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  • Should I put actors in the Domain-Model/Class-Diagram?

    - by devoured elysium
    When designing both the domain-model and class-diagrams I am having some trouble understanding what to put in them. I'll give an example of what I mean: I am doing a vacations scheduler program, that has an Administrator and End-Users. The Administrator does a couple of things like registering End-Users in the program, changing their previleges, etc. The End-User can choose his vacations days, etc. I initially defined an Administrator and End-User as concepts in the domain-model, and later as classes in the class-diagram. In the class-diagram, both classes ended up having a couple of methods like Administrator.RegisterNewUser(); Administrator.UnregisterUser(int id); etc. Only after some time I realised that actually both Administrator and End-User are actors, and maybe I got this design totally wrong. Instead of filling Administrator and End-User classes with methods to do what my Use-Cases request, I could define other classes from the domain to do them, and have controllers handle the Use-Cases(actually, I decided to do one for each Use-Case). I could have a UserDatabase.RegisterNewUser() and UserDatabase.UnregisterUser(int id);, for example, instead of having those methods on the Administrator class. The idea would be to try to think of the whole vacation-scheduler as a "closed-program" that has a set of features and doesn't bother with things such as authentication, that should be internal/protected, being that the only public things I'd let the outside world see would be its controllers. Is this the right approach? Or am I getting this totally wrong? Is it generally bad idea to put Actors in the domain-model/class-diagrams? What are good rules of thumb for this? My lecturer is following Applying UML and Patterns, which I find awful, so I'd like to know where I could look up more info on this described actor-models situation. I'm still a bit confused about all of this, as this new approach is radically different from anything I've done before.

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  • Rate my C# code (~300 SLOC) using GDI+/Backgroundworker

    - by sebastianlarsson
    Hi, I want to get some feedback on my code! Below is some background info. I am taking a pre-certification course in C# (Sweden, 15 ECTS). The focus of the course is theoretical and only limited practical work. I dont find the assignments very hard at all to tell you the truth, but since I only have very limited work experience as a developer (I have worked 15h/week at Ericsson since November) I think I would benefit from having the certificate (70-536 and more probably). I am currently reading Martin Fowler's "Refactoring: Improving the design of existing code" and I tried to apply his techniques to my latest lab in the course. I have been on the lookout for a website which have the idea of providing feedback on code, but so far I have yet to discover any. Please take a look on my code and tell me what you think. It is only roughly 300 lines of code divided into a couple of classes. GDI+, backgroundworker and user controls are what the lab is about. I reckon you may have to spend as little as a couple of minutes on looking on the solution. Link to solution: http://www.filefactory.com/file/b18h7d5/n/Lab4_Lab5_SebastianLarsson.zip Regards and thank you, Sebastian

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  • .NET: bool vs enum as a method parameter

    - by Julien Lebosquain
    Each time I'm writing a method that takes a boolean parameter representing an option, I find myself thinking: "should I replace this by an enum which would make reading the method calls much easier?". Consider the following with an object that takes a parameter telling whether the implementation should use its thread-safe version or not (I'm not asking here if this way of doing this is good design or not, only the use of the boolean): public void CreateSomeObject(bool makeThreadSafe); CreateSomeObject(true); When the call is next to the declaration the purpose of the parameter seems of course obvious. When it's in some third party library you barely know, it's harder to immediately see what the code does, compared to: public enum CreationOptions { None, MakeThreadSafe } public void CreateSomeObject(CreationOptions options); CreateSomeObject(CreationOptions.MakeThreadSafe); which describes the intent far better. Things get worse when there's two boolean parameters representing options. See what happened to ObjectContext.SaveChanges(bool) between Framework 3.5 and 4.0. It has been obsoleted because a second option has been introduced and the whole thing has been converted to an enum. While it seems obvious to use an enumeration when there's three elements or more, what's your opinion and experiences about using an enum instead a boolean in these specific cases?

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  • Is "tip-of-the-day" good?

    - by Jonta
    Many programs (often large ones, like MS Office, The GIMP, Maxthon) have a feature called "tip-of-the-day". It explains a small part of the program, like this one in Maxthon: "You can hide/show the main menu bar by pressing Ctrl+F11" You can usually browse through them by clicking next. And other options provided are "Previous", "Close", "Do not show at startup". I think I like the way Maxthon used to handle this; in the browser's statusbar (down at the bottom usually, together with "Done", the progress-bar etc), there would sometimes be a small hint or tip on what else you could do with it. As Joel Spolsky wrote in his article-series "User Interface Design for Programmers", people don't like reading manuals. But we still want them to use the program, and the features they could benefit from, don't we? Therefore, I think it is useful to have such a feature, without the annoyance of the pop-up on startup. What do you think? Pop-up? Maxthonstyle? No way?

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  • Structuring iPhone/iPad application views

    - by Mark
    I have an idea about an application that I want to build and Im new to iPhone/iPad development (but not new to development in other languages/frameworks such as .NET and Java). I want to layout some views on the screen so that they animate (slide in) from different directions into their places. The question is about the strucuture of the application, if I have say 4 rectanglular areas on the screen that contain business data, such as contacts (name, photo, etc...) and they all take up different widths of the screen (say the first contact takes up one row of the screen, but the next 2 take up half the width of the next row each, and so on). Should I create a custom view for the different sized contact views, (i.e. LargeCustomView and SmallCustomView, and any other special type that I make) or should it all be one type, say, CustomerDetailsView which could be stretched to fit at design time? Also, if there were, say, 3 different instances of the same custom view on the one screen, are there 3 instances of the view controller also? Im a little confused about powering the data behind a view, can someone shed some light on this for me? Do I just set the properties (say an instance variable ContactForView) on the view controller for each instance? Thanks for any help you can give Cheers, Mark

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  • How security of the systems might be improved using database procedures?

