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• Is C++ (one of) the best language to learn at first

  - by AlexV

  C++ is one of the most used programming language in the world since like 25+ years. My first job as programmer was in C++ and I coded in C++ everyday for nearly 4 years. Now I do mostly PHP, but I will forever cherish this C++ background. C++ has helped me understand many "under the hood" features/behaviors/restrictions of many other (and different) programming languages like PHP and Delphi. I'm a full time programmer for 6+ years now and since I have a quite varied programming background I often get questions by "newbies" as where to start to become a "good" programmer. I think C++ is one of the best language to start with because it gives you a real usefull experience that will last and will teach you how things work under the hood. It's not the easier one to learn for a newbie, but in my opinion it's one that will reward in the long term. I would like to know your opinion on this matter to add to my arguments when I guide "newbies". After this introduction, here's my question : Is C++ (one of) the best language to learn at first for you. Since it's subjective, I've marked this question as community wiki. EDIT: This question is not about why Java (or C# or any other language) is better than C++ to start with, it's about what's make C++ a good choice or not a good choice to learn as one of your firsts languages. For example, for me C++ made me understand how the memory works. Now today in many languages everything is managed by the garbadge collector and some people don't even know that. I'm glad I know how it works underneath and I think it can help you to write better code.

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• Right Language for the Job

  - by Manoj

  Using the right language for the job is the key - this is the comment I read in SO and I also belive thats the right thing to do. Because of this we ended up using different languages for different parts of the project - like perl, VBA(Excel Macros), C# etc. We have three to four languages currently in use inside the project. Using the right language for the job has made it immensly more easy to do automate a job, but of late people are complaining that any new person who has to take over the project will have to learn so many different languages to get started. Also it is difficult to find such kind of person. Please note that this is a one to two person working on the project maximum at a given point of time. I would like to know if the method we are following is right or should we converge to single language and try to use it across all the job even though another language might be better suited for it. Your experenece related to this would also help. Languages used and their purpose: Perl - Processing large text file(log files) C# with Silverlight for web based reporting. LabVIEW for automation Excel macros for processing data in excel sheets, generating graphs and exporting to powerpoint.

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• Build system for multi-language project

  - by Epcylon

  I am getting ready to embark on a project mainly for experimenting with languages, but also with a hint of usefulness. It will consist of a server-application, written in Erlang, and client-libraries in a number of languages. Initially I will want to write clients in Java, Ruby and Python. The actual protocol for communication will be Thrift. I'm looking for a build system that will allow me to build the server and all the client libraries in one go, running unit-tests in each language, then packaging up a releasable artifact of some sort in whatever way is the "standard" for each language. That means a Jar for Java, a RubyGem and a distribute/setuptools tarball for Python. Erlang probably has something too, but I'm not yet familiar with that. It should also be able to run the Thrift compiler to generate the various Thrift-stubs in each language. On the pad at the start is Maven. I'm fairly certain Maven can do all I need, but I fear it's too Java-centric, and leaves me with a ton of work for every new language I need to add.

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• Effectively implementing a game view using java

  - by kdavis8

  I am writing a 2d game in java. The game mechanics are similar to the Pokémon game boy advance series e.g. fire red, ruby, diamond and so on. I need a way to draw a huge map maybe 5000 by 5000 pixels and then load individual in game sprites to across the entirety of the map, like rendering a scene. Game sprites would be things like terrain objects, trees, rocks, bushes, also houses, castles, NPC's and so on. But i also need to implement some kind of camera view class that focuses on the player. the camera view class needs to follow the characters movements throughout the game map but it also needs to clip the rest of the map away from the user's field of view, so that the user can only see the arbitrary proximity adjacent to the player's sprite. The proximity's range could be something like 500 pixels in every direction around the player’s sprite. On top of this, i need to implement an independent resolution for the game world so that the game view will be uniform on all screen sizes and screen resolutions. I know that this does sound like a handful and may fall under the category of multiple questions, but the questions are all related and any advice would be very much appreciated. I don’t need a full source code listing but maybe some pointers to effective java API classes that could make doing what i need to do a lot simpler. Also any algorithmic/ design advice would greatly benefit me as well. example of what i am trying to do in source code form below package myPackage; /** * The Purpose of GameView is to: Render a scene using Scene class, Create a * clipping pane using CameraView class, and finally instantiate a coordinate * grid using Path class. * * Once all of these things have been done, GameView class should then be * instantiated and used jointly with its helper classes. CameraView should be * used as the main drawing image. CameraView is the the window to the game * world.Scene passes data constantly to CameraView so that the entire map flows * smoothly. Path uses the x and y coordinates from camera view to construct * cells for path finding algorithms. */ public class GameView { // Scene is a helper class to game view. it renders the entire map to memory // for the camera view. Scene scene; // Camera View is a helper class to game view. It clips the Scene into a // small image that follows the players coordinates. CameraView Camera; // Path is a helper class to game view. It observes and calculates the // coordinates of camera view and divides them into Grids/Cells for Path // finding. Path path; // this represents the player and has a getSprite() method that will return // the current frame column row combination of the passed sprite sheet. Sprite player; }

