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• Blog Buzz - Devoxx 2011

  - by Janice J. Heiss

  Some day I will make it to Devoxx – for now, I’m content to vicariously follow the blogs of attendees and pick up on what’s happening.  I’ve been doing more blog "fishing," looking for the best commentary on 2011 Devoxx. There’s plenty of food for thought – and the ideas are not half-baked.The bloggers are out in full, offering useful summaries and commentary on Devoxx goings-on.Constantin Partac, a Java developer and a member of Transylvania JUG, a community from Cluj-Napoca/Romania, offers an excellent summary of the Devoxx keynotes. Here’s a sample:“Oracle Opening Keynote and JDK 7, 8, and 9 Presentation•    Oracle is committed to Java and wants to provide support for it on any device.•    JSE 7 for Mac will be released next week.•    Oracle would like Java developers to be involved in JCP, to adopt a JSR and to attend local JUG meetings.•    JEE 7 will be released next year.•    JEE 7 is focused on cloud integration, some of the features are already implemented in glassfish 4 development branch.•    JSE 8 will be release in summer of 2013 due to “enterprise community request” as they can not keep the pace with an 18    month release cycle.•    The main features included in JSE8 are lambda support, project Jigsaw, new Date/Time API, project Coin++ and adding   support for sensors. JSE 9 probably will focus on some of these features:1.    self tuning JVM2.    improved native language integration3.    processing enhancement for big data4.    reification (adding runtime class type info for generic types)5.    unification of primitive and corresponding object classes6.    meta-object protocol in order to use type and methods define in other JVM languages7.    multi-tenancy8.    JVM resource management” Thanks Constantin! Ivan St. Ivanov, of SAP Labs Bulgaria, also commented on the keynotes with a different focus.  He summarizes Henrik Stahl’s look ahead to Java SE 8 and JavaFX 3.0; Cameron Purdy on Java EE and the cloud; celebrated Java Champion Josh Bloch on what’s good and bad about Java; Mark Reinhold’s quick look ahead to Java SE 9; and Brian Goetz on lambdas and default methods in Java SE 8. Here’s St. Ivanov’s account of Josh Bloch’s comments on the pluses of Java:“He started with the virtues of the platform. To name a few:    Tightly specified language primitives and evaluation order – int is always 32 bits and operations are executed always from left  to right, without compilers messing around    Dynamic linking – when you change a class, you need to recompile and rebuild just the jar that has it and not the whole application    Syntax  similarity with C/C++ – most existing developers at that time felt like at home    Object orientations – it was cool at that time as well as functional programming is today    It was statically typed language – helps in faster runtime, better IDE support, etc.    No operator overloading – well, I’m not sure why it is good. Scala has it for example and that’s why it is far better for defining DSLs. But I will not argue with Josh.”It’s worth checking out St. Ivanov’s summary of Bloch’s views on what’s not so great about Java as well. What's Coming in JAX-RS 2.0Marek Potociar, Principal Software Engineer at Oracle and currently specification lead of Java EE RESTful web services API (JAX-RS), blogged on his talk about what's coming in JAX-RS 2.0, scheduled for final release in mid-2012.  Here’s a taste:“Perhaps the most wanted addition to the JAX-RS is the Client API, that would complete the JAX-RS story, that is currently server-side only. In JAX-RS 2.0 we are adding a completely interface-based and fluent client API that blends nicely in with the existing fluent response builder pattern on the server-side. When we started with the client API, the first proposal contained around 30 classes. Thanks to the feedback from our Expert Group we managed to reduce the number of API classes to 14 (2 of them being exceptions)! The resulting is compact while at the same time we still managed to create an API that reflects the method invocation context flow (e.g. once you decide on the target URI and start setting headers on the request, your IDE will not try to offer you a URI setter in the code completion). This is a subtle but very important usability aspect of an API…” Obviously, Devoxx is a great Java conference, one that is hitting this year at a time when much is brewing in the platform and beginning to be anticipated.