    - by Centurion
    The usage of Oracle PL/SQL procedures for controlling access to data often emphasized in PL/SQL books and other sources as being more secure approach. I'v seen several systems where all business logic related with data is performed through packages, procedures and functions, so application code becomes quite "dumb" and is only responsible for visualization part. I even heard some devs call such approaches and driving architects as database nazi :) because all logic code resides in database. I do know about DB procedure performance benefits, but now I'm interested in a "better security" when using thick client model. I assume such design mostly used when Oracle (and maybe MS SQL Server) databases are used. I do agree such approach improves security but only if there are not much users and every system user has a database account, so we might control and monitor data access through standard database user security. However, how such approach could increase the security for an average web system where thick clients are used: for example one database user with DML grants on all tables, and other users are handled using "users" and"user_rights" tables? We could use DB procedures, save usernames into context use that for filtering but vulnerability resides at the root - if the main database account is compromised than nothing will help. Of course in a real system we might consider at least several main users (for example frontend_db_user, backend_db_user).

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  • Multiple Foreign keys to a single table and single key pointing to more than one table

    - by user1216775
    I need some suggestions from the database design experts here. I have around six foreign keys into a single table (defect) which all point to primary key in user table. It is like: defect (.....,assigned_to,created_by,updated_by,closed_by...) If I want to get information about the defect I can make six joins. Do we have any better way to do it? Another one is I have a states table which can store one of the user-defined set of values. I have defect table and task table and I want both of these tables to share the common state table (New, In Progress etc.). So I created: task (.....,state_id,type_id,.....) defect(.....,state_id,type_id,...) state(state_id,state_name,...) importance(imp_id,imp_name,...) There are many such common attributes along with state like importance(normal, urgent etc), priority etc. And for all of them I want to use same table. I am keeping one flag in each of the tables to differentiate task and defect. What is the best solution in such a case? If somebody is using this application in health domain, they would like to assign different types, states, importances for their defect or tasks. Moreover when a user selects any project I want to display all the types,states etc under configuration parameters section.

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  • [MVC] logic before dispatcher + controller?

    - by Spoonface
    I believe for a typical MVC web application the router / dispatcher routine is used to decide which controller is loaded based primarily on the area requested in the url by the user. However, in addition to checking the url query string, I also like to use the dispatcher to check whether the user is currently logged in or not to decide which controller is loaded. For example if they are logged in and request the login page, the dispatcher would load their account instead. But is this a fairly non-standard design? Would it violate MVC in any way? I only ask as the examples I've read through this weekend have had no major calculations performed before the dispatcher routine, and commonly check whether the user is logged in or not per controller, and then redirect where necessary. But to me it seems odd to redirect a logged in user from the login area to account area if you could just load the account controller in the first place? I hope I've explained my consternation well enough, but could anyone offer some details on how they handle logged in users, and similar session data?

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  • Designing a database for a user/points system? (in Django)

    - by AP257
    First of all, sorry if this isn't an appropriate question for StackOverflow. I've tried to make it as generalisable as possible. I want to create a database (MySQL, site running Django) that has users, who can be allocated a certain number of points for various types of action - it's a collaborative game. My requirements are to obtain: the number of points a user has the user's ranking compared to all other users and the overall leaderboard (i.e. all users ranked in order of points) This is what I have so far, in my Django models.py file: class SiteUser(models.Model): name = models.CharField(max_length=250 ) email = models.EmailField(max_length=250 ) date_added = models.DateTimeField(auto_now_add=True) def points_total(self): points_added = PointsAdded.objects.filter(user=self) points_total = 0 for point in points_added: points_total += point.points return points_total class PointsAdded(models.Model): user = models.ForeignKey('SiteUser') action = models.ForeignKey('Action') date_added = models.DateTimeField(auto_now_add=True) def points(self): points = Action.objects.filter(action=self.action) return points class Action(models.Model): points = models.IntegerField() action = models.CharField(max_length=36) However it's rapidly becoming clear to me that it's actually quite complex (in Django query terms at least) to figure out the user's ranking and return the leaderboard of users. At least, I'm finding it tough. Is there a more elegant way to do something like this? This question seems to suggest that I shouldn't even have a separate points table - what do people think? It feels more robust to have separate tables, but I don't have much experience of database design.

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  • Social Networking & Network Affiliations

    - by Code Sherpa
    Hi. I am in the process of planning a database for a social networking project and stumbled upon this url which is a (crude) reverse engineered guess at facebook's schema: http://www.flickr.com/photos/ikhnaton2/533233247/ What is of interest to me is the notion of "Affiliations" and I am trying to fully understand how they work, technically speaking. Where I am somewhat confused is the NetworkID column in the FacebookGroups", "FacebookEvent", and "Affiliations" tables (NID in Affiliations). How are these network affiliations interconnected? In my own project, I have a simple profile table: CREATE TABLE [dbo].[Profiles]( [profileid] [int] IDENTITY(1,1) NOT NULL, [userid] [uniqueidentifier] NOT NULL, [username] [varchar](255) COLLATE Latin1_General_CI_AI NOT NULL, [applicationname] [varchar](255) COLLATE Latin1_General_CI_AI NOT NULL, [isanonymous] [bit] NULL, [lastactivity] [datetime] NULL, [lastupdated] [datetime] NULL, CONSTRAINT [PK__Profiles__1DB06A4F] PRIMARY KEY CLUSTERED ( [profileid] ASC )WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY], CONSTRAINT [PKProfiles] UNIQUE NONCLUSTERED ( [username] ASC, [applicationname] ASC )WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY] ) ON [PRIMARY] One profile can have many affiliations. And one affiliation can have many profiles. And I would like to design it in such a way that relationships between affiliations tells me something about the associated profiles. In fact, based on the affiliations that users select, I would like to know how to infer as many things as possible about that person. My question is, how should I be designing my network affiliation tables and how do they operate per my above requirements? A rough SQL schema would be appreciated in your response. Thanks in advance...

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  • Common Properties: Consolidating Loan, Purchase, Inventory and Sale tables into one Transaction tabl

    - by Frank Computer
    Pawnshop Application: I have separate tables for Loan, Purchase, Inventory & Sales transactions. Each tables rows are joined to their respective customer rows by: customer.pk [serial] = loan.fk [integer]; = purchase.fk [integer]; = inventory.fk [integer]; = sale.fk [integer]; Since there are so many common properties within the four tables, I consolidated the four tables into one table called "transaction", where a column: transaction.trx_type char(1) {L=Loan, P=Purchase, I=Inventory, S=Sale} Scenario: A customer initially pawns merchandise, makes a couple of interest payments, then decides he wants to sell the merchandise to the pawnshop, who then places merchandise in Inventory and eventually sells it to another customer. I designed a generic transaction table where for example: transaction.main_amount DECIMAL(7,2) in a loan transaction holds the pawn amount, in a purchase holds the purchase price, in inventory and sale holds sale price. This is clearly a denormalized design, but has made programming alot easier and improved performance. Any type of transaction can now be performed from within one screen, without the need to change to different tables.