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• MVC Architecture

  Model-View-Controller (MVC) is an architectural design pattern first written about and implemented by  in 1978. Trygve developed this pattern during the year he spent working with Xerox PARC on a small talk application. According to Trygve, “The essential purpose of MVC is to bridge the gap between the human user's mental model and the digital model that exists in the computer. The ideal MVC solution supports the user illusion of seeing and manipulating the domain information directly. The structure is useful if the user needs to see the same model element simultaneously in different contexts and/or from different viewpoints.”  Trygve Reenskaug on MVC The MVC pattern is composed of 3 core components. Model View Controller The Model component referenced in the MVC pattern pertains to the encapsulation of core application data and functionality. The primary goal of the model is to maintain its independence from the View and Controller components which together form the user interface of the application. The View component retrieves data from the Model and displays it to the user. The View component represents the output of the application to the user. Traditionally the View has read-only access to the Model component because it should not change the Model’s data. The Controller component receives and translates input to requests on the Model or View components. The Controller is responsible for requesting methods on the model that can change the state of the model. The primary benefit to using MVC as an architectural pattern in a project compared to other patterns is flexibility. The flexibility of MVC is due to the distinct separation of concerns it establishes with three distinct components.  Because of the distinct separation between the components interaction is limited through the use of interfaces instead of classes. This allows each of the components to be hot swappable when the needs of the application change or needs of availability change. MVC can easily be applied to C# and the .Net Framework. In fact, Microsoft created a MVC project template that will allow new project of this type to be created with the standard MVC structure in place before any coding begins. The project also creates folders for the three key components along with default Model, View and Controller classed added to the project. Personally I think that MVC is a great pattern in regards to dealing with web applications because they could be viewed from a myriad of devices. Examples of devices include: standard web browsers, text only web browsers, mobile phones, smart phones, IPads, IPhones just to get started. Due to the potentially increasing accessibility needs and the ability for components to be hot swappable is a perfect fit because the core functionality of the application can be retained and the View component can be altered based on the client’s environment and the View component could be swapped out based on the calling device so that the display is targeted to that specific device.

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• Do unit tests sometimes break encapsulation?

  - by user1288851

  I very often hear the following: "If you want to test private methods, you'd better put that in another class and expose it." While sometimes that's the case and we have a hiding concept inside our class, other times you end up with classes that have the same attributes (or, worst, every attribute of one class become a argument on a method in the other class) and exposes functionality that is, in fact, implementation detail. Specially on TDD, when you refactor a class with public methods out of a previous tested class, that class is now part of your interface, but has no tests to it (since you refactored it, and is a implementation detail). Now, I may be not finding an obvious better answer, but if my answer is the "correct", that means that sometimes writting unit tests can break encapsulation, and divide the same responsibility into different classes. A simple example would be testing a setter method when a getter is not actually needed for anything in the real code. Please when aswering don't provide simple answers to specific cases I may have written. Rather, try to explain more of the generic case and theoretical approach. And this is neither language specific. Thanks in advance. EDIT: The answer given by Matthew Flynn was really insightful, but didn't quite answer the question. Altough he made the fair point that you either don't test private methods or extract them because they really are other concern and responsibility (or at least that was what I could understand from his answer), I think there are situations where unit testing private methods is useful. My primary example is when you have a class that has one responsibility but the output (or input) that it gives (takes) is just to complex. For example, a hashing function. There's no good way to break a hashing function apart and mantain cohesion and encapsulation. However, testing a hashing function can be really tough, since you would need to calculate by hand (you can't use code calculation to test code calculation!) the hashing, and test multiple cases where the hash changes. In that way (and this may be a question worth of its own topic) I think private method testing is the best way to handle it. Now, I'm not sure if I should ask another question, or ask it here, but are there any better way to test such complex output (input)? OBS: Please, if you think I should ask another question on that topic, leave a comment. :)

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• Best Platform/Engine for turn based Client/Server Android game

  - by Paradine

  I'm currently designing a turn based game for tablets. Initially for Android with porting to iOS later considered in design. I'm having trouble narrowing down the available technologies to even know where to spend my research time. I am hoping that if I explain what I am trying to achieve someone may be able to suggest a platform and/or engine. I've looked into some of the open source Engines ( http://www.cuteandroid.com/ten-open-source-android-2d-or-3d-game-engine-for-android-developers ) and some appear to handle much of what I might require - although with a higher focus on graphics than i need. Mages looks interesting although development appears to have ceased. If I could somehow leverage GoogleApps that would be excellent. Here is what I am trying to achieve: PvP turn based strategy game over internet - minimal animation and bandwidth required Players match up online using MetaGame system MatchID created on Resolution Server and Game starts Clients have 30 second countdown to select MoveString Clients sends small secure timestamped and MatchIDed MoveString to Resolution server Resolution server looks up Move String for each player, Resolves and Updates Players status in MatchID on Server Resolution server updates Client Views Repeat until victory conditions met - MatchID Closed, Rewards earned in MetaGame There will also need to be a full social and account system and metagame backend - but this could be running on separate system(s) Tablet in Offline mode would be catalog browsing and perhaps single player AI - bum I'm focusing on the Resolution Server at this point I'm not even certain if I would be looking at an Android App or a WebApp at this stage! I want a custom GUI so I guess an app - but maybe as I have little animation a WebApp might also work. Probably some combination of both. There will be very small overhead in data between client server - essentially a small text string every 30 seconds sent to the Resolution server which looks up the Effect and applies it to the Opponents string and determines some results to apply to the match. The client view is updated minimally with the results (only 5 in game Integers tracked) - perhaps triggering small animations/popups on the client to show the end result. e.g Explosion. If you have suggestions for a good technology or platform to best achieving the Resolution Server I'd love to hear. Also if you have experience with open source Engines - and could narrow down which (if any ) might be most suitable that would be a big help. Thanks in advance

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• Music Notation Editor - Refactoring view creation logic elsewhere

