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  • When to