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  • How to get java singleton object manager to return any type of object?

    - by Robert
    I'm writing an interactive fiction game in java from scratch. I'm currently storing all of my game object references in a hashmap in a singleton called ObjectManager. ObjectManager has a function called get which takes an integer ID and returns the appropriate reference. The problem is that it returns a BaseObject when I need to return subclasses of BaseObject with more functionality. So, what I've done so far is I've added a getEntity function which returns BaseEntity (which is a subclass of BaseObject). However, when I need the function to return to an object that is a subclass of BaseEntity that has added, required functionality, I will need to make another function. I know there is a better way, but I don't know what it is. I know very little of design patterns, and I'm not sure which one to use here. I tried passing 'class' as a parameter, but that didn't get me anywhere. public BaseObject get(int ID){ return (BaseObject)refMap.get(ID); } public BaseEntity getEntity(int ID){ return (BaseEntity)refMap.get(ID); } Thanks, java ninjas!

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  • Entity Attribute Value Database vs. strict Relational Model Ecommerce question

    - by Dr. Zim
    It is safe to say that the EAV/CR database model is bad. That said, Question: What database model, technique, or pattern should be used to deal with "classes" of attributes describing e-commerce products which can be changed at run time? In a good E-commerce database, you will store classes of options (like TV resolution then have a resolution for each TV, but the next product may not be a TV and not have "TV resolution"). How do you store them, search efficiently, and allow your users to setup product types with variable fields describing their products? If the search engine finds that customers typically search for TVs based on console depth, you could add console depth to your fields, then add a single depth for each tv product type at run time. There is a nice common feature among good e-commerce apps where they show a set of products, then have "drill down" side menus where you can see "TV Resolution" as a header, and the top five most common TV Resolutions for the found set. You click one and it only shows TVs of that resolution, allowing you to further drill down by selecting other categories on the side menu. These options would be the dynamic product attributes added at run time. Further discussion: So long story short, are there any links out on the Internet or model descriptions that could "academically" fix the following setup? I thank Noel Kennedy for suggesting a category table, but the need may be greater than that. I describe it a different way below, trying to highlight the significance. I may need a viewpoint correction to solve the problem, or I may need to go deeper in to the EAV/CR. Love the positive response to the EAV/CR model. My fellow developers all say what Jeffrey Kemp touched on below: "new entities must be modeled and designed by a professional" (taken out of context, read his response below). The problem is: entities add and remove attributes weekly (search keywords dictate future attributes) new entities arrive weekly (products are assembled from parts) old entities go away weekly (archived, less popular, seasonal) The customer wants to add attributes to the products for two reasons: department / keyword search / comparison chart between like products consumer product configuration before checkout The attributes must have significance, not just a keyword search. If they want to compare all cakes that have a "whipped cream frosting", they can click cakes, click birthday theme, click whipped cream frosting, then check all cakes that are interesting knowing they all have whipped cream frosting. This is not specific to cakes, just an example.

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  • Looking for efficient scaling patterns for Silverlight application with distributed text-file data s

    - by Edward Tanguay
    I'm designing a Silverlight software solution for students and teachers to record flashcards, e.g. words and phrases that students find while reading and errors that teachers notice while teaching. Requirements are: each person publishes his own flashcards in a file on a web server, e.g. http://:www.mywebserver.com/flashcards.txt other people subscribe to that person's flashcards by using a Silverlight flashcard reader that I have developed and entering the URLs of flashcard files they want to subscribe to, URLs and imported flashcards being saved in IsolatedStorage the flashcards.txt file has the following simple format: title, then blocks of question/answers: Jim Smith's flashcards from English class 53-222, winter semester 2009 ==fla Das kann nicht sein. That can't be. ==fla Es sei denn, er kommt nicht. Unless he doesn't come. The user then makes public the URL to his flashcard file and other readers begin reading in his flashcards. In order to lower the bar for non-technical users to contribute, it will even be possible for them to save this text in a Google Document, which they publish and distribute the URL. The flashcard readers will then recognize it is a google document and perform the necessary screen scraping to get at the raw text. I have two technical questions about this approach: What is a best way to plan now for scalability issues: e.g. if your reader is subscribed to 10 flashcard files that are each 200K, it will have to download 2MB of text just to find out if any new flashcards are available. Or can I somehow accurately and consistently get at the last update date/time of text files on servers and published google docs? Each reader will have the ability to allow the person to test himself on imported flashcards and add meta information to them, e.g. categorize them, edit them, etc. This information will be stored in IsolatedStorage along with the important flashcards themselves. What is a good pattern to allow these readers to share and synchronize this meta data, e.g. so when you are looking at a flashcard you can see that 5 other people have made corrections to it. The best solution I can think of now is that the Silverlight readers will have to republish their data to a central database, but then there is the problem of uniquely identifying each flashcard, the best approach seems to be URL + position-in-file, or even better URL + original text of both question and answer fields, but both of these have their obvious drawbacks. The main requirement is that the bar for participation is kept as low as possible, i.e. type text in a google document, publish it, distribute the URL, and you're publishing within the flashcard community. So I want to come up with the most efficient technical solutions in order to compensate for the lack of database, lack of unique ids, etc. For those who have designed or developed similar non-traditional, distributed database projects like this, what advice, experience or best-practice tips you can share on the above two points?

