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  • How do we know to favour composition over generalisation is always the right choice?

    - by Carnotaurus
    Whether an object physically exists or not, we can choose to model it in different ways. We could arbitarily use generalisation or composition in many cases. However, the GoF principle of "favour composition over generalisation [sic]" guides us to use composition. So, when we model, for example, a line then we create a class that contains two members PointA and PointB of the type Point (composition) instead of extending Point (generalisation). This is just a simplified example of how we can arbitarily choose composition or inheritance to model, despite that objects are usually much more complex. How do we know that this is the right choice? It matters at least because there could be a ton of refactoring to do if it is wrong?

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  • Do delegates defy OOP

    - by Dave Rook
    I'm trying to understand OOP so I can write better OOP code and one thing which keeps coming up is this concept of a delegate (using .NET). I could have an object, which is totally self contained (encapsulated); it knows nothing of the outside world... but then I attach a delegate to it. In my head, this is still quite well separated as the delegate only knows what to reference, but this by itself means it has to know about something else outside it's world! That a method exists within another class! Have I got myself it total muddle here, or is this a grey area, or is this actually down to interpretation (and if so, sorry as that will be off topic I'm sure). My question is, do delegates defy/muddy the OOP pattern?

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  • Collision in PyGame for spinning rectangular object.touching circles

    - by OverAchiever
    I'm creating a variation of Pong. One of the differences is that I use a rectangular structure as the object which is being bounced around, and I use circles as paddles. So far, all the collision handling I've worked with was using simple math (I wasn't using the collision "feature" in PyGame). The game is contained within a 2-dimensional continuous space. The idea is that the rectangular structure will spin at different speed depending on how far from the center you touch it with the circle. Also, any extremity of the rectangular structure should be able to touch any extremity of the circle. So I need to keep track of where it has been touched on both the circle and the rectangle to figure out the direction it will be bounced to. I intend to have basically 8 possible directions (Up, down, left, right and the half points between each one of those). I can work out the calculation of how the objected will be dislocated once I get the direction it will be dislocated to based on where it has been touch. I also need to keep track of where it has been touched to decide if the rectangular structure will spin clockwise or counter-clockwise after it collided. Before I started coding, I read the resources available at the PyGame website on the collision class they have (And its respective functions). I tried to work out the logic of what I was trying to achieve based on those resources and how the game will function. The only thing I could figure out that I could do was to make each one of these objects as a group of rectangular objects, and depending on which rectangle was touched the other would behave accordingly and give the illusion it is a single object. However, not only I don't know if this will work, but I also don't know if it is gonna look convincing based on how PyGame redraws the objects. Is there a way I can use PyGame to handle these collision detections by still having a single object? Can I figure out the point of collision on both objects using functions within PyGame precisely enough to achieve what I'm looking for? P.s: I hope the question was specific and clear enough. I apologize if there were any grammar mistakes, English is not my native language.

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  • How get and set accessors work

    - by Chris Halcrow
    The standard method of implementing get and set accessors in C# and VB.NET is to use a public property to set and retrieve the value of a corresponding private variable. Am I right in saying that this has no effect of different instances of a variable? By this I mean, if there are different instantiations of an object, then those instances and their properties are completely independent right? So I think my understanding is correct that setting a private variable is just a construct to be able to implement the get and set pattern? Never been 100% sure about this.

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  • Rotation, further I go from 0:0, the further the object positions around the origin while rotating

    - by Serguei Fedorov
    For some reason I am having the issue where the following code: global.spriteBatch.Draw(obj.sprite, obj.getPosition(), null, Color.White, obj.rotation, obj.center, 2f, SpriteEffects.None, 1); causes the object to rotate around the origin in such a way, as though there is an offset to the position relative to its location. The calculation for the center it correct and this happens even if I set the pivot to be the location of the object. The further I get from 0:0 the larger the radius or rotation. I am not sure what is going on here because given the following tutorial http://www.riemers.net/eng/Tutorials/XNA/Csharp/Series2D/Rotation.php I have done the code setup correctly. Any ideas? Any help is greatly appreciated!!!

