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  • How can I reuse a base class function in a derived class

    - by Armen Ablak
    Let's say we have these four classes: BinaryTree, SplayTree (which is a sub-class of BinaryTree), BinaryNode and SplayNode (which is a sub-class of BinaryNode). In class BinaryTree I have 2 Find functions, like this bool Find(const T &) const; virtual Node<T> * Find(const T &, Node<T> *) const; and in SplayTree I would like to reuse the second one, because it works in the same way (for example) as in SplayTree, the only thing different is the return type, which is SplayNode. I thought it might be enough if I use this line in SplayTree.cpp using BinaryTree::Find; but it isn't. So, how can I do this?

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  • How to initialize one class from a library?

    - by daemonsvk
    Hi, I have a few classes in the class library (separate assembly). I referenced it to my project and I want to initialize one specific class from that library. I know only its name. All of the classes implements one interface. And here comes the problem. My code so far: using MyLibrary; ... IMyInterface dll = Activator.CreateInstance("MyLibrary", "MyLibrary.NameOfClass") as IMyInterface; But dll is always null. Any ideas? Thanks

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  • Class Library Project VS App_Code - Pros / Cons?

    - by rockinthesixstring
    I currently use the App_Code folder for all of my classes, and for me (for now) it seems to be working just fine. I have however been considering making the switch over to a Class Library Project inside my Solution instead of the App_Code folder. Can anyone tell me the pros and cons of doing this? One thought I had was with regards to testing my web app. If I use a Class Library, do I have to compile it every time I want to tweak/test? Obviously in the App_Code folder I don't have to since all of the Classes compile at runtime.

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  • how to create property of type generic class?

    - by Anish
    public class SelectionList<T> : ObservableCollection<SelectionItem<T>> where T : IComparable<T> { // Code } public class SelectionItem<T> : INotifyPropertyChanged { // Code } I need to create a property which is of the type SelectionList...as follows: public SelectionList<string> Sports { get; set; }. But when I replace string with DataRowView, as public SelectionList<DataRowView> Sports { get; set; }. I am getting error. Please help

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  • Python. Strange class attributes behavior

    - by Eugene
    >>> class Abcd: ... a = '' ... menu = ['a', 'b', 'c'] ... >>> a = Abcd() >>> b = Abcd() >>> a.a = 'a' >>> b.a = 'b' >>> a.a 'a' >>> b.a 'b' It's all correct and each object has own 'a', but... >>> a.menu.pop() 'c' >>> a.menu ['a', 'b'] >>> b.menu ['a', 'b'] How could this happen? And how to use list as class attribute?

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  • Load class based on SDK version

    - by Bostjan
    Is there any way I can load a class based on what version of the OS the phone is running? For example: I made an app which requires 1.6+ Android. Is there a way for me to load one class or the other based on what OS the phone is running? I'm asking this specifically for contacts. The database was changed from 1.6 to 2.0 and the old version doesn't retrieve contacts on the new OS phone. I'd still like to keep my 1.6 requirement, but at the same time I'd like 2.0+ phones to access the contact part of the app. So can I make 2 APIs, somehow pack them with the app and decide on the fly which I choose to import?

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  • Access to an "upper" instance of a class from another instance of a different class

    - by BorrajaX
    Hello everyone! I have a tricky question and probably what I want to do is not even possible but... who knows... Python seems very flexible and powerful... I'd like to know if there's a way to access to the class (or its fields) where an object is instanciated. Let's say I have: def Class1: def __init__(self): self.title = "randomTitle" self.anotherField = float() self.class2Field = Class2() and the class whose type will be the class2Field: def Class2: def __init__(self): self.field1 = "" self.field2 = "" # . . . # I'd like to know if there's a way to access the instance of Class1 from the instance of Class2 that is declared in Class1 (meaning, accessing the fields of Class1 from the variable self.class2Field in that Class1 instance) I know I can always change the init in Class2 to accept a Class1 parameter, but I'd like to know if there's another way of "climbing" through the class hierachy... Thank you very much!