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• JQuery Mobile: Fire Mobileinit Event

  - by Yousef_Jadallah

   Many people asked that the Mobileinit event didn't work. Simplicity just you need to follow this sequence: <link rel="stylesheet" href="http://code.jquery.com/mobile/1.0b1/jquery.mobile-1.0b1.min.css" />     <script src="http://code.jquery.com/jquery-1.6.1.min.js"></script>     <script>         $(document).bind("mobileinit", function () {             alert('mobileinit is fired');         });     </script>     <script src="http://code.jquery.com/mobile/1.0b1/jquery.mobile-1.0b1.min.js"></script> Hope that helps.  

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• Which programming language should I learn? [on hold]

  - by Ashkan

  I'm Ashkan and I'm from Iran, I started programming when I was 13 and I learned a lot of stuff since then, But now I'm totally lost. Since I live in Iran there are no counselor or any professionals out there to help me, so I decided to ask here. I started with Visual Basic and after 1 year I started to learn HTML , CSS , Javascript and JQuery. And for the past 6 months I've been learning PHP,and I have a basic understanding of OOP. I want to move to America to continue my studies and I was wondering which programming language helps me the most to get there? Should I learn C++ or JAVA or should I study Computer Science and Math? also since We are not in a good place financially, I want a programming language that helps me in college and lets me make some money? Thanks in advance and sorry for my poor English skills.

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• Do I need a degree in Computer Science to get a junior Programming job?

  - by t84

  Do I need to go to Uni to get a job as a Junior C# coder? I'm 26 and have been working in Games (Production) for 6 years and I am thinking of a change, I've had exposure to VB6, VBA, HTML, CSS, PHP, JavaScript over the past few years and did a web design NCFE at College, but other than that, nothing else! I'm teaching myself C# at the moment with books and I was wondering 'how much' I need to learn and also how I can improve my chances of getting a programming job! Am I a late started to learn coding? (I know many people who started at a very young age!) Thanks for the help :)

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• Is it legal and ethical to reverse engineer software to port it to another system?

  - by Igor Zinov'yev

  I love gaming, I love games that allow modding and I love linux. But the fact that most games right now are targeted for windows (consoles aside), most mods and modding tools are also targeted for windows. There is a certain modder called Boris Vorontsov that makes a famous visual overhaul mod series called ENB. What he does (or I think he does) is he enhances or changes the behavior of classes defined in the d3d9.dll library. Needless to say it almost never works under wine. Recently I have asked him if he would ever release his version of the library under some open license, and he said "no". Now that I think of it, even if he did release his code, he would have surely faced some legal problems. Now there is my question. Is it legal and ethical to reverse engineer his version of the library to adapt the wine's open source version of d3d9.dll to be able to run his mods?

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• C++ - Constructor or Initialize Method to Startup

  - by Bob Fincheimer

  I want to determine when to do non-trivial initialization of a class. I see two times to do initialization: constructor and other method. I want to figure out when to use each. Choice 1: Constructor does initialization MyClass::MyClass(Data const& data) : m_data() { // does non-trivial initialization here } MyClass::~MyClass() { // cleans up here } Choice 2: Defer initialization to an initialize method MyClass::MyClass() : m_data() {} MyClass::Initialize(Data const& data) { // does non-trivial initialization here } MyClass::~MyClass() { // cleans up here } So to try and remove any subjectivity I want to figure out which is better in a couple of situations: Class that encapsulates a resource (window/font/some sort of handle) Class that composites resources to do something (a control/domain object) Data structure classes (tree/list/etc.) [Anything else you can think of] Things to analyze: Performance Ease of use by other developers How error-prone/opportunities for bugs [Anything else you can think of]

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• How do I overcome paralysis by analysis when coding?