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  • redoing object model construction to fit with asynchronous data fetching

    - by Andrew Patterson
    I have a modeled a set of objects that correspond with some real world concepts. TradeDrug, GenericDrug, TradePackage, DrugForm Underlying the simple object model I am trying to provide is a complex medical terminology that uses numeric codes to represent relationships and concepts, all accessible via a REST service - I am trying to hide away some of that complexity with an object wrapper. To give a concrete example I can call TradeDrug d = Searcher.FindTradeDrug("Zoloft") or TradeDrug d = new TradeDrug(34) where 34 might be the code for Zoloft. This will consult a remote server to find out some details about Zoloft. I might then call GenericDrug generic = d.EquivalentGeneric() System.Out.WriteLine(generic.ActiveIngredient().Name) in order to get back the generic drug sertraline as an object (again via a background REST call to the remote server that has all these drug details), and then perhaps find its ingredient. This model works fine and is being used in some applications that involve data processing. Recently however I wanted to do a silverlight application that used and displayed these objects. The silverlight environment only allows asynchronous REST/web service calls. I have no problems with how to make the asychhronous calls - but I am having trouble with what the design should be for my object construction. Currently the constructors for my objects do some REST calls sychronously. public TradeDrug(int code) { form = restclient.FetchForm(code) name = restclient.FetchName(code) etc.. } If I have to use async 'events' or 'actions' in order to use the Silverlight web client (I know silverlight can be forced to be a synchronous client but I am interested in asychronous approaches), does anyone have an guidance or best practice for how to structure my objects. I can pass in an action callback to the constructor public TradeDrug(int code, Action<TradeDrug> constructCompleted) { } but this then allows the user to have a TradeDrug object instance before what I want to construct is actually finished. It also doesn't support an 'event' async pattern because the object doesn't exist to add the event to until it is constructed. Extending that approach might be a factory object that itself has an asynchronous interface to objects factory.GetTradeDrugAsync(code, completedaction) or with a GetTradeDrugCompleted event? Does anyone have any recommendations?

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  • Register all GUI components as Observers or pass current object to next object as a constructor argu

    - by Jack
    First, I'd like to say that I think this is a common issue and there may be a simple or common solution that I am unaware of. Many have probably encountered a similar problem. Thanks for reading. I am creating a GUI where each component needs to communicate (or at least be updated) by multiple other components. Currently, I'm using a Singleton class to accomplish this goal. Each GUI component gets the instance of the singleton and registers itself. When updates need to be made, the singleton can call public methods in the registered class. I think this is similar to an Observer pattern, but the singleton has more control. Currently, the program is set up something like this: class c1 { CommClass cc; c1() { cc = CommClass.getCommClass(); cc.registerC1( this ); C2 c2 = new c2(); } } class c2 { CommClass cc; c2() { cc = CommClass.getCommClass(); cc.registerC2( this ); C3 c3 = new c3(); } } class c3 { CommClass cc; c3() { cc = CommClass.getCommClass(); cc.registerC3( this ); C4 c4 = new c4(); } } etc. Unfortunately, the singleton class keeps growing larger as more communication is required between the components. I was wondering if it's a good idea to instead of using this singleton, pass the higher order GUI components as arguments in the constructors of each GUI component: class c1 { c1() { C2 c2 = new c2( this ); } } class c2 { C1 c1; c2( C1 c1 ) { this.c1 = c1 C3 c3 = new c3( c1, this ); } } class c3 { C1 c1; C2 c2; c3( C1 c1, C2 c2 ) { this.c1 = c1; this.c2 = c2; C4 c4 = new c4( c1, c2, this ); } } etc. The second version relies less on the CommClass, but it's still very messy as the private member variables increase in number and the constructors grow in length. Each class contains GUI components that need to communicate through CommClass, but I can't think of a good way to do it. If this seems strange or horribly inefficient, please describe some method of communication between classes that will continue to work as the project grows. Also, if this doesn't make any sense to anyone, I'll try to give actual code snippets in the future and think of a better way to ask the question. Thanks.

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  • How can i convert this to a factory/abstract factory?

    - by Amitd
    I'm using MigraDoc to create a pdf document. I have business entities similar to the those used in MigraDoc. public class Page{ public List<PageContent> Content { get; set; } } public abstract class PageContent { public int Width { get; set; } public int Height { get; set; } public Margin Margin { get; set; } } public class Paragraph : PageContent{ public string Text { get; set; } } public class Table : PageContent{ public int Rows { get; set; } public int Columns { get; set; } //.... more } In my business logic, there are rendering classes for each type public interface IPdfRenderer<T> { T Render(MigraDoc.DocumentObjectModel.Section s); } class ParagraphRenderer : IPdfRenderer<MigraDoc.DocumentObjectModel.Paragraph> { BusinessEntities.PDF.Paragraph paragraph; public ParagraphRenderer(BusinessEntities.PDF.Paragraph p) { paragraph = p; } public MigraDoc.DocumentObjectModel.Paragraph Render(MigraDoc.DocumentObjectModel.Section s) { var paragraph = s.AddParagraph(); // add text from paragraph etc return paragraph; } } public class TableRenderer : IPdfRenderer<MigraDoc.DocumentObjectModel.Tables.Table> { BusinessEntities.PDF.Table table; public TableRenderer(BusinessEntities.PDF.Table t) { table =t; } public MigraDoc.DocumentObjectModel.Tables.Table Render(Section obj) { var table = obj.AddTable(); //fill table based on table } } I want to create a PDF page as : var document = new Document(); var section = document.AddSection();// section is a page in pdf var page = GetPage(1); // get a page from business classes foreach (var content in page.Content) { //var renderer = createRenderer(content); // // get Renderer based on Business type ?? // renderer.Render(section) } For createRenderer() i can use switch case/dictionary and return type. How can i get/create the renderer generically based on type ? How can I use factory or abstract factory here? Or which design pattern better suits this problem?

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  • Is it ok to dynamic cast "this" as a return value?

    - by Panayiotis Karabassis
    This is more of a design question. I have a template class, and I want to add extra methods to it depending on the template type. To practice the DRY principle, I have come up with this pattern (definitions intentionally omitted): template <class T> class BaseVector: public boost::array<T, 3> { protected: BaseVector<T>(const T x, const T y, const T z); public: bool operator == (const Vector<T> &other) const; Vector<T> operator + (const Vector<T> &other) const; Vector<T> operator - (const Vector<T> &other) const; Vector<T> &operator += (const Vector<T> &other) { (*this)[0] += other[0]; (*this)[1] += other[1]; (*this)[2] += other[2]; return *dynamic_cast<Vector<T> * const>(this); } } template <class T> class Vector : public BaseVector<T> { public: Vector<T>(const T x, const T y, const T z) : BaseVector<T>(x, y, z) { } }; template <> class Vector<double> : public BaseVector<double> { public: Vector<double>(const double x, const double y, const double z); Vector<double>(const Vector<int> &other); double norm() const; }; I intend BaseVector to be nothing more than an implementation detail. This works, but I am concerned about operator+=. My question is: is the dynamic cast of the this pointer a code smell? Is there a better way to achieve what I am trying to do (avoid code duplication, and unnecessary casts in the user code)? Or am I safe since, the BaseVector constructor is private?

