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  • How should I structure the implementation of turn-based board game rules?

    - by Setzer22
    I'm trying to create a turn-based strategy game on a tilemap. I'm using design by component so far, but I can't find a nice way to fit components into the part I want to ask. I'm struggling with the "game rules" logic. That is, the code that displays the menu, allows the player to select units, and command them, then tells the unit game objects what to do given the player input. The best way I could thing of handling this was using a big state machine, so everything that could be done in a "turn" is handled by this state machine, and the update code of this state machine does different things depending on the state. However, this approach leads to a large amount of code (anything not model-related) going into a big class. Of course I can subdivide this big class into more classes, but it doesn't feel modular and upgradable enough. I'd like to know of better systems to handle this in order to be able to upgrade the game with new rules without having a monstruous if/else chain (or switch / case, for that matter). Any ideas? What specific design pattern other than MVC should I be using?

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  • JavaScript and callback nesting

    - by Jake King
    A lot of JavaScript libraries (notably jQuery) use chaining, which allows the reduction of this: var foo = $(".foo"); foo.stop(); foo.show(); foo.animate({ top: 0 }); to this: $(".foo").stop().show().animate({ top: 0 }); With proper formatting, I think this is quite a nice syntactic capability. However, I often see a pattern which I don't particularly like, but appears to be a necessary evil in non-blocking models. This is the ever-present nesting of callback functions: $(".foo").animate({ top: 0, }, { callback: function () { $.ajax({ url: 'ajax.php', }, { callback: function () { ... } }); } }); And it never ends. Even though I love the ease non-blocking models provide, I hate the odd nesting of function literals it forces upon the programmer. I'm interesting in writing a small JS library as an exercise, and I'd love to find a better way to do this, but I don't know how it could be done without feeling hacky. Are there any projects out there that have resolved this problem before? And if not, what are the alternatives to this ugly, meaningless code structure?

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  • Data Access Objects old fashioned? [on hold]

    - by Bono
    A couple of weeks ago I delivered some work for a university project. After a code review with some teachers I got some snarky remarks about the fact that I was (still) using Data Access Objects. The teacher in question who said this mentions the use of DAO's in his classes and always says something along the lines of "Back then we always used DAO's". He's a big fan of Object Relational Mapping, which I also think is a great tool. When I was talking about this with some of my fellow students, they also mentioned that they prefer the use of ORM, which I can understand. It did make me wonder though, is using DAO's really so old fashioned? I know that at my work DAO's are still being used, but this is due to the fact that some of the code is rather old and therefor can't be coupled with ORM. We also do use ORM at my work. Trying to find some more information on Google or Stack Exchange sites didn't really enlighten me. Should I step away from the use of DAO's and only start implementing ORM? I just feel that ORM's can be a bit overkill for some simple projects. I'd love to hear your opinions (or facts) about this.

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  • Correct way to inject dependencies in Business logic service?

    - by Sri Harsha Velicheti
    Currently the structure of my application is as below Web App -- WCF Service (just a facade) -- Business Logic Services -- Repository - Entity Framework Datacontext Now each of my Business logic service is dependent on more than 5 repositories ( I have interfaces defined for all the repos) and I am doing a Constructor injection right now(poor mans DI instead of using a proper IOC as it was determined that it would be a overkill for our project). Repositories have references to EF datacontexts. Now some of the methods in the Business logic service require only one of the 5 repositories, so If I need to call that method I would end up instantiating a Service which will instatiate all 5 repositories which is a waste. An example: public class SomeService : ISomeService { public(IFirstRepository repo1, ISecondRepository repo2, IThirdRepository repo3) {} // My DoSomething method depends only on repo1 and doesn't use repo2 and repo3 public DoSomething() { //uses repo1 to do some stuff, doesn't use repo2 and repo3 } public DoSomething2() { //uses repo2 and repo3 to do something, doesn't require repo1 } public DoSomething3() { //uses repo3 to do something, doesn't require repo1 and repo2 } } Now if my I have to use DoSomething method on SomeService I end up creating both IFirstRepository,ISecondRepository and IThirdRepository but using only IFirstRepository, now this is bugging me, I can seem to accept that I am un-necessarily creating repositories and not using them. Is this a correct design? Are there any better alternatives? Should I be looking at Lazy instantiation Lazy<T> ?