  - by LuxuryMode

  When I start a new project, I often times immediately start thinking about the details of implementation. "Where am I gonna put the DataBaseHandler? How should I use it? Should classes that want to use it extend from some Abstract superclass..? Should I an interface? What level of abstraction am I going to use in my class that contains methods for sending requests and parsing data?" I end up stalling for a long time because I want to code for extensibility and reusability. But I feel it almost impossible to get past thinking about how to implement perfectly. And then, if I try to just say "screw it, just get it done!", I hit a brick wall pretty quickly because my code isn't organized, I mixed levels of abstractions, etc. What are some techniques/methods you have for launching into a new project while also setting up a logical/modular structure that will scale well?

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• C++ Library API Design

  - by johannes

  I'm looking for a good resource for learning about good API design for C++ libraries, looking at shared objects/dlls etc. There are many resources on writing nice APIs, nice classes, templates and so on at source level, but barely anything about putting things together in shared libs and executables. Books like Large-Scale C++ Software Design by John Lakos are interesting but massively outdated. What I'm looking for is advice i.e. on handling templates. With templates in my API I often end up with library code in my executable (or other library) so if I fix a bug in there I can't simply roll out the new library but have to recompile and redistribute all clients of that code. (and yes, I know some solutions like trying to instantiate at least the most common versions inside the library etc.) I'm also looking for other caveats and things to mind for keeping binary compatibility while working on C++ libraries. Is there a good website or book on such things?

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• How can I break out of ssh when it locks?

  - by Wayne Werner

  Hi, I frequently ssh into my box at home from school, but usually when I change classes and my computer suspends, the pipe will be broken. However, ssh simply locks up - ^c, ^z and ^d have no effect. It's annoying to have to restart my terminal, and even more annoying to have to close and re-create a new screen window. So my question, is there an easy way to make ssh die properly (i.e. when the pipe fails "normally" it will exit with a message about a broken pipe)? Or do I have to figure out what the PID is and manually kill it? Thanks!

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• Prewritten App for Used Car Dealer?

  - by Shawn Eary

  Is there somewhere I can find a prewritten WebApp (with database) for a used car dealer? The application would need to support the following: Easy setup in a low cost Shared or Cloud Host Give potential customers easy way to browse current inventory (cars on lot) with suggested prices Give dealership easy way to login and update inventory (cars on lot) and suggested prices Give potential customers easy way to send the dealership an inquiry about a specific vehicle on the lot with CAPTCHA style SPAM protection I prefer ASP.NET MVC and Microsoft SQL Server, but I might consider other technologies such as WebForms and LightSwitch (HTML5). I am reasonably comfortable with MVC and WebForms, but I really don't want to waste a bunch of time writing an application that might already exist. I did find a few interesting templates via Bing that seem to control CSS and Layout, but I'm not sure if they contain any business logic or if they would integrate well into an MVC App.

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• 1st Issue of GIMP Magazine now Available [Free Download]

  - by Asian Angel

  Are you ready for an awesome (and free) magazine that is all about GIMP? Then GIMP Magazine is the publication that you have been looking for! This free quarterly magazine focuses on photography, digital arts, tips and tricks, step by step tutorials, master classes, help desk questions, and so much more. You can access the 1st issue in three ways: As a direct PDF download As a Bit-Torrent download View it online at Issuu Choose the option that works best for you! Note: The PDF file is 47.1 MB in size. A sample page from the magazine for your viewing pleasure… HTG Explains: Is ReadyBoost Worth Using? HTG Explains: What The Windows Event Viewer Is and How You Can Use It HTG Explains: How Windows Uses The Task Scheduler for System Tasks

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• Is there a language between C and C++?

  - by Robert Martin

  I really like the simple and transparent nature of C: when I write C code I feel unencumbered by "leaky abstractions" and can almost always make a shrewd guess as to the assembly I'm producing. I also like the simple, familiar syntax for C. However, C doesn't have these simple, helpful doodads that C++ offers like classes, simplified non-cstring handling, etc. I know that it's all possible to implement in C using jump tables and the like, but that's a bit wordy at times, and not very type-safe for various reasons. I'm not a fan of the over-emphasis on objects in C++, though, and I'm gun shy of the 'new' operator and the like. C++ seems to have just a few too many hiccups to, for instance, be used as a system programming language. Does there exist a language that sits between C and C++ on the scale of widgets and doodads? Disclaimer: I mean this as purely a factual question. I do not intend to anger you because I don't share your view that C{,++} is good enough to do whatever I'm planning.