  - by Cyril Silverman

  Let me preface by saying that knowing some elementary music theory and music notation may be helpful in grasping the problem at hand. I'm currently building a Music Notation and Tablature Editor (in Javascript). But I've come to a point where the core parts of the program are more or less there. All functionality I plan to add at this point will really build off the foundation that I've created. As a result, I want to refactor to really solidify my code. I'm using an API called VexFlow to render notation. Basically I pass the parts of the editor's state to VexFlow to build the graphical representation of the score. Here is a rough and stripped down UML diagram showing you the outline of my program: In essence, a Part has many Measures which has many Notes which has many NoteItems (yes, this is semantically weird, as a chord is represented as a Note with multiple NoteItems, individual pitches or fret positions). All of the relationships are bi-directional. There are a few problems with my design because my Measure class contains the majority of the entire application view logic. The class holds the data about all VexFlow objects (the graphical representation of the score). It contains the graphical Staff object and the graphical notes. (Shouldn't these be placed somewhere else in the program?) While VexFlowFactory deals with actual creation (and some processing) of most of the VexFlow objects, Measure still "directs" the creation of all the objects and what order they are supposed to be created in for both the VexFlowStaff and VexFlowNotes. I'm not looking for a specific answer as you'd need a much deeper understanding of my code. Just a general direction to go in. Here's a thought I had, create an MeasureView/NoteView/PartView classes that contains the basic VexFlow objects for each class in addition to any extraneous logic for it's creation? but where would these views be contained? Do I create a ScoreView that is a parallel graphical representation of everything? So that ScoreView.render() would cascade down PartView and call render for each PartView and casade down into each MeasureView, etc. Again, I just have no idea what direction to go in. The more I think about it, the more ways to go seem to pop into my head. I tried to be as concise and simplistic as possible while still getting my problem across. Please feel free to ask me any questions if anything is unclear. It's quite a struggle trying to dumb down a complicated problem to its core parts.

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• Where and how to reference composite MVP components?

  - by Lea Hayes

  I am learning about the MVP (Model-View-Presenter) Passive View flavour of MVC. I intend to expose events from view interfaces rather than using the observer pattern to remove explicit coupling with presenter. Context: Windows Forms / Client-Side JavaScript. I am led to believe that the MVP (or indeed MVC in general) pattern can be applied at various levels of a user interface ranging from the main "Window" to an embedded "Text Field". For instance, the model to the text field is probably just a string whereas the model to the "Window" contains application specific view state (like a persons name which resides within the contained text field). Given a more complex scenario: Documentation viewer which contains: TOC navigation pane Document view Search pane Since each of these 4 user interface items are complex and can be reused elsewhere it makes sense to design these using MVP. Given that each of these user interface items comprises of 3 components; which component should be nested? where? who instantiates them? Idea #1 - Embed View inside View from Parent View public class DocumentationViewer : Form, IDocumentationViewerView { public DocumentationViewer() { ... // Unclear as to how model and presenter are injected... TocPane = new TocPaneView(); } protected ITocPaneView TocPane { get; private set; } } Idea #2 - Embed Presenter inside View from Parent View public class DocumentationViewer : Form, IDocumentationViewerView { public DocumentationViewer() { ... // This doesn't seem like view logic... var tocPaneModel = new TocPaneModel(); var tocPaneView = new TocPaneView(); TocPane = new TocPanePresenter(tocPaneModel, tocPaneView); } protected TocPanePresenter TocPane { get; private set; } } Idea #3 - Embed View inside View from Parent Presenter public class DocumentationViewer : Form, IDocumentationViewerView { ... // Part of IDocumentationViewerView: public ITocPaneView TocPane { get; set; } } public class DocumentationViewerPresenter { public DocumentationViewerPresenter(DocumentationViewerModel model, IDocumentationViewerView view) { ... var tocPaneView = new TocPaneView(); var tocPaneModel = new TocPaneModel(model.Toc); var tocPanePresenter = new TocPanePresenter(tocPaneModel, tocPaneView); view.TocPane = tocPaneView; } } Some better idea...

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• Game timings and formats

  - by topright

  There are more or less standardized TV-show/movie formats and recommended timings: 1. By the early 1960s, television companies commonly presented half-hour long "comedy" series, or one hour long "dramas." Half-hour series were mostly restricted to situation comedy or family comedy, and were usually aired with either a live or artificial laugh track. One hour dramas included genre series such as police and detective series, westerns, science fiction, and, later, serialized prime time soap operas. Programs today still overwhelmingly conform to these half-hour and one hour guidelines. Source 2. In the United States, most medical dramas are one hour long. Source 3. Traditionally serials were broadcast as fifteen minute installments each weekday in daytime slots. In 1956 As the World Turns debuted as the first half-hour soap opera. All soap operas broadcast half-hour episodes by the end of the 1960s. With increased popularity in the 1970s most soap operas expanded to an hour (Another World even expanded to ninety minutes for a short time). More than half of the serials had expanded to one hour episodes by 1980. As of 2010, six of the seven US serials air one hour episodes each weekday. Source Interesting. Are there any standards of timing in game development? Well, 5-20 minutes casual games, of course. There is even a "5-minutes-game" site. And 1-hour-gamer site. Are there 1-week, 1-year, 1-eternity game formats? Chess and Go - deep games that you can study all your life; but they are played in hour or several days (pro games). Addictive long-term online role-playing games (without win-condition) are played in monthes and, possibly, years. Replayability is an important factor to consider. It's good when game design document contains a line: "A game is designed for solving in X hours". How can it be measured before there is any prototype or demo? When you know your game format, you know your audience (and vice versa). It is practical question. Are there psychological researches about dynamic of gaming interest and involvement? And is there a correlation between game format and game genre?

