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• How should I implement Transaction database EJB 3.0

  - by JamesBoyZ

  In the CustomerTransactions entity, I have the following field to record what the customer bought: @ManyToMany private List<Item> listOfItemsBought; When I think more about this field, there's a chance it may not work because merchants are allowed to change item's information (e.g. price, discount, etc...). Hence, this field will not be able to record what the customer actually bought when the transaction occurred. At the moment, I can only think of 2 ways to make it work. I will record the transaction details into a String field. I feel that this way would be messy if I need to extract some information about the transaction later on. Whenever the merchant changes an item's information, I will not update directly to that item's fields. Instead, I will create another new item with all the new information and keep the old item untouched. I feel that this way is better because I can easily extract information about the transaction later on. However, the bad side is that my Item table may contain a lot of rows. I'd be very grateful if someone could give me an advice on how I should tackle this problem. UPDATE: I'd like to add more information about the current design. public class Customer implements Serializable { @OneToMany private List<CustomerTransactions> listOfTransactions; } public class CustomerTransactions implements Serializable { @ManyToMany private List<Item> listOfItemsBought; } public class Merchant implements Serializable { @OneToMany private List<Item> listOfSellingItems; }

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• Why using Fragments?

  - by ahmed_khan_89

  I have read the documentation and some other questions' threads about this topic and I don't really feel convinced; I don't see clearly the limits of use of this technique. Fragments are now seen as a Best Practice; every Activity should be basically a support for one or more Fragments and not call a layout directly. Fragments are created in order to: allow the Activity to use many fragments, to change between them, to reuse these units... == the Fragment is totally dependent to the Context of an activity , so if I need something generic that I can reuse and handle in many Activities, I can create my own custom layouts or Views ... I will not care about this additional Complexity Developing Layer that fragments would add. a better handling to different resolution == OK for tablets/phones in case of long process that we can show two (or more) fragments in the same Activity in Tablets, and one by one in phones. But why would I use fragments always ? handling callbacks to navigate between Fragments (i.e: if the user is Logged-in I show a fragment else I show another fragment). === Just try to see how many bugs facebook SDK Log-in have because of this, to understand that it is really (?) ... considering that an Android Application is based on Activities... Adding another life cycles in the Activity would be better to design an Application... I mean the modules, the scenarios, the data management and the connectivity would be better designed, in that way. === This is an answer of someone who's used to see the Android SDK and Android Framework with a Fragments vision. I don't think it's wrong, but I am not sure it will give good results... And it is really abstract... ==== Why would I complicate my life, coding more, in using them always? else, why is it a best practice if it's just a tool for some cases? what are these cases?

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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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• Best Creational Pattern for loggers in a multi-threaded system?

  - by Dipan Mehta

  This is a follow up question on my past questions : Concurrency pattern of logger in multithreaded application As suggested by others, I am putting this question separately. As the learning from the last question. In a multi-threaded environment, the logger should be made thread safe and probably asynchronous (where in messages are queued while a background thread does writing releasing the requesting object thread). The logger could be signleton or it can be a per-group logger which is a generalization of the above. Now, the question that arise is how does logger should be assigned to the object? There are two options I can think of: 1. Object requesting for the logger: Should each of the object call some global API such as get_logger()? Such an API returns "the" singleton or the group logger. However, I feel this involves assumption about the Application environment to implement the logger -which I think is some kind of coupling. If the same object needs to be used by other application - this new application also need to implement such a method. 2. Assign logger through some known API The other alternative approach is to create a kind of virtual class which is implemented by application based on App's own structure and assign the object sometime in the constructor. This is more generalized method. Unfortunately, when there are so many objects - and rather a tree of objects passing on the logger objects to each level is quite messy. My question is there a better way to do this? If you need to pick any one of the above, which approach is would you pick and why? Other questions remain open about how to configure them: How do objects' names or ID are assigned so that will be used for printing on the log messages (as the module names) How do these objects find the appropriate properties (such as log levels, and other such parameters) In the first approach, the central API needs to deal with all this varieties. In the second approach - there needs to be additional work. Hence, I want to understand from the real experience of people, as to how to write logger effectively in such an environment.

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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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• Testing for Active Directory Schema modification (not upgrade)

  - by Darktux

  I am trying to test a schema modification. That is i need to add one of the attributes to global catalog by modifying schema , initially in a lab which is exact replica.My questions are below; - What tests need to be done post schema change to determine if its safe for production? - Apart from measuring changes in DIT size post change, is there a way to find the whole size increase for adding an attribute to GC pre change? please let me know if any extra questions or info required.

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• Testing performance from around the world - how do I get a linux shell easily in multiple countries?

