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  • Can you have an extension method on a type instead of on an instance of a type?

    - by SLC
    I can have an extension method like this: DateTime d = new DateTime(); d = d.GetRandomDate(); GetRandomDate is my extension method. However the above doesn't make much sense. What would be better is: DateTime d = DateTime.GetRandomDate(); However, I don't know how to do this. An extension method created as: public static DateTime GetRandomDate(this System.DateTime dt) will only add the GetRandomDate() in the first example above, not the second one. Is there a way to achieve the desired behaviour?

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  • Is there a way to cause a new C++ class instance to fail, if certain conditions in the contructor ar

    - by Jim Fell
    As I understand it, when a new class is instantiated in C++, a pointer to the new class is returned, or NULL, if there is insufficient memory. I am writing a class that initializes a linked list in the constructor. If there is an error while initializing the list, I would like the class instantiator to return NULL. For example: MyClass * pRags = new MyClass; If the linked list in the MyClass constructor fails to initialize properly, I would like pRags to equal NULL. I know that I can use flags and additional checks to do this, but I would like to avoid that, if possible. Does anyone know of a way to do this? Thanks.

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  • How to pass variables to slot methods in QT?

    - by Neko
    Hi. I'm making a little chat messenger program, which needs a list of chat channels the user has joined. To represent this list graphically, I have made a list of QPushButtons, which all represent a different channel. These buttons are made with the following method, and that's where my problem kicks in: void Messenger::addToActivePanels(std::string& channel) { activePanelsContents = this->findChild<QWidget *>(QString("activePanelsContents")); pushButton = new QPushButton(activePanelsContents); pushButton->setObjectName("pushButton"); pushButton->setGeometry(QRect(0, 0, 60, 60)); pushButton->setText(""); pushButton->setToolTip(QString(channel.c_str())); pushButton->setCheckable(true); pushButton->setChecked(false); connect(pushButton, SIGNAL(clicked()), this, SLOT(switchTab(channel))); } (activePanelContents is a QWidget that holds the list.) The point is that each button should call the switchTab(string& tabname) method when clicked, including the specific channel's name as variable. This implementation doesn't work though, and I haven't been able to find out how to properly do this, even after reading several pages on it on the internet. Can anybody please tell me how to do this? It'd be greatly appreciated, as always. :)

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  • Can g++ fill uninitialized POD variables with known values?

    - by Bob Lied
    I know that Visual Studio under debugging options will fill memory with a known value. Does g++ (any version, but gcc 4.1.2 is most interesting) have any options that would fill an uninitialized local POD structure with recognizable values? struct something{ int a; int b; }; void foo() { something uninitialized; bar(uninitialized.b); } I expect uninitialized.b to be unpredictable randomness; clearly a bug and easily found if optimization and warnings are turned on. But compiled with -g only, no warning. A colleague had a case where code similar to this worked because it coincidentally had a valid value; when the compiler upgraded, it started failing. He thought it was because the new compiler was inserting known values into the structure (much the way that VS fills 0xCC). In my own experience, it was just different random values that didn't happen to be valid. But now I'm curious -- is there any setting of g++ that would make it fill memory that the standard would otherwise say should be uninitialized?

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  • how to add a variables which comes from dataset in for loop Collection array in c#?

    - by leventkalay1986
    I have a collection of RSS items protected Collection<Rss.Items> list = new Collection<Rss.Items>(); The class RSS.Items includes properties such as Link, Text, Description, etc. But when I try to read the XML and set these properties: for (int i = 0; i < dt.Rows.Count; i++) { row = dt.Rows[i]; list[i].Link.Equals(row[0].ToString()); list[i].Description.Equals( row[1].ToString()); list[i].Title.Equals( row[2].ToString()); list[i].Date.Equals( Convert.ToDateTime(row[3])); } I get a null reference exception on the line list[i].Link.Equals(row[0].ToString()); What am I doing wrong?