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• Questions re: Eclipse Jobs API

  - by BenCole

  Similar to http://stackoverflow.com/questions/8738160/eclipse-jobs-api-for-a-stand-alone-swing-project This question mentions the Jobs API from the Eclipse IDE: ...The disadvantage of the pre-3.0 approach was that the user had to wait until an operation completed before the UI became responsive again. The UI still provided the user the ability to cancel the currently running operation but no other work could be done until the operation completed. Some operations were performed in the background (resource decoration and JDT file indexing are two such examples) but these operations were restricted in the sense that they could not modify the workspace. If a background operation did try to modify the workspace, the UI thread would be blocked if the user explicitly performed an operation that modified the workspace and, even worse, the user would not be able to cancel the operation. A further complication with concurrency was that the interaction between the independent locking mechanisms of different plug-ins often resulted in deadlock situations. Because of the independent nature of the locks, there was no way for Eclipse to recover from the deadlock, which forced users to kill the application... ...The functionality provided by the workspace locking mechanism can be broken down into the following three aspects: Resource locking to ensure multiple operations did not concurrently modify the same resource Resource change batching to ensure UI stability during an operation Identification of an appropriate time to perform incremental building With the introduction of the Jobs API, these areas have been divided into separate mechanisms and a few additional facilities have been added. The following list summarizes the facilities added. Job class: support for performing operations or other work in the background. ISchedulingRule interface: support for determining which jobs can run concurrently. WorkspaceJob and two IWorkspace#run() methods: support for batching of delta change notifications. Background auto-build: running of incremental build at a time when no other running operations are affecting resources. ILock interface: support for deadlock detection and recovery. Job properties for configuring user feedback for jobs run in the background. The rest of this article provides examples of how to use the above-mentioned facilities... In regards to above API, is this an implementation of a particular design pattern? Which one?

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• Javascript Implementation Patterns for Server-side MVC Websites

  - by tmo256

  I'm looking for information on common patterns for initializing and executing Javascript page by page in a "traditional" server-side MVC website architecture. A few months ago, my development team began, but abandoned, a major re-architecture of our company's primary web app, including a full front-end redesign. In the process, there was some debate about the architecture of the Javascript in the current version of the site, and whether it fit into a clear, modern design pattern. Now I've returned to the process of overhauling the front end of this and several other MVC websites (Ruby on Rails and MVC.net) to implement a responsive framework (Bootstrap), and in the process will again need to review then revamp and update a lot of Javascript. These web applications are NOT single-page Javascript applications (in fact, we are ripping out a lot of Ajax) or designed to require a Javascript MVC pattern; these apps are basically brochure, catalog and administrative sites that follow a server-side MVC pattern. The vast majority of the Javascript required is behavioral, pre-built plugins (JQuery and Bootstrap, et al) that execute on specific DOM nodes. I'm going to give a very brief (as brief as I can be) run-down of the current architecture only in order to illustrate the scope and type of paradigm I'm talking about. Hopefully, it will help you understand the nature of the patterns I'm looking for, but I'm not looking for commentary on the specifics of this code. What I've done in the past is relatively straight-forward and easy to maintain, but, as mentioned above, some of the other developers don't like the current architecture. Currently, on document ready, I execute whatever global Javascript needs to occur on every page, and then call a page-specific init function to initialize node-specific functionality, retrieving the init method from a JS object. On each page load, something like this will happen: $(document).ready(function(){ $('header').menuAction(); App.pages.executePage('home','show'); //dynamic from framework request object }); And the main App javascript is like App = { usefulGlobalVar: 0, pages: { executePage: function(action, controller) { // if exists, App.pages[action][controller].init() }, home: { show: { init: function() { $('#tabs').tabs(); //et. al }, normalizeName: function() { // dom-specific utility function that // doesn't require a full-blown component/class/module } }, edit: ... }, user_profile: ... } } Any common features and functionality requiring modularization or compotentizing is done as needed with prototyping. For common implementation of plugins, I often extend JQuery, so I can easily initialize a plugin with the same options throughout the site. For example, $('[data-tabs]').myTabs() with this code in a utility javascript file: (function($) { $.fn.myTabs = function() { this.tabs( { //...common options }); }; }) Pointers to articles, books or other discussions would be most welcome. Again, I am looking for a site-wide implementation pattern, NOT a JS MVC framework or general how-tos on creating JS classes or components. Thanks for your help!

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• Is throwing an error in unpredictable subclass-specific circumstances a violation of LSP?

  - by Motti Strom

  Say, I wanted to create a Java List<String> (see spec) implementation that uses a complex subsystem, such as a database or file system, for its store so that it becomes a simple persistent collection rather than an basic in-memory one. (We're limiting it specifically to a List of Strings for the purposes of discussion, but it could extended to automatically de-/serialise any object, with some help. We can also provide persistent Sets, Maps and so on in this way too.) So here's a skeleton implementation: class DbBackedList implements List<String> { private DbBackedList() {} /** Returns a list, possibly non-empty */ public static getList() { return new DbBackedList(); } public String get(int index) { return Db.getTable().getRow(i).asString(); // may throw DbExceptions! } // add(String), add(int, String), etc. ... } My problem lies with the fact that the underlying DB API may encounter connection errors that are not specified in the List interface that it should throw. My problem is whether this violates Liskov's Substitution Principle (LSP). Bob Martin actually gives an example of a PersistentSet in his paper on LSP that violates LSP. The difference is that his newly-specified Exception there is determined by the inserted value and so is strengthening the precondition. In my case the connection/read error is unpredictable and due to external factors and so is not technically a new precondition, merely an error of circumstance, perhaps like OutOfMemoryError which can occur even when unspecified. In normal circumstances, the new Error/Exception might never be thrown. (The caller could catch if it is aware of the possibility, just as a memory-restricted Java program might specifically catch OOME.) Is this therefore a valid argument for throwing an extra error and can I still claim to be a valid java.util.List (or pick your SDK/language/collection in general) and not in violation of LSP? If this does indeed violate LSP and thus not practically usable, I have provided two less-palatable alternative solutions as answers that you can comment on, see below. Footnote: Use Cases In the simplest case, the goal is to provide a familiar interface for cases when (say) a database is just being used as a persistent list, and allow regular List operations such as search, subList and iteration. Another, more adventurous, use-case is as a slot-in replacement for libraries that work with basic Lists, e.g if we have a third-party task queue that usually works with a plain List: new TaskWorkQueue(new ArrayList<String>()).start() which is susceptible to losing all it's queue in event of a crash, if we just replace this with: new TaskWorkQueue(new DbBackedList()).start() we get a instant persistence and the ability to share the tasks amongst more than one machine. In either case, we could either handle connection/read exceptions that are thrown, perhaps retrying the connection/read first, or allow them to throw and crash the program (e.g. if we can't change the TaskWorkQueue code).