  - by Matthew O'Riordan

  We are building a socket based service where latency is paramount, and as such we have servers distributed into 7 data centres around the world. However, whilst we know we're bringing the servers closer to the clients, it's very difficult to know how effective this is, and importantly, what difference this makes compared to our competitors. As such, we want to run simple scripts that test latency and throughput for both our service and our competitors, which is easy enough using Amazon, however Amazon only have 7 data centres. We would like to know for example how we perform in locations all over the world such as South Africa, Australia, China, Peru etc. Does anyone know of any service where we could piggy back off their global infrastructure and run some scripts to test this performance? The obvious contenders are people like Monitis, but I don't think they would allow us to run custom scripts, only standard protocol monitors. Thanks for your help. Matt

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• The Incremental Architect&acute;s Napkin - #2 - Balancing the forces

  - by Ralf Westphal

  Originally posted on: http://geekswithblogs.net/theArchitectsNapkin/archive/2014/06/02/the-incremental-architectacutes-napkin---2---balancing-the-forces.aspxCategorizing requirements is the prerequisite for ecconomic architectural decisions. Not all requirements are created equal. However, to truely understand and describe the requirement forces pulling on software development, I think further examination of the requirements aspects is varranted. Aspects of Functionality There are two sides to Functionality requirements. It´s about what a software should do. I call that the Operations it implements. Operations are defined by expressions and control structures or calls to frameworks of some sort, i.e. (business) logic statements. Operations calculate, transform, aggregate, validate, send, receive, load, store etc. Operations are about behavior; they take input and produce output by considering state. I´m not using the term “function” here, because functions - or methods or sub-programs - are not necessary to implement Operations. Functions belong to a different sub-aspect of requirements (see below). Operations alone are not enough, though, to make a customer happy with regard to his/her Functionality requirements. Only correctly implemented Operations provide full value. This should make clear, why testing is so important. And not just manual tests during development of some operational feature, but automated tests. Because only automated tests scale when over time the number of operations increases. Without automated tests there is no guarantee formerly correct operations are still correct after more got added. To retest all previous operations manually is infeasible. So whoever relies just on manual tests is not really balancing the two forces Operations and Correctness. With manual tests more weight is put on the side of the scale of Operations. That might be ok for a short period of time - but in the long run it will bite you. You need to plan for Correctness in the long run from the first day of your project on. Aspects of Quality As important as Functionality is, it´s not the driver for software development. No software has ever been written to just implement some operation in code. We don´t need computers just to do something. All computers can do with software we can do without them. Well, at least given enough time and resources. We could calculate the most complex formulas without computers. We could do auctions with millions of people without computers. The only reason we want computers to help us with this and a million other Operations is… We don´t want to wait for the results very long. Or we want less errors. Or we want easier accessability to complicated solutions. So the main reason for customers to buy/order software is some Quality. They want some Functionality with a higher Quality (e.g. performance, scalability, usability, security…) than without the software. But Qualities come in at least two flavors: Most important are Primary Qualities. That´s the Qualities software truely is written for. Take an online auction website for example. Its Primary Qualities are performance, scalability, and usability, I´d say. Auctions should come within reach of millions of people; setting up an auction should be very easy; finding a suitable auction and bidding on it should be as fast as possible. Only if those Qualities have been implemented does security become relevant. A secure auction website is important - but not as important as a fast auction website. Nobody would want to use the most secure auction website if it was unbearably slow. But there would be people willing to use the fastest auction website even it was lacking security. That´s why security - with regard to online auction software - is not a Primary Quality, but just a Secondary Quality. It´s a supporting quality, so to speak. It does not deliver value by itself. With a password manager software this might be different. There security might be a Primary Quality. Please get me right: I don´t want to denigrate any Quality. There´s a long list of non-functional requirements at Wikipedia. They are all created equal - but that does not mean they are equally important for all software projects. When confronted with Quality requirements check with the customer which are primary and which are secondary. That will help to make good economical decisions when in a crunch. Resources are always limited - but requirements are a bottomless ocean. Aspects of Security of Investment Functionality and Quality are traditionally the requirement aspects cared for most - by customers and developers alike. Even today, when pressure rises in a project, tunnel vision will focus on them. Any measures to create and hold up Security of Investment (SoI) will be out of the window pretty quickly. Resistance to customers and/or management is futile. As long as SoI is not placed on equal footing with Functionality and Quality it´s bound to suffer under pressure. To look closer at what SoI means will help to become more conscious about it and make customers and management aware of the risks of neglecting it. SoI to me has two facets: Production Efficiency (PE) is about speed of delivering value. Customers like short response times. Short response times mean less money spent. So whatever makes software development faster supports this requirement. This must not lead to duct tape programming and banging out features by the dozen, though. Because customers don´t just want Operations and Quality, but also Correctness. So if Correctness gets compromised by focussing too much on Production Efficiency it will fire back. Customers want PE not just today, but over the whole course of a software´s lifecycle. That means, it´s not just about coding speed, but equally about code quality. If code quality leads to rework the PE is on an unsatisfactory level. Also if code production leads to waste it´s unsatisfactory. Because the effort which went into waste could have been used to produce value. Rework and waste cost money. Rework and waste abound, however, as long as PE is not addressed explicitly with management and customers. Thanks to the Agile and Lean movements that´s increasingly the case. Nevertheless more could and should be done in many teams. Each and every developer should keep in mind that Production Efficiency is as important to the customer as Functionality and Quality - whether he/she states it or not. Making software development more efficient is important - but still sooner or later even agile projects are going to hit a glas ceiling. At least as long as they neglect the second SoI facet: Evolvability. Delivering correct high quality functionality in short cycles today is good. But not just any software structure will allow this to happen for an indefinite amount of time.