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  • Django model class and custom property

    - by dArignac
    Howdy - today a weird problem occured to me: I have a modle class in Django and added a custom property to it that shall not be saved into the database and therefore is not represent in the models structure: class Category(models.Model): groups = models.ManyToManyField(Group) title = defaultdict() Now, when I'm within the shell or writing a test and I do the following: c1 = Category.objects.create() c1.title['de'] = 'german title' print c1.title['de'] # prints "german title" c2 = Category.objects.create() print c2.title['de'] # prints "german title" <-- WTF? It seems that 'title' is kind of global. If I change title to a simple string it works as expected, so it has to do something with the dict? I also tried setting title as a property: title = property(_title) But that did not work, too. So, how can I solve this? Thank you in advance! enter code here

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  • Basic class returns object reference instead of Array

    - by php-b-grader
    I have very basic class: class Customer { protected $id; protected $customer; public function __construct($customer_id) { $this->id = $customer_id; return $this->set_customer(); } protected function set_customer() { $query = mysql_query("SELECT * FROM customer WHERE id = '$this->id'"); $this->customer = mysql_fetch_row($query); return $this->customer; } } $customer = new Customer($order->customer->id); print_r($customer); This is not doing what I want it to but I understand why... $customer returns a reference to the Customer Object... What I want is the MySQL row array from the mysql_fetch_row() - How do I return the array? What am I missing?

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  • Using pipes inside a class in C++

    - by Paul
    I'm trying to use this tutorial to make plots with Gnuplot in C++. However I will be using the pipe to Gnuplot from within a class, but then I run into some problems: I've got a header file where I declare all variables etc. I need to declare the pipe-variable here too, but how do I do that? I've tried doing it straight away, but it doesn't work: Logger.h: class Logger { FILE pipe; } Logger.cpp: Logger::Logger() { //Constructor *pipe = popen("gnuplot -persist","w"); } Gives the error Logger.cpp:28: error: no match for ‘operator=’ in ‘*((Logger*)this)->Logger::pipe = popen(((const char*)"gnuplot -persist"), ((const char*)"w"))’ Suggestions?

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  • Error: cant find main class

    - by Vurb
    ok so im a newbie java dev using netbeans IDE 7.1.1 and im watching this tutorial and right off the bat i get an error in my program even after 5 retypes to make sure its exactly the same as in the video so anyways this is the error Error: Could not find or load main class javagame.JavaGame Java Result: 1 and this is the code i have written package JavaGame; import javax.swing.JFrame; public class JavaGame extends JFrame { public JavaGame(){ setTitle("java game"); setSize(500, 500); setResizable(false); setVisible(true); //setDefaultCloseOperation(); } public static void main(String[] args){ } }

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  • is counter has certain value inside a class in python

    - by mazlor
    i am learning classes in python and when i was reading the documentation i found this example that i didn't understand : class MyClass: """A simple example class""" def __init__(self): self.data = [] i = 12345 def f(self): return 'hello world' then if we assign : x = MyClass() x.counter = 1 now if we implement while loop : while x.counter < 10: x.counter = x.counter * 2 so the value of x.counter will be : 16 while for example if we have a variable y : y = 1 while y < 1 : y = y *2 then if we look for the value of y we find it 1 so i don't know how is the value of counter became 16 . thanks

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  • Problem about C++ class (inheritance, variables scope and functions)

    - by Luigi Giaccari
    I have a class that contains some data: class DATA Now I would to create some functions that uses those data. I can do it easily by writing member functions like DATA::usedata(); Since there are hundreds of functions, I would to keep an order in my code, so I would like to have some "categories" (not sure of the correct name) like: DATA data; data.memory.free(); data.memory.allocate(); data.file.import(); data.whatever.foo(); where memory, file and whatever are the "categories" and free, allocate and foo are the functions. I tried the inheritance way, but I got lost since I can not declare inside DATA a memory or file object, error C2079 occurs: http://msdn.microsoft.com/en-us/library/9ekhdcxs%28VS.80%29.aspx Since I am not a programmer please don't be too complicated and if you have an easier way I am all ears.

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  • What are the differences between struct and class in C++

    - by palm3D
    This question was already asked in the context of C#/.Net. Now I'd like to learn the differences between a struct and a class in (unmanaged) C++. Please discuss the technical differences as well as reasons for choosing one or the other in OO design. I'll start with an obvious difference: If you don't specify public: or private:, members of a struct are public by default; members of a class are private by default. I'm sure there are other differences to be found in the obscure corners of the C++ specification.

