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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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  • C++ (g++) Compile Error, Expected "="/etc. Before 'MyWindow" (my class name)

    - by Ell
    Hi all, I have a very strange problem and the following code wont compile: #ifndef MYWINDOW_HPP_INCLUDED #define MYWINDOW_HPP_INCLUDED class MyWindow{ private: WNDCLASSEX window_class; HWND window_handle; HDC device_context_handle; HGLRC open_gl_render_context; MSG message; BOOL quit; public: Window(int height=416, int width=544, WindowStyle window_style=WINDOWED); void Show(); void Close(); ~Window(); }; #endif // MYWINDOW_HPP_INCLUDED I get the following error: error: expected '=', ',', ';', 'asm' or 'attribute' before 'MyWindow' I can't see any syntax errors here, although I coukd be wrong as I am very (very) new in c++. Thanks in advance, ell.

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  • How do you determine how coarse or fine-grained a 'responsibility' should be when using the single r

    - by Mark Rogers
    In the SRP, a 'responsibility' is usually described as 'a reason to change', so that each class (or object?) should have only one reason someone should have to go in there and change it. But if you take this to the extreme fine-grain you could say that an object adding two numbers together is a responsibility and a possible reason to change. Therefore the object should contain no other logic, because it would produce another reason for change. I'm curious if there is anyone out there that has any strategies for 'scoping', the single-responsibility principle that's slightly less objective?

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  • Is it OK to write a constructor which does nothing?

    - by Roman
    To use methods of a class I need to instantiate a class. At the moment the class has not constructor (so I want to write it). But than I have realized that the constructor should do nothing (I do need to specify values of fields). In this context I have a question if it is OK to write constructor which does nothing. For example: public Point() { }

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  • Confuse about which object should i assign the function to

    - by CliffC
    i have the following two class which convert object into xml string should i do something like class Person { public string GetXml() { //return a xml string } } or it is better to create another class which accept the person as a parameter and convert it into XML something like class PersonSerializer { public string Serialize(Person person) { // return a xml string } } Thanks

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  • Define a class dynamically?

    - by Pekka
    Is there a way to dynamically and conditionally create a class definition in PHP, i.e. if (condition matches) include file containing class definition else class myclass extends ancestor_class { .................... } without eval()? My background is the accepted answer to this question. I am looking for the best way to build a untouchable core library, with user-defined empty classes extending the core library if necessary. I want to create the final class definition "on the fly" if there is no user-defined empty class for a certain ancestor class.

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  • How do I write object classes effectively when dealing with table joins?

    - by Chris
    I should start by saying I'm not now, nor do I have any delusions I'll ever be a professional programmer so most of my skills have been learned from experience very much as a hobby. I learned PHP as it seemed a good simple introduction in certain areas and it allowed me to design simple web applications. When I learned about objects, classes etc the tutor's basic examnples covered the idea that as a rule of thumb each database table should have its own class. While that worked well for the photo gallery project we wrote, as it had very simple mysql queries, it's not working so well now my projects are getting more complex. If I require data from two separate tables which require a table join I've instead been ignoring the class altogether and handling it on a case by case basis, OR, even worse been combining some of the data into the class and the rest as a separate entity and doing two queries, which to me seems inefficient. As an example, when viewing content on a forum I wrote, if you view a thread, I retrieve data from the threads table, the posts table and the user table. The queries from the user and posts table are retrieved via a join and not instantiated as an object, whereas the thread data is called using my Threads class. So how do I get from my current state of affairs to something a little less 'stupid', for want of a better word. Right now I have a DB class that deals with connection and escaping values etc, a parent db query class that deals with the common queries and methods, and all of the other classes (Thread, Upload, Session, Photo and ones thats aren't used Post, User etc ) are children of that. Do I make a big posts class that has the relevant extra attributes that I retrieve from the users (and potentially threads) table? Do I have separate classes that populate each of their relevant attributes with a single query? If so how do I do that? Because of the way my classes are written, based on what I was taught, my db update row method, or insert method both just take the attributes as an array and update all of that, if I have extra attributes from other db tables in each class then how do I rewrite those methods as obbiously updating automatically like that would result in errors? In short I think my understanding is limited right now and I'd like some pointers when it comes to the fundamentals of how to write more complex classes.

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  • Would this constructor be acceptable practice?

    - by Robb
    Let's assume I have a c++ class that have properly implemented a copy constructor and an overloaded = operator. By properly implemented I mean they are working and perform a deep copy: Class1::Class1(const Class1 &class1) { // Perform copy } Class1& Class1::operator=(const Class1 *class1) { // perform copy return *this; } Now lets say I have this constructor as well: Class1::Class1(Class1 *class1) { *this = *class1; } My question is would the above constructor be acceptable practice? This is code that i've inherited and maintaining.

