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  • Am I trying to Implement Multiple Inheritance. How can I do this.

    - by Shantanu Gupta
    I have created a class say A which has some functions defined as protected. Now Class B inherits A and class C inherits B. Class A has private default constructor and protected parameterized constructor. I want Class B to be able to access all the protected functions defined in Class A but class C can have access on some of the functions only not all the functions and class C is inheriting class B. How can I restrict access to some of the functions of Class A from Class C ? EDIT: namespace Db { public Class A { private A(){} protected A(string con){assign this value} protected DataTable getTable(){return Table;} protected Sqlparameters setParameters(){return parameter;} } } namespace Data { public Class B:A { protected B():base("constring"){} protected DataTable output(){return getTable();} protected sqlparameter values(param IDataParameter[] parameter){} } } namespace Bsns { public Class C:B { protected C():base(){} protected DataTable show() {return values(setparameter());} } } EDIT I think what I am trying to do here is Multiple inheritance. Please check. Class A { //suppose 10 functions are declared } Class B:A { //5 functions declared which are using A's function in internal body } Class C:B { //using all functions of B but require only 4 functions of A to be accessible by C. }

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  • Overriding Ruby's spaceship operator <=>

    - by ericsteen1
    I am trying to override Ruby's <= (spaceship) operator to sort apples and oranges so that apples come first sorted by weight, and oranges second, sorted by sweetness. Like so: module Fruity attr_accessor :weight, :sweetness def <=>(other) # use Array#<=> to compare the attributes [self.weight, self.sweetness] <=> [other.weight, other.sweetness] end include Comparable end class Apple include Fruity def initialize(w) self.weight = w end end class Orange include Fruity def initialize(s) self.sweetness = s end end fruits = [Apple.new(2),Orange.new(4),Apple.new(6),Orange.new(9),Apple.new(1),Orange.new(22)] p fruits #should work? p fruits.sort But this does not work, can someone tell what I am doing wrong here, or a better way to do this?

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  • Using the same modules in multiple projects

    - by Andreas Vinther
    I'm using Visual Studio 2010 and coding in VB.NET. My problem is that I've collected all the modules I've written and intend to reuse and placed them in a separate folder. When I want to add a module from the above folder to any given project, it takes a copy of the module and places in the project's source code folder, instead of referencing the module in the folder containing all the other modules. Is it possible to include a module in my project and leave it in the folder with all the other modules, so that when I improve upon a module, it'll affect all the projects that uses/references that module. Instead of me having to manually copy the new module to all the projects that uses/references the module. Right now I have multiple instances of the exact same module that i need to update manually when I improve code or add functionality?

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  • Manually setting object's position or have the object do it all?

    - by N. Lucas
    I'm stuck thinking about the best way to go about setting a line segment's position, I have a class Line(length, angle, previous) being called from a class Polygon.. Right now I have: public function Line(length:Number, angle:Number, previous:Line = null) { if (previous != null) { this.x = previous.end.x; this.y = previous.end.y; } /**/ } Now, is this the best practice or should I be doing: Polygon.addLine(length:Number, angle:Number):void { var previous = _line[_line.length - 1]; // Array containing all Lines var line:Line = new Line(length, angle, previous); line.x = previous.end.x; line.y = previous.end.y; /**/ }

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  • Which class should store the lookup table?