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  • Getting all inner classes by reflection

    - by Roman
    I have the following problem. I have this pretty class and now I want to get all the classes that extend that class (inner classes ) and fill 'classList' with it. ( in an automatic way of course ) public abstract class CompoundReference { private static List<Class<? extends CompoundReference>> classList = new ArrayList<Class<? extends CompoundReference>>(); @CompoundKey(gsType = User.class, dbType = UserDetailsMappings.class) public static class CUser extends CompoundReference { } @CompoundKey(gsType = Catalog.class, dbType = CatalogDetailsMappings.class) public static class CCatalog extends CompoundReference { } @CompoundKey(gsType = Product.class, dbType = ProductDetailsMappings.class) public static class CProduct extends CompoundReference { } @CompoundKey(gsType = Category.class) public static class CCategory extends CompoundReference { } @CompoundKey(gsType = Poll.class, dbType = PollDetailsMappings.class) public static class CPoll extends CompoundReference { } // much mroe inner classes Some manual solution would be just to main such a static block , that is something that I dont want to do. static { classList.addAll(Arrays.asList(CUser.class, CCatalog.class, CProduct.class, CCategory.class, CPoll.class, CComment.class, CWebPage.class, CReview.class, CPost.class, CMessage.class, CStory.class,CPicture.class)); }

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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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  • Passing a class ("Country.class") as an argument in Java

    - by Coronatus
    I'm trying to make a method that takes an argument of Country.class, User.class etc, and returns argument.count(). All the possible classes that I would give to this method extend from Model and have the method count(). My code: private static long <T> countModel(Model<T> clazz) { return clazz.count(); } Called by: renderArgs.put("countryCount", countModel(Country.class)); However this just doesn't work at all. How do I do this, please?

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  • Do Portable Class Libraries work with .net 3.5?

    - by Eric
    I am running Windows 8 and have both Visual Studio 2010 Ultimate w/sp1 and Visual Studio 2012 Ultimate and I am trying to create a Portable Class Library that supports .net 3.5 and greater. When I first try to create a PCL I get a screen like this: I noticed that .net 3.5 is not in the list so I clicked on "Install additional frameworks" and found a Targeting Pack for version 3.5. But when I download and run "dotnetfx35setup.exe" nothing happens. And when I go back into VS and try to create a new Portable Class Library, it lists the same target frameworks as before. I have also turned on the Windows Features for .NET Framework 3.5 and am now out of ideas. Here is a screen shot in case I missed something else. Thanks,

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  • Segfaults with singletons

    - by Ockonal
    Hello, I have such code: // Non singleton class MyLogManager { void write(message) {Ogre::LogManager::getSingletonPtr()->logMessage(message);} } class Utils : public singleton<Utils> { MyLogManager *handle; MyLogManager& getHandle { return *handle; } }; namespace someNamespace { MyLogManager &Log() { return Utils::get_mutable_instance().getHandle(); } } int main() { someNamespace::Log().write("Starting game initializating..."); } In this code I'm using boost's singleton (from serialization) and calling Ogre's log manager (it's singleton-type too). The program fails at any trying to do something with Ogre::LogManager::getSingletonPtr() object with code User program stopped by signal (SIGSEGV) I checked that getSingletonPtr() returns address 0x000 But using code Utils::get_mutable_instance().getHandle().write("foo") works good in another part of program. What's wrong could be there with calling singletons?

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  • Python: Give a class its own `self` at instantiation time

    - by SuperDisk
    I've got a button class that you can instantiate like so: engine.createElement((0, 0), Button(code=print, args=("Stuff!",))) And when it is clicked it will print "Stuff!". However, I need the button to destroy itself whenever it is clicked. Something like this: engine.createElement((0, 0), Button(code=engine.killElement, args=(self,))) However, that would just kill the caller, because self refers to the caller at that moment. What I need to do is give the class its own 'self' in advance... I thought of just making the string 'self' refer to the self variable upon click, but what if I wanted to use the string 'self' in the arguments? What is the way to do this? Is my architecture all wrong or something? Thanks.

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