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  • I know of three ways in which SRP helps reduce coupling. Are there even more? [closed]

    - by user1483278
    I'd like to figure all the possible ways SRP helps us reduce coupling. Thus far I can think of three: 1) If class A has more than one responsibility, these responsibilities become coupled and as such changes to one of these responsibilities may require changes to other of A's responsibilities. 2) Related functionality usually needs to be changed for the same reason and by grouping it togerther in a single class, the changes can be made in as few places as possible ( at best changes only need be made to the class which groups together these functionalities) 3) Assuming class A performs two tasks ( thus may change for two reasons ), then number of classes utilising A will be greater than if A performed just a single task ( reason being that some classes will need A to perform first task, other will need A for second task, and still others will utilise it for both tasks ).This also means that when A breaks, the number of classes ( utilising A ) being impaired will be greater than if A performed just a single task. Can SRP also help reduce coupling in any other way, not described above? Thank you

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  • Implenting ActiveRecord with inheritance?

    - by King
    I recently converted an old application that was using XML files as the data store to use SQL instead. To avoid a lot of changes I basically created ActiveRecord style classes that inherited from the original business objects. For example SomeClassRecord :SomeClass //ID Property //Save method I then used this new class in place of the other one, because of polymorphism I didn't need to change any methods that took SomeClass as a parameter. Would this be considered 'Bad'? What would be a better alternative?

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  • How to choose between using a Domain Event, or letting the application layer orchestrate everything

    - by Mr Happy
    I'm setting my first steps into domain driven design, bought the blue book and all, and I find myself seeing three ways to implement a certain solution. For the record: I'm not using CQRS or Event Sourcing. Let's say a user request comes into the application service layer. The business logic for that request is (for whatever reason) separated into a method on an entity, and a method on a domain service. How should I go about calling those methods? The options I have gathered so far are: Let the application service call both methods Use method injection/double dispatch to inject the domain service into the entity, letting the entity do it's thing and then let it call the method of the domain service (or the other way around, letting the domain service call the method on the entity) Raise a domain event in the entity method, a handler of which calls the domain service. (The kind of domain events I'm talking about are: http://www.udidahan.com/2009/06/14/domain-events-salvation/) I think these are all viable, but I'm unable to choose between them. I've been thinking about this a long time and I've come to a point where I no longer see the semantic differences between the three. Do you know of some guidelines when to use what?

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  • Pending and Approval process

    - by zen
    So let's say I have a DB table with 8 columns, one is a unique auto-incrementing used as ID. So I have a page that pulls in the info for each row based on query string ID. I want to give my users the ability to propose changes. Kinda like a wiki setup. So I was thinking I should just have another duplicate table or maybe database altogether (without the auto-incrementing column and maybe with a date edited column) that keeps all proposed changes in queue and then when I approve them, the script can move the row from the proposed DB to the real DB. Does this sound good or is there a better process for this?

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  • Can you recommend a good test plan template?

    - by Ethel Evans
    Can you recommend a good test plan template for an agile testing team? I know there are templates for testing on the web and have already looked at some found by search engines, but I could really use something lightweight and something that has already been tried by skilled testers and is known to work well. Many templates I've seen give me the feeling that writing test documents is expected to be a third of the work that those testers are doing, but my team really prefers to use less documentation and more actual test writing. We use a wiki for documentation, so an approach that lends itself to living documents would be great. My hope is that using a more structured approach to test planning will increase the usefulness of my test plan while reducing the effort to create it by allowing me to think about the tests, and not the format and structure of the plan. My workplace does not have something already on hand, so whatever I start doing might be adopted by the company.