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• Using WebStorm for Razor Syntax MVC

  - by Jay Stevens

  I am building a lot of client-side heavy SPA-like apps with VS2010 and MVC3/4. VS2010 Javascript/HTML/CSS editing (mostly javascript) is interminably slow and sluggish. I'd love to use something like JetBrains' WebStorm to edit my .CSHTML files (with embedded javascript, etc. because I am using RAzor to pop in URL names, etc.) WebStorm seems to have all of the things I want.. better language recognition ("intellisense") and the ability to integrate additional outside libraries into this (I'm using Kendo), etc. Is this possible? How do you get WebStorm to recognize the @"" invoked Razor language inserts? Any help or suggestions would be appreciated.

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• What programming languages should every computer science student be taught?

  - by Anto

  What languages (or classes (as in paradigms) of programming languages, plus a recommended language of that class) should every computer science student be taught in college according to you? Motivate your answers; why that language? What use will one have from it? What concepts does it teach (better than language X does)? Note/clarification: This question is about computer science with heavy focus on software engineering, not pure computer science. It is still computer science education and not software engineering education which is the focus.

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• data maintenance/migrations in image based sytems

  - by User

  Web applications usually have a database. The code and the database work hand in hand together. Therefore Frameworks like Ruby on Rails and Django create migration files Sure there are also servers written in Self or Smalltalk or other image-based systems that face the same problem: Code is not written on the server but in a separate image of the programmer. How do these systems deal with a changing schema, changing classes/prototypes. Which way do the migrations go? Example: What is the process of a new attribute going from programmer's idea to the server code and all objects? I found the Gemstone/S manual chapter 8 but it does not really talk about the process of shipping code to the server.

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• How do I learn Python from zero to web development? [closed]

  - by Terence Ponce

  I am looking into learning Python for web development. Assuming I already have some basic web development experience with Java (JSP/Servlets), I'm already familiar with web design (HTML, CSS, JS), basic programming concepts and that I am completely new to Python, how do I go about learning Python in a structured manner that will eventually lead me to web development with Python and Django? I'm not in a hurry to make web applications in Python so I really want to learn it thoroughly so as not to leave any gaps in my knowledge of the technologies involving web development in Python. Are there any books, resource or techniques to help me in my endeavor? In what order should I do/read them? UPDATE: When I say learning in a structured manner, I mean starting out from the basics then learning the advanced stuff without leaving some of the important details/features that Python has to offer. I want to know how to apply the things that I already know in programming to Python.

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• LSP vs OCP / Liskov Substitution VS Open Close

  - by Kolyunya

  I am trying to understand the SOLID principles of OOP and I've come to the conclusion that LSP and OCP have some similarities (if not to say more). the open/closed principle states "software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification". LSP in simple words states that any instance of Foo can be replaced with any instance of Bar which is derived from Foo and the program will work the same very way. I'm not a pro OOP programmer, but it seems to me that LSP is only possible if Bar, derived from Foo does not change anything in it but only extends it. That means that in particular program LSP is true only when OCP is true and OCP is true only if LSP is true. That means that they are equal. Correct me if I'm wrong. I really want to understand these ideas. Great thanks for an answer.

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• Test case as a function or test case as a class

  - by GodMan

  I am having a design problem in test automation:- Requirements - Need to test different servers (using unix console and not GUI) through automation framework. Tests which I'm going to run - Unit, System, Integration Question: While designing a test case, I am thinking that a Test Case should be a part of a test suite (test suite is a class), just as we have in Python's pyunit framework. But, should we keep test cases as functions for a scalable automation framework or should be keep test cases as separate classes(each having their own setup, run and teardown methods) ? From automation perspective, Is the idea of having a test case as a class more scalable, maintainable or as a function?