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  • Why must use "out" instead of ref ?

    - by Phsika
    i wrote some code blocks about ref -out declaration. i think that ref is most useful out. Ok. why i need to use out. i can use always ref everytime: namespace out_ref { class Program { static void Main(string[] args) { sinifA sinif = new sinifA(); int test = 100; sinif.MethodA(out test); Console.WriteLine(test.ToString()); sinif.MethodB(ref test); Console.WriteLine(test.ToString()); Console.ReadKey(); } } class sinifA { public void MethodA(out int a) { a = 200; } int _b; public void MethodB(ref int b) { _b = b; b = 2*b; } } }

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  • C# and Objects/Classes

    - by user1192890
    I have tried to compile code from Deitel's C# 2010 for programmers. I copied it exactly out of the book, but it still can't find main, even though I declared it in one of the classes. Here is a look at the two classes: For GradeBookTest: // Fig. 4.2: GradeBookTest.cs // Create a GradeBook object and call its DisplayMessage method. public class GradeBookTest { // Main method begins program execution public static void Main(string[] args) { // create a GradeBook object and assign it to myGradeBook GradeBook myGradeBook = new GradeBook(); // call myGradeBook's DisplayMessage method myGradeBook.DisplayMessage(); } // end Main } // end class GradeBookTest Now for the GradeBook class: // Fig. 4.1: GradeBook.cs // Class declaration with one method. using System; public class GradeBook { // display a welcome message to the GradeBook user public void DisplayMessage() { Console.WriteLine( "Welcome to the Grade Book!" ); } // end method DisplayMessage } // end class GradeBook That is how I copied them. Here is how they appeared in the book: 1 // Fig. 4.2: GradeBookTest.cs 2 // Create a GradeBook object and call its DisplayMessage method. 3 public class GradeBookTest 4 { 5 // Main method begins program execution 6 public static void Main( string[] args ) 7 { 8 // create a GradeBook object and assign it to myGradeBook 9 GradeBook myGradeBook = new GradeBook(); 10 11 // call myGradeBook's DisplayMessage method 12 myGradeBook.DisplayMessage(); 13 } // end Main 14 } // end class GradeBookTest and // Fig. 4.1: GradeBook.cs // Class declaration with one method. using System; public class GradeBook { // display a welcome message to the GradeBook user public void DisplayMessage() { Console.WriteLine( "Welcome to the Grade Book!" ); } // end method DisplayMessage } // end class GradeBook I don't see why they are not working. Right now I am using Visual Studio Pro 2010. Any Thoughts?

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  • How do I organize C# classes that inherit from one another, but also have properties that inherit from one another?

    - by Chris
    I have an application that has a concept of a Venue, a place where events happen. A Venue is owned by a Company and has many VenueParts. So, it looks like this: public abstract class Venue { public int Id { get; set; } public string Name { get; set; } public virtual Company Company { get; set; } public virtual ICollection<VenuePart> VenueParts { get; set; } } A Venue can be a GolfCourseVenue, which is a Venue that has a Slope and a specific kind of VenuePart called a HoleVenuePart: public class GolfCourseVenue { public string Slope { get; set; } public virtual ICollection<HoleVenuePart> Holes { get; set; } } In the future, there may also be other kinds of Venues that all inherit from Venue. They might add their own fields, and will always have VenueParts of their own specific type. My declarations above seem wrong, because now I have a GolfCourseVenue with two collections, when really it should just have the one. I can't override it, because the type is different, right? When I run reports, I would like to refer to the classes generically, where I just spit out Venues and VenueParts. But, when I render forms and such, I would like to be specific. I have a lot of relationships like this and am wondering what I am doing wrong. For example, I have an Order that has OrderItems, but also specific kinds of Orders that have specific kinds of OrderItems.

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  • Is there anything bad in declaring nested class inside interface in java?

    - by Roman
    I have an interface ProductService with method findByCriteria. This method had a long list of nullable parameters, like productName, maxCost, minCost, producer and so on. I refactored this method by introducing Parameter Object. I created class SearchCriteria and now method signature looks like this: findByCriteria (SearchCriteria criteria) I thought that instances of SearchCriteria are only created by method callers and are only used inside findByCriteria method, i.e.: void processRequest() { SearchCriteria criteria = new SearchCriteria () .withMaxCost (maxCost) ....... .withProducer (producer); List<Product> products = productService.findByCriteria (criteria); .... } and List<Product> findByCriteria(SearchCriteria criteria) { return doSmthAndReturnResult(criteria.getMaxCost(), criteria.getProducer()); } So I did not want to create a separate public class for SearchCriteria and put it inside ProductServiceInterface: public interface ProductService { List<Product> findByCriteria (SearchCriteria criteria); static class SearchCriteria { ... } } Is there anything bad with this interface? Where whould you place SearchCriteria class?

