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• What patterns book for iOS development contains this specific information? [closed]

  - by Brett Ryan

  I've read several books on iOS development and Objective-C, however what a lot of them teach is how to work with interfaces and all contain the model inside the view controller, i.e. a UITableViewController based view will simply have an NSArray as it's model. I'm interested in what the best practices are for designing the structure of an application. Specifically I'm interested in best practices for the following: How to separate a model from the view controller. I think I know how to do this by simply replacing the NSArray style example with a specific model object, however what I do not know how to do is alert the view when the model changes. For example in .NET I would solve this by conforming to INotifyPropertyChanged and databinding, and similarly with Java I would use PropertyChangeListener. How to create a service model for my domain objects. For example I want to learn the best way to create a service for a hypothetical Widget object to manage an internal DB and also services for communicating with remote endpoints. I need to learn the best ways to do this in a way that interface components can subscribe to events such as widgetUpdated. These services should be singleton classes and some how dependency injected into model/controller objects. Books I've read so far are: Programming in Objective-C (4th Edition) Beginning iOS 5 Development: Exploring the iOS SDK The iOS 5 Developer's Cookbook: Expanded Electronic Edition: Essentials and Advanced Recipes for iOS Programmers Learn Objective-C on the Mac: For OS X and iOS I've also purchased the following updated books but not yet read them. The Core iOS 6 Developer's Cookbook (4th edition Programming in Objective-C (5th Edition) I come from a Java and C# background with 15 years experience, I understand that many of the ways I would do things in these languages may not fit to the ObjC way of developing applications. Would someone be able to provide me with the book on this topic containing this specific subject matter?

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• Encapsulating code in F# (Part 2)

  - by MarkPearl

  In part one of this series I showed an example of encapsulation within a local definition. This is useful to know so that you are aware of the scope of value holders etc. but what I am more interested in is encapsulation with regards to generating useful F# code libraries in .Net, this is done by using Namespaces and Modules. Lets have a look at some C# code first… using System; namespace EncapsulationNS { public class EncapsulationCLS { public static void TestMethod() { Console.WriteLine("Hello"); } } } Pretty simple stuff… now the F# equivalent…. namespace EncapsulationNS module EncapsulationMDL = let TestFunction = System.Console.WriteLine("Hello") ()   Even easier… lets look at some specifics about F# namespaces… Namespaces are open. meaning you can have multiple source files and assemblies can contribute to the same namespace. So, Namespaces are a great way to group modules together, so the question needs to be asked, what role do modules play. For me, the F# module is in many ways similar to the vb6 days of modules. In vb6 modules were separate files and simply allowed us to group certain methods together. I find it easier to visualize F# modules this way than to compare them to the C# classes. However that being said one is not restricted to one module per file – there is flexibility to have multiple modules in one code file however with my limited F# experience I would still recommend using the file as the standard level of separating modules as it is very easy to then find your way around a solution. An important note about interop with F# and other .Net languages. I wrote a blog post a while back about a very basic F# to C# interop. If I were to reference an F# library in a C# project (for instance ‘TestFunction’), in C# it would show this method as a static method call, meaning I would not have to instantiate an instance of the module.

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• Cookie access within a HTTP Class

  - by James Jeffery

  I have a HTTP class that has a Get, and Post, method. It's a simple class I created to encapsulate Post and Get requests so I don't have to repeat the get/post code throughout the application. In C#: class HTTP { private CookieContainer cookieJar; private String userAgent = "..."; public HTTP() { this.cookieJar = new CookieContainer(); } public String get(String url) { // Make get request. Return the JSON } public String post(String url, String postData) { // Make post request. Return the JSON } } I've made the CookieJar a property because I want to preserve the cookie values throughout the session. If the user is logged into Twitter with my application, each request I make (be it get or post) I want to use the cookies so they remain logged in. That's the basics of it anyway. But, I don't want to return a string in all instances. Sometimes I may want the cookie, or a header value, or something else from the request. Ideally I'd like to be able to do this in my code: Cookie cookie = http.get("http://google.com").cookie("g_user"); String g_user = cookie.value; or String source = http.get("http://google.com").body; My question - To do this, would I need to have a Get class, and a Post class, that are included within the HTTP class and are accessible via accessors? Within the Get and Post class I would then have the Cookie method, and the body property, and whatever else is needed. Should I also use an interface, or create a Request class and have Post and Get extend it so that common methods and properties are available to both classes? Or, am I thinking totally wrong?