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  • Initialization of components with interdependencies - possible antipattern?

    - by Rosarch
    I'm writing a game that has many components. Many of these are dependent upon one another. When creating them, I often get into catch-22 situations like "WorldState's constructor requires a PathPlanner, but PathPlanner's constructor requires WorldState." Originally, this was less of a problem, because references to everything needed were kept around in GameEngine, and GameEngine was passed around to everything. But I didn't like the feel of that, because it felt like we were giving too much access to different components, making it harder to enforce boundaries. Here is the problematic code: /// <summary> /// Constructor to create a new instance of our game. /// </summary> public GameEngine() { graphics = new GraphicsDeviceManager(this); Components.Add(new GamerServicesComponent(this)); //Sets dimensions of the game window graphics.PreferredBackBufferWidth = 800; graphics.PreferredBackBufferHeight = 600; graphics.ApplyChanges(); IsMouseVisible = true; screenManager = new ScreenManager(this); //Adds ScreenManager as a component, making all of its calls done automatically Components.Add(screenManager); // Tell the program to load all files relative to the "Content" directory. Assets = new CachedContentLoader(this, "Content"); inputReader = new UserInputReader(Constants.DEFAULT_KEY_MAPPING); collisionRecorder = new CollisionRecorder(); WorldState = new WorldState(new ReadWriteXML(), Constants.CONFIG_URI, this, contactReporter); worldQueryUtils = new WorldQueryUtils(worldQuery, WorldState.PhysicsWorld); ContactReporter contactReporter = new ContactReporter(collisionRecorder, worldQuery, worldQueryUtils); gameObjectManager = new GameObjectManager(WorldState, assets, inputReader, pathPlanner); worldQuery = new DefaultWorldQueryEngine(collisionRecorder, gameObjectManager.Controllers); gameObjectManager.WorldQueryEngine = worldQuery; pathPlanner = new PathPlanner(this, worldQueryUtils, WorldQuery); gameObjectManager.PathPlanner = pathPlanner; combatEngine = new CombatEngine(worldQuery, new Random()); } Here is an excerpt of the above that's problematic: gameObjectManager = new GameObjectManager(WorldState, assets, inputReader, pathPlanner); worldQuery = new DefaultWorldQueryEngine(collisionRecorder, gameObjectManager.Controllers); gameObjectManager.WorldQueryEngine = worldQuery; I hope that no one ever forgets that setting of gameObjectManager.WorldQueryEngine, or else it will fail. Here is the problem: gameObjectManager needs a WorldQuery, and WorldQuery needs a property of gameObjectManager. What can I do about this? Have I found an anti-pattern?

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  • C++ game designing & polymorphism question

    - by Kotti
    Hi! I'm trying to implement some sort of 'just-for-me' game engine and the problem's plot goes the following way: Suppose I have some abstract interface for a renderable entity, e.g. IRenderable. And it's declared the following way: interface IRenderable { // (...) // Suppose that Backend is some abstract backend used // for rendering, and it's implementation is not important virtual void Render(Backend& backend) = 0; }; What I'm doing right now is something like declaring different classes like class Ball : public IRenderable { virtual void Render(Backend& backend) { // Rendering implementation, that is specific for // the Ball object // (...) } }; And then everything looks fine. I can easily do something like std::vector<IRenderable*> items, push some items like new Ball() in this vector and then make a call similiar to foreach (IRenderable* in items) { item->Render(backend); } Ok, I guess it is the 'polymorphic' way, but what if I want to have different types of objects in my game and an ability to manipulate their state, where every object can be manipulated via it's own interface? I could do something like struct GameState { Ball ball; Bonus bonus; // (...) }; and then easily change objects state via their own methods, like ball.Move(...) or bonus.Activate(...), where Move(...) is specific for only Ball and Activate(...) - for only Bonus instances. But in this case I lose the opportunity to write foreach IRenderable* simply because I store these balls and bonuses as instances of their derived, not base classes. And in this case the rendering procedure turns into a mess like ball.Render(backend); bonus.Render(backend); // (...) and it is bad because we actually lose our polymorphism this way (no actual need for making Render function virtual, etc. The other approach means invoking downcasting via dynamic_cast or something with typeid to determine the type of object you want to manipulate and this looks even worse to me and this also breaks this 'polymorphic' idea. So, my question is - is there some kind of (probably) alternative approach to what I want to do or can my current pattern be somehow modified so that I would actually store IRenderable* for my game objects (so that I can invoke virtual Render method on each of them) while preserving the ability to easily change the state of these objects? Maybe I'm doing something absolutely wrong from the beginning, if so, please point it out :) Thanks in advance!

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  • CodePlex Daily Summary for Wednesday, March 17, 2010