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  • How do I refer to an instance from inside it's own code in Adobe Flash.

    - by matt1024
    In Adobe Flash, I have a movie clip that is added to the stage when the keyboard is pressed. I want it to travel across the screen and disappear once it reaches the edge of the stage. At the moment I use this but the image appears and then stops. Here is my code: addEventListener(Event.ADDED_TO_STAGE,runtime); var c = 0 function runtime(){ while(this.x<800){ this.x += 12; } removeChild(this); } Thanks

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  • Is it possible to create a C++ factory system that can create an instance of any "registered" object

    - by chrensli
    Hello, I've spent my entire day researching this topic, so it is with some scattered knowledge on the topic that i come to you with this inquiry. Please allow me to describe what I am attempting to accomplish, and maybe you can either suggest a solution to the immediate question, or another way to tackle the problem entirely. I am trying to mimic something related to how XAML files work in WPF, where you are essentially instantiating an object tree from an XML definition. If this is incorrect, please inform. This issue is otherwise unrelated to WPF, C#, or anything managed - I solely mention it because it is a similar concept.. So, I've created an XML parser class already, and generated a node tree based on ObjectNode objects. ObjectNode objects hold a string value called type, and they have an std::vector of child ObjectNode objects. The next step is to instantiate a tree of objects based on the data in the ObjectNode tree. This intermediate ObjectNode tree is needed because the same ObjectNode tree might be instantiated multiple times or delayed as needed. The tree of objects that is being created is such that the nodes in the tree are descendants of a common base class, which for now we can refer to as MyBase. Leaf nodes can be of any type, not necessarily derived from MyBase. To make this more challenging, I will not know what types of MyBase derived objects might be involved, so I need to allow for new types to be registered with the factory. I am aware of boost's factory. Their docs have an interesting little design paragraph on this page: o We may want a factory that takes some arguments that are forwarded to the constructor, o we will probably want to use smart pointers, o we may want several member functions to create different kinds of objects, o we might not necessarily need a polymorphic base class for the objects, o as we will see, we do not need a factory base class at all, o we might want to just call the constructor - without #new# to create an object on the stack, and o finally we might want to use customized memory management. I might not be understanding this all correctly, but that seems to state that what I'm trying to do can be accomplished with boost's factory. But all the examples I've located, seem to describe factories where all objects are derived from a base type. Any guidance on this would be greatly appreciated. Thanks for your time!

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  • Wouldn't it be nice to have a type variable referring to the class's instance.

    - by user93197
    I often have a pattern like this: class VectorBase<SubClass, Element> where SubClass : VectorBase<SubClass, Element>, new() where Element : Addable<Element> { Element[] data; public VectorBase(Element[] data) { this.data = data; } public SubClass add(SubClass second) { Element[] newData = new Element[data.Length]; for (int i = 0; i < newData.Length; i++) { newData[i] = data[i].add(second.data[i]); } SubClass result = new SubClass(); result.data = newData; return result; } } class VectorInt : VectorBase<VectorInt, Int32> { } class MyInt : Addable<MyInt> { int data; public MyInt(int data) { this.data = data; } public MyInt add(MyInt t) { return new MyInt(data + t.data); } } interface Addable<T> { T add(T t); } But I would rather just have: class VectorBase2<Element> where Element : Addable<Element> { Element[] data; public VectorBase(Element[] data) { this.data = data; } public SubClass add(SubClass second) { Element[] newData = new Element[data.Length]; for (int i = 0; i < newData.Length; i++) { newData[i] = data[i].add(second.data[i]); } SubClass result = new SubClass(data); return result; } } class VectorInt2 : VectorBase2<Int32> { } Why not make the subclass type available to all classes? Is this technically impossible?

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  • Is there any convinient way that i can deepclone 'style' instance in silverlight?

