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  • How to implement an abstract class in ruby?

    - by Chirantan
    I know there is no concept of abstract class in ruby. But if at all it needs to be implemented, how to go about it? I tried something like... class A def self.new raise 'Doh! You are trying to instantiate an abstract class!' end end class B < A ... ... end But when I try to instantiate B, it is internally going to call A.new which is going to raise the exception. Also, modules cannot be instantiated but they cannot be inherited too. making the new method private will also not work. Any pointers?

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  • Python: saving and loading a class definition

    - by Peterstone
    Hi! I am interested in saving and load objects using the pickle module as you can read in a question I asked before: Python: Errors saving and loading objects with pickle module Someone commment: 1, In an other way: the error is raise because pickle wanted to load an instance of the class Fruits and search for the class definition where it was defined, but it didn't find it so it raise the error Now I want to save and load a class definition in order to solve the problem I describe in the question mentioned before. Thank you so much!

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  • iPhone - extending a class delegate

    - by Digital Robot
    OK, I know how to create a class extension, using something like that: on .h @interface UIButton (myExtensionName) // my extended methods @end and then on .m @implementation UIButton (myExtensionName) // my implementations @end But how do I declare the extended delegates I may create? If this was a normal class I would do @protocol myExtensionName <NSObject> // my delegate declarations @end but how do I do that on a class extension? thanks

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  • Qt: default value of variable in class

    - by Martin
    When creating my own class in Qt I would like my variables in the class to have a standard/default value if I haven't set them to anything. It would be perfect if this was possible to set in the h-file so I don't have to do it in each instance method of my class. You can see what I want to do in the code below. In the example myBool would have the value of false and myInt the value of 0 when the object have been created. Is this possible at all? In myclass.h: class MyClass { Q_OBJECT public: MyClass(); ~MyClass(); bool myBool = false; //I want to set myBool and myInt to a default/standard value int myInt = 0; };

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  • Python: Data Object or class

    - by arg20
    I enjoy all the python libraries for scraping websites and I am experimenting with BeautifulSoup and IMDB just for fun. As I come from Java, I have some Java-practices incorporated into my programming styles. I am trying to get the info of a certain movie, I can either create a Movie class or just use a dictionary with keys for the attributes. My question is, should I just use dictionaries when a class will only contain data and perhaps almost no behaviour? In other languages creating a type will help you enforce certain restrictions and because of type checks the IDE will help you program, this is not always the case in python, so what should I do? Should I resort to creating a class only when there's both, behaviour and data? Or create a movie class even though it'll probably be just a data container? This all depends on your model, in this particular case either one is fine but I'm wondering about what's a good practice.

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  • Automatically decorating every instance method in a class

    - by max
    I want to apply the same decorator to every method in a given class, other than those that start and end with __. It seems to me it should be doable using a class decorator. Are there any pitfalls to be aware of? Ideally, I'd also like to be able to: disable this mechanism for some methods by marking them with a special decorator enable this mechanism for subclasses as well enable this mechanism even for methods that are added to this class in runtime [Note: I'm using Python 3.2, so I'm fine if this relies on features added recently.] Here's my attempt: _methods_to_skip = {} def apply(decorator): def apply_decorator(cls): for method_name, method in get_all_instance_methods(cls): if (cls, method) in _methods_to_skip: continue if method_name[:2] == `__` and method_name[-2:] == `__`: continue cls.method_name = decorator(method) return apply_decorator def dont_decorate(method): _methods_to_skip.add((get_class_from_method(method), method)) return method Here are things I have problems with: how to implement get_all_instance_methods function not sure if my cls.method_name = decorator(method) line is correct how to do the same to any methods added to a class in runtime how to apply this to subclasses how to implement get_class_from_method

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  • C# Container Class

    - by Jamie
    I'm building a game in c# which allows you to script your own level, although I have come across a bit of a thought. I have a base class called "World" as an object. This was made with a simple: class World { However, when the user is scripting their level, all of the game objects will be contained in the world object. I want them to be able to do something on the lines of: World.ParentObjectName.ParentObjectProperty = "abc"; I know that the System.Windows.Forms.Panel and other classes are like containers and can have objects in them and be accessed in that kind of way... my question is how can I make a class which is like a container in which I can add objects to, and then access them with a World.ObjectName I have tried class World : System.Collections.CollectionBase, but with this method, I have to keep typing World.Item("ObjectName") Can anyone help? Thanks!