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• Design in "mixed" languages: object oriented design or functional programming?

  - by dema80

  In the past few years, the languages I like to use are becoming more and more "functional". I now use languages that are a sort of "hybrid": C#, F#, Scala. I like to design my application using classes that correspond to the domain objects, and use functional features where this makes coding easier, more coincise and safer (especially when operating on collections or when passing functions). However the two worlds "clash" when coming to design patterns. The specific example I faced recently is the Observer pattern. I want a producer to notify some other code (the "consumers/observers", say a DB storage, a logger, and so on) when an item is created or changed. I initially did it "functionally" like this: producer.foo(item => { updateItemInDb(item); insertLog(item) }) // calls the function passed as argument as an item is processed But I'm now wondering if I should use a more "OO" approach: interface IItemObserver { onNotify(Item) } class DBObserver : IItemObserver ... class LogObserver: IItemObserver ... producer.addObserver(new DBObserver) producer.addObserver(new LogObserver) producer.foo() //calls observer in a loop Which are the pro and con of the two approach? I once heard a FP guru say that design patterns are there only because of the limitations of the language, and that's why there are so few in functional languages. Maybe this could be an example of it? EDIT: In my particular scenario I don't need it, but.. how would you implement removal and addition of "observers" in the functional way? (I.e. how would you implement all the functionalities in the pattern?) Just passing a new function, for example?

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• What's the right/standard way of achieving separation of concerns?

  - by Ghanima

  Some background: I want to start developing games, and taking some of the advice given in this site, I've started with something simple and familiar, such as pong, tetris, etc. I want to take as much time as needed to make sure that I have the basics right before moving on to something bigger. I have medium programming experience but I realize making games is a different thing. I find myself wondering many things like should this be in a separate class? Should this module handle this stuff or is it better to let other modules have that kind of functionality? For example, the bouncing of a ball in pong, right now is handled in the ball module, but maybe it's better that some other module did it. Right now I have different modules: one for the graphics, one for the game logic, and others for the objects (depending on the kind of movement required, not all the objects are alike). I know I am asking a lot, any tips you have will be very much appreciated. Short question: What's the right or standard way of separating the modules? What have you found most effective? Is it enough to just keep the drawing (graphics) and the logic separate? Is it necessary to have a lot of classes? (for example for the objects in the game, to handle the movement, etc)

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• Matrices: Arrays or separate member variables?

  - by bjz

  I'm teaching myself 3D maths and in the process building my own rudimentary engine (of sorts). I was wondering what would be the best way to structure my matrix class. There are a few options: Separate member variables: struct Mat4 { float m11, m12, m13, m14, m21, m22, m23, m24, m31, m32, m33, m34, m41, m42, m43, m44; // methods } A multi-dimensional array: struct Mat4 { float[4][4] m; // methods } An array of vectors struct Mat4 { Vec4[4] m; // methods } I'm guessing there would be positives and negatives to each. From 3D Math Primer for Graphics and Game Development, 2nd Edition p.155: Matrices use 1-based indices, so the first row and column are numbered 1. For example, a12 (read “a one two,” not “a twelve”) is the element in the first row, second column. Notice that this is different from programming languages such as C++ and Java, which use 0-based array indices. A matrix does not have a column 0 or row 0. This difference in indexing can cause some confusion if matrices are stored using an actual array data type. For this reason, it’s common for classes that store small, fixed size matrices of the type used for geometric purposes to give each element its own named member variable, such as float a11, instead of using the language’s native array support with something like float elem[3][3]. So that's one vote for method one. Is this really the accepted way to do things? It seems rather unwieldy if the only benefit would be sticking with the conventional math notation.

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• I still can't figure out how to program!

  - by Mark K.