    - by Kevin Yang
    if a style is used, it can not be modified agaign. so i need a clone method. but its hard to implement. what i want to do is implementing a cascading 'style' mechanism. for example, i set two style to the same frameworkelement. the same property of latter style will override the former one, while the different property remain unchanged. but if i set the style property of the frameworkelement twice directly, the 1st style will be gone. so i use the baseon property of style class to do that. but now come across another problem, the style can not be modified after it's been set to a frameworkelement. so now i need a clone method.

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  • How can I efficiently retrieve a large number of database settings as PHP variables?

    - by Steven
    Currently all of my script's settings are located in a PHP file which I 'include'. I'm in the process of moving these settings (about 100) to a database table called 'settings'. However I'm struggling to find an efficient way of retrieving all of them into the file. The settings table has 3 columns: ID (autoincrements) name value Two example rows might be: 1 admin_user john 2 admin_email_address [email protected] The only way I can think of retrieving each setting is like this: $result = mysql_query("SELECT value FROM settings WHERE name = 'admin_user'"); $row = mysql_fetch_array($result); $admin_user = $row['value']; $result = mysql_query("SELECT value FROM settings WHERE name = 'admin_email_address'"); $row = mysql_fetch_array($result); $admin_email_address = $row['value']; etc etc Doing it this way will take up a lot of code and will likely be slow. Is there a better way? Thanks.

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  • Any way to define getters for lazy variables in Javascript arrays?

    - by LLer
    I'm trying to add elements to an array that are lazy-evaluated. This means that the value for them will not be calculated or known until they are accessed. This is like a previous question I asked but for objects. What I ended up doing for objects was Object.prototype.lazy = function(var_name, value_function) { this.__defineGetter__(var_name, function() { var saved_value = value_function(); this.__defineGetter__(var_name, function() { return saved_value; }); return saved_value; }); } lazy('exampleField', function() { // the code that returns the value I want }); But I haven't figured out a way to do it for real Arrays. Arrays don't have setters like that. You could push a function to an array, but you'd have to call it as a function for it to return the object you really want. What I'm doing right now is I created an object that I treat as an array. Object.prototype.lazy_push = function(value_function) { if(!this.length) this.length = 0; this.lazy(this.length++, value_function); } So what I want to know is, is there a way to do this while still doing it on an array and not a fake array?

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  • How can I find out how much memory an instance of a C++ class consumes?

    - by Shadow
    Hi, I am developing a Graph-class, based on boost-graph-library. A Graph-object contains a boost-graph, so to say an adjacency_list, and a map. When monitoring the total memory usage of my program, it consumes quite a lot (checked with pmap). Now, I would like to know, how much of the memory is exactly consumed by a filled object of this Graph-class? With filled I mean when the adjacency_list is full of vertices and edges. I found out, that using sizeof() doesn't bring me far. Using valgrind is also not an alternative as there is quite some memory allocation done previously and this makes the usage of valgrind impractical for this purpose. I'm also not interested in what other parts of the program cost in memory, I want to focus on one single object. Thank you.

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  • how to Add-in load again n again for every instance of an application?

    - by Ashwin Upadhyay
    I have one qus. i created one shared add-in in c#.net. This add-in is working fine. now i want this add-in is load again n again when any office application is opened. For e.g. when i open any MS word document then add-in is load for that and if after that i opened another MS word document without closing previously opened document then add-in is again load for newly opend MS word document. But when i opened MS word at first time the add-in is load and if i opened MS word again but add-in is already loaded. my requirement is like that-my add-in is worked backgroundly that is its work only to record the opening,closing time of the word document and how much time spend onto that word document and also the name of this document. But when i opened one word document then add-in is loaded for that and if againg opened new word document then becaz of previously opened document add-in is not load for that document remember that priviously opened document is not closed. but if i closed previously opened document then for new document add-in is load.

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  • Can I have multiple instance of the mandlebrot example in one program?