    CodePlex Daily Summary for Wednesday, March 17, 2010New Projectschaosreader: A simple RSS reader.CRM 4.0 Customization GUID Update: The CRM 4.0 customization GUID update is an open source C# console application that automatically replaces GUID values in your exported workflow cu...DotNetNuke® Skin Bright: A DotNetNuke Design Challenge skin package submitted to the "Modern Business" category by Noel Jerke of SiteToolset. This simple and clean business...DotNetNuke® Skin Go: A DotNetNuke Design Challenge skin package submitted to the "Modern Business" category by DnnGo Corporation. The skin uses web standard DIV+CSS tec...DotNetNuke® Skin J10blend: A DotNetNuke Design Challenge skin package submitted to the "Out of the box" category by Timthy Maler of 2M Studio Design. J10-Black v01.00.00 inc...DotNetNuke® Skin Recipe: A DotNetNuke Design Challenge skin package submitted to the "Standards" category by dnnprofis.at. For mobile devices the skin changes to a mobile...DotNetNuke® Skin SpaceSmurfs: A DotNetNuke Design Challenge skin package submitted to the "Personal" category by Eric Johnson of Personify Design. This fun personal skin was ins...ERDOS6 - Web: A Web Project about ERDOS 6Flickrlight: Flickrlight is a personal fun project out of love of Flickr and Silverlight. You can experience it here: http://www.flickrlight.net.GsGrid: Extracting data from Gaussian grid file and grid file calculationiLocator: iLocator is a collaborative educational mapping game for children developed on Microsoft Surface. This game encourages players to collaborate with ...Javascript CallObject SOAP AJAX Helper: CallObject is a Javascript based AJAX helper, it facilitates wrapping of basic soap calls (as long as simple data types are used), asynchronous ret...kbTrainer: kbTrainer is a simple to use HTML application for typing speed training. A lot of features completed in basic. 2 learning keywords layouts -- engli...Laboratório de Engenharia de Software - Projeto: Criado para estudar e aplicar novas tecnologias web.Maxilds Powershell Scripts: Repo of my powershell scriptsNamespacifier: Namespacifier is a C#.NET library and console application to fix XML documents containing multiple default namespaces. It gives prefixes to defaul...OData SDK for Objective-C: This is a CTP of the OData SDK for Objective-C. The library targets iPhone devices and Mac OS X and it is designed to facilitate the connection wit...Open Data App Framework (ODAF): The Open Data Application Framework (ODAF) is a framework that allows cities to easily map existing civic Open Data landmarks, and allow users to r...QuickieB2B: QuickieB2B is web application which main target is to provide quick info about products. It's designed for small companies who have a big number of...RayView: Rayview is an easy-to-use Raytracing-Framework based on Microsoft XNA.Robotics Studio application to navigate Lego Mindstorms robot through labyrinth: A project for Software Systems Analysis and Design Tools subject at the Kaunas University of Technology. The main point of the project is to code L...SharePoint Icon Integration: SharePoint Icon Integration makes it easier for SharePoint Administrators / Developers to add a icon (pdf) to the SharePoint farm. You will no long...TestVersion: Testing VersionieringTimecard: SoftSource Timecard project.T-shirt Cannon: So the Coding4Fun team had two weeks to build two robots able to drive, aim, and shoot t-shirts with a Windows Phone during a MIX10 Keynote demo of...USTF: This project is a bit secretive right now.Windows Azure Command-line Tools for PHP Developers: The “Windows Azure Command-line tools for PHP” provide a command-line experience to developers who wish to develop, package, and deploy PHP applic...New ReleasesCaramel Engine: CaramelEngine Alpha Build 0.0.0.1a: This is an early alpha release of the Engine and it's functionality. Be sure to have the using CaramelEngine statement. This release is for people...Coot: Preview: Basic preview On the first use you have to click Create New Session and Login. After this you can just click Screen Saver each time. Settings sho...CycleMania Starter Kit EAP - ASP.NET 4.0 Problem - Design - Solution: Cyclemania 0.08.32: The latest alpha release.DeepZoomContainer, Expanded DeepZoom for Silverlight & Windows Phone 7 Series: Release ver. 1.20 for Windows Phone 7 Series: SolutionMerge PathAnimation solution into one MouseWheel elimination PathAnimationWP7 Port DeepZoomContainerProject rebuilt for WP7 support De...Desktop Google Reader: 1.3 (the social release): NewsSharing Liking Mail item Labels / Tags Send to Twitter Read It Later http://readitlaterlist.com/ Instapaper http://www.instapaper.com/ Favicons...DotNetNuke® Blog: 04.00.00 RC 2: PLEASE NOTE: Please do not upgrade previous version of the Beta releases - please start from 03.05.01 This is a RELEASE CANDIDATE, and as such ...DotNetNuke® Community Edition: 05.03.00: New FeaturesTemplated User Profiles - User profile pages are now publicly viewable Photo field in User Profile - Users can upload a photo to thei...DotNetNuke® Skin Bright: Bright Package 1.0.0: A DotNetNuke Design Challenge skin package submitted to the "Modern Business" category by Noel Jerke of SiteToolset. This simple and clean business...DotNetNuke® Skin Go: Go Package 1.0.0: A DotNetNuke Design Challenge skin package submitted to the "Modern Business" category by DnnGo Corporation. The skin uses web standard DIV+CSS tec...DotNetNuke® Skin J10blend: J10 Blend Package 1.0.0: A DotNetNuke Design Challenge skin package submitted to the "Out of the box" category by Timthy Maler of 2M Studio Design. J10-Black v01.00.00 incl...DotNetNuke® Skin Recipe: Recipe Package 1.0.0: A DotNetNuke Design Challenge skin package submitted to the "Standards" category by dnnprofis.at. For mobile devices the skin changes to a mobile f...DotNetNuke® Skin SpaceSmurfs: Space Smurfs Package 1.0.0: A DotNetNuke Design Challenge skin package submitted to the "Personal" category by Eric Johnson of Personify Design. This fun personal skin was ins...Dynamo: Dynamo v0.1 Beta: The following is included: Dynamo dlls Antlr dlls Hello world Simple Plugin example Application Dependency injection Singleton Managment ...ExtremeML: ExtremeML v1.0 Beta 1: Timed to accompany the RTM release of the OpenXML SDK v2.0, this is the first Beta release of ExtremeML (it was previously classified as a preview ...Family Tree Analyzer: Version 1.1.1.1: Version 1.1.1.1 Lots of Gedcom parsing fixes it should crash a whole lot less often and tolerate more "interesting" or "quirky" Gedcom entries. Add...Family Tree Analyzer: Version 1.2.0.1: Version 1.2.0.1 Added option to treat residence facts as Census Facts IGI Search now permits default country selection ie: what to use if it doesn...Flickrlight: Flickrlight: Current release is for idea sharing. There are not many design patterns being used. Please bare with the mess. :-) In order to run the applicat...Gherkin editor: Alpha 0.1: Most of the code at this point is the same as the Avalon.Sample from code project, just changed the name, removed extra languages and added syntax ...GsGrid: gsgrid1.6.4: gsgrid1.6.4GsGrid: gsgrid1.6.4-src: gsgrid1.6.4-srcHTML Template Repeater Module: Version 01.00.02: GeneralThe HTML Template Repeater Module is a direct replacement for the Core DotNetNuke Text/HTML module. Use it where you need to repeat the form...Images Compiler: Release 0.1: Last alpha buildJavascript CallObject SOAP AJAX Helper: Beta Release, 0.2.1: Beta Release, 0.2.1 Contains only core objectskbTrainer: kbtrainer 1.25u: kbTrainer is a simple to use speed typing training HTML application. A lot of features. All ither info availiable on http://code.google.com/p/kbtr...MapWindow6: MapWindow 6.0 msi (March 16): This version fixes a bug where selected points were not drawing correctly.Mesopotamia Experiment: Mesopotamia 1.2.43: Release Notes New Features - Scenario Name on title bar - Show organisms in Scnearios with simple stats Bug Fixes - Removed app domain recyling an...MFCMAPI: March 2010 Release: If you just want to run the tool, get the executable. If you want to debug it, get the symbol file and the source. Build: 6.0.0.1018 The 64 bit bu...MVVM Light Toolkit: MVVM Light Toolkit V3: Download the Zip file and extract it to a local folder. Then, follow the instructions on the Installation page http://www.galasoft.ch/mvvm/installi...NETXPF: 1.0.2: Changes: - Added a class "IOUtils" with methods for reading streams and GZip-compressing HTTP responses - Fixed a bug in the size formatter (excep...OData SDK for Objective-C: OData SDK for Objective-C CTP: The current release supports read-only operations only and it has been tested on a limited set of scenarios. The download include a sample iPhone a...Open Data App Framework (ODAF): ODAF 1.0: Initial beta release.Selection Maker: Selection Maker 1.1: New FeaturesContext Menu for ListView added Bug FixesFixed: If the users press Copy/Cut Button when no item is selected in ListView the ListView cl...Selection Maker: Selection Maker 1.2: Bug Fixes:a minor bug fixedSimple.NET: Simple.Mocking 1.0.0.5: Initial version of a new mocking framework for .NET Revision 1: Expect.AnyInocationOn<T>(T target) changed to Expect.AnyInocationOn(object target...SQL Server Extended Properties Quick Editor: New release 1.5.4: Whats new: Move preferences to application settings and add a form to edit preferences. Support to add, modify and delete operations could be made ...SuperModel - A Dynamic View-Model Generator: 1.0.0.0 - Tyra: The final 1.0 release, now less intrusive! If you don't want to implement ISuperModel, simply implement INotifyPropertyChanged.Timecard: Timecard Initial Release: The zipped version of the Initial Checkin.Transparent Persistence.Net: TP.Net 0.1.0: This is the initial alpha release. It's working for small set of use-cases (basic access to Cassandra).VCC: Latest build, v2.1.30316.0: Automatic drop of latest buildVFPnfe: Projeto Ajuda PAF-ECF: Este projeto visa ajudar aos desenvolvedores para homologação do PAF-ECF , sob licença publica GNU/GPL para ver mais detalhes do mesmo assista o vi...Visual Studio DSite: Gif Animator: This program will make an animate gif. (Program written in Vb.Net 2008)Most Popular ProjectsMetaSharpLiveUpload to FacebookSkype Voice ChangerLiveUpload to YouTubeSIPSorceryChartPart for SharePointTFS Branching Guide 2.0TouchFlo DetacherNPandaySnippet EditorMost Active ProjectsLINQ to TwitterRawrOData SDK for PHPDirectQpatterns & practices – Enterprise LibraryBlogEngine.NETN2 CMSOpen Data App Framework (ODAF)NB_Store - Free DotNetNuke Ecommerce Catalog ModuleMapWindow6