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• Explanation of the definition of interface inheritance as described in GoF book

  - by Geek

  I am reading the first chapter of the Gof book. Section 1.6 discusses about class vs interface inheritance: Class versus Interface Inheritance It's important to understand the difference between an object's class and its type. An object's class defines how the object is implemented.The class defines the object's internal state and the implementation of its operations.In contrast,an object's type only refers to its interface--the set of requests on which it can respond. An object can have many types, and objects of different classes can have the same type. Of course, there's a close relationship between class and type. Because a class defines the operations an object can perform, it also defines the object's type . When we say that an object is an instance of a class, we imply that the object supports the interface defined by the class. Languages like c++ and Eiffel use classes to specify both an object's type and its implementation. Smalltalk programs do not declare the types of variables; consequently,the compiler does not check that the types of objects assigned to a variable are subtypes of the variable's type. Sending a message requires checking that the class of the receiver implements the message, but it doesn't require checking that the receiver is an instance of a particular class. It's also important to understand the difference between class inheritance and interface inheritance (or subtyping). Class inheritance defines an object's implementation in terms of another object's implementation. In short, it's a mechanism for code and representation sharing. In contrast,interface inheritance(or subtyping) describes when an object can be used in place of another. I am familiar with the Java and JavaScript programming language and not really familiar with either C++ or Smalltalk or Eiffel as mentioned here. So I am trying to map the concepts discussed here to Java's way of doing classes, inheritance and interfaces. This is how I think of of these concepts in Java: In Java a class is always a blueprint for the objects it produces and what interface(as in "set of all possible requests that the object can respond to") an object of that class possess is defined during compilation stage only because the class of the object would have implemented those interfaces. The requests that an object of that class can respond to is the set of all the methods that are in the class(including those implemented for the interfaces that this class implements). My specific questions are: Am I right in saying that Java's way is more similar to C++ as described in the third paragraph. I do not understand what is meant by interface inheritance in the last paragraph. In Java interface inheritance is one interface extending from another interface. But I think the word interface has some other overloaded meaning here. Can some one provide an example in Java of what is meant by interface inheritance here so that I understand it better?

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• How to build a 4x game?

  - by Marco

  I'm trying to study how succefully implement a 4x game. Area of interest: 1) map data: how to store stellars systems (graphs?), how to generate them and so on.. 2) multiplayer: how to organize code in a non graphical server and a client to display it 3) command system: what are patters to catch user and ai decisions and handle them, adding at first "explore" and "colonize" then "combat", "research", "spy" and so on (commands can affect ships, planets, research, etc..) 4) ai system: ai can use commands to expand, upgrade planets and ship I know is a big questions, so help is appreciated :D 1) Map data Best choice is have a graph to model a galaxy. A node is a stellar system and every system have a list of planets. Ship cannot travel outside of predefined paths, like in Ascendancy: http://www.abandonia.com/files/games/221/Ascendancy_2.png Every connection between two stellar systems have a cost, in turns. Generate a galaxy is only a matter of: - dimension: number of stellar systems, - variety: randomize number of planets and types (desertic, earth, etc..), - positions of each stellar system on game space - connections: assure that exist a path between every node, so graph is "connected" (not sure if this a matematically correct term) 2) Multiplayer Game is organized in turns: player 1, player 2, ai1, ai2. Server take care of all data and clients just diplay it and collect data change. Because is a turn game, latency is not a problem :D 3) Command system I would like to design a hierarchy of commands to take care of this aspect: abstract Genericcommand (target) ExploreCommand (Ship) extends genericcommand colonizeCommand (Ship) buildcommand(planet, object) and so on. In my head all this commands are stored in a queue for every planets, ships or reasearch center or spy, and each turn a command is sent to a server to apply command and change data state 4) ai system I don't have any idea about this. Is a big topic and what I want is a simple ai. Something like "expand and fight against everyone". I think about a behaviour tree to control ai moves, so I can develop an ai that try to build ships to expand and then colonize planets, upgrade them throught science and combat enemies. Could be done with a finite state machine too ? any ideas, resources, article are welcome!

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• Music Notation Editor - Refactoring view creation logic elseware

  - by Cyril Silverman

  Let me preface by saying that knowing some elementary music theory and music notation may be helpful in grasping the problem at hand. I'm currently building a Music Notation and Tablature Editor (in Javascript). But I've come to a point where the core parts of the program are more or less there. All functionality I plan to add at this point will really build off the foundation that I've created. As a result, I want to refactor to really solidify my code. I'm using an API called VexFlow to render notation. Basically I pass the parts of the editor's state to VexFlow to build the graphical representation of the score. Here is a rough and stripped down UML diagram showing you the outline of my program: In essence, a Part has many Measures which has many Notes which has many NoteItems (yes, this is semantically weird, as a chord is represented as a Note with multiple NoteItems, individual pitches or fret positions). All of the relationships are bi-directional. There are a few problems with my design because my Measure class contains the majority of the entire application view logic. The class holds the data about all VexFlow objects (the graphical representation of the score). It contains the graphical Staff object and the graphical notes. (Shouldn't these be placed somewhere else in the program?) While VexFlowFactory deals with actual creation (and some processing) of most of the VexFlow objects, Measure still "directs" the creation of all the objects and what order they are supposed to be created in for both the VexFlowStaff and VexFlowNotes. I'm not looking for a specific answer as you'd need a much deeper understanding of my code. Just a general direction to go in. Here's a thought I had, create an MeasureView/NoteView/PartView classes that contains the basic VexFlow objects for each class in addition to any extraneous logic for it's creation? but where would these views be contained? Do I create a ScoreView that is a parallel graphical representation of everything? So that ScoreView.render() would cascade down PartView and call render for each PartView and casade down into each MeasureView, etc. Again, I just have no idea what direction to go in. The more I think about it, the more ways to go seem to pop into my head. I tried to be as concise and simplistic as possible while still getting my problem across. Please feel free to ask me any questions if anything is unclear. It's quite a struggle trying to dumb down a complicated problem to its core parts.