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  • Help with MVC design pattern?

    - by user3681240
    I am trying to build a java program for user login but I am not sure if my MVC design is accurate. I have the following classes: LoginControl - servlet LoginBean - data holder java class with private variables getters and setters LoginDAO - concrete java class where I am running my SQL queries and doing rest of the logical work. Connection class - java class just to connect to the database view - jsp to display the results html - used for form Is this how you design a java program based on MVC design pattern? Please provide some suggestions?

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  • Where we should put validation for domain model

    - by adisembiring
    I still looking best practice for domain model validation. Is that good to put the validation in constructor of domain model ? my domain model validation example as follows: public class Order { private readonly List<OrderLine> _lineItems; public virtual Customer Customer { get; private set; } public virtual DateTime OrderDate { get; private set; } public virtual decimal OrderTotal { get; private set; } public Order (Customer customer) { if (customer == null) throw new ArgumentException("Customer name must be defined"); Customer = customer; OrderDate = DateTime.Now; _lineItems = new List<LineItem>(); } public void AddOderLine //.... public IEnumerable<OrderLine> AddOderLine { get {return _lineItems;} } } public class OrderLine { public virtual Order Order { get; set; } public virtual Product Product { get; set; } public virtual int Quantity { get; set; } public virtual decimal UnitPrice { get; set; } public OrderLine(Order order, int quantity, Product product) { if (order == null) throw new ArgumentException("Order name must be defined"); if (quantity <= 0) throw new ArgumentException("Quantity must be greater than zero"); if (product == null) throw new ArgumentException("Product name must be defined"); Order = order; Quantity = quantity; Product = product; } } Thanks for all of your suggestion.

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  • Is this a pattern? Should it be?

    - by Arkadiy
    The following is more of a statement than a question - it describes something that may be a pattern. The question is: is this a known pattern? Or, if it's not, should it be? I've had a situation where I had to iterate over two dissimilar multi-layer data structures and copy information from one to the other. Depending on particular use case, I had around eight different kinds of layers, combined in about eight different combinations: A-B-C B-C A-C D-E A-D-E and so on After a few unsuccessful attempts to factor out the repetition of per-layer iteration code, I realized that the key difficulty in this refactoring was the fact that the bottom level needed access to data gathered at higher levels. To explicitly accommodate this requirement, I introduced IterationContext class with a number of get() and set() methods for accumulating the necessary information. In the end, I had the following class structure: class Iterator { virtual void iterateOver(const Structure &dataStructure1, IterationContext &ctx) const = 0; }; class RecursingIterator : public Iterator { RecursingIterator(const Iterator &below); }; class IterateOverA : public RecursingIterator { virtual void iterateOver(const Structure &dataStructure1, IterationContext &ctx) const { // Iterate over members in dataStructure1 // locate corresponding item in dataStructure2 (passed via context) // and set it in the context // invoke the sub-iterator }; class IterateOverB : public RecursingIterator { virtual void iterateOver(const Structure &dataStructure1, IterationContext &ctx) const { // iterate over members dataStructure2 (form context) // set dataStructure2's item in the context // locate corresponding item in dataStructure2 (passed via context) // invoke the sub-iterator }; void main() { class FinalCopy : public Iterator { virtual void iterateOver(const Structure &dataStructure1, IterationContext &ctx) const { // copy data from structure 1 to structure 2 in the context, // using some data from higher levels as needed } } IterationContext ctx(dateStructure2); IterateOverA(IterateOverB(FinalCopy())).iterate(dataStructure1, ctx); } It so happens that dataStructure1 is a uniform data structure, similar to XML DOM in that respect, while dataStructure2 is a legacy data structure made of various structs and arrays. This allows me to pass dataStructure1 outside of the context for convenience. In general, either side of the iteration or both sides may be passed via context, as convenient. The key situation points are: complicated code that needs to be invoked in "layers", with multiple combinations of layer types possible at the bottom layer, the information from top layers needs to be visible. The key implementation points are: use of context class to access the data from all levels of iteration complicated iteration code encapsulated in implementation of pure virtual function two interfaces - one aware of underlying iterator, one not aware of it. use of const & to simplify the usage syntax.