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  • How much abstraction is too much?

    - by Daniel Bingham
    In an Object Oriented Program: How much abstraction is too much? How much is just right? I have always been a nuts and bolts kind of guy. I understood the concept behind high levels of encapsulation and abstraction, but always felt instinctively that adding too much would just confuse the program. I always tried to shoot for an amount of abstraction that left no empty classes or layers. And where in doubt, instead of adding a new layer to the hierarchy, I would try and fit something into the existing layers. However, recently I've been encountering more highly abstracted systems. Systems where everything that could require a representation later in the hierarchy gets one up front. This leads to a lot of empty layers, which at first seems like bad design. However, on second thought I've come to realize that leaving those empty layers gives you more places to hook into in the future with out much refactoring. It leaves you greater ability to add new functionality on top of the old with out doing nearly as much work to adjust the old. The two risks of this seem to be that you could get the layers you need wrong. In this case one would wind up still needing to do substantial refactoring to extend the code and would still have a ton of never used layers. But depending on how much time you spend coming up with the initial abstractions, the chance of screwing it up, and the time that could be saved later if you get it right - it may still be worth it to try. The other risk I can think of is the risk of over doing it and never needing all the extra layers. But is that really so bad? Are extra class layers really so expensive that it is much of a loss if they are never used? The biggest expense and loss here would be time that is lost up front coming up with the layers. But much of that time still might be saved later when one can work with the abstracted code rather than more low level code. So when is it too much? At what point do the empty layers and extra "might need" abstractions become overkill? How little is too little? Where's the sweet spot? Are there any dependable rules of thumb you've found in the course of your career that help you judge the amount of abstraction needed?