  Please help! I've read lots of programming books for various languages, Java, Python, C, etc. I understand and know all of the basics of the languages and I understand algorithms and data structures. (Equivilant of say 2 years of CompSci classes) BUT, I still can't figure how to write a program that does anything useful. All of the programming books show you how to write the language, but NOT how to use it! The programming examples are all very basic like build a card catalog for a library or a simple game or use algorithms etc... They dont't show you how to develop complex programs that actually do anything useful! I've looked a open-source programs on sourceforge, but they don't make much sense to me. There are hundreds of files in each program & thousands of lines of code. But how do I learn how to do this? There's nothing in any book I can buy on Amazon that will give me the tools to write any of these programs. How do you go from reading Intro to Java or Programming Python, or C Programming Language, etc.. to actually being able to say, I have an idea for X Program.. this is how I go about developing it? It seems like there is so much more involved in writing a program than you can learn in a book or from a class. I feel like there is someth Can anyone put me on the right track?

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• Seperation of drawing and logic in games

  - by BFree

  I'm a developer that's just now starting to mess around with game development. I'm a .Net guy, so I've messed with XNA and am now playing around with Cocos2d for the iPhone. My question really is more general though. Let's say I'm building a simple Pong game. I'd have a Ball class and a Paddle class. Coming from the business world development, my first instinct is to not have any drawing or input handling code in either of these classes. //pseudo code class Ball { Vector2D position; Vector2D velocity; Color color; void Move(){} } Nothing in the ball class handles input, or deals with drawing. I'd then have another class, my Game class, or my Scene.m (in Cocos2D) which would new up the Ball, and during the game loop, it would manipulate the ball as needed. The thing is though, in many tutorials for both XNA and Cocos2D, I see a pattern like this: //pseudo code class Ball : SomeUpdatableComponent { Vector2D position; Vector2D velocity; Color color; void Update(){} void Draw(){} void HandleInput(){} } My question is, is this right? Is this the pattern that people use in game development? It somehow goes against everything I'm used to, to have my Ball class do everything. Furthermore, in this second example, where my Ball knows how to move around, how would I handle collision detection with the Paddle? Would the Ball need to have knowledge of the Paddle? In my first example, the Game class would have references to both the Ball and the Paddle, and then ship both of those off to some CollisionDetection manager or something, but how do I deal with the complexity of various components, if each individual component does everything themselves? (I hope I'm making sense.....)

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• Advantages of Scala vs. Groovy with JAVA EE 6 Applications.

  - by JAVA EE Wannabe

  Please let me first emphasize that I am not looking for flare wars. I just want advices from people who have real experiences. I started learning JAVA EE 6 as real newbie and am having had time choosing what tools to use. First problem is what is the advantage of using Scala vs. Groovy with Java EE 6 apps over Java? I've seen on some blogs people mentioning you gonna write less code but as a newbie I don't know what other advantages and disadvantages are there. Second problem is Netbeans 6.9 or Helios 3.6.1? I realized that with eclipse I can easily mix EE 6 applications with Groovy or Scala without any problems (I only did this by displaying a String message from Scala and Groovy classes.). With Netbeans the only I can think of is having separate Java project libraries and using the jars in my web app. But also realize to the extent of my little knowledge Netbeans has better support for Java EE 6. Please need your expert advice. Thanks.

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• Is wrapping a third party code the only solution to unit test its consumers? [closed]

  - by Songo

  I'm doing unit testing and in one of my classes I need to send a mail from one of the methods, so using constructor injection I inject an instance of Zend_Mail class which is in Zend framework. Now some people argue that if a library is stable enough and won't change often then there is no need to wrap it. So assuming that Zend_Mail is stable and won't change and it fits my needs entirely, then I won't need a wrapper for it. Now take a look at my class Logger that depends on Zend_Mail: class Logger{ private $mailer; function __construct(Zend_Mail $mail){ $this->mail=$mail; } function toBeTestedFunction(){ //Some code $this->mail->setTo('some value'); $this->mail->setSubject('some value'); $this->mail->setBody('some value'); $this->mail->send(); //Some } } However, Unit testing demands that I test one component at a time, so I need to mock the Zend_Mail class. In addition I'm violating the Dependency Inversion principle as my Logger class now depends on concretion not abstraction. Now is wrapping Zend_Mail the only solution or is there a better approach to this problem? The code is in PHP, but answers doesn't have to be. This is more of a design issue than a language specific feature