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  • Do we ethically have the right to use the MAC Address for verification purposes?

    - by Matt Ridge
    I am writing a program, or starting at the very beginning of it, and I am thinking of purchase verification systems as a final step. I will be catering to Macs, PCs, and possibly Linux if all is said and done. I will also be programming this for smartphones as well using C++ and Objective-C. (I am writing a blueprint before going head first into it) That being said, I am not asking for help on doing it yet, but what I’m looking for is a realistic measurement for what could be expected as a viable and ethical option for purchase verification systems. Apple through the Apple Store, and some other stores out there have their own "You bought it" check. I am looking to use a three prong verification system. Email/password 16 to 32 character serial number using alpha/numeric and symbols with Upper and lowercase variants. MAC Address. The first two are in my mind ok, but I have to ask on an ethical standpoint, is a MAC Address to lock the software to said hardware unethical, or is it smart? I understand if an Ethernet card changes if not part of the logic board, or if the logic board changes so does the MAC address, so if that changes it will have to be re-verified, but I have to ask with how everything is today... Is it ethical to actually use the MAC address as a validation key or no? Should I be forward with this kind of verification system or should I keep it hidden as a secret? Yes I know hackers and others will find ways of knowing what I am doing, but in reality this is why I am asking. I know no verification is foolproof, but making it so that its harder to break is something I've always been interested in, and learning how to program is bringing up these questions, because I don't want to assume one thing and find out it's not really accepted in the programming world as a "you shouldn't do that" maneuver... Thanks in advance... I know this is my first programming question, but I am just learning how to program, and I am just making sure I'm not breaking some ethical programmer credo I shouldn't...

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  • What Part of Your Project Should be in Source Code Control?

    - by muffinista
    A fellow developer has started work on a new Drupal project, and the sysadmin has suggested that they should only put the sites/default subdirectory in source control, because it "will make updates easily scriptable." Setting aside that somewhat dubious claim, it raises another question -- what files should be under source control? And is there a situation where some large chunk of files should be excluded? My opinion is that the entire tree for the project should be under control, and this would be true for a Drupal project, rails, or anything else. This seems like a no-brainer -- you clearly need versioning for your framework as much as you do for any custom code you write. That said, I would love to get other opinions on this. Are there any arguments for not having everything under control? Is this sysadmin a BOFH?

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  • Dynamic Components

    - by Alex
    I am attempting to design a component-based architecture that allows Components to be dynamically enabled and disabled, much like the system employed by Unity3D. For example, all Components are implicitly enabled by default; however, if one desires to halt execution of code for a particular Component, one can disable it. Naively, I want to have a boolean flag in Component (which is an abstract class), and somehow serialize all method calls into strings, so that some sort of ComponentManager can check if a given Component is enabled/disabled before processing a method call on it. However, this is a pretty bad solution. I feel like I should employ some variation of the state paradigm, but I have yet to make progress. Any help would be greatly appreciated,

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  • IXRepository and test problems