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• Interconnect nodes in a Java distributed infrastructure for tweet processing

  - by David Moreno García

  I'm working in a new version of an old project that I used to download and process user statuses from Twitter. The main problem of that project was its infrastructure. I used multiple instances of a java application (trackers) to download from Twitter given an specific task (basically terms to search for), connected with a central node (a web application) that had to process all tweets once per day and generate a new task for each trackers once each 15 minutes. The central node also had to monitor all trackers and enable/disable them under user petition. This, as I said, was too slow because I had multiple bottlenecks, so in this new version I want to improve the infrastructure and isolate all functionalities in specific nodes. I also need a good notification system to receive notifications for any node. So, in the next diagram I show the components that I'll need in this new version: As you can see, there are more nodes. Here are some notes about them: Dashboard: Controls trackers statuses and send a single task to each of them (under user request). The trackers will use this task until replaced with a new one (if done, not each 15 minutes like before). Search engine: I need to store all the tweets. They are firstly stored in a local database for each tracker but after that I'm thinking on using something like Elasticsearch to be able to do fast searches. Tweet processor: Just and isolated component with its own database (maybe something like the search engine to have fast access to info generated by the module). In the future more could be added. Application UI: A web application with a shared database with the Dashboard (mainly to store users information and preferences). Indeed, both could be merged into a single web. The main difference with the previous version of the project is that now they will be isolated and they will only show information and send requests. I will not do any heavy task in them (like process tweets as I did before). So, having this components, my main headache is how to structure all to not have to rewrite a lot of code every time I need to access any new data. Another headache is how can I interconnect nodes. I could use sockets but that is a pain in the ass. Maybe a REST layer? And finally, if all the nodes are isolated, how could I generate notifications for each user which info is only in the database used by the Application UI? I'm programming this using Java and Spring (at least I used them in the last version) but I have no problems with changing the language if I can take advantage of a tool/library/engine to make my life easier and have a better platform. Any comment will be appreciated.

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• JS closures - Passing a function to a child, how should the shared object be accessed

  - by slicedtoad

  I have a design and am wondering what the appropriate way to access variables is. I'll demonstrate with this example since I can't seem to describe it better than the title. Term is an object representing a bunch of time data (a repeating duration of time defined by a bunch of attributes) Term has some print functionality but does not implement the print functions itself, rather they are passed in as anonymous functions by the parent. This would be similar to how shaders can be passed to a renderer rather than defined by the renderer. A container (let's call it Box) has a Schedule object that can understand and use Term objects. Box creates Term objects and passes them to Schedule as required. Box also defines the print functions stored in Term. A print function usually takes an argument and uses it to return a string based on that argument and Term's internal data. Sometime the print function could also use data stored in Schedule, though. I'm calling this data shared. So, the question is, what is the best way to access this shared data. I have a lot of options since JS has closures and I'm not familiar enough to know if I should be using them or avoiding them in this case. Options: Create a local "reference" (term used lightly) to the shared data (data is not a primitive) when defining the print function by accessing the shared data through Schedule from Box. Example: var schedule = function(){ var sched = Schedule(); var t1 = Term( function(x){ // Term.print() return (x + sched.data).format(); }); }; Bind it to Term explicitly. (Pass it in Term's constructor or something). Or bind it in Sched after Box passes it. And then access it as an attribute of Term. Pass it in at the same time x is passed to the print function, (from sched). This is the most familiar way for my but it doesn't feel right given JS's closure ability. Do something weird like bind some context and arguments to print. I'm hoping the correct answer isn't purely subjective. If it is, then I guess the answer is just "do whatever works". But I feel like there are some significant differences between the approaches that could have a large impact when stretched beyond my small example.

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• .Net Application & Database Modularity/Reuse

  - by Martaver

  I'm looking for some guidance on how to architect an app with regards to modularity, separation of concerns and re-usability. I'm working on an application (ASP.Net, C#) that has distinctly generic chunks of functionality, that I'd love to be able to lift out, all layers, into re-usable components. This means the module handles the database schema, data access, API, everything so that the next time I want to use it I can just register the module and hook into it. Developing modules of re-usable functionality is a no-brainer, but what is really confusing me is what to do when it comes to handling a core re-usable database schema that serves the module's functionality. In an ideal world, I would register a module and it would ensure that the associated database schema exists in the DB. I would code on the assumption that the tables exist, calling the module's functionality through the DLL, agnostic of the database layer. Kind of like Enterprise Library's Caching/Logging Application Block, which can create a DB schema in the target DB to use as a data store. My Questions is: What do you think is the best way to achieve this, firstly, in terms design architecture, and secondly solution structure. What patterns/frameworks do you know that exist & support this kind of thing? My thoughts so far: I mostly use Entity Framework and SQL Server DB Projects. I thought about a 'black box' approach to modules of functionality. I could use use a code-first approach in EF4, and use the ObjectContext to create a database when the module is initialized. However this means that all of the entities that my module encapsulates would be disconnected from the rest of the application because they belonged to an abstracted ObjectContext. Further - Creating appropriate indexes and references between domain entities and the module's entities would be impossible to do practically. I've thought of adopting Enterprise Library and creating my own Application Blocks. I'm not sure how this would play nice with Entity Framework (if at all) though. I like the idea of building on proven patterns & practices to encapsulate established, reusable functionality. I thought of abandoning Entity Framework for the Module, and just creating a separate DB schema for the module with its own set of stored procedures & ADO.Net. Then deploying the script at run-time if interrogation shows that it doesn't exist. But once again, for application developing outside of the application, I would want to use Entity Framework and I would have to use the module separately, disconnected from the domain ObjectContext. Has anyone had experience developing these sorts of full-stack modules? What advice can you offer? Am I biting off more than I can chew?