    - by yan bellavance
    Basically what I did is I took the Mandlebrot example and have 3 instances of it in my program. So the program would look like a mainwindow that has 3 mandlebrot widgets in it, one besides the other. Is it possible that GDB doesnt support debugging multiple intances of a classe that derives from qthread or is it thread-unsafe to do so? I don't have any problems at run-time but when I put breakpoints in a function called by the QThread run() function I get a segmentation fault. I can clearly see that the function doesn't complete before returning to the breakpoint ie I the program stops at the breakpoint, I step into the lines of codes one by one but after a couple of instructions another thread startS using the function(even though they are different instances).

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  • Should member variables of global objects be made global as well?

    - by David Wong
    I'm developing plugins in Eclipse which mandates the use of singleton pattern for the Plugin class in order to access the runtime plugin. The class holds references to objects such as Configuration and Resources. In Eclipse 3.0 plug-in runtime objects are not globally managed and so are not generically accessible. Rather, each plug-in is free to declare API which exposes the plug-in runtime object (e.g., MyPlugin.getInstance() In order for the other components of my system to access these objects, I have to do the following: MyPlugin.getInstance().getConfig().getValue(MyPlugin.CONFIGKEY_SOMEPARAMETER); , which is overly verbose IMO. Since MyPlugin provides global access, wouldn't it be easier for me to just provide global access to the objects it manages as well? MyConfig.getValue(MyPlugin.CONFIGKEY_SOMEPARAMETER); Any thoughts? (I'm actually asking because I was reading about the whole "Global variable access and singletons are evil" debates)

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  • Why use of session name and session id in the get variables does not work?

    - by Roman
    I have the following code: $location .= 'red=no&'.session_name() . "=". session_id(); $content = file_get_contents($location); echo $content; If I run it, noting is displayed in my browser. However, if I modify it in the following way: $location .= 'red=no'; $content = file_get_contents($location); echo $content; everything works fine (I see the content in my browser). What is also strange, if I display the value of the $location variable from the first example (url) and manually paste it in the address line of my browser, I do see the content. So, my browser is able to use this URL and file_get_contents not. Does anybody know how it can be explained?

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  • How do I force MyEclipse to hot-deploy a JavaScript file to my JBoss instance?

    - by Mike Cialowicz
    I'm having trouble with MyEclipse 7.1.1 hot-deployment of files to my JBoss 4 server. The problem is this: while my server is running, I can make changes to various JAVA and HTML files, which are then hot-deployed immediately (I can see the changes reflected in my browser when I refresh the page). However, while working on a particular JavaScript file, my changes are not being hot-deployed. This makes it very difficult to work on and debug this file, since I have to stop my server, redeploy, and start it again each time I make changes. This is a new problem - it didn't used to happen with this file, so I think something got screwed up in my MyEclipse configuration. I've verified that my projects (JBoss 4 instances) are all set up in "Exploded" mode for hot-deployment. I'm also 99% sure that this isn't an issue with my browser, since I always refresh with CTRL+F5, and I've tried a number of things like clearing my browser cache to get the currently deployed version of the file. I've also tried doing a "clean" on the project while the server is running, and that didn't force a deployment either. Any sort of solution would be helpful. I'd love for MyEclipse to deploy the file automatically, but I'm also open to manually forcing hot-deployment of this particular file while I work on it. Thank you.

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  • Rails 3: Create an instance with 3 foreign keys.

    - by donald
    Hello, Having a reviews table: # Table name: reviews # # id :integer not null, primary key # wsp_id :integer # service_id :integer # user_id :integer # description :text # rating :integer # created_at :datetime # updated_at :datetime # belongs_to :wsp belongs_to :service belongs_to :user How can I create a review for a service and pass the wsp_id and user_id? Do I need to use nested routes? I am able to do @user.reviews.new(params[:review]) but I'm not being able of passing the wsp_id and the service_id. Here's my Reviews create controller. def create @review = current_user.reviews.new(params[:review]) if @review.save #Saved else #Error, not saved end end What am I doing wrong? Thank you!

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