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  • How to Create a Skin Object from an OWS Configuration - 2 Videos

    In this video tutorial we walk you through how to create and place Open Web Studio skin objects directly into your DotNetNuke skin.We cover how to create an OWS menu and feedback form and how to convert those modules into DNN Skin Objects.The videos contain:Video 1 - Building the New OWS Configuration and Creating the Menu SystemVideo 2 - Placing the OWS Skin Object within the Skin File and Creating a Feedback Skin ObjectHow to Create a Skin Object from an OWS Configuration - 2 Videos Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Cocos2d Box2d contact listener call different method in collided object

    - by roma86
    I have the building object, wen it hit with other, i want to call some method inside it. Building.mm -(void)printTest { NSLog(@"printTest method work correctly"); } in my ContactListener i trying to call it so: ContactListener.mm #import "ContactListener.h" #import "Building.h" void ContactListener::BeginContact(b2Contact* contact) { b2Body* bodyA = contact->GetFixtureA()->GetBody(); b2Body* bodyB = contact->GetFixtureB()->GetBody(); Building *buildA = (Building *)bodyA->GetUserData(); Building *buildB = (Building *)bodyB->GetUserData(); if (buildB.tag == 1) { NSLog(@"tag == 1"); } if (buildA.tag == 2) { NSLog(@"tag == 2"); [buildA printTest]; } } NSLog(@"tag == 2"); work correctly, but [buildA printTest]; get error Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[CCSprite printTest]: unrecognized selector sent to instance 0x18595f0' Obviously I'm referring to the wrong object. How i can get different method and property in contacted objects from contactlistener class? Thanks.

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  • How to move an object along a circumference of another object?

    - by Lumis
    I am so out of math that it hurts, but for some of you this should be a piece of cake. I want to move an object around another along its ages or circumference on a simple circular path. At the moment my game algorithm knows how to move and position a sprite just at the edge of an obstacle and now it waits for the next point to move depending on various conditions. So the mathematical problem here is how to get (aX, aY) and (bX, bY) positions, when I know the Centre (cX, cY), the object position (oX, oY) and the distance required to move (d)

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  • Getting started with object detection - Image segmentation algorithm

    - by Dev Kanchen
    Just getting started on a hobby object-detection project. My aim is to understand the underlying algorithms and to this end the overall accuracy of the results is (currently) more important than actual run-time. I'm starting with trying to find a good image segmentation algorithm that provide a good jump-off point for the object detection phase. The target images would be "real-world" scenes. I found two techniques which mirrored my thoughts on how to go about this: Graph-based Image Segmentation: http://www.cs.cornell.edu/~dph/papers/seg-ijcv.pdf Contour and Texture Analysis for Image Segmentation: http://www.eng.utah.edu/~bresee/compvision/files/MalikBLS.pdf The first one was really intuitive to understand and seems simple enough to implement, while the second was closer to my initial thoughts on how to go about this (combine color/intensity and texture information to find regions). But it's an order of magnitude more complex (at least for me). My question is - are there any other algorithms I should be looking at that provide the kind of results that these two, specific papers have arrived at. Are there updated versions of these techniques already floating around. Like I mentioned earlier, the goal is relative accuracy of image segmentation (with an eventual aim to achieve a degree of accuracy of object detection) over runtime, with the algorithm being able to segment an image into "naturally" or perceptually important components, as these two algorithms do (each to varying extents). Thanks! P.S.1: I found these two papers after a couple of days of refining my search terms and learning new ones relevant to the exact kind of techniques I was looking for. :) I have just about reached the end of my personal Google creativity, which is why I am finally here! Thanks for the help. P.S.2: I couldn't find good tags for this question. If some relevant ones exist, @mods please add them. P.S.3: I do not know if this is a better fit for cstheory.stackexchange (or even cs.stackexchange). I looked but cstheory seems more appropriate for intricate algorithmic discussions than a broad question like this. Also, I couldn't find any relevant tags there either! But please do move if appropriate.