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• What are the differences between abstract classes, interfaces, and when to use them

  - by user66662

  Recently I have started to wrap my head around OOP, and I am now to the point where the more I read about the differences between Abstract classes and Interfaces the more confused I become. So far, neither can be instantiated. Interfaces are more or less structural blueprints that determine the skeleton and abstracts are different by being able to partially develop code. I would like to learn more about these through my specific situation. Here is a link to my first question if you would like a little more background information: What is a good design model for my new class? Here are two classes I created: class Ad { $title; $description $price; function get_data($website){ } function validate_price(){ } } class calendar_event { $title; $description $start_date; function get_data($website){ //guts } function validate_dates(){ //guts } } So, as you can see these classes are almost identical. Not shown here, but there are other functions, like get_zip(), save_to_database() that are common across my classes. I have also added other classes Cars and Pets which have all the common methods and of course properties specific to those objects (mileage, weight, for example). Now I have violated the DRY principle and I am managing and changing the same code across multiple files. I intend on having more classes like boats, horses, or whatever. So is this where I would use an interface or abstract class? From what I understand about abstract classes I would use a super class as a template with all of the common elements built into the abstract class, and then add only the items specifically needed in future classes. For example: abstract class content { $title; $description function get_data($website){ } function common_function2() { } function common_function3() { } } class calendar_event extends content { $start_date; function validate_dates(){ } } Or would I use an interface and, because these are so similar, create a structure that each of the subclasses are forced to use for integrity reasons, and leave it up to the end developer who fleshes out that class to be responsible for each of the details of even the common functions. my thinking there is that some 'common' functions may need to be tweaked in the future for the needs of their specific class. Despite all that above, if you believe I am misunderstanding the what and why of abstracts and interfaces altogether, by all means let a valid answer to be stop thinking in this direction and suggest the proper way to move forward! Thanks!

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• Turn-Based RPG Battle Instance Layout For Larger Groups

  - by SoulBeaver

  What a title, eh? I'm currently designing a videogame; a turn-based RPG like Final Fantasy (because everybody knows Final Fantasy). It's a 2D sprite game. These are my ideas for combat: -The player has a group of 15 members (main character included) -During battle, five of the group are designated as active, and appear in the battle. -These five may be switched out at leisure, or when one of the five die. -At any time, the Waiting members can cast buffs, be healed by the active members, or perform special attacks. -Battles should contain 10+ monsters at least. I'm aiming for 20, but I'm not sure if that's possible yet. -Battles should feel larger than normal due to the interaction of Waiting members, active members and the increased amount of monsters per battle. -The player has two rows in which to put the Active members: front and back. -Depending on the implementation, I might allow comboing of player attacks and skills. These are just design ideas, so beware! I have not been able to test this out yet- I have no idea yet if any of these ideas bunched together will make for a compelling game. What sounds good on paper doesn't necessarily have to be good in practice! What I'm asking now is how to create the layout for this. My starting point are the battles in Final Fantasy VI, with up to 5-6 monsters on the left and the characters on the right- monsters on both sides if it's a pincer attack. However, this view would not work feasible with my goal of 20 monsters and 5 characters. All the monsters on the left would appear cluttered unless I scale them far far back. If I create a pincer-like map, then there would be no real pincer-attack possible. If I space the monsters out I force the player to scroll the screen- a game mechanic I've come across and not enjoyed imho. My question is: does anybody have any layouts or guides for designing battle maps in turn-based RPGs, especially with a larger number of enemies taken into consideration? How should it look? I am not asking for specific combat mechanics, just the layout for the moment.

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• How do you take into account usability and user requirements for your application?

  - by voroninp

  Our team supports BackOffice application: a mix of WinForm and WPF windows. (about 80 including dialogs). Really a kind of a Swiss Army Knife. It is used by developers, tech writers, security developers, testers. The requirements for new features come quite often and sometimes we play Wizard of Oz to decide which GUI our users like the most. And it usually happens (I admit it can be just my subjective interpretation of the reality) that one tiny detail giving the flavor of good usability to our app requires a lot of time. This time is being spent on 'fighting' with GUI framework making it act like we need. And it very difficult to make estimations for this type of tasks (at least for me and most members of our team). Scrum poker is not a help either. Management often considers this usability perfectionism to be a waste of time. On the other hand an accumulated affect of features where each has some little usability flaw frustrates users. But the same users want frequent releases and instant bug fixes. Hence, no way to get the positive feedback: there is always somebody who is snuffy. I constantly feel myself as competing with ourselves: more features - more bugs/tasks/architecture. We are trying to outrun the cart we are pushing. New technologies arrive and some of them can potentially help to improve the design or decrease task implementation time but these technologies require learning, prototyping and so on. Well, that was a story. And now is the question: How do you balance between time pressure, product quality, users and management satisfaction? When and how do you decide to leave the problem with not a perfect but to some extent acceptable solution, how often do you make these decisions? How do you do with your own satisfaction? What are your priorities? P.S. Please keep in mind, we are a BackOffice team, we have neither dedicated technical writer nor GUI designer. The tester have joined us recently. We've much work to do and much freedom concerning 'how'. I like it because it fosters creativity but I don't want to become too nerdy perfectionist.