    - by Ridermansb
    Recently had a doubt about how and where to test repository methods. Let the following situation: I have an interface IRepository like this: public interface IRepository<T> where T: class, IEntity { IQueryable<T> Query(Expression<Func<T, bool>> expression); // ... Omitted } And a generic implementation of IRepository public class Repository<T> : IRepository<T> where T : class, IEntity { public IQueryable<T> Query(Expression<Func<T, bool>> expression) { return All().Where(expression).AsQueryable(); } } This is an implementation base that can be used by any repository. It contains the basic implementation of my ORM. Some repositories have specific filters, in which case we will IEmployeeRepository with a specific filter: public interface IEmployeeRepository : IRepository<Employee> { IQueryable<Employee> GetInactiveEmployees(); } And the implementation of IEmployeeRepository: public class EmployeeRepository : Repository<Employee>, IEmployeeRepository // TODO: I have a dependency with ORM at this point in Repository<Employee>. How to solve? How to test the GetInactiveEmployees method { public IQueryable<Employee> GetInactiveEmployees() { return Query(p => p.Status != StatusEmployeeEnum.Active || p.StartDate < DateTime.Now); } } Questions Is right to inherit Repository<Employee>? The goal is to reuse code once all implementing IRepository already been made. If EmployeeRepository inherit only IEmployeeRepository, I have to literally copy and paste the code of Repository<T>. In our example, in EmployeeRepository : Repository<Employee> our Repository lies in our ORM layer. We have a dependency here with our ORM impossible to perform some unit test. How to create a unit test to ensure that the filter GetInactiveEmployees return all Employees in which the Status != Active and StartDate < DateTime.Now. I can not create a Fake/Mock of IEmployeeRepository because I would be testing? Need to test the actual implementation of GetInactiveEmployees. The complete code can be found on Github

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  • What's is the point of PImpl pattern while we can use interface for same purpose in C++?

    - by ZijingWu
    I see a lot of source code which using PIMPL idiom in C++. I assume Its purposes are hidden the private data/type/implementation, so it can resolve dependence, and then reduce compile time and header include issue. But interface class in C++ also have this capability, it can also used to hidden data/type and implementation. And to hidden let the caller just see the interface when create object, we can add an factory method in it declaration in interface header. The comparison is: Cost: The interface way cost is lower, because you doesn't even need to repeat the public wrapper function implementation void Bar::doWork() { return m_impl->doWork(); }, you just need to define the signature in the interface. Well understand: The interface technology is more well understand by every C++ developer. Performance: Interface way performance not worse than PIMPL idiom, both an extra memory access. I assume the performance is same. Following is the pseudocode code to illustrate my question: // Forward declaration can help you avoid include BarImpl header, and those included in BarImpl header. class BarImpl; class Bar { public: // public functions void doWork(); private: // You doesn't need to compile Bar.cpp after change the implementation in BarImpl.cpp BarImpl* m_impl; }; The same purpose can be implement using interface: // Bar.h class IBar { public: virtual ~IBar(){} // public functions virtual void doWork() = 0; }; // to only expose the interface instead of class name to caller IBar* createObject(); So what's the point of PIMPL?

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  • What to leave when you're leaving