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  • how to add class using javascript in div

    - by Fahim Parkar
    I have so many modules and I am showing border to each module. Below is what I have div.ja-moduletable-inner, div.moduletable-inner { background: none; padding: 1.5em; box-shadow: 0px 0px 3px 3px rgba(0,0,0,.25); } <div id="Mod143"> <div class="moduletable-inner clearfix"> </div> </div> <div id="Mod148"> <div class="moduletable-inner clearfix"> </div> </div> <div id="Mod149"> <div class="moduletable-inner clearfix"> </div> </div> Note : These modules are added by-default by Joomla, so I can't handle this. What I want is using Javascript, I want to add class in Mod149 so that I will have it as <div id="Mod149"> <div class="moduletable-inner clearfix newMyOwnClass">` ^^^^^^^^^^^^^^ </div> and I will have in css as div.newMyOwnClass { box-shadow: 0px 0px 0px 0px rgba(0,0,0,.25); ^^^^^^^ } Any idea how to get this done in Javascript? No jQuery... Only Javascript AND only with div id Mod149

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  • What is the right way to pass class parameters to a method

    - by Schneider
    Let's suppose I have three classes A, B and C public class A { public int A1; public string A2; } public class B { public char B1; public double B2; public decimal B3; } public class C { public string DoSomething(A a, B b) { var a1 = a.A1; var b2 = b.B2; var b3 = b.B3; // DoSomething return string.Empty; } } If DoSomething() is using just some fields of the A and B classes, do you prefer to pass the whole object in parameters or create an intermediate class that has just the needed fields by the DoSomething method ?

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  • abstract class need acces to subclass atribute

    - by user1742980
    I have a problem with my code. public abstract class SimplePolygon implements Polygon { ... public String toString(){ String str = "Polygon: vertices ="; for(int i = 0;i<varray.length;i++){ str += " "; str += varray[i]; } return str; } } public class ArrayPolygon extends SimplePolygon { private Vertex2D[] varray; public ArrayPolygon(Vertex2D[] array){ varray = new Vertex2D[array.length]; if (array == null){} for(int i = 0;i<array.length;i++){ if (array[i] == null){} varray[i] = array[i]; } ... } Problem is, that i'm not allowed to add any atribute or method to abstract class SimplePolygon, so i'cant properly initialize varray. It could simply be solved with protected atrib in that class, but for some (stupid) reason i'cant do that. Has anybody an idea how to solve it without that? Thanks for all help.

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  • How to use the variable declared in one class in another class in Obj C.

    - by srikanth rongali
    I have a NSDate *date1 in class1 implementation file(I initialized it as Global variable). I have NSDate *date2 in class 2 implementation file (initialized it as Global variable). I need to calculate the NSTimeInterval between the two dates in class 2. But I could not do it. I could not access date1 in this class. It is giving error as (date2 undeclared). Please give me help in how to call other class variables in this class. Thank you.

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  • Mix and match class in C++/MFC

    - by Coder
    I'm trying to re-factor a code base, and there is some common functionality among unrelated classes that I'd love to unite. I would like to add that functionality in common base class, but I'm not sure if it's clean and good approach. Say I have CMyWnd class and CMyDialogEx class, both different, so they cannot inherit from one base class. I want to add a button to both classes and add the message handlers to both classes as well. So I'd like to do something like this: CMyWnd : public CWnd, public COnOkBtnFunctionality, public COnCancelBtnFunctionality CMyDialogEx: public CWnd, public COnOkBtnFunctionality Where COnOkBtnFunctionality would define CButton m_buttonOk, and all the afx_msg functions it should have. And so on. Is this approach doable/good? Or are there better patterns I should resort to?

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  • system crash after declaring global object of the class

    - by coming out of void
    hi, i am very new to c++. i am getting system crash (not compilation error) in doing following: i am declaring global pointer of class. BGiftConfigFile *bgiftConfig; class BGiftConfigFile : public EftBarclaysGiftConfig { } in this class i am reading tags from xml file. it is crashing system when this pointer is used to retrieve value. i am doing coding for verifone terminal. int referenceSetting = bgiftConfig->getreferencesetting(); //system error getreferencesetting() is member fuction of class EftBarclaysGiftConfig i am confused about behavior of pointer in this case. i know i am doing something wrong but couldn't rectify it. When i declare one object of class locally it retrieves the value properly. BGiftConfigFile bgiftConfig1; int referenceSetting = bgiftConfig1->getreferencesetting(); //working But if i declare this object global it also crashes the system. i need to fetch values at different location in my code so i forced to use someting global. please suggest me how to rectify this problem.

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  • Coolest Class Names?

    - by Starx
    Whenever, working on a big project. Using Technical names for your class can be pretty harsh on yourself to remember. So, what are the coolest class name that you can think of which is descriptive, funny and easy to remember. PS also include parent and class names just to add a little spice

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  • Get class constant names in php?