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  • PHP Object Oriented forum example

    - by Martin Trigaux
    Hello, I'm trying to learn to use PHP with an object oriented scheme. I think I understand the concept but I need real example, a forum exactly. I know PhpBB but it's maybe too complicated to fully understand it so I'm looking for something simpler but still in object oriented. Thank you

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  • where are the frameworks for creating libraries?

    - by fayer
    whenever i create a php library (not a framework) i tend to reinvent everything everytime. "where to put configuration options" "which design pattern to use here" "how should all the classes extend each other" and so on... then i think, isn't there a good library framework to use anywhere? it's like a framework for a web application (symfony, cakephp...) but instead of creating a web application, this framework will help coder to create a library, providing all the standard structure and classes (observer pattern, dependency injection etc). i think that will be the next major thing if not available right now. in this way there will be a standard to follow when creating libraries, or else, it's like a djungle when everyone creates their own structure, and a lot of coders just code without thinking of reusability etc. there isn't any framework for creating libraries at the moment? if not, don't u agree with me that this is the way to do it, with a library framework? cause i am really throwing a lot of time (weeks!) just thinking about how to organize things, both in code and file level, when i should just start to code the logic. share your thoughts!

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  • How can i split up a component using cfinclude and still use inheritance?

    - by rip747
    Note: this is just a simplized example of what i'm trying to do to get the idea across. The problem I'm having is that I want to use cfinclude inside cfcomponent so that i can group like methods into separate files for more manageability. The problem I'm running into is when i try to extend another component that also uses cfinclude to manage it's method as demostrated below. Note that ComponentA extends ComponentB: ComponentA ========== <cfcomponent output="false" extends="componentb"> <cfinclude template="componenta/methods.cfm"> </cfcomponent> componenta/methods.cfm ====================== <cffunction name="a"><cfreturn "componenta-a"></cffunction> <cffunction name="b"><cfreturn "componenta-b"></cffunction> <cffunction name="c"><cfreturn "componenta-c"></cffunction> <cffunction name="d"><cfreturn super.a()></cffunction> ComponentB ========== <cfcomponent output="false"> <cfinclude template="componentb/methods.cfm"> </cfcomponent> componentb/methods.cfm ====================== <cffunction name="a"><cfreturn "componentb-a"></cffunction> <cffunction name="b"><cfreturn "componentb-b"></cffunction> <cffunction name="c"><cfreturn "componentb-c"></cffunction> The issue is that when i try to initialize ComponentA I get an the error: "Routines cannot be declared more than once. The routine a has been declared twice in different templates." The whole reason for this is because when you use cfinclude it's evaluated at RUN TIME instead of COMPILE TIME. Short of moving the methods into the components themselves and eliminating the use of cfinclude, how can i get around this or does someone have a better idea splitting up large components?

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  • Who needs singletons?

    - by sexyprout
    Imagine you access your MySQL database via PDO. You got some functions, and in these functions, you need to access the database. The first thing I thought of is global, like: $db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'root', 'pwd'); function some_function() { global $db; $db->query('...'); } But it's considered as a bad practice. So, after a little search, I ended up with the Singleton pattern, which "applies to situations in which there needs to be a single instance of a class." According to the example of the manual, we should do this: class Database { private static $instance, $db; private function __construct(){} static function singleton() { if(!isset(self::$instance)) self::$instance = new __CLASS__; return self:$instance; } function get() { if(!isset(self::$db)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd') return self::$db; } } function some_function() { $db = Database::singleton(); $db->get()->query('...'); } some_function(); But I just can't understand why you need that big class when you can do it merely with: class Database { private static $db; private function __construct(){} static function get() { if(!isset(self::$rand)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd'); return self::$db; } } function some_function() { Database::get()->query('...'); } some_function(); This last one works perfectly and I don't need to worry about $db anymore. But maybe I'm forgetting something. So, who's wrong, who's right?

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  • Accessing a function of an instance which is in an arraylist

    - by fadeir
    I'm tring to access a function of an instance which is in an arraylist. Is there any way to do that without using the class name of the instance? import java.util.ArrayList; import java.util.List; class apple{ int price; public void myFunction(int iPrice) { price=iPrice; } } class orange{ int price; public void myFunction(int iPrice) { price=iPrice; } } public class main { public static void main(String[] args) { List list= new ArrayList(); //create 3 apple object to list list.add( new apple() ); list.add( new apple() ); list.add( new orange() ); list.get(0).myFunction(1); /* Error: The method myFunction(int) is undefined for the type Object*/ } } I know that;((apple) list.get(0)).myFunction(1); is a way but I'dont want to use any class name while calling the function.