    - by BuckWoody
    There's already a post on this topic - sort of. I read this entry, where the author did a good job on a few steps, but I found that a few other tips might be useful, so if you want to check that one out and then this post, you might be able to put together your own plan for when you leave your job.  I once took over the system administrator (of which the Oracle and SQL Server servers were a part) at a mid-sized firm. The outgoing administrator had about a two- week-long scheduled overlap with me, but was angry at the company and told me "hey, I know this is going to be hard on you, but I want them to know how important I was. I'm not telling you where anything is or what the passwords are. Good luck!" He then quit that day. It took me about three days to find all of the servers and crack the passwords. Yes, the company tried to take legal action against the guy and all that, but he moved back to his home country and so largely got away with it. Obviously, this isn't the way to leave a job. Many of us have changed jobs in the past, and most of us try to be very professional about the transition to a new team, regardless of the feelings about a particular company. I've been treated badly at a firm, but that is no reason to leave a mess for someone else. So here's what you should put into place at a minimum before you go. Most of this is common sense - which of course isn't very common these days - and another good rule is just to ask yourself "what would I want to know"? The article I referenced at the top of this post focuses on a lot of documentation of the systems. I think that's fine, but in actuality, I really don't need that. Even with this kind of documentation, I still perform a full audit on the systems, so in the end I create my own system documentation. There are actually only four big items I need to know to get started with the systems: 1. Where is everything/everybody?The first thing I need to know is where all of the systems are. I mean not only the street address, but the closet or room, the rack number, the IU number in the rack, the SAN luns, all that. A picture here is worth a thousand words, which is why I really like Visio. It combines nice graphics, full text and all that. But use whatever you have to tell someone the physical locations of the boxes. Also, tell them the physical location of the folks in charge of those boxes (in case you aren't) or who share that responsibility. And by "where" in this case, I mean names and phones.  2. What do they do?For both the servers and the people, tell them what they do. If it's a database server, detail what each database does and what application goes to that, and who "owns" that application. In my mind, this is one of hte most important things a Data Professional needs to know. In the case of the other administrtors or co-owners, document each person's responsibilities.   3. What are the credentials?Logging on/in and gaining access to the buildings are things that the new Data Professional will need to do to successfully complete their job. This means service accounts, certificates, all of that. The first thing they should do, of course, is change the passwords on all that, but the first thing they need is the ability to do that!  4. What is out of the ordinary?This is the most tricky, and perhaps the next most important thing to know. Did you have to use a "special" driver for that video card on server X? Is the person that co-owns an application with you mentally unstable (like me) or have special needs, like "don't talk to Buck before he's had coffee. Nothing will make any sense"? Do you have service pack requirements for a specific setup? Write all that down. Anything that took you a day or longer to make work is probably a candidate here. This is my short list - anything you care to add? Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • Is it dangerous for me to give some of my Model classes Control-like methods?

    - by Pureferret
    In my personal project I have tried to stick to MVC, but I've also been made aware that sticking to MVC too tightly can be a bad thing as it makes writing awkward and forces the flow of the program in odd ways (i.e. some simple functions can be performed by something that normally wouldn't, and avoid MVC related overheads). So I'm beginning to feel justified in this compromise: I have some 'manager programs' that 'own' data and have some way to manipulate it, as such I think they'd count as both part of the model, and part of the control, and to me this feels more natural than keepingthem separate. For instance: One of my Managers is the PlayerCharacterManager that has these methods: void buySkill(PlayerCharacter playerCharacter, Skill skill); void changeName(); void changeRole(); void restatCharacter(); void addCharacterToGame(); void createNewCharacter(); PlayerCharacter getPlayerCharacter(); List<PlayerCharacter> getPlayersCharacter(Player player); List<PlayerCharacter> getAllCharacters(); I hope the mothod names are transparent enough that they don't all need explaining. I've called it a manager because it will help manage all of the PlayerCharacter 'model' objects the code creates, and create and keep a map of these. I may also get it to store other information in the future. I plan to have another two similar classes for this sort of control, but I will orchestrate when and how this happens, and what to do with the returned data via a pure controller class. This splitting up control between informed managers and the controller, as opposed to operating just through a controller seems like it will simplify my code and make it flow more. My question is, is this a dangerous choice, in terms of making the code harder to follow/test/fix? Is this somethign established as good or bad or neutral? I oculdn't find anything similar except the idea of Actors but that's not quite why I'm trying to do. Edit: Perhaps an example is needed; I'm using the Controller to update the view and access the data, so when I click the 'Add new character to a player button' it'll call methods in the controller that then go and tell the PlayerCharacterManager class to create a new character instance, it'll call the PlayerManager class to add that new character to the player-character map, and then it'll add this information to the database, and tell the view to update any GUIs effected. That is the sort of 'control sequence' I'm hoping to create with these manager classes.

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  • How do you balance between "do it right" and "do it ASAP" in your daily work?