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• Web and Flex developer career question [closed]

  - by abhilashm86

  Possible Duplicate: should i concentrate on logical and puzzles part in programming, i want to be a web (flex)developer? I'm a computer science student and have been learning Flex and Actionscript 3.0 for 4 months. I know it's easy to program in MXML, and Actionscript 3.0 is pretty easy with bunch of classes, but when I try to code in C++ or C, I struggle, I feel I'm being inefficient and it scares me. Since I'm a student, I've no experience in developing algorithms and tough program solving? I'd like to be a web developer. Does a web developer need strong fundamentals when it comes to things such as complex algorithms and high end coding?

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• Real-world SignalR example, ditching ghetto long polling

  - by Jeff

  One of the highlights of BUILD last week was the announcement that SignalR, a framework for real-time client to server (or cloud, if you will) communication, would be a real supported thing now with the weight of Microsoft behind it. Love the open source flava! If you aren’t familiar with SignalR, watch this BUILD session with PM Damian Edwards and dev David Fowler. Go ahead, I’ll wait. You’ll be in a happy place within the first ten minutes. If you skip to the end, you’ll see that they plan to ship this as a real first version by the end of the year. Insert slow clap here. Writing a few lines of code to move around a box from one browser to the next is a way cool demo, but how about something real-world? When learning new things, I find it difficult to be abstract, and I like real stuff. So I thought about what was in my tool box and the decided to port my crappy long-polling “there are new posts” feature of POP Forums to use SignalR. A few versions back, I added a feature where a button would light up while you were pecking out a reply if someone else made a post in the interim. It kind of saves you from that awkward moment where someone else posts some snark before you. While I was proud of the feature, I hated the implementation. When you clicked the reply button, it started polling an MVC URL asking if the last post you had matched the last one the server, and it did it every second and a half until you either replied or the server told you there was a new post, at which point it would display that button. The code was not glam: // in the reply setup PopForums.replyInterval = setInterval("PopForums.pollForNewPosts(" + topicID + ")", 1500); // called from the reply setup and the handler that fetches more posts PopForums.pollForNewPosts = function (topicID) { $.ajax({ url: PopForums.areaPath + "/Forum/IsLastPostInTopic/" + topicID, type: "GET", dataType: "text", data: "lastPostID=" + PopForums.currentTopicState.lastVisiblePost, success: function (result) { var lastPostLoaded = result.toLowerCase() == "true"; if (lastPostLoaded) { $("#MorePostsBeforeReplyButton").css("visibility", "hidden"); } else { $("#MorePostsBeforeReplyButton").css("visibility", "visible"); clearInterval(PopForums.replyInterval); } }, error: function () { } }); }; What’s going on here is the creation of an interval timer to keep calling the server and bugging it about new posts, and setting the visibility of a button appropriately. It looks like this if you’re monitoring requests in FireBug: Gross. The SignalR approach was to call a message broker when a reply was made, and have that broker call back to the listening clients, via a SingalR hub, to let them know about the new post. It seemed weird at first, but the server-side hub’s only method is to add the caller to a group, so new post notifications only go to callers viewing the topic where a new post was made. Beyond that, it’s important to remember that the hub is also the means to calling methods at the client end. Starting at the server side, here’s the hub: using Microsoft.AspNet.SignalR.Hubs; namespace PopForums.Messaging { public class Topics : Hub { public void ListenTo(int topicID) { Groups.Add(Context.ConnectionId, topicID.ToString()); } } } Have I mentioned how awesomely not complicated this is? The hub acts as the channel between the server and the client, and you’ll see how JavaScript calls the above method in a moment. Next, the broker class and its associated interface: using Microsoft.AspNet.SignalR; using Topic = PopForums.Models.Topic; namespace PopForums.Messaging { public interface IBroker { void NotifyNewPosts(Topic topic, int lasPostID); } public class Broker : IBroker { public void NotifyNewPosts(Topic topic, int lasPostID) { var context = GlobalHost.ConnectionManager.GetHubContext<Topics>(); context.Clients.Group(topic.TopicID.ToString()).notifyNewPosts(lasPostID); } } } The NotifyNewPosts method uses the static GlobalHost.ConnectionManager.GetHubContext<Topics>() method to get a reference to the hub, and then makes a call to clients in the group matched by the topic ID. It’s calling the notifyNewPosts method on the client. The TopicService class, which handles the reply data from the MVC controller, has an instance of the broker new’d up by dependency injection, so it took literally one line of code in the reply action method to get things moving. _broker.NotifyNewPosts(topic, post.PostID); The JavaScript side of things wasn’t much harder. When you click the reply button (or quote button), the reply window opens up and fires up a connection to the hub: var hub = $.connection.topics; hub.client.notifyNewPosts = function (lastPostID) { PopForums.setReplyMorePosts(lastPostID); }; $.connection.hub.start().done(function () { hub.server.listenTo(topicID); }); The important part to look at here is the creation of the notifyNewPosts function. That’s the method that is called from the server in the Broker class above. Conversely, once the connection is done, the script calls the listenTo method on the server, letting it know that this particular connection is listening for new posts on this specific topic ID. This whole experiment enables a lot of ideas that would make the forum more Facebook-like, letting you know when stuff is going on around you.

