any suggestion yield in better design is appreciated.

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  • Problem with default member functions of class in C++ (constructor, destructor, operator=, copy cons

    - by Narek
    We know that compiler generates some member functions for user-defined class if that member functions are not defined but used, isn't it. So I have this kind of code: class AA { }; void main() { AA a; AA b(a); a = b; } This code works fine. I mean no compiler error. But the following code.... class AA { int member1; int member2; }; But this code gives an run time error, because variable "a" is used without being iniltialized!!! So my question is this: when we instantiate an int, it has a value. So why the default constructer doesn't work and by using those two int numbers initializes variable "a"??

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  • Overload and hide methods in Java

    - by Marco
    Hi, i have an abstract class BaseClass with a public insert() method: public abstract class BaseClass { public void insert(Object object) { // Do something } } which is extended by many other classes. For some of those classes, however, the insert() method must have additional parameters, so that they instead of overriding it I overload the method of the base class with the parameters required, for example: public class SampleClass extends BaseClass { public void insert(Object object, Long param){ // Do Something } } Now, if i instantiate the SampleClass class, i have two insert() methods: SampleClass sampleClass = new SampleClass(); sampleClass.insert(Object object); sampleClass.insert(Object object, Long param); what i'd like to do is to hide the insert() method defined in the base class, so that just the overload would be visible: SampleClass sampleClass = new SampleClass(); sampleClass.insert(Object object, Long param); Could this be done in OOP?

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  • Application.Current changes when using reflection to create an instance of another Application class

    - by markti
    Let's say I have the following Silverlight Applications: App1.xap App2.xap App3.xap Let's say that I start App1.xap as the default xap file. If I load App2.xap and App3.xap and instantiate an Application class within one of the other two XAPs. The Application.Current changes to be that new instance. System.Windows.Application obj = Activator.CreateInstance(type) as System.Windows.Application; I don't want the current application to change. I just want to get the merged Resource Dictionaries off the Application class.

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  • Is it possible to use inheritance in this situation? (Java)

    - by they changed my name
    I have ClassA and ClassB, with ClassA being the superclass. ClassA uses NodeA, ClassB uses NodeB. First problem: method parameters. ClassB needs NodeB types, but I can't cast from the subclass to the superclass. That means I can't set properties which are unique to NodeB's. Second problem: When I need to add nodes toClassB, I have to instantiate a new NodeB. But, I can't do this in the superclass, so I'd have to rewrite the insertion to use NodeB. Is there a way around it or am I gonna have to rewrite the whole thing?

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  • PHP inheriting/extending a particular instance of an Object

    - by delta9
    Is there any way to force PHP to extend an existing/particular (and for that matter, already instantiated) instance of an object? This imaginary code should explain what I am wondering: class Base { public $var; function __construct($var){ $this->var = $name; } } class Extender extends Base { function __construct($parent) { parent = $parent; } } $base = new Base('yay!'); $extender = new Extender($base); echo 'Extended base var value: '.$extender->var.'<br/>'; Output (would be): Extended base var value: yay! To be clear, I am wanting to instantiate an object that extends a PARTICULAR INSTANCE of another object, one that has already been instantiated. I am aware that I can pass a reference to an object to another object (via it's constructor function) and then add it as a property of the receiving object, I'm wondering if there is a real way to do this?

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  • WorkFlow and WCF dynamically launching WorkFlows

    - by Raj73
    I have a WF which will be hosted on WCF . The service Contract will contain a single operation containing two parameters. Parameter1 will be a string and will contain the name of the workflow to invoke and parameter two will contain the input for the invoked Work Flow. All operations will take the same parameter. All the operations will return the same return value. I have created the service implementation and I would like to depending on the value of parameter1 start executing the appropriate workflow and return the value (There can be number of workflow classes say Operation1, Operation2...which will be the passed in as the value in Parameter1). How can I instantiate different workflow classes and pass parameters and get the return values from them which I should then pass back to the calling Client. (Also Should I be using ReceiveActivities in all of my Launchable WorkFlow Classes ? ) Any code samples or pointers would help

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  • what's the right way to do polymorphism with protocol buffers?

    - by user364003
    I'm trying to long-term serialize a bunch of objects related by a strong class hierarchy in java, and I'd like to use protocol buffers to do it due to their simplicity, performance, and ease of upgrade. However, they don't provide much support for polymorphism. Right now, the way I'm handling it is by having a "one message to rule them all" solution that has a required string uri field that allows me to instantiate the correct type via reflection, then a bunch of optional fields for all the other possible classes I could serialize, only one of which will be used (based on the value of the uri field). Is there a better way to handle polymorphism, or is this as good as I'm going to get?