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  • Is OOP becoming easier or harder?

    - by tunmise fasipe
    When the concepts of Object Oriented Programming were introduced to programmers years back it looks interesting and programming was cleaner. OOP was like this Stock stock = new Stock(); stock.addItem(item); stock.removeItem(item); That was easier to understand with self-descriptive name. But now OOP, with pattern like Data Transfer Objects (or Value Objects), Repository, Dependency Injection etc, has become more complex. To achieve the above you may have to create several classes (e.g. abstract, factory, DAO etc) and Implement several interfaces Note: I am not against best practices that makes Collaboration, Testing and Integration easier

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  • How to Create a DotNetNuke Skin Object from an OWS Configuration - 2 Videos

    In this tutorial we walk you through how to create and place Open Web Studio skin objects directly into your DotNetNuke skin. We cover how to create an OWS menu and feedback form and how to convert those modules into DNN Skin Objects. The videos contain: Video 1 - Building the New OWS Configuration and Creating the Menu System Video 2 - Placing the OWS Skin Object within the Skin File and Creating a Feedback Skin Object Total Time Length: 18minsDid you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Get and set accessors do they protect different instances of a variable?

    - by Chris Halcrow
    The standard method of implementing get and set accessors in C# and VB.NET is to use a public property to set and retrieve the value of a corresponding private variable. Am I right in saying that this has no effect of different instances of a variable? By this I mean, if there are different instantiations of an object, then those instances and their properties are completely independent right? So I think my understanding is correct that setting a private variable is just a construct to be able to implement the get and set pattern? Never been 100% sure about this.

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  • What makes C so popular in the age of OOP?

    - by GradGuy
    I code a lot both in C and C++ but did not expect C to be the second popular language, slightly behind Java! http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html I'm curious as why, in this age of OOP, C is still all that popular? Note that 4 out of top 5 popular languages are all "modern" object-oriented capable languages. Now I agree that you can do OOP in C to some extend, but that's sort of painful and not quite elegant! (well at least compared to C++ I guess) So what makes C this popular? efficiency? being low-level? or the vast majority of libraries that already exist? ... or something else?

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  • Where should I put a method that returns a list of active entries of a table?

    - by darga33
    I have a class named GuestbookEntry that maps to the properties that are in the database table named "guestbook". Very simple! Originally, I had a static method named getActiveEntries() that retrieved an array of all GuestbookEntry objects. Each row in the guestbook table was an object that was added to that array. Then while learning how to properly design PHP classes, I learned some things: Static methods are not desirable. Separation of Concerns Single Responsibility Principle If the GuestbookEntry class should only be responsible for managing single guestbook entries then where should this getActiveEntries() method most properly go? Update: I am looking for an answer that complies with the SOLID acronym principles and allows for test-ability. That's why I want to stay away from static calls/standard functions. DAO, repository, ...? Please explain as though your explanation will be part of "Where to Locate FOR DUMMIES"... :-)

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  • Visual C++, CMap object save to blob column

    - by ilansch
    I have a MFC CMap object, each object stores 160K~ entries of long data. I need to store it on Oracle SQL. we decided to save it as a blob. since we do not want to make additional table. we also thought about saving it as local file and point the SQL column to that file, but we rather just keep it as blob on the server and clear the table every couple of weeks. The table has a sequential key as ID, and 2 column of time. I need to add the blob column in order to store on every row that CMap. Can you recommend a guide to do so (read/write Map to blob or maybe a clob) ? Thanks.

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  • How to access functions in extended classes efficiently?