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  • multiple-inheritance substitution

    - by Luigi
    I want to write a module (framework specific), that would wrap and extend Facebook PHP-sdk (https://github.com/facebook/php-sdk/). My problem is - how to organize classes, in a nice way. So getting into details - Facebook PHP-sdk consists of two classes: BaseFacebook - abstract class with all the stuff sdk does Facebook - extends BaseFacebook, and implements parent abstract persistance-related methods with default session usage Now I have some functionality to add: Facebook class substitution, integrated with framework session class shorthand methods, that run api calls, I use mostly (through BaseFacebook::api()), authorization methods, so i don't have to rewrite this logic every time, configuration, sucked up from framework classes, insted of passed as params caching, integrated with framework cache module I know something has gone very wrong, because I have too much inheritance that doesn't look very normal.Wrapping everything in one "complex extension" class also seems too much. I think I should have few working togheter classes - but i get into problems like: if cache class doesn't really extend and override BaseFacebook::api() method - shorthand and authentication classes won't be able to use the caching. Maybe some kind of a pattern would be right in here? How would you organize these classes and their dependencies? EDIT 04.07.2012 Bits of code, related to the topic: This is how the base class of Facebook PHP-sdk: abstract class BaseFacebook { // ... some methods public function api(/* polymorphic */) { // ... method, that makes api calls } public function getUser() { // ... tries to get user id from session } // ... other methods abstract protected function setPersistentData($key, $value); abstract protected function getPersistentData($key, $default = false); // ... few more abstract methods } Normaly Facebook class extends it, and impelements those abstract methods. I replaced it with my substitude - Facebook_Session class: class Facebook_Session extends BaseFacebook { protected function setPersistentData($key, $value) { // ... method body } protected function getPersistentData($key, $default = false) { // ... method body } // ... implementation of other abstract functions from BaseFacebook } Ok, then I extend this more with shorthand methods and configuration variables: class Facebook_Custom extends Facebook_Session { public funtion __construct() { // ... call parent's constructor with parameters from framework config } public function api_batch() { // ... a wrapper for parent's api() method return $this->api('/?batch=' . json_encode($calls), 'POST'); } public function redirect_to_auth_dialog() { // method body } // ... more methods like this, for common queries / authorization } I'm not sure, if this isn't too much for a single class ( authorization / shorthand methods / configuration). Then there comes another extending layer - cache: class Facebook_Cache extends Facebook_Custom { public function api() { $cache_file_identifier = $this->getUser(); if(/* cache_file_identifier is not null and found a valid file with cached query result */) { // return the result } else { try { // call Facebook_Custom::api, cache and return the result } catch(FacebookApiException $e) { // if Access Token is expired force refreshing it parent::redirect_to_auth_dialog(); } } } // .. some other stuff related to caching } Now this pretty much works. New instance of Facebook_Cache gives me all the functionality. Shorthand methods from Facebook_Custom use caching, because Facebook_Cache overwrited api() method. But here is what is bothering me: I think it's too much inheritance. It's all very tight coupled - like look how i had to specify 'Facebook_Custom::api' instead of 'parent:api', to avoid api() method loop on Facebook_Cache class extending. Overall mess and ugliness. So again, this works but I'm just asking about patterns / ways of doing this in a cleaner and smarter way.

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  • Network communication for a turn based board game

    - by randooom
    Hi all, my first question here, so please don't be to harsh if something went wrong :) I'm currently a CS student (from Germany, if this info is of any use ;) ) and we got a, free selectable, programming assignment, which we have to write in a C++/CLI Windows Forms Application. My team, two others and me, decided to go for a network-compatible port of the board game Risk. We divided the work in 3 Parts, namely UI, game logic and network. Now we're on the part where we have to get everything working together and the big question mark is, how to get the clients synchronized with each other? Our approach so far is, that each client has all information necessary to calculate and/or execute all possible actions. Actually the clients have all information available at all, aside from the game-initializing phase (add players, select map, etc.), which needs one "super-client" with some extra stuff to control things. This is the standard scenario of our approach: player performs action, the action is valid and got executed on the players client action is sent over the network action is executed on the other clients The design (i.e. no or code so far) we came up with so far, is something like the following pseudo sequence diagram. Gui, Controller and Network implement all possible actions (i.e. all actions which change data) as methods from an interface. So each part can implement the method in a way to get their job done. Example with Action(): On the player side's Client: Player-->Gui.Action() Gui-->Controller.Action() Controller-->Logic.Action (Logic.Action() == NoError)? Controller-->Network.Action() Network-->Parser.ParseAction() Network.Send(msg) On all other clients: Network.Recv(msg) Network-->Parser.Deparse(msg) Parser-->Logic.Action() Logic-->Gui.Action() The questions: Is this a viable approach to our task? Any better/easier way to this? Recommendations, critique? Our knowledge (so you can better target your answer): We are on the beginner side, in regards to programming on a somewhat larger projects with a small team. All of us have some general programming experience and basic understanding of the .Net Libraries and Windows Forms. If you need any further information, please feel free to ask.

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  • Have problems designing input and output for a calculator app

    - by zoul
    Hello! I am writing a button calculator. I have the code split into model, view and a controller. The model knows nothing about formatting, it is only concerned with numbers. All formatting is done in the view. The model gets its input as keypresses, each keypress is a part of an enum: typedef enum { kButtonUnknown = 0, kButtonMemoryClear = 100, kButtonMemoryPlus = 112, kButtonMemoryMinus = 109, kButtonMemoryRecall = 114, kButtonClear = 99, … }; When the user presses a button (say 1), the model receives a button code (kButtonNum1), adds the corresponding number to a string input buffer ("1") and updates the numeric output value (1.0). The controller then passes the numeric output value to the view that formats it (1). This is all plain, simple and clean, but does not really work. The problem is that when user enters a part of a number (say 0.00, going to enter 0.001), the input does not survive the way through model to view and the display says 0 instead of 0.00. I know why this happens ("0.00"::string parses to 0::double and that gets formatted as 0). What I don’t know is how to design the calculator so that the code stays clean and simple and the numbers will show up on screen exactly as the user types them. I’ve already come with some kind of solution, but that’s essentially a hack and breaks the beautiful and simple flow from the calculator model to the display. Ideas? Current solution keeps track of the calculator state. If the calculator is building a number, I take the calculator input buffer (a string) and directly set the display contents (also a string). Otherwise I take the proper path, ie. take the numeric calculator output, pass it to the view as a double and the view uses its internal formatter to create a string for the display. Example input: input | display | mode ------+---------+------------ 0 | 0 | from string 0. | 0. | from string 0.0 | 0.0 | from string 0.0+ | 0 | from number This is ugly. (1) The calculator has to expose its input buffer and state. (2) The view has to expose its display and allow setting its contents directly using a string. (3) I have to duplicate some of the formatting code to format the string I got from the calculator input buffer. If user enters 12345.000, I have to display 12,345.000 and therefore I’ve got to have a commification code for strings. Yuck.

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