    - by Flot2011
    I find myself pondering this question times and times again. I want to do things the right way, to write a clean, understandable, correct code that is easy to maintain, but what I really do pretty often is writing a patch upon patch just because there is no time, clients are waiting, a bug should be fixed overnight, the company is losing money on this problem, a manager is pressing hard etc. etc. I know perfectly well that in a long shot I am wasting much more time on these patches, but as this time is spread over months of work, nobody cares. Also, as one of my managers used to say, we don't know if there will be this long shot if we will not fix it now. I am sure I am not the only one entrapped in this endless real/ideal choices. So how you, fellow programmers, are coping with this?

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  • How should I implement the repository pattern for complex object models?

    - by Eric Falsken
    Our data model has almost 200 classes that can be separated out into about a dozen functional areas. It would have been nice to use domains, but the separation isn't that clean and we can't change it. We're redesigning our DAL to use Entity Framework and most of the recommendations that I've seen suggest using a Repository pattern. However, none of the samples really deal with complex object models. Some implementations that I've found suggest the use of a repository-per-entity. This seems ridiculous and un-maintainable for large, complex models. Is it really necessary to create a UnitOfWork for each operation, and a Repository for each entity? I could end up with thousands of classes. I know this is unreasonable, but I've found very little guidance implementing Repository, Unit Of Work, and Entity Framework over complex models and realistic business applications.

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  • What languages do you support when localizing?

    - by Javoid
    I recently converted an iphone app to support different languages, and was wondering which ones I should include, and which ones aren't worth the trouble. What I mean by that is best illustrated by an example. In Ireland, the Irish language is spoken by very few of the people there. It could be considered a dying language. Almost everybody speaks English (if not everybody). So in this example, I don't think it's worth the trouble to support. In addition, the number of people using modern technology may be limited as well. For example, most people in Cambodia would not be likely to purchase software, and therefore the benefits of localization are reduced. What languages do you support when localizing?

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  • Web programming, standard way to deal with a response that takes time to complete

    - by wobbily_col
    With normal form submission I use the pattern Post / Redirect / Get, when processing the forms. I have a database application built with Django. I want to allow the users to select a number of items from the database, then launch a computationally intensive task based on those items. I expect the task to take between 10 minutes and 2 hours to complete. Is there a standard approach to dealing with requests like this (i.e. that don't return immediately)? Ideally there would be some way to display the progress.

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  • How to implement string matching based on a pattern

    - by Vincent Rischmann
    I was asked to build a tool that can identify if a string match a pattern. Example: {1:20} stuff t(x) {a,b,c} would match: 1 stuff tx a 20 stuff t c It is a sort of regex but with a different syntax Parentheses indicate an optional value {1:20} is a interval; I will have to check if the token is a number and if it is between 1 and 20 {a,b,c} is just an enumeration; it can be either a or b or c Right now I implemented this with a regex, and the interval stuff was a pain to do. On my own time I tried implementing some kind of matcher by hand, but it turns out it's not that easy to do. By experimenting I ended up with a function that generates a state table from the pattern and a state machine. It worked well until I tried to implement the optional value, and I got stuck and how to generate the state table. After that I searched how I could do this, and that led me to stuff like LL parser, LALR parser, recursive-descent parser, context-free grammars, etc. I never studied any of this so it's hard to know what is relevant here, but I think this is what I need: A grammar A parser which generates states from the grammar and a pattern A state machine to see if a string match the states So my first question is: Is this right ? And second question, what do you recommend I read/study to be able to implement this ?

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  • Dynamic Fields/Columns

    - by DanMark
    What is the best way to allow for dynamic fields/database columns? For example, let's say we have a payroll system that allows a user to create unique salary structures for each employee. How could/should one handle this scenario? I thought of using a "salary" table that hold the salary component fields and joining these columns to a "salary_values" table that hold the actual values. Does this make sense? Example Salary Structures: Notice how the components of the salary can be shared or unique. -- Jon's Salary -- Basic 100 Annual Bonus 25 Tel. Allowances 15 -- Jane's Salary -- Basic 100 Travel Allowances 10 Bi-annual Bonus 30

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