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• Learning how to design knowledge and data flow [closed]

  - by max

  In designing software, I spend a lot of time deciding how the knowledge (algorithms / business logic) and data should be allocated between different entities; that is, which object should know what. I am asking for advice about books, articles, presentations, classes, or other resources that would help me learn how to do it better. I code primarily in Python, but my question is not really language-specific; even if some of the insights I learn don't work in Python, that's fine. I'll give a couple examples to clarify what I mean. Example 1 I want to perform some computation. As a user, I will need to provide parameters to do the computation. I can have all those parameters sent to the "main" object, which then uses them to create other objects as needed. Or I can create one "main" object, as well as several additional objects; the additional objects would then be sent to the "main" object as parameters. What factors should I consider to make this choice? Example 2 Let's say I have a few objects of type A that can perform a certain computation. The main computation often involves using an object of type B that performs some interim computation. I can either "teach" A instances what exact parameters to pass to B instances (i.e., make B "dumb"); or I can "teach" B instances to figure out what needs to be done when looking at an A instance (i.e., make B "smart"). What should I think about when I'm making this choice?

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• Finding the best practice for a game simulating tool

  - by Tougheart

  I'm studying Java right now, and I'm thinking of this tool as my practice project. The game is "League of Legends" in case anyone knows it, I'm not actually simulating the game as in simulating game play, I'm just trying to create a tool that can compare different champions to each other based on their own abilities and items bought inside the game. The game basics are: Every player has a champion in a team of 5 players playing against another team. Each champion has a different set of abilities (usually 4) that s/he uses to do damage to opposing champions. Each champion gets stronger by buying different items, increasing the attack it deals or decreasing the damage received. What I want to do is to create a tool to be used outside the game enabling players to try out different builds for their champions and compare the figures against other champions they usually fight against. The goal is to enable players get a deeper understanding of the different item combinations (builds) that can be used during the games, instead of trying them out in real games which can be somehow very time consuming. What I'm stuck at is the best practice I should follow to make this possible using Java, I can't figure out which classes should inherit from which, should I make champions and items specs in the code or extracted from other files, specially that I'm talking about hundreds of items and champions to use in that tool. I'm self studying Java, and I don't have much practice at it, so I would really appreciate any broad guidelines regarding this, and sorry if my question doesn't fit here, I tried to follow the rules. English isn't my native language, so I'm really sorry if I wasn't clear enough, I would be more than happy to explain anything that's not understood.

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• Two components offering the same functionality, required by different dependencies

  - by kander

  I'm building an application in PHP, using Zend Framework 1 and Doctrine2 as the ORM layer. All is going well. Now, I happened to notice that both ZF1 and Doctrine2 come with, and rely on, their own caching implementation. I've evaluated both, and while each has its own pro's and cons, neither of them stand out as superior to the other for my simple needs. Both libraries also seem to be written against their respective interfaces, not their implementations. Reasons why I feel this is an issue is that during the bootstrapping of my application, I have to configure two caching drivers - each with its own syntax. A mismatch is easily created this way, and it feels inefficient to set up two connections to the caching backend because of this. I'm trying to determine what the best way forward is, and would welcome any insights you may be able to offer. What I've thought up so far are four options: Do nothing, accept that two classes offering caching functionality are present. Create a Facade class to stick Zend's interface onto Doctrine's caching implementation. Option 2, the other way around - create a Facade to map Doctrine's interface on a Zend Framework backend. Use multiple-interface-inheritance to create one interface to rule them all, and pray that there aren't any overlaps (ie: if both have a "save" method, they'll need to accept params in the same order due to PHP's lack of proper polymorphism). What option is best, or is there a "None of the above" variant that I'm not aware of?

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• Using C++ but not using the language's specific features, should switch to C?