[1] The less explicitly software was designed the sooner it´s going to get stuck. Big ball of mud, monolith, brownfield, legacy code, technical debt… there are many names for software structures that have lost the ability to evolve, to be easily changed to accomodate new requirements. An evolvable code base is the opposite of a brownfield. It´s code which can be easily understood (by developers with sufficient domain expertise) and then easily changed to accomodate new requirements. Ideally the costs of adding feature X to an evolvable code base is independent of when it is requested - or at least the costs should only increase linearly, not exponentially.[2] Clean Code, Agile Architecture, and even traditional Software Engineering are concerned with Evolvability. However, it seems no systematic way of achieving it has been layed out yet. TDD + SOLID help - but still… When I look at the design ability reality in teams I see much room for improvement. As stated previously, SoI - or to be more precise: Evolvability - can hardly be measured. Plus the customer rarely states an explicit expectation with regard to it. That´s why I think, special care must be taken to not neglect it. Postponing it to some large refactorings should not be an option. Rather Evolvability needs to be a core concern for every single developer day. This should not mean Evolvability is more important than any of the other requirement aspects. But neither is it less important. That´s why more effort needs to be invested into it, to bring it on par with the other aspects, which usually are much more in focus. In closing As you see, requirements are of quite different kinds. To not take that into account will make it harder to understand the customer, and to make economic decisions. Those sub-aspects of requirements are forces pulling in different directions. To improve performance might have an impact on Evolvability. To increase Production Efficiency might have an impact on security etc. No requirement aspect should go unchecked when deciding how to allocate resources. Balancing should be explicit. And it should be possible to trace back each decision to a requirement. Why is there a null-check on parameters at the start of the method? Why are there 5000 LOC in this method? Why are there interfaces on those classes? Why is this functionality running on the threadpool? Why is this function defined on that class? Why is this class depending on three other classes? These and a thousand more questions are not to mean anything should be different in a code base. But it´s important to know the reason behind all of these decisions. Because not knowing the reason possibly means waste and having decided suboptimally. And how do we ensure to balance all requirement aspects? That needs practices and transparency. Practices means doing things a certain way and not another, even though that might be possible. We´re dealing with dangerous tools here. Like a knife is a dangerous tool. Harm can be done if we use our tools in just any way at the whim of the moment. Over the centuries rules and practices have been established how to use knifes. You don´t put them in peoples´ legs just because you´re feeling like it. You hand over a knife with the handle towards the receiver. You might not even be allowed to cut round food like potatos or eggs with it. The same should be the case for dangerous tools like object-orientation, remote communication, threads etc. We need practices to use them in a way so requirements are balanced almost automatically. In addition, to be able to work on software as a team we need transparency. We need means to share our thoughts, to work jointly on mental models. So far our tools are focused on working with code. Testing frameworks, build servers, DI containers, intellisense, refactoring support… That´s all nice and well. I don´t want to miss any of that. But I think it´s not enough. We´re missing mental tools, tools for making thinking and talking about software (independently of code) easier. You might think, enough of such tools already exist like all those UML diagram types or Flow Charts. But then, isn´t it strange, hardly any team is using them to design software? Or is that just due to a lack of education? I don´t think so. It´s a matter value/weight ratio: the current mental tools are too heavy weight compared to the value they deliver. So my conclusion is, we need lightweight tools to really be able to balance requirements. Software development is complex. We need guidance not to forget important aspects. That´s like with flying an airplane. Pilots don´t just jump in and take off for their destination. Yes, there are times when they are “flying by the seats of their pants”, when they are just experts doing thing intuitively. But most of the time they are going through honed practices called checklist. See “The Checklist Manifesto” for very enlightening details on this. Maybe then I should say it like this: We need more checklists for the complex businss of software development.[3] But that´s what software development mostly is about: changing software over an unknown period of time. It needs to be corrected in order to finally provide promised operations. It needs to be enhanced to provide ever more operations and qualities. All this without knowing when it´s going to stop. Probably never - until “maintainability” hits a wall when the technical debt is too large, the brownfield too deep. Software development is not a sprint, is not a marathon, not even an ultra marathon. Because to all this there is a foreseeable end. Software development is like continuously and foreever running… ? And sometimes I dare to think that costs could even decrease over time. Think of it: With each feature a software becomes richer in functionality. So with each additional feature the chance of there being already functionality helping its implementation increases. That should lead to less costs of feature X if it´s requested later than sooner. X requested later could stand on the shoulders of previous features. Alas, reality seems to be far from this despite 20+ years of admonishing developers to think in terms of reusability.[1] ? Please don´t get me wrong: I don´t want to bog down the “art” of software development with heavyweight practices and heaps of rules to follow. The framework we need should be lightweight. It should not stand in the way of delivering value to the customer. It´s purpose is even to make that easier by helping us to focus and decreasing waste and rework. ?