    - by max
    The world contains agents at different locations, with only a single agent at any location. Each agent knows where he's at, but I also need to quickly check if there's an agent at a given location. Hence, I also maintain a map from locations to agents. I have a problem deciding where this map belongs to: class World, class Agent (as a class attribute) or elsewhere. In the following I put the lookup table, agent_locations, in class World. But now agents have to call world.update_agent_location every time they move. This is very annoying; what if I decide later to track other things about the agents, apart from their locations - would I need to add calls back to the world object all across the Agent code? class World: def __init__(self, n_agents): # ... self.agents = {} self.agent_locations = {} for id in range(n_agents): x, y = self.find_location() agent = Agent(self,x,y) self.agents.append(agent) self.agent_locations[x,y] = agent def update_agent_location(self, agent, x, y): del self.agent_locations[agent.x, agent.y] self.agent_locations[x, y] = agent def update(self): # next step in the simulation for agent in self.agents: agent.update() # next step for this agent # ... class Agent: def __init__(self, world, x, y): self.world = world self.x, self.y = x, y def move(self, x1, y1): self.world.update_agent_location(self, x1, y1) self.x, self.y = x1, y1 def update(): # find a good location that is not occupied and move there for x, y in self.valid_locations(): if not self.location_is_good(x, y): continue if self.world.agent_locations[x, y]: # location occupied continue self.move(x, y) I can instead put agent_locations in class Agent as a class attribute. But that only works when I have a single World object. If I later decide to instantiate multiple World objects, the lookup tables would need to be world-specific. I am sure there's a better solution... EDIT: I added a few lines to the code to show how agent_locations is used. Note that it's only used from inside Agent objects, but I don't know if that would remain the case forever.

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  • mysqli and php requesting rows returned in object oriented scripting...

    - by Matt
    in object oriented php mysqli I am trying to request a username, and return if it matches a row, without actually returning any user data. How would I write this?...so far I have... $sql = "SELECT NULL FROM database WHERE usernick=?"; $stmt = $link->prepare($sql) $stmt->bind_param('s', $snr); $stmt->execute(); After this step I need to see if a row matched the query...but I have no idea how to write it, everyone here pretty much writes in mysql if I dont mention I want object oriented mysqli :S

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  • Extend DOMElement object

    - by Comma
    How could I exdend objects provided with Document Object Model? Seems that there is no way according to this [issue][2]. class Application_Model_XmlSchema extends DOMElement { const ELEMENT_NAME = 'schema'; /** * @var DOMElement */ private $_schema; /** * @param DOMDocument $document * @return void */ public function __construct(DOMDocument $document) { $this->setSchema($document->getElementsByTagName(self::ELEMENT_NAME)->item(0)); } /** * @param DOMElement $schema * @return void */ public function setSchema(DOMElement $schema){ $this->_schema = $schema; } /** * @return DOMElement */ public function getSchema(){ return $this->_schema; } /** * @param string $name * @param array $arguments * @return mixed */ public function __call($name, $arguments) { if (method_exists($this->_schema, $name)) { return call_user_func_array( array($this->_schema, $name), $arguments ); } } } $version = $this->getRequest()->getParam('version', null); $encoding = $this->getRequest()->getParam('encoding', null); $source = 'http://www.w3.org/2001/XMLSchema.xsd'; $document = new DOMDocument($version, $encoding); $document->load($source); $xmlSchema = new Application_Model_XmlSchema($document); $xmlSchema->getAttribute('version'); I got an error: Warning: DOMElement::getAttribute(): Couldn't fetch Application_Model_XmlSchema in C:\Nevermind.php on line newvermind

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  • Abstract attributes in Python

    - by deamon
    What is the shortest / most elegant way to implement the following Scala code with an abstract attribute in Python? abstract class Controller { val path: String } A subclass of Controller is enforced to define "path" by the Scala compiler. A subclass would look like this: class MyController extends Controller { override val path = "/home" }

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  • Interview question: difference between object and object-oriented languages.

    - by Bar
    My friend was asked the following question: what's the difference between object language and object-oriented language? It's a little unintelligible question. What does term «object language» correspond to? Does that mean «pure» object-oriented language, like the Wikipedia article says: Languages called "pure" OO languages, because everything in them is treated consistently as an object, from primitives such as characters and punctuation, all the way up to whole classes, prototypes, blocks, modules, etc. They were designed specifically to facilitate, even enforce, OO methods. Examples: Smalltalk, Eiffel, Ruby, JADE, VB.NET.