  - by Petruza

  I'm developing a NES emulator as a hobby, in my free time. I use C++ because is the language I use mostly, know mostly and like mostly. But now that I made some advance into the project I realize I'm not using almost any specific features of C++, and could have done it in plain C and getting the same result. I don't use templates, operator overloading, polymorphism, inheritance. So what would you say? should I stay in C++ or rewrite it in C? I won't do this to gain in performance, it could come as a side effect, but the idea is why should I use C++ if I don't need it? The only features of C++ I'm using is classes to encapsulate data and methods, but that can be done as well with structs and functions, I'm using new and delete, but could as well use malloc and free, and I'm using inheritance just for callbacks, which could be achieved with pointers to functions. Remember, it's a hobby project, I have no deadlines, so the overhead time and work that would require a re-write are not a problem, might be fun as well. So, the question is C or C++?

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• Informing GUI objects about screen size - Designing

  - by Mosquito

  I have a problem with designing classes for my game which I create. In my app, there is: class CGame which contains all the information about game itself, e.g. screen width, screen height, etc. In the main() function I create a pointer to CGame instance. class CGUIObject which includes fields specifying it's position and draw() method, which should know how to draw an object according to screen size. class CGUIManager which is a singleton and it includes a list of CGUIObject's. For each object in a list it just calls draw() method. For clarity's sake, I'll put some simple code: class CGame { int screenWidth; int screenHeight; }; class CGUIObject { CPoint position; void draw(); // this one needs to know what is a screen's width and height }; class CGUIManager // it's a singleton { vector<CGUIObject*> guiObjects; void drawObjects(); }; And the main.cpp: CGame* g; int main() { g = new CGame(); while(1) { CGUIManager::Instance().drawObjects(); } return 0; } Now the problem is, that each CGUIObject needs to know the screen size which is held by CGame, but I find it very dumb to include pointer to CGame instance in every object. Could anyone, please, tell me what would be the best approach to achieve this?

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• Oracle College Rehire Program -China by Camilla!!

  - by Nadiya

  Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 In China,for the R&D campus hire, we launched a Oracle College Hire Program, all the new graduates in R&D team could join it, the purpose is to let them understand Oracle’s culture and value, get them quickly to be familiar and productive on their new work, provide meaningful events and get them engaged.  They’re divided into classes by location, each class would have around 20 people, and each class would have a monitor, who is in charge of the whole class activity, the program has 3 modules, including social activity, Speaker Series and Career Development. The pictures show one class, which is having the social activity session,exciting isnt it?   /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

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• What to do as a new team lead on a project with maintainability problems?

  - by Mr_E

  I have just been put in charge of a code project with maintainability problems. What things can I do to get the project on a stable footing? I find myself in a place where we are working with a very large multi-tiered .NET system that is missing a lot of the important things such as unit tests, IOC, MEF, too many static classes, pure datasets etc. I'm only 24 but I've been here for almost three years (this app has been in development for 5) and mostly due to time constraints we've been just adding in more crap to fit the other crap. After doing a number of projects in my free time I have begun to understand just how important all those concepts are. Also due to employee shifting I find myself to now be the team lead on this project and I really want to come up with some smart ways to improve this app. Ways where the value can be explained to management. I have ideas of what I would like to do but they all seem so overwhelming without much upfront gain. Any stories of how people have or would have dealt with this would be a very interesting read. Thanks.

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• Loading images in XNA 4.0; "Cannot Open File" Problems

  - by user32623

  Okay, I'm writing a game in C#/XNA 4.0 and am utterly stumped at my current juncture: Sprite animation. I understand how it works and have all the code in place, but my ContentLoader won't open my file... Basically, my directory looks like this: //WindowsGame1 - "Game1.cs" - //Classes - "NPC.cs" - Content Reference - //Images - "Monster.png" Inside my NPC class, I have all the essential drawing functions, i.e. LoadContent, Draw, Update. And I can get the game to find the correct file and attempt to open it, but when it tries, it throws an exception and tells me it can't open the file. This is how my code in my NPC class looks: Texture2D NPCImage; Vector2 NPCPosition; Animation NPCAnimation = new Animation(); public void Initialize() { NPCAnimation.Initialize(NPCPosition, new Vector2(4, 4)); } public void LoadContent(ContentManager Content) { NPCImage = Content.Load<Texture2D>("_InsertImageFilePathHere_"); NPCAnimation.AnimationImage = NPCImage; } The rest of the code is irrelevant at this point because I can't even get the image to load. I think it might have to do with a directory problem, but I also know little to nothing about spriting or working with images or animations in my code. Any help is appreciated. Not sure if I provided enough information here, so let me know if more is needed! Also, what would be the correct way to direct that Content.Load to Monster.png given the current directory situation? Right now I just have it using the full path from the C:// drive. Thanks in advance!