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• UI design in flash games

  - by anon

  This question is more UI/Design-ish than hard-core programming is. Background: I've been coding in VIM/C++/OpenGL for a long time. I've come to realize that this (VIM/C++/OpenGL) isn't the way to learn about programming fancy/cool-looking/futuristic UIs; and that the design of such UIs belongs more so in the artistic/designer world of Flash. Anyway, I currently have a machine with MacOSX. What software should I install? What book should I read to learn about the artistic/design side of these futuristic UIs? [It's okay if the tools to design them are mouse clicking + graphical rather than coding based]. Question: what software packages + books to read to learn about creating fancy-looking / futuristic UIs in flash? Thanks! EDIT: PS these questions seem to get closed frequently. If you're going to vote to close for "duplicate question"; atleast provide a link to the question (with an answer).

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• Give WPF design mode default objects

  - by Janko R

  In my application I have <Rectangle.Margin> <MultiBinding Converter="{StaticResource XYPosToThicknessConverter}"> <Binding Path="XPos"/> <Binding Path="YPos"/> </MultiBinding> </Rectangle.Margin> The Data Context is set during runtime. The application works, but the design window in VS does not show a preview but System.InvalidCastException. That’s why I added a default object in the XYPosToThicknessConverter which is ugly. class XYPosToThicknessConverter : IMultiValueConverter { public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture) { // stupid check to give the design window its default object. if (!(values[0] is IConvertible)) return new System.Windows.Thickness(3, 3, 0, 0); // useful code and exception throwing starts here // ... } } My Questions: What does VS/the process that builds the design window pass to XYPosToThicknessConverter and what is way to find it out by myself. How do I change my XAML code, so that the design window gets its default object and is this the best way to handle this problem? I’m using VS2010RC with Net4.0

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• When virtual inheritance IS a good design?

  - by 7vies

  EDIT3: Please be sure to clearly understand what I am asking before answering (there are EDIT2 and lots of comments around). There are (or were) many answers which clearly show misunderstanding of the question (I know that's also my fault, sorry for that) Hi, I've looked over the questions on virtual inheritance (class B: public virtual A {...}) in C++, but did not find an answer to my question. I know that there are some issues with virtual inheritance, but what I'd like to know is in which cases virtual inheritance would be considered a good design. I saw people mentioning interfaces like IUnknown or ISerializable, and also that iostream design is based on virtual inheritance. Would those be good examples of a good use of virtual inheritance, is that just because there is no better alternative, or because virtual inheritance is the proper design in this case? Thanks. EDIT: To clarify, I'm asking about real-life examples, please don't give abstract ones. I know what virtual inheritance is and which inheritance pattern requires it, what I want to know is when it is the good way to do things and not just a consequence of complex inheritance. EDIT2: In other words, I want to know when the diamond hierarchy (which is the reason for virtual inheritance) is a good design

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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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• Automating Solaris 11 Zones Installation Using The Automated Install Server