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• A solution for a PHP website without a framework

  - by lortabac

  One of our customers asked us to add some dynamic functionality to an existent website, made of several static HTML pages. We normally work with an MVC framework (mostly CodeIgniter), but in this case moving everything to a framework would require too much time. Since it is not a big project, not having the full functionality of a framework is not a problem. But the question is how to keep code clean. The solution I came up with is to divide code in libraries (the application's API) and models. So inside HTML there will only be API calls, and readability will not be sacrificed. I implemented this with a sort of static Registry (sorry if I'm wrong, I am not a design pattern expert): <?php class Custom_framework { //Global database instance private static $db; //Registered models private static $models = array(); //Registered libraries private static $libraries = array(); //Returns a database class instance static public function get_db(){ if(isset(self::$db)){ //If instance exists, returns it return self::$db; } else { //If instance doesn't exists, creates it self::$db = new DB; return self::$db; } } //Returns a model instance static public function get_model($model_name){ if(isset(self::$models[$model_name])){ //If instance exists, returns it return self::$models[$model_name]; } else { //If instance doesn't exists, creates it if(is_file(ROOT_DIR . 'application/models/' . $model_name . '.php')){ include_once ROOT_DIR . 'application/models/' . $model_name . '.php'; self::$models[$model_name] = new $model_name; return self::$models[$model_name]; } else { return FALSE; } } } //Returns a library instance static public function get_library($library_name){ if(isset(self::$libraries[$library_name])){ //If instance exists, returns it return self::$libraries[$library_name]; } else { //If instance doesn't exists, creates it if(is_file(ROOT_DIR . 'application/libraries/' . $library_name . '.php')){ include_once ROOT_DIR . 'application/libraries/' . $library_name . '.php'; self::$libraries[$library_name] = new $library_name; return self::$libraries[$library_name]; } else { return FALSE; } } } } Inside HTML, API methods are accessed like this: <?php echo Custom_framework::get_library('My_library')->my_method(); ?> It looks to me as a practical solution. But I wonder what its drawbacks are, and what the possible alternatives.

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• Should library classes be wrapped before using them in unit testing?

  - 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. Example: 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'); $this->mail->send(); //Some } } However, Unit testing demands that I test one component at a time, so I need to mock the Zend_Mail class. In addition I'm violating the Dependency Inversion principle as my Logger class now depends on concretion not abstraction. Does that mean that I can never use a library class directly and must always wrap it in a class of my own? Example: interface Mailer{ public function setTo($to); public function setSubject($subject); public function setBody($body); public function send(); } class MyMailer implements Mailer{ private $mailer; function __construct(){ $this->mail=new Zend_Mail; //The class isn't injected this time } function setTo($to){ $this->mailer->setTo($to); } //implement the rest of the interface functions similarly } And now my Logger class can be happy :D class Logger{ private $mailer; function __construct(Mailer $mail){ $this->mail=$mail; } //rest of the code unchanged } Questions: Although I solved the mocking problem by introducing an interface, I have created a totally new class Mailer that now needs to be unit tested although it only wraps Zend_Mail which is already unit tested by the Zend team. Is there a better approach to all this? Zend_Mail's send() function could actually have a Zend_Transport object when called (i.e. public function send($transport = null)). Does this make the idea of a wrapper class more appealing? 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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• reference list for non-IT driven algorithmic patterns

  - by Quicker

  I am looking for a reference list for non-IT driven algorithmic patterns (which still can be helped with IT implementations of IT). An Example List would be: name; short desc; reference Travelling Salesman; find the shortest possible route on a multiple target path; http://en.wikipedia.org/wiki/Travelling_salesman_problem Ressource Disposition (aka Regulation); Distribute a limited/exceeding input on a given number output receivers based on distribution rules; http://database-programmer.blogspot.de/2010/12/critical-analysis-of-algorithm-sproc.html If there is no such list, but you instantly think of something specific, please 'put it on the desk'. Maybe I can compile something out of the input I get here (actually I am very frustrated as I did not find any such list via research by myself). Details on Scoping: I found it very hard to formulate what I want in a way everything is out that I do not need (which may be the issue why I did not find anything at google). There is a database centric definition for what I am looking for in the section 'Processes' of the second example link. That somehow fits, but the database focus sort of drifts away from the pattern thinking, which I have in mind. So here are my own thoughts around what's in and what's out: I am NOT looking for a foundational algo ref list, which is implemented as basis for any programming language. Eg. the php reference describes substr and strlen. That implements algos, but is not what I am looking for. the problem the algo does address would even exist, if there were no computers (or other IT components) the main focus of the algo is NOT to help other algo's chances are high, that there are implementions of the solution or any workaround without any IT support out there in the world however the algo could be benefitialy implemented/fully supported by a software application = means: the problem of the algo has to be addressed anyway, but running an algo implementation with software automates the process (that is why I posted it on stackoverflow and not somewhere else) typically such algo implementations have more than one input field value and more than one output field value - which implies it could not be implemented as simple function (which is fixed to produce not more than one output value) in a normalized data model often times such algo implementation outputs span accross multiple rows (sometimes multiple tables), whereby the number of output rows depends on the input paraters and rows in the table(s) at start time - which implies that any algo implementation/procedure must interact with a database (read and/or write) I am mainly looking for patterns, not for specific implementations. Example: The Travelling Salesman assumes any coordinates, however it does not say: You need a table targets with fields x and y. - however sometimes descriptions are focussed on examples with specific implementations very much - no worries, as long as the pattern gets clear

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