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  • Segmentation fault on instationation of more than 1 object

    - by ECE
    I have a class called "Vertex.hpp" which is as follows: #include <iostream> #include "Edge.hpp" #include <vector> using namespace std; /** A class, instances of which are nodes in an HCTree. */ class Vertex { public: Vertex(char * str){ *name=*str; } vector<Vertex*> adjecency_list; vector<Edge*> edge_weights; char *name; }; #endif When I instantiate an object of type Vector as follows: Vertex *first_read; Vertex *second_read; in.getline(input,256); str=strtok(input," "); first_read->name=str; str=strtok(NULL, " "); second_read->name=str; A segmentation fault occurs when more than 1 object of type Vector is instantiated. Why would this occur if more than 1 object is instantiated, and how can i allow multiple objects to be instantiated?

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  • 1067: Implicit coercion of a value of type theplayclass to an unrelated type main

    - by Minelava
    I need help because I want to create a gameover screen that display score. However, there's an error that prevent me from transferring the score from theplayclass.as to thegameoverclass.as. Are there ways to pass a value to another movieclip without causing any errors. I refer the source code from this website : http://www.emanueleferonato.com/2008/12/17/designing-the-structure-of-a-flash-game-as3-version/ Here's the error C:\Users\xxx\Downloads\Migrate\test\theplayclass.as, Line 54, Column 41 1067: Implicit coercion of a value of type theplayclass to an unrelated type main. main.as package { import flash.display.MovieClip; import flash.events.Event; public class main extends MovieClip { public var playClass:theplayclass; public var gameOverClass:thegameoverclass; public function main() { showWin(); } public function showWin() { playClass = new theplayclass(this); addChild(playClass); } public function showGameOver() { gameOverClass = new thegameoverclass(this); addChild(gameOverClass); removeChild(playClass); playClass = null; } } } theplayclass.as package { import flash.display.MovieClip; import flash.events.*; public class theplayclass extends MovieClip { private var mainClass:main; var gameScore:Number; var gameOverScore:thegameoverclass; public function theplayclass(passedClass:main) { mainClass = passedClass; scoreText.text ="0"; gameScore = 0; win.addEventListener(MouseEvent.CLICK, showwinFunction); next.addEventListener(MouseEvent.CLICK, showgameoverFunction); addEventListener(Event.ADDED_TO_STAGE, addToStage); addEventListener(Event.ENTER_FRAME, changeScore); } public function addToStage(e:Event):void { this.x = 0; this.y = 0; } private function showwinFunction(e:MouseEvent):void { gameScore+=50; } private function changeScore(e:Event):void { scoreText.text =""+gameScore; } public function showgameoverFunction(e:MouseEvent) { mainClass.showGameOver(); gameOverScore = new thegameoverclass(this); gameOverScore.setTextScore(gameScore); } } } thegameoverclass.as package { import flash.display.MovieClip; import flash.events.MouseEvent; import flash.events.*; public class thegameoverclass extends MovieClip { var mainClass:main; var scorePoints:Number; public function thegameoverclass(passedClass:main) { mainClass = passedClass; finalScore.text = "test"; } public function setTextScore(textToSet:Number) { finalScore.text = ""+scorePoints; } } }

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  • Creating an interface and swappable implementations in python

    - by Blankman
    Hi, Would it be possible to create a class interface in python and various implementations of the interface. Example: I want to create a class for pop3 access (and all methods etc.). If I go with a commercial component, I want to wrap it to adhere to a contract. In the future, if I want to use another component or code my own, I want to be able to swap things out and not have things very tightly coupled. Possible? I'm new to python.

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  • What Patterns Should I Consider For a Html Widget Generator?

    - by DaveDev
    I'm looking to see if I can design a HtmlHelper extension method that will generate the Html for different types of widgets I want to produce. Each different type of widget implements functionality to get and prepare any data it needs to render. Can anyone suggest any patterns I could refer to for approaches to take? I know there are probably frameworks available that will do this for me, but I thought I'd give it a try anyway. Any points of advice? Thanks

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  • What does Protected Internal means in .Net

    - by vaibhav
    Protected Means, we can access this member only in a deriving class, and internal means we can access this member in any type in the same assembly using a object. So can I consider a Protected Internal member as a public member in the same assembly. and as a protected member in the different assembly.

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  • Running a method after the constructor of any derived class

    - by Alexey Romanov
    Let's say I have a Java class abstract class Base { abstract void init(); ... } and I know every derived class will have to call init() after it's constructed. I could, of course, simply call it in the derived classes' constructors: class Derived1 extends Base { Derived1() { ... init(); } } class Derived2 extends Base { Derived2() { ... init(); } } but this breaks "don't repeat yourself" principle rather badly (and there are going to be many subclasses of Base). Of course, the init() call can't go into the Base() constructor, since it would be executed too early. Any ideas how to bypass this problem? I would be quite happy to see a Scala solution, too.

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