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  • Actionscript 2.0 Functions problem

    - by Joshua
    I have two problems. The first problem is with the following functions; when I call the function in (enterFrame), it doesn't work: onClipEvent (load) { function failwhale(levelNum) { _root.gotoAndStop("fail"); failFrom = levelNum; } function guardSightCollision(guardName, guardSightName) { if (_root.guardName.guardSightName.hitTest(_x, _y+radius, true)) { failwhale(1); } if (_root.guardName.guardSightName.hitTest(_x, _y-radius, true)) { failwhale(1); } if (_root.guardName.guardSightName.hitTest(_x-radius, _y, true)) { failwhale(1); } if (_root.guardName.guardSightName.hitTest(_x+radius, _y, true)) { failwhale(1); } } } onClipEvent (enterFrame) { guardSightCollision(guard1, guard1Sight); } Why doesn't it work?... The second problem lies in the failFrom variable: function failwhale(levelNum) { _root.gotoAndStop("fail"); failFrom = levelNum; } How do I make failFrom a "global" variable in that it can be accessed anywhere (from actionscript in frames and even movieclips)...Right now, when I try to trace failFrom in a different frame, it is "undefined".

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  • Dependency Injection & Singleton Design pattern

    - by SysAdmin
    How do we identify when to use dependency injection or singleton pattern. I have read in lot of websites where they say "Use Dependency injection over singleton pattern". But I am not sure if I totally agree with them. For my small or medium scale projects I definitely see the use of singleton pattern straightforward. For example Logger. I could use Logger.GetInstance().Log(...) But, instead of this, why do I need to inject every class I create, with the logger's instance?.

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  • 'is instanceof' Interface bad design

    - by peterRit
    Say I have a class A class A { Z source; } Now, the context tells me that 'Z' can be an instance of different classes (say, B and C) which doesn't share any common class in their inheritance tree. I guess the naive approach is to make 'Z' an Interface class, and make classes B and C implement it. But something still doesn't convince me because every time an instance of class A is used, I need to know the type of 'source'. So all finishes in multiple 'ifs' making 'is instanceof' which doesn't sound quite nice. Maybe in the future some other class implements Z, and having hardcoded 'ifs' of this type definitely could break something. The escence of the problem is that I cannot resolve the issue by adding functions to Z, because the work done in each instance type of Z is different. I hope someone can give me and advice, maybe about some useful design pattern. Thanks

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  • Exporting to CSV with dynamic field type handling

    - by serhio
    I have to do an export from DB to CSV. field; fileld; field... etc Have 3 types of fields: Alpha, Numeric and Bool respresented as "alphaValue",intValue and True/False. I try to encapsulate this in a fields collection, in order to export if alpha then set "", if Bool=True/False if numeric let as is. and try to build a CsvField class: Public Structure?Class CsvField(Of T As ???) End Structure Enum FieldType Alpha Bool Numeric End Enum any suggestions welcomed.

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  • In what circumstances are instance variables declared as '_var' in 'use fields' readonly?

    - by Pedro Silva
    I'm trying to understand the behavior of the fields pragma, which I find poorly documented, regarding fields prefixed with underscores. This is what the documentation has to say about it: Field names that start with an underscore character are made private to the class and are not visible to subclasses. Inherited fields can be overridden but will generate a warning if used together with the -w switch. This is not consistent with its actual behavior, according to my test, below. Not only are _-prefixed fields visible within a subclass, they are visible within foreign classes as well (unless I don't get what 'visible' means). Also, directly accessing the restricted hash works fine. Where can I find more about the behavior of the fields pragma, short of going at the source code? { package Foo; use strict; use warnings; use fields qw/a _b __c/; sub new { my ( $class ) = @_; my Foo $self = fields::new($class); $self->a = 1; $self->b = 2; $self->c = 3; return $self; } sub a : lvalue { shift->{a} } sub b : lvalue { shift->{_b} } sub c : lvalue { shift->{__c} } } { package Bar; use base 'Foo'; use strict; use warnings; use Data::Dumper; my $o = Bar->new; print Dumper $o; ##$VAR1 = bless({'_b' => 2, '__c' => 3, 'a' => 1}, 'Foo'); $o->a = 4; $o->b = 5; $o->c = 6; print Dumper $o; ##$VAR1 = bless({'_b' => 5, '__c' => 6, 'a' => 4}, 'Foo'); $o->{a} = 7; $o->{_b} = 8; $o->{__c} = 9; print Dumper $o; ##$VAR1 = bless({'_b' => 8, '__c' => 9, 'a' => 7}, 'Foo'); }