  - by Orgad Kimchi

  Introduction How to use the Oracle Solaris 11 Automated install server in order to automate the Solaris 11 Zones installation. In this document I will demonstrate how to setup the Automated Install server in order to provide hands off installation process for the Global Zone and two Non Global Zones located on the same system. Architecture layout: Figure 1. Architecture layout Prerequisite Setup the Automated install server (AI) using the following instructions “How to Set Up Automated Installation Services for Oracle Solaris 11” The first step in this setup will be creating two Solaris 11 Zones configuration files. Step 1: Create the Solaris 11 Zones configuration files  The Solaris Zones configuration files should be in the format of the zonecfg export command. # zonecfg -z zone1 export > /var/tmp/zone1# cat /var/tmp/zone1 create -b set brand=solaris set zonepath=/rpool/zones/zone1 set autoboot=true set ip-type=exclusive add anet set linkname=net0 set lower-link=auto set configure-allowed-address=true set link-protection=mac-nospoof set mac-address=random end  Create a backup copy of this file under a different name, for example, zone2. # cp /var/tmp/zone1 /var/tmp/zone2 Modify the second configuration file with the zone2 configuration information You should change the zonepath for example: set zonepath=/rpool/zones/zone2 Step2: Copy and share the Zones configuration files  Create the NFS directory for the Zones configuration files # mkdir /export/zone_config Share the directory for the Zones configuration file # share –o ro /export/zone_config Copy the Zones configuration files into the NFS shared directory # cp /var/tmp/zone1 /var/tmp/zone2  /export/zone_config Verify that the NFS share has been created using the following command # share export_zone_config      /export/zone_config     nfs     sec=sys,ro Step 3: Add the Global Zone as client to the Install Service Use the installadm create-client command to associate client (Global Zone) with the install service To find the MAC address of a system, use the dladm command as described in the dladm(1M) man page. The following command adds the client (Global Zone) with MAC address 0:14:4f:2:a:19 to the s11x86service install service. # installadm create-client -e “0:14:4f:2:a:19" -n s11x86service You can verify the client creation using the following command # installadm list –c Service Name  Client Address     Arch   Image Path ------------  --------------     ----   ---------- s11x86service 00:14:4F:02:0A:19  i386   /export/auto_install/s11x86service We can see the client install service name (s11x86service), MAC address (00:14:4F:02:0A:19 and Architecture (i386). Step 4: Global Zone manifest setup  First, get a list of the installation services and the manifests associated with them: # installadm list -m Service Name   Manifest        Status ------------   --------        ------ default-i386   orig_default   Default s11x86service  orig_default   Default Then probe the s11x86service and the default manifest associated with it. The -m switch reflects the name of the manifest associated with a service. Since we want to capture that output into a file, we redirect the output of the command as follows: # installadm export -n s11x86service -m orig_default >  /var/tmp/orig_default.xml Create a backup copy of this file under a different name, for example, orig-default2.xml, and edit the copy. # cp /var/tmp/orig_default.xml /var/tmp/orig_default2.xml Use the configuration element in the AI manifest for the client system to specify non-global zones. Use the name attribute of the configuration element to specify the name of the zone. Use the source attribute to specify the location of the config file for the zone.The source location can be any http:// or file:// location that the client can access during installation. The following sample AI manifest specifies two Non-Global Zones: zone1 and zone2 You should replace the server_ip with the ip address of the NFS server. <!DOCTYPE auto_install SYSTEM "file:///usr/share/install/ai.dtd.1"> <auto_install>   <ai_instance>     <target>       <logical>         <zpool name="rpool" is_root="true">           <filesystem name="export" mountpoint="/export"/>           <filesystem name="export/home"/>           <be name="solaris"/>         </zpool>       </logical>     </target>     <software type="IPS">       <source>         <publisher name="solaris">           <origin name="http://pkg.oracle.com/solaris/release"/>         </publisher>       </source>       <software_data action="install">         <name>pkg:/entire@latest</name>         <name>pkg:/group/system/solaris-large-server</name>       </software_data>     </software>     <configuration type="zone" name="zone1" source="file:///net/server_ip/export/zone_config/zone1"/>     <configuration type="zone" name="zone2" source="file:///net/server_ip/export/zone_config/zone2"/>   </ai_instance> </auto_install> The following example adds the /var/tmp/orig_default2.xml AI manifest to the s11x86service install service # installadm create-manifest -n s11x86service -f /var/tmp/orig_default2.xml -m gzmanifest You can verify the manifest creation using the following command # installadm list -n s11x86service  -m Service/Manifest Name  Status   Criteria ---------------------  ------   -------- s11x86service    orig_default        Default  None    gzmanifest          Inactive None We can see from the command output that the new manifest named gzmanifest has been created and associated with the s11x86service install service. Step 5: Non Global Zone manifest setup The AI manifest for non-global zone installation is similar to the AI manifest for installing the global zone. If you do not provide a custom AI manifest for a non-global zone, the default AI manifest for Zones is used The default AI manifest for Zones is available at /usr/share/auto_install/manifest/zone_default.xml. In this example we should use the default AI manifest for zones The following sample default AI manifest for zones # cat /usr/share/auto_install/manifest/zone_default.xml <?xml version="1.0" encoding="UTF-8"?> <!--  Copyright (c) 2011, 2012, Oracle and/or its affiliates. All rights reserved. --> <!DOCTYPE auto_install SYSTEM "file:///usr/share/install/ai.dtd.1"> <auto_install>     <ai_instance name="zone_default">         <target>             <logical>                 <zpool name="rpool">                     <!--                       Subsequent <filesystem> entries instruct an installer                       to create following ZFS datasets:                           <root_pool>/export         (mounted on /export)                           <root_pool>/export/home    (mounted on /export/home)                       Those datasets are part of standard environment                       and should be always created.                       In rare cases, if there is a need to deploy a zone                       without these datasets, either comment out or remove                       <filesystem> entries. In such scenario, it has to be also                       assured that in case of non-interactive post-install                       configuration, creation of initial user account is                       disabled in related system configuration profile.                       Otherwise the installed zone would fail to boot.                     -->                     <filesystem name="export" mountpoint="/export"/>                     <filesystem name="export/home"/>                     <be name="solaris">                         <options>                             <option name="compression" value="on"/>                         </options>                     </be>                 </zpool>             </logical>         </target>         <software type="IPS">             <destination>                 <image>                     <!-- Specify locales to install -->                     <facet set="false">facet.locale.