    - by user151841
    I have a php class with some class constants that indicate the status of an instance. When I'm using the class, after I run some methods on it, I do some checks to make sure that the status is what I expect it to be. For instance, after calling some methods, I expect the status to be MEANINGFUL_STATUS_NAME. $objInstance->method1(); $objInstance->method2(); if ( $objInstance->status !== class::MEANINGFUL_STATUS_NAME ) { throw new Exception("Status is wrong, should not be " . class::MEANINGFUL_STATUS_NAME . "."); } However, this gives me the exception message "Status is wrong, should not be 2" when what I really want to see is "Status is wrong, should not be MEANINGFUL_STATUS_NAME" So I've lost the meaningfulness of the constant name. I was thinking of making an 'translation table' array, so I can take the constant values and translate them back into their name, but this seems cumbersome. How should I translate this back, so I get an error message that gives me a better idea of what went wrong?

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  • C# - Erase all property values from a class?

    - by John M
    In a C# Winforms (3.5) application I have added a class that contains many properties (get/set) used to stored values from a 12 form long process. After form 12 I would like wipe out all the property values in the storing class so that the next user won't accidentally record values when starting the process at form 1. Is it possible to erase/destroy/dispose of all property values in a class? My class looks like this: private static int battery; public int Battery { get { return storeInspectionValues.battery; } set { storeInspectionValues.battery = value; } }

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  • Class Members Over Exports

    - by VirusEcks
    When Using DLLs or Code-injecting to be Specific this is an example class only intended for explaining class test { int newint1; char newchararray[512]; void (*newfunction1)( int newarg1 ); int newfunction2( bool newarg1, char newarg2 ) { return newint1; } } mynewclass1; that covers most common elements that's included in classes now when exporting this function to another DLL or application and missed an element of those, either data member or function member, private or public what happens or changed their order ? and if each function is assigned it's value when Code-Injecting like mynewclass1.newfunction1 = (void *)(newexportedfunction); what's the happens in this case, if members of the class are pointers that are assigned after class construction and then missed one member or changed their order ?

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  • java - find out the type of class which implements of other classes

    - by Johnzzz
    i have a kind of specific problem, let's say, that i have public interface A { } //------------------------------ public class B implements A{ static int countx = 0; } //---------------------------------- public class C implements A{ static int county = 0; } //---------------------------------- public class Arc { public A from; public A to; //======================================== and now I have an object a (which is an instance of Arc) and I want to find out whether it is an instance of B or C and get to the atributes countX or countY (stg like a.from.countX) any ideas? :)

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  • C++ : Swapping template class elements of different types?

    - by metamemetics
    template< class T1, class T2 > class Pair { T1 first; T2 second; }; I'm being asked to write a swap() method so that the first element becomes the second and the second the first. I have: Pair<T2,T1> swap() { return Pair<T2,T1>(second, first); } But this returns a new object rather than swapping, where I think it needs to be a void method that changes its own data members. Is this possible to do since T1 and T2 are potentially different class types? In other words I can't simply set temp=first, first=second, second=temp because it would try to convert them to different types. I'm not sure why you would potentially want to have a template object that changes order of its types as it seems that would cause confusion but that appears to be what I'm being asked to do.

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  • Looping class, for template engine kind of thing

    - by tarnfeld
    Hey, I am updating my class Nesty so it's infinite but I'm having a little trouble.... Here is the class: <?php Class Nesty { // Class Variables private $text; private $data = array(); private $loops = 0; private $maxLoops = 0; public function __construct($text,$data = array(),$maxLoops = 5) { // Set the class vars $this->text = $text; $this->data = $data; $this->maxLoops = $maxLoops; } // Loop funtion private function loopThrough($data) { if( ($this->loops +1) > $this->maxLoops ) { die("ERROR: Too many loops!"); } else { $keys = array_keys($data); for($x = 0; $x < count($keys); $x++) { if(is_array($data[$keys[$x]])) { $this->loopThrough($data[$keys[$x]]); } else { return $data[$keys[$x]]; } } } } // Templater method public function template() { echo $this->loopThrough($this->data); } } ?> Here is the code you would use to create an instance of the class: <?php // The nested array $data = array( "person" => array( "name" => "Tom Arnfeld", "age" => 15 ), "product" => array ( "name" => "Cakes", "price" => array ( "single" => 59, "double" => 99 ) ), "other" => "string" ); // Retreive the template text $file = "TestData.tpl"; $fp = fopen($file,"r"); $text = fread($fp,filesize($file)); // Create the Nesty object require_once('Nesty.php'); $nesty = new Nesty($text,$data); // Save the newly templated text to a variable $message $message = $nesty->template(); // Print out $message on the page echo("<pre>".$message."</pre>"); ?> Any ideas?