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  • Doubt about a particular pattern of Javascript class definition

    - by fenderplayer
    Recently i saw the following code that creates a class in javascript: var Model.Foo = function(){ // private stuff var a, b; // public properties this.attr1 = ''; this.attr2 = ''; if(Model.Foo._init === 'undefined'){ Model.Foo.prototype = { func1 : function(){ //...}, func2 : function(){ //... }, //other prototype functions } } Model.Foo._init = true; } // Instantiate and use the class as follows: var foo = new Model.Foo(); foo.func1(); I guess the _init variable is used to make sure we don't define the prototypes again. Also, i feel the code is more readable since i am placing everything in a function block (so in oop-speak, all attributes and methods are in one place). Do you see any issues with the code above? Any pitfalls of using this pattern if i need to create lots of classes in a big project?

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  • is this possible: c# collection of Type with constrains, or collection of generic type?

    - by Jon
    I'm trying to store types in a collection, so that i can later instantiate objects of the types in the collection. But I'm not sure how to do this the best way. What i have so far: List<Type> list = new List<Type>(); list.Add(typeof(MyClass)); var obj = (MyClass)Activator.CreateInstance(list[0]); I would like to have some constrains on the Type, or better yet, just a generic type in the collection instead of an instantiated Type object. Is this possible?

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  • Two phase Construction in C++

    - by tommieb75
    I have as part of assignment to look into a development kit that uses the "two-phase" construction for C++ classes: // Include Header class someFubar{ public: someFubar(); bool Construction(void); ~someFubar(); private: fooObject _fooObj; } In the source // someFubar.cpp someFubar::someFubar : _fooObj(null){ } bool someFubar::Construction(void){ bool rv = false; this->_fooObj = new fooObject(); if (this->_fooObj != null) rv = true; return rv; } someFubar::~someFubar(){ if (this->_fooObj != null) delete this->_fooObj; } Why would this "two-phase" be used and what benefits are there? Why not just instantiate the object initialization within the actual constructor?

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  • What are the disadvantages of using a StringBuilder?

    - by stickman
    I know that StringBuilder is more efficient than a normal string when processing code which modifies the string value a lot because although strings act like value types, they are actually reference, which makes them immutable so every time we change it, we need to create a new reference in memory. My question is that, why doesn't .NET just use stringBuilder by default? There must be some disadvantages of it over just using String. Can anyone tell me what they are? The only thing I can think of is perhaps it is a heavier object and it takes more time to instantiate so if you aren't changing the string too much, this would override the benefits of StringBuilder

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  • Java: Best approach to have a long list of variables needed all the time without consuming memory?

    - by evilReiko
    I wrote an abstract class to contain all rules of the application because I need them almost everywhere in my application. So most of what it contains is static final variables, something like this: public abstract class appRules { public static final boolean IS_DEV = true; public static final String CLOCK_SHORT_TIME_FORMAT = "something"; public static final String CLOCK_SHORT_DATE_FORMAT = "something else"; public static final String CLOCK_FULL_FORMAT = "other thing"; public static final int USERNAME_MIN = 5; public static final int USERNAME_MAX = 16; // etc. } The class is big and contains LOTS of such variables. My Question: Isn't setting static variables means these variables are floating in memory all the time? Do you suggest insteading of having an abstract class, I have a instantiable class with non-static variables (just public final), so I instantiate the class and use the variables only when I need them. Or is what am I doing is completely wrong approach and you suggest something else?

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  • Showing an image after laoding it from sql database

    - by user330075
    I have a problem showing the image form database in a view Details and a ImageController. Inside the view i have: img src=Url.Action("GetFile","Image", new {id= Model.id}) and in controller: public FileContentResult GetFile(int idl) { //int idl = 32; SqlDataReader rdr; byte[] fileContent = null; ........... return File(,,); } When the view is called, function GetFile it just wont work,but if i cut out the parameter int id1 and i instantiate it as a variable it'l work. public FileContentResult GetFile() { int idl = 32; SqlDataReader rdr; byte[] fileContent = null; ........... return File(,,); } Why?

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  • WPF + MvvM + Prism

    - by 2Fast4YouBR
    Hi all, I am new in the Wpf & Mvvm world , but I have found a couple of examples and just found that there is some different way to instantiate the model. I would like to know the best/correct way to do it. both ways are using Unity What I've foud: var navigatorView = new MainView(); navigatorView.DataContext = m_Container.Resolve<INavigatorViewModel>(); m_RegionManager.Regions["NavigatorRegion"].Add(navigatorView); What I did: var navigatorView = m_Container.Resolve<MainView>; m_RegionManager.Regions["NavigatorRegion"].Add(navigatorView); and I changed the constructor to receive viewmodel so I can point the datacontext to it: public MainView(NavigatorViewModel navigatorViewModel) { this.DataContext = navigatorViewModel; } Other examples I've found another way like: ...vm = new viewmodel ...m = new model v.model = vm; get/set DataContext cheers

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