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  • Why is sqrt() not a method on Float?

    - by KaptajnKold
    In Ruby everything is an object. That's why I don't understand why we have the Math module. It seems to me that most (all?) of the functions in the Math module should have been methods on the numeric types like Integer, Float and so on. E.g. instead of Math.sqrt(5) it would make more sense to have 5.sqrt The same goes for sin, cos, tan, log10 and so on. Does anyone know why all these functions ended up in the Math module?

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  • how to integrate Zend Framework MVC with existing site

    - by Joel
    Hi guys, So I'm slowly tackling OO and Zend Framework and their MVC process in particular. I have an existing website and web-based calendar application that was designed by me, but coded by a different person and done procedurally. I understand that it will be very difficult for my application to ever be completely OO without a full re-write, and I'm fine with that. I have a lot of updates and modifications I want to do in the future, so I'm wanting to start replacing some of the basic components (login, authentication. etc) now, and continue to learn as I go. Again, I'm really a newbie at programming and OO. What I'm wondering is if I'm wanting to incorporate the Framework, then would I just first drop my whole site into the /public folder of the Framework and then start pulling functionality out from there?

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  • How to pass a linc to class function and call it?

    - by Kabumbus
    So I have a class like class mySafeData { public: void Set( int i ) { myMutex.lock(); myData = i; myMutex.unlock(); } void Get( int& i) { myMutex.lock(); i = myData; myMutex.unlock(); } private: int myData; boost::mutex myMutex; }; its instance is running. Lets call instance A. I want to create a new class that would take as a start up argument some kind of link to Getter from A and would be capable to somehow save link to thet getter for calling it inside its private methods vhen needed. how to do such thing?

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  • Flash AS3: automate property assignment to new instance from arguments in constructor

    - by matt lohkamp
    I like finding out about tricky new ways to do things. Let's say you've got a class with a property that gets set to the value of an argument in the constructor, like so: package{ public class SomeClass{ private var someProperty:*; public function SomeClass(_someProperty:*):void{ someProperty = _someProperty; } } } That's not exactly a hassle. But imagine you've got... I don't know, five properties. Ten properties, maybe. Rather then writing out each individual assignment, line by line, isn't there a way to loop through the constructor's arguments and set the value of each corresponding property on the new instance accordingly? I don't think that the ...rest or arguments objects will work, since they only keep an enumerated list of the arguments, not the argument names - I'm thinking something like this would be better: for(var propertyName:String in argsAsAssocArray){this[propertyName] = argsAsAssocArray[propertyName];} ... does something like this exist?

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  • How do you keep application logic separate from UI when UI components have built-in functionality?

    - by Al C
    I know it's important to keep user interface code separated from domain code--the application is easier to understand, maintain, change, and (sometimes) isolate bugs. But here's my mental block ... Delphi comes with components with methods that do what I want, e.g., a RichText Memo component lets me work with rich text. Other components, like TMS's string grid not only do what I want, but I paid extra for the functionality. These features put the R in RAD. It seems illogical to write my own classes to do things somebody else has already done for me. It's reinventing the wheel [ever tried working directly with rich text? :-) ] But if I use the functionality built into components like these, then I will end up with lots of intermingled UI and domain code--I'll have a form with most of my code built into its event handlers. How do you deal with this issue? ... Or, if I want to continue using the code others have already written for me, how would you suggest I deal with the issue?