    - by nischayn22
    In PHP I have classes as below class Animal { //some vars public function printname(){ echo $this->name; } } class AnimalMySql extends Animal { static public function getTableFields(){ return array(); } } class AnimalPostgreSql extends Animal { static public function getTableFields(){ return array(); } } Now I have an object $lion = new Animal(); and I want to do if($store == mysql) //getTableFields from class AnimalMySql else //getTableFields form class AnimalPostgreSql I am new to OOP and not sure what is the best way to call the method from the specific class P.S. Please leave a note with the answer to explain the efficiency of the approach

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  • using static methods and classes

    - by vedant1811
    I know that static methods/variables are associated with the class and not the objects of the class and are useful in situations when we need to keep count of, say the number of objects of the class that were created. Non-static members on the other hand may need to work on the specific object (i.e. to use the variables initialized by the constructor) My question what should we do when we need neither of the functionalities? Say I just need a utility function that accepts value(s) and returns a value besed solely on the values passed. I want to know whether such methods should be static or not. How is programming efficiency affected and which is a better coding practice/convention and why. PS: I don't want to spark off a debate, I just want a subjective answer and/or references.

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  • How should I define my Java Objects?

    - by HonorGod
    I have a data grid where I sort of show the following information - All Guests Total Adults = 22 Total Children = 27 Confirmed Total Adults = 9 Total Children = 13 Country = Germany Total Adults = 5 Total Childres = 6 Friends Adults = 2 Children = 2 Relatives Adults = 3 Children = 4 Country = USA Total Adults = 4 Total Childres = 7 Friends Adults = 2 Children = 5 Relatives Adults = 2 Children = 2 Tentative Total Adults = 13 Total Children - 14 Country = Australia Total Adults = 7 Total Childres = 8 Friends Adults = 2 Children = 3 Relatives Adults = 5 Children = 5 Country = China Total Adults = 6 Total Childres = 6 Friends Adults = 2 Children = 4 Relatives Adults = 4 Children = 2 And in the database what I have is data at the lowest level which is Friends / Relatives and the corresponding countries set as a look-up value which in indirectly connected to another look-up that can tell me if they fall under confirmed or tentative. I guess my question is how do I layout my Java Object and perform the aggregations and give it back to the client. I am not sure if I am clear with my question, but feel free to comment so I can update the question accordingly.

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  • Rotate an object given only by its points?

    - by d33tah
    I was recently writing a simple 3D maze FPP game. Once I was done fiddling with planes in OpenGL, I wanted to add support for importing Blender objects. The approach I used was triangulization of the object, then using Three.js to export the points to plaintext and then parsing the result JSON in my app. The example file can be seen here: https://github.com/d33tah/tinyfpp/blob/master/Data/Models/cross.txt The numbers represent x,y,z,u,v of a single vertex, which combined in three make a triangle. Then I rendered such an object triangle-by-triangle and played with it. I could move it back and forth and sideways, but I still have no idea how to rotate it by some axis. Let's say I'd like to rotate all the points by five degrees to the left, how would a code doing it look like?

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  • Settings object with singleton pattern

    - by axis
    I need to build an object that will have only one instance because this Object is dedicated to the storage of vital settings for my application and I would like to avoid a misuse of this type or a conflict at run-time. The most popular solution for this, according to the internet, is the Singleton pattern. But I would like to know about other ideas or solutions for this; also I would like to know if other solutions can be much more easy to grasp for an user of this hypothetical library. Thanks.

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  • Where would a senior PHP developer locate the method getActiveEntries()?

    - by darga33
    I have a class named GuestbookEntry that maps to the properties that are in the database table named "guestbook". Very simple! Originally, I had a static method named getActiveEntries() that retrieved an array of all GuestbookEntry objects. Each row in the guestbook table was an object that was added to that array. Then while learning how to properly design PHP classes, I learned some things: Static methods are not desirable. Separation of Concerns Single Responsibility Principle If the GuestbookEntry class should only be responsible for managing single guestbook entries then where should this getActiveEntries() method most properly go? Update: I am looking for an answer that complies with the SOLID acronym principles and allows for test-ability. That's why I want to stay away from static calls/standard functions. DAO, repository, ...? Please explain as though your explanation will be part of "Where to Locate FOR DUMMIES"... :-)

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