*</facet>                     <facet set="true">facet.locale.de</facet>                     <facet set="true">facet.locale.de_DE</facet>                     <facet set="true">facet.locale.en</facet>                     <facet set="true">facet.locale.en_US</facet>                     <facet set="true">facet.locale.es</facet>                     <facet set="true">facet.locale.es_ES</facet>                     <facet set="true">facet.locale.fr</facet>                     <facet set="true">facet.locale.fr_FR</facet>                     <facet set="true">facet.locale.it</facet>                     <facet set="true">facet.locale.it_IT</facet>                     <facet set="true">facet.locale.ja</facet>                     <facet set="true">facet.locale.ja_*</facet>                     <facet set="true">facet.locale.ko</facet>                     <facet set="true">facet.locale.ko_*</facet>                     <facet set="true">facet.locale.pt</facet>                     <facet set="true">facet.locale.pt_BR</facet>                     <facet set="true">facet.locale.zh</facet>                     <facet set="true">facet.locale.zh_CN</facet>                     <facet set="true">facet.locale.zh_TW</facet>                 </image>             </destination>             <software_data action="install">                 <name>pkg:/group/system/solaris-small-server</name>             </software_data>         </software>     </ai_instance> </auto_install> (optional) We can customize the default AI manifest for Zones Create a backup copy of this file under a different name, for example, zone_default2.xml and edit the copy # cp /usr/share/auto_install/manifest/zone_default.xml /var/tmp/zone_default2.xml Edit the copy (/var/tmp/zone_default2.xml) The following example adds the /var/tmp/zone_default2.xml AI manifest to the s11x86service install service and specifies that zone1 and zone2 should use this manifest. # installadm create-manifest -n s11x86service -f /var/tmp/zone_default2.xml -m zones_manifest -c zonename="zone1 zone2" Note: Do not use the following elements or attributes in a non-global zone AI manifest:     The auto_reboot attribute of the ai_instance element     The http_proxy attribute of the ai_instance element     The disk child element of the target element     The noswap attribute of the logical element     The nodump attribute of the logical element     The configuration element Step 6: Global Zone profile setup We are going to create a global zone configuration profile which includes the host information for example: host name, ip address name services etc… # sysconfig create-profile –o /var/tmp/gz_profile.xml You need to provide the host information for example:     Default router     Root password     DNS information The output should eventually disappear and be replaced by the initial screen of the System Configuration Tool (see Figure 2), where you can do the final configuration. Figure 2. Profile creation menu You can validate the profile using the following command # installadm validate -n s11x86service –P /var/tmp/gz_profile.xml Validating static profile gz_profile.xml...  Passed Next, instantiate a profile with the install service. In our case, use the following syntax for doing this # installadm create-profile -n s11x86service  -f /var/tmp/gz_profile.xml -p  gz_profile You can verify profile creation using the following command # installadm list –n s11x86service  -p Service/Profile Name  Criteria --------------------  -------- s11x86service    gz_profile         None We can see that the gz_profie has been created and associated with the s11x86service Install service. Step 7: Setup the Solaris Zones configuration profiles The step should be similar to the Global zone profile creation on step 6 # sysconfig create-profile –o /var/tmp/zone1_profile.xml # sysconfig create-profile –o /var/tmp/zone2_profile.xml You can validate the profiles using the following command # installadm validate -n s11x86service -P /var/tmp/zone1_profile.xml Validating static profile zone1_profile.xml...  Passed # installadm validate -n s11x86service -P /var/tmp/zone2_profile.xml Validating static profile zone2_profile.xml...  Passed Next, associate the profiles with the install service The following example adds the zone1_profile.xml configuration profile to the s11x86service  install service and specifies that zone1 should use this profile. # installadm create-profile -n s11x86service  -f  /var/tmp/zone1_profile.xml -p zone1_profile -c zonename=zone1 The following example adds the zone2_profile.xml configuration profile to the s11x86service  install service and specifies that zone2 should use this profile. # installadm create-profile -n s11x86service  -f  /var/tmp/zone2_profile.xml -p zone2_profile -c zonename=zone2 You can verify the profiles creation using the following command # installadm list -n s11x86service -p Service/Profile Name  Criteria --------------------  -------- s11x86service    zone1_profile      zonename = zone1    zone2_profile      zonename = zone2    gz_profile         None We can see that we have three profiles in the s11x86service  install service     Global Zone  gz_profile     zone1            zone1_profile     zone2            zone2_profile. Step 8: Global Zone setup Associate the global zone client with the manifest and the profile that we create in the previous steps The following example adds the manifest and profile to the client (global zone), where: gzmanifest  is the name of the manifest. gz_profile  is the name of the configuration profile. mac="0:14:4f:2:a:19" is the client (global zone) mac address s11x86service is the install service name. # installadm set-criteria -m  gzmanifest  –p  gz_profile  -c mac="0:14:4f:2:a:19" -n s11x86service You can verify the manifest and profile association using the following command # installadm list -n s11x86service -p  -m Service/Manifest Name  Status   Criteria ---------------------  ------   -------- s11x86service    gzmanifest                   mac  = 00:14:4F:02:0A:19    orig_default        Default  None Service/Profile Name  Criteria --------------------  -------- s11x86service    gz_profile         mac      = 00:14:4F:02:0A:19    zone2_profile      zonename = zone2    zone1_profile      zonename = zone1 Step 9: Provision the host with the Non-Global Zones The next step is to boot the client system off the network and provision it using the Automated Install service that we just set up. First, boot the client system. Figure 3 shows the network boot attempt (when done on an x86 system): Figure 3. Network Boot Then you will be prompted by a GRUB menu, with a timer, as shown in Figure 4. The default selection (the "Text Installer and command line" option) is highlighted.  Press the down arrow to highlight the second option labeled Automated Install, and then press Enter. The reason we need to do this is because we want to prevent a system from being automatically re-installed if it were to be booted from the network accidentally. Figure 4. GRUB Menu What follows is the continuation of a networked boot from the Automated Install server,. The client downloads a mini-root (a small set of files in which to successfully run the installer), identifies the location of the Automated Install manifest on the network, retrieves that manifest, and then processes it to identify the address of the IPS repository from which to obtain the desired software payload. Non-Global Zones are installed and configured on the first reboot after the Global Zone is installed. You can list all the Solaris Zones status using the following command # zoneadm list -civ Once the Zones are in running state you can login into the Zone using the following command # zlogin –z zone1 Troubleshooting Automated Installations If an installation to a client system failed, you can find the client log at /system/volatile/install_log. NOTE: Zones are not installed if any of the following errors occurs:     A zone config file is not syntactically correct.     A collision exists among zone names, zone paths, or delegated ZFS datasets in the set of zones to be installed     Required datasets are not configured in the global zone. For more troubleshooting information see “Installing Oracle Solaris 11 Systems” Conclusion This paper demonstrated the benefits of using the Automated Install server to simplify the Non Global Zones setup, including the creation and configuration of the global zone manifest and the Solaris Zones profiles.