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  • Delegation, is this just opinionated or is there a common pattern?

    - by user1446714
    If I have a java class containing substantial code and I wish to add extra features, am I right in thinking the delegate class would have the additional features added as methods. Then my original class would create the delegate object and just call the extra functionality via the delegate instance? I am being told by somebody else that my original class should become the delegate and that the class containing the new functionality should contain an instance of the original class, to use as a delegate? This seemed a little backward to me, because there would be far more delegate calls because most of the code is now in the delegate.... I was always under the impression the delegate object would contain the additional new behaviour and an instance of it would be in the original class to inboke the new behaviour from?

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  • Cannot redeclare class but there are no other classes with that name

    - by hsz
    Hello ! I am working right now with Zend Framework and I've created a Model_User_Row in app\models\User\Row.php. When I try to create an instance of that class in IndexController I get an error: Fatal error: Cannot redeclare class Model_User_Row in F:\Projekty\www\inz\app\models\User\Row.php on line 14 14th line is a close brace. <?php class Model_User_Row extends Zend_Db_Table_Row { /** * @return array */ public function toArray() { $res = parent::toArray(); unset($res['password']); return $res; } } // #14 In my project I have no other class called Model_User_Row. I am a bit confused - how to debug this case ?

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  • How would you go to "design" a cart within a Zend Framework project?

    - by ÉricP
    Hi, I know ZF well, and a little bit of Magento, but I'm new to E-commerce, and I'm sure there are best practice to follow when designing a cart model. How would go to design a cart? I though of two models, Model_Cart and Model_Cart_Item used in conjonction with Zend_Session to store the cart in session. What are your feedbacks? How would you go to do that? What should I know about writing a cart system? Note that I need a simple system, I even don't need to work with quantity

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  • Data Application based on OO Concepts

    - by The King
    Hi... I'm looking for an application developed in C# with following qualities, which is available as source code... Based on OO Architecture Must connect to DB. Must handle atleast a "one to many master child" relationship (eg: Order and items ordered) Should display the data using Datagrid or other similar controls. Reports (either with report buider or otherwise) I want to understand the layering of objects better... Do you have any links... Thanks.

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  • Lambda Functions in PHP aren't Logical

    - by Chacha102
    Note: I have condensed this article into my person wiki: http://wiki.chacha102.com/Lambda - Enjoy I am having some troubles with Lambda style functions in PHP. First, This Works: $foo = function(){ echo "bar"; }; $foo(); Second, This Works: class Bar{ public function foo(){ echo "Bar"; } Third, This works: $foo = new stdClass; $foo->bar = function(){ echo "bar"; }; $test = $foo->bar; $test(); But, this does not work: $foo = new stdClass; $foo->bar = function(){ echo "bar"; }; $foo->bar(); And, this does not work class Bar{ public function foo(){ echo "Bar"; } $foo = new Bar; $foo->foo = function(){ echo "foo"; }; $foo->foo(); // echo's bar instead of Foo. My Question is Why?, and how can I assure that both this: $foo->bar = function(){ echo "test"; }; $foo->bar(); and this $foo = new Bar; $foo->bar(); are called properly? Extra Points if you can point to documentation stating why this problem occurs.

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  • Page inheritance in mixed asp.net Forms and MVC application

    - by Rising Star
    I'm working on a web application. One of my co-workers has written some asp.net forms pages. The page classes all inherit from BasePageClass, which of course inherits from the Page class. I wish to add some MVC controllers that I've been told need to use the same logic implemented in the BasePageClass. Ordinarily, I would want to inherit the functions in the BasePageClass in the controller classes, but this breaks the inheritance heirarchy. What is the best practice for solving this problem?

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