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  • Any good class diagram editors out there for Java (not UML)

    - by user85116
    I'm looking for an editor that can create class diagrams, similar to the typical UML class diagram, but specifically for java (so using java terminology; instead of terms like "generalization, realization etc", we use the java equivalents "interface, abstract class, extends etc"). I've looked into UML several times, but each time I've been turned off by the shear amount of "stuff" that comes with UML. I just want to be able to model my java classes quickly and intuitively, without getting bogged down by all the cruft that comes with UML. Preferably, it would come with a source reader that can keep the diagram up to date, and with a few nice features like "show only public methods in this class" etc. As well, it would automatically "know" about the classes in the standard java library, and possibly even be able to read classes from jars. Performance is also a big thing for me, I don't like having to wait 2 seconds for a popup menu to appear, or watch the diagram jerk crazily while resizing an element in the model. What do you think, am I asking too much?

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  • Union results of two functions in php class

    - by Max
    I have php class(simple example): <?php class test{ public function __construct() { //some code } public function __destruct() { //some code } public function echo1 { //some code return 1; } public function echo2 { //some code return 2; } } How could I return results of this two functions echo1 and echo2 in class in one row don't creating two new objects for each function?

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  • Keep getting error class, interface, or enum expected

    - by user1746605
    I can't see the problem with this short class. I get 8 class, interface, or enum expected errors. Thanks public class BankAccount { public BankAccount { private double balance = 0; } public BankAccount(double balanceIn) { private double balance = balanceIn; } public double checkBalance { return balance; } public void deposit(double amount) { if(amount > 0) balance += amount; } public void withdraw(double amount) { if(amount <= balance) balance -= amount; } }

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  • Best way to design a class in python

    - by Fraz
    So, this is more like a philosophical question for someone who is trying to understand classes. Most of time, how i use class is actually a very bad way to use it. I think of a lot of functions and after a time just indent the code and makes it a class and replacing few stuff with self.variable if a variable is repeated a lot. (I know its bad practise) But anyways... What i am asking is: class FooBar: def __init__(self,foo,bar): self._foo = foo self._bar = bar self.ans = self.__execute() def __execute(self): return something(self._foo, self._bar) Now there are many ways to do this: class FooBar: def __init__(self,foo): self._foo = foo def execute(self,bar): return something(self._foo, bar) Can you suggest which one is bad and which one is worse? or any other way to do this. This is just a toy example (offcourse). I mean, there is no need to have a class here if there is one function.. but lets say in __execute something() calls a whole set of other methods.. ?? Thanks

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  • Make an abstract class or use a processor?

    - by Tim Murphy
    I'm developing a class to compare two directories and run an action when a directory/file in the source directory does not exist in destination directory. Here is a prototype of the class: public abstract class IdenticalDirectories { private DirectoryInfo _sourceDirectory; private DirectoryInfo _destinationDirectory; protected abstract void DirectoryExists(DirectoryInfo sourceDirectory, DirectoryInfo destinationDirectory); protected abstract void DirectoryDoesNotExist(DirectoryInfo sourceDirectory, DirectoryInfo destinationDirectory); protected abstract void FileExists(DirectoryInfo sourceDirectory, DirectoryInfo destinationDirectory); protected abstract void FileDoesNotExist(DirectoryInfo sourceDirectory, DirectoryInfo destinationDirectory); public IdenticalDirectories(DirectoryInfo sourceDirectory, DirectoryInfo destinationDirectory) { ... } public void Run() { foreach (DirectoryInfo sourceSubDirectory in _sourceDirectory.GetDirectories()) { DirectoryInfo destinationSubDirectory = this.GetDestinationDirectoryInfo(subDirectory); if (destinationSubDirectory.Exists()) { this.DirectoryExists(sourceSubDirectory, destinationSubDirectory); } else { this.DirectoryDoesNotExist(sourceSubDirectory, destinationSubDirectory); } foreach (FileInfo sourceFile in sourceSubDirectory.GetFiles()) { FileInfo destinationFile = this.GetDestinationFileInfo(sourceFile); if (destinationFile.Exists()) { this.FileExists(sourceFile, destinationFile); } else { this.FileDoesNotExist(sourceFile, destinationFile); } } } } } The above prototype is an abstract class. I'm wondering if it would be better to make the class non-abstract and have the Run method receiver a processor? eg. public void Run(IIdenticalDirectoriesProcessor processor) { foreach (DirectoryInfo sourceSubDirectory in _sourceDirectory.GetDirectories()) { DirectoryInfo destinationSubDirectory = this.GetDestinationDirectoryInfo(subDirectory); if (destinationSubDirectory.Exists()) { processor.DirectoryExists(sourceSubDirectory, destinationSubDirectory); } else { processor.DirectoryDoesNotExist(sourceSubDirectory, destinationSubDirectory); } foreach (FileInfo sourceFile in sourceSubDirectory.GetFiles()) { FileInfo destinationFile = this.GetDestinationFileInfo(sourceFile); if (destinationFile.Exists()) { processor.FileExists(sourceFile, destinationFile); } else { processor.FileDoesNotExist(sourceFile, destinationFile); } } } } What do you see as the pros and cons of each implementation?

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