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• Significance and role of Node.js in Web development

  - by Pankaj Upadhyay

  I have read that Node.js is a server-side javascript enviroment. This has put few thought and tinkers in my mind. Can we develop a complete data-drivent web application utilizing just JavaScript (along with node.js), HTML5 and CSS? Do we still need to use some server-side scripting language (e.g. C#, PHP)? In case we still need to use other scripting languages, what is node.js worth for, or useful? NOTE: Pardon with my knowledge about node.js.

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• SEO optimisation problems after Google Panda [on hold]

  - by Daniel West

  I am currently trying to improve a website's SEO after it took quite a hit from the Google Panda upgrades. What are the main things I need to look at improving when trying to improve its ranking in Google? I have already made sure that the pages validate to W3C Standards, minimized css and js and done the obvious meta tags and header optimization but this hasn't made any difference yet. It could possibly be a content issue as the pages currently read much like a brochure and there were some pages with just a video and no text content on them which is also an issue. I've added a rel="nofollow" attribute to the links to these pages although i'm told this doesn't really work anymore. If anyone has any ideas let me know. Cheers!

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• Using DLLEXPORT to export DLL function With Class to C#

  - by SICGames2013

  In my previous revision game engine I deported major functions for the game editor for C#. Now, I'm beginning to revise the game engine with a static library. There's a already dynamic library created in C++ to use DLLEXPORT for C#. Just now I want to test out the newer functions and created a DLL file from C++. Because the DLL contains classes I was wondering how would I be able to use DLL Export. Would I do this: [DLLEXPORT("GameEngine.dll", EntryPoint="SomeClass", Conventional=_stdcall)] static extern void functionFromClass(); I have a feeling it's probably DLLImport and not DLLExport. I was wondering how would I go about this? Another way I was thinking was because I already have the DLL in C++ prepared already to go the C# Class Library. I could just keep the new engine as a lib, and link the lib with the old DLL C++ file. Wouldn't the EntryPoint be able to point to the class the function is in?

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• Organizing code for iOS app development

  - by KronoS

  I've been developing an app for the iOS platform, and as I've been going along, I've noticed that I've done a terrible job of keeping my files (.h, .m, .mm) organized. Is there any industry standards or best practices when it comes to organizing files for an iOS project? My files include custom classes (beside the view controllers), customized View Controllers, third-party content, code that works only on iOS 5.0+ and code that works on previous versions. What I'm looking for is a solution to keep things organized in a manner that others (or myself in years to come) can look at this and understand the basic structure of the application and not get lost in the multiple files found therein.