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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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• As a web designer, which language should I learn first for my feature career? (PHP or JavaScript) [closed]

  - by kdevs3

  Possible Duplicates: Best Programming Language for Web Development How can I choose a web development language? What language will you choose if you are going to build something big? What is the right option of programming languages and tools for building our website? What is the easiest web programing language at....? Well, I'm more of a basic web designer. I know the easy stuff pretty well. (Ya know, html, css) But I've been trying to take it to the next step and I'm contemplating about what I should learn that will help me out the most in my future web design/programming career, should it be JavaScript or maybe I should try to learn a back end programming language such as PHP. Lately, I have been hearing about a lot how JavaScript is so great and useful now, because of libraries such as jQuery and what possibility's it can bring by using Node.js and other frameworks. I've only learned the most basic of JavaScript and used some jQuery (mostly plugins) so i wouldn't know at all of what it can actually do. Would JS being so popular as it is now and useful, be a reason to stick with JavaScript and only learn it that for now? Or as a web designer, how important would it be to learn how to make a web application/website operate and functional, and know how to work with servers, etc? (Such as getting forms to work and sending data to the server and back) I've took a look at frameworks such as Code Igniter before, and looks really simple to get started with if I try to learn PHP, But I'm not sure how important it is for my career and what I would gain out of it. I'm asking because I can't decide what I should learn first. When I select it, I really want to take my time and learn the language. I don't want to spend time on learning multiple languages at the same time, so I need to pick wisely. I'm trying to turn the right direction so my career can hopefully be successful in the feature. (If money/gaining a job asked if its important, then its a yeah, it is a bit) I'm hoping I can get opinions and suggestions on this question, thanks for giving me your thoughts also.