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• WINAPI beginner guidance question

  - by gekod

  I'm learning to develop windows applications using WINAPI and plain C. Now I got a bit confused with all those handles and would like to ask if you guys could teach me some good practices to structure and handle controls and windows. Here's where I get confused: Using the IDs declared in the resources for each object, we can get their handles using GetDlgItem(). Now what if we don't know their parent, which is needed by this function. One example: We have the main window created at launch. Then we register two new window classes and create a window for each new class and we create a message function for each too. Now if inside one of the children windows I create a button and inside the other child window I create a text label. Now when we click the button inside of child window A the label in child window B shall be modified to whatever. The WM_COMMAND for the button is interpreted inside the message loop for child window A. Now what would be the best and more elegant way to access the text label inside the child window B? I am in the process of learning the WINAPI and just want to learn it right from the start instead of producing Hacked code that someday becomes unreadable and to later have to adapt to a new way of programing.

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• Use decorator and factory together to extend objects?

  - by TheClue

  I'm new to OOP and design pattern. I've a simple app that handles the generation of Tables, Columns (that belong to Table), Rows (that belong to Column) and Values (that belong to Rows). Each of these object can have a collection of Property, which is in turn defined as an enum. They are all interfaces: I used factories to get concrete instances of these products, depending on circumnstances. Now I'm facing the problem of extending these classes. Let's say I need another product called "SpecialTable" which in turn has some special properties or new methods like 'getSomethingSpecial' or an extended set of Property. The only way is to extend/specialize all my elements (ie. build a SpecialTableFactory, a SpecialTable interface and a SpecialTableImpl concrete)? What to do if, let's say, I plan to use standard methods like addRow(Column column, String name) that doesn't need to be specialized? I don't like the idea to inherit factories and interfaces, but since SpecialTable has more methods than Table i guess it cannot share the same factory. Am I wrong? Another question: if I need to define product properties at run time (a Table that is upgraded to SpecialTable at runtime), i guess i should use a decorator. Is it possible (and how) to combine both factory and decorator design? Is it better to use a State or Strategy pattern, instead?

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• How to start Sharepoint Development - Resources wanted [closed]

  - by user1249641

  I'm a apprentice for software development here in good ol' Germany and I've been doing fairly well with c#, asp.net mvc, entity framework and LINQ so far. My superiors want me to focus solely on our intranet development and Sharepoint development. They don't provide me with any resources to start. No books, no co-workers with actual webpart-dev-experience, seminars and the likes. There for it's do it on your own or die. I bought a book and started working through it on my virtual machine messing with the infrastructure and everything i can get a grip on. My main problem however stays the actual development. I have managed to write 2 webparts which can be used as a rudimentary ticket system(using WSP Builder and SP2007). But there it stops. Are there any comprehensive step by step tutorials or blogs out there, like the asp.net tutorials on www.asp.net which take you by the hand go over each step with you? Starting with the basic classes, going over custom css implementation, Jquery/Javascript ajax and async calls? No matter how trivial, I appreciate every help and hint you can give.

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• Interfaces on an abstract class

  - by insta

  My coworker and I have different opinions on the relationship between base classes and interfaces. I'm of the belief that a class should not implement an interface unless that class can be used when an implementation of the interface is required. In other words, I like to see code like this: interface IFooWorker { void Work(); } abstract class BaseWorker { ... base class behaviors ... public abstract void Work() { } protected string CleanData(string data) { ... } } class DbWorker : BaseWorker, IFooWorker { public void Work() { Repository.AddCleanData(base.CleanData(UI.GetDirtyData())); } } The DbWorker is what gets the IFooWorker interface, because it is an instantiatable implementation of the interface. It completely fulfills the contract. My coworker prefers the nearly identical: interface IFooWorker { void Work(); } abstract class BaseWorker : IFooWorker { ... base class behaviors ... public abstract void Work() { } protected string CleanData(string data) { ... } } class DbWorker : BaseWorker { public void Work() { Repository.AddCleanData(base.CleanData(UI.GetDirtyData())); } } Where the base class gets the interface, and by virtue of this all inheritors of the base class are of that interface as well. This bugs me but I can't come up with concrete reasons why, outside of "the base class cannot stand on its own as an implementation of the interface". What are the pros & cons of his method vs. mine, and why should one be used over another?