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• Clean way to use mutable implementation of Immutable interfaces for encapsulation

  - by dsollen

  My code is working on some compost relationship which creates a tree structure, class A has many children of type B, which has many children of type C etc. The lowest level class, call it bar, also points to a connected bar class. This effectively makes nearly every object in my domain inter-connected. Immutable objects would be problematic due to the expense of rebuilding almost all of my domain to make a single change to one class. I chose to go with an interface approach. Every object has an Immutable interface which only publishes the getter methods. I have controller objects which constructs the domain objects and thus has reference to the full objects, thus capable of calling the setter methods; but only ever publishes the immutable interface. Any change requested will go through the controller. So something like this: public interface ImmutableFoo{ public Bar getBar(); public Location getLocation(); } public class Foo implements ImmutableFoo{ private Bar bar; private Location location; @Override public Bar getBar(){ return Bar; } public void setBar(Bar bar){ this.bar=bar; } @Override public Location getLocation(){ return Location; } } public class Controller{ Private Map<Location, Foo> fooMap; public ImmutableFoo addBar(Bar bar){ Foo foo=fooMap.get(bar.getLocation()); if(foo!=null) foo.addBar(bar); return foo; } } I felt the basic approach seems sensible, however, when I speak to others they always seem to have trouble envisioning what I'm describing, which leaves me concerned that I may have a larger design issue then I'm aware of. Is it problematic to have domain objects so tightly coupled, or to use the quasi-mutable approach to modifying them? Assuming that the design approach itself isn't inherently flawed the particular discussion which left me wondering about my approach had to do with the presence of business logic in the domain objects. Currently I have my setter methods in the mutable objects do error checking and all other logic required to verify and make a change to the object. It was suggested that this should be pulled out into a service class, which applies all the business logic, to simplify my domain objects. I understand the advantage in mocking/testing and general separation of logic into two classes. However, with a service method/object It seems I loose some of the advantage of polymorphism, I can't override a base class to add in new error checking or business logic. It seems, if my polymorphic classes were complicated enough, I would end up with a service method that has to check a dozen flags to decide what error checking and business logic applies. So, for example, if I wanted to have a childFoo which also had a size field which should be compared to bar before adding par my current approach would look something like this. public class Foo implements ImmutableFoo{ public void addBar(Bar bar){ if(!getLocation().equals(bar.getLocation()) throw new LocationException(); this.bar=bar; } } public interface ImmutableChildFoo extends ImmutableFoo{ public int getSize(); } public ChildFoo extends Foo implements ImmutableChildFoo{ private int size; @Override public int getSize(){ return size; } @Override public void addBar(Bar bar){ if(getSize()<bar.getSize()){ throw new LocationException(); super.addBar(bar); } My colleague was suggesting instead having a service object that looks something like this (over simplified, the 'service' object would likely be more complex). public interface ImmutableFoo{ ///original interface, presumably used in other methods public Location getLocation(); public boolean isChildFoo(); } public interface ImmutableSizedFoo implements ImmutableFoo{ public int getSize(); } public class Foo implements ImmutableSizedFoo{ public Bar bar; @Override public void addBar(Bar bar){ this.bar=bar; } @Override public int getSize(){ //default size if no size is known return 0; } @Override public boolean isChildFoo return false; } } public ChildFoo extends Foo{ private int size; @Override public int getSize(){ return size; } @Override public boolean isChildFoo(); return true; } } public class Controller{ Private Map<Location, Foo> fooMap; public ImmutableSizedFoo addBar(Bar bar){ Foo foo=fooMap.get(bar.getLocation()); service.addBarToFoo(foo, bar); returned foo; } public class Service{ public static void addBarToFoo(Foo foo, Bar bar){ if(foo==null) return; if(!foo.getLocation().equals(bar.getLocation())) throw new LocationException(); if(foo.isChildFoo() && foo.getSize()<bar.getSize()) throw new LocationException(); foo.setBar(bar); } } } Is the recommended approach of using services and inversion of control inherently superior, or superior in certain cases, to overriding methods directly? If so is there a good way to go with the service approach while not loosing the power of polymorphism to override some of the behavior?

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