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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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• Programming and Ubiquitous Language (DDD) in a non-English domain

  - by Sandor Drieënhuizen

  I know there are some questions already here that are closely related to this subject but none of them take Ubiquitous Language as the starting point so I think that justifies this question. For those who don't know: Ubiquitous Language is the concept of defining a (both spoken and written) language that is equally used across developers and domain experts to avoid inconsistencies and miscommunication due to translation problems and misunderstanding. You will see the same terminology show up in code, conversations between any team member, functional specs and whatnot. So, what I was wondering about is how to deal with Ubiquitous Language in non-English domains. Personally, I strongly favor writing programming code in English completely, including comments but ofcourse excluding constants and resources. However, in a non-English domain, I'm forced to make a decision either to: Write code reflecting the Ubiquitous Language in the natural language of the domain. Translate the Ubiquitous Language to English and stop communicating in the natural language of the domain. Define a table that defines how the Ubiquitous Language translates to English. Here are some of my thoughts based on these options: 1) I have a strong aversion against mixed-language code, that is coding using type/member/variable names etc. that are non-English. Most programming languages 'breathe' English to a large extent and most of the technical literature, design pattern names etc. are in English as well. Therefore, in most cases there's just no way of writing code entirely in a non-English language so you end up with mixed languages anyway. 2) This will force the domain experts to start thinking and talking in the English equivalent of the UL, something that will probably not come naturally to them and therefore hinders communication significantly. 3) In this case, the developers communicate with the domain experts in their native language while the developers communicate with each other in English and most importantly, they write code using the English translation of the UL. I'm sure I don't want to go for the first option and I think option 3 is much better than option 2. What do you think? Am I missing other options? UPDATE Today, about year later, having dealt with this issue on a daily basis, I have to say that option 3 has worked out pretty well for me. It wasn't as tedious as I initially feared and translating in real time while talking to the client wasn't a problem either. I also found the following advantages to be true, based on my experience. Translating the UL makes you pay more attention to defining the UL and even the domain itself, especially when you don't know how to translate a term and you have to start looking through dictionaries etc. This has even caused me to reconsider domain modeling decisions a few times. It helps you make your knowledge of the English language more profound. Obviously, your code is much more pleasant to look at instead of being a mind boggling obscenity.

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• Designing for an algorithm that reports progress

  - by Stefano Borini

  I have an iterative algorithm and I want to print the progress. However, I may also want it not to print any information, or to print it in a different way, or do other logic. In an object oriented language, I would perform the following solutions: Solution 1: virtual method have the algorithm class MyAlgoClass which implements the algo. The class also implements a virtual reportIteration(iterInfo) method which is empty and can be reimplemented. Subclass the MyAlgoClass and override reportIteration so that it does what it needs to do. This solution allows you to carry additional information (for example, the file unit) in the reimplemented class. I don't like this method because it clumps together two functionalities that may be unrelated, but in GUI apps it may be ok. Solution 2: observer pattern the algorithm class has a register(Observer) method, keeps a list of the registered observers and takes care of calling notify() on each of them. Observer::notify() needs a way to get the information from the Subject, so it either has two parameters, one with the Subject and the other with the data the Subject may pass, or just the Subject and the Observer is now in charge of querying it to fetch the relevant information. Solution 3: callbacks I tend to see the callback method as a lightweight observer. Instead of passing an object, you pass a callback, which may be a plain function, but also an instance method in those languages that allow it (for example, in python you can because passing an instance method will remain bound to the instance). C++ however does not allow it, because if you pass a pointer to an instance method, this will not be defined. Please correct me on this regard, my C++ is quite old. The problem with callbacks is that generally you have to pass them together with the data you want the callback to be invoked with. Callbacks don't store state, so you have to pass both the callback and the state to the Subject in order to find it at callback execution, together with any additional data the Subject may provide about the event is reporting. Question My question is relative to the fact that I need to implement the opening problem in a language that is not object oriented, namely Fortran 95, and I am fighting with my usual reasoning which is based on python assumptions and style. I think that in Fortran the concept is similar to C, with the additional trouble that in C you can store a function pointer, while in Fortran 95 you can only pass it around. Do you have any comments, suggestions, tips, and quirks on this regard (in C, C++, Fortran and python, but also in any other language, so to have a comparison of language features that can be exploited on this regard) on how to design for an algorithm that must report progress to some external entity, using state from both the algorithm and the external entity ?

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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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• 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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