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• Interface (contract), Generics (universality), and extension methods (ease of use). Is it a right design?

  - by Saeed Neamati

  I'm trying to design a simple conversion framework based on these requirements: All developers should follow a predefined set of rules to convert from the source entity to the target entity Some overall policies should be able to be applied in a central place, without interference with developers' code Both the creation of converters and usage of converter classes should be easy To solve these problems in C# language, A thought came to my mind. I'm writing it here, though it doesn't compile at all. But let's assume that C# compiles this code: I'll create a generic interface called IConverter public interface IConverter<TSource, TTarget> where TSource : class, new() where TTarget : class, new() { TTarget Convert(TSource source); List<TTarget> Convert(List<TSource> sourceItems); } Developers would implement this interface to create converters. For example: public class PhoneToCommunicationChannelConverter : IConverter<Phone, CommunicationChannle> { public CommunicationChannel Convert(Phone phone) { // conversion logic } public List<CommunicationChannel> Convert(List<Phone> phones) { // conversion logic } } And to make the usage of this conversion class easier, imagine that we add static and this keywords to methods to turn them into Extension Methods, and use them this way: List<Phone> phones = GetPhones(); List<CommunicationChannel> channels = phones.Convert(); However, this doesn't even compile. With those requirements, I can think of some other designs, but they each lack an aspect. Either the implementation would become more difficult or chaotic and out of control, or the usage would become truly hard. Is this design right at all? What alternatives I might have to achieve those requirements?

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• 25 years old and considering a career change...possible? practical?

  - by mq330

  Hi all, I'm new to this site and new to programming as well. I've spent some time going through an intro cs book that uses python as the language of choice. I find the exercises interesting and engaging and I generally have had a favorable experience programming so far. I've gone through some of the basics with python like writing simple programs, basics of GUIs, manipulating strings, lists, defining functions, etc. And I've always loved technology. Although I've never done any real hardcore programming yet, I was inclined to building websites from a very young age but I never really developed my skills. Now, the thing is I'm 25, I have my bacholors in environmental studies and two masters degrees in urban planning and landscape architecture respectively. I know, it would be quite a departure to pursue a career in programming at this point. Currently, I'm working as a geographic information systems intern. I've taken some GIS classes and have a lot of experience with making maps, doing spatial analysis etc. So what I'm thinking is maybe I can learn some solid programming skills and apply these skills in the field of GIS. From what I've seen, .net languages are the norm in this arena. Could you perhaps provide some guidance to me in terms of what languages I should focus on or courses I should take at this point? What about for building web mapping applications? Also, I was thinking about getting a certificate in programming from a university extension program. Do you think it would be worth it? And furthermore, do you think potential employers would be interested in hiring someone like me (once I get a couple of languages down pretty well) as an intern or in an entry level position? I'll be living in the bay area so I feel that there should be decent opportunities even though I don't have a b.s. in cs.

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• Client-server application design issue

  - by user2547823

  I have a collection of clients on server's side. And there are some objects that need to work with that collection - adding and removing clients, sending message to them, updating connection settings and so on. They should perform these actions simultaneously, so mutex or another synchronization primitive is required. I want to share one instance of collection between these objects, but all of them require access to private fields of collection. I hope that code sample makes it more clear[C++]: class Collection { std::vector< Client* > clients; Mutex mLock; ... } class ClientNotifier { void sendMessage() { mLock.lock(); // loop over clients and send message to each of them } } class ConnectionSettingsUpdater { void changeSettings( const std::string& name ) { mLock.lock(); // if client with this name is inside collection, change its settings } } As you can see, all these classes require direct access to Collection's private fields. Can you give me an advice about how to implement such behaviour correctly, i.e. keeping Collection's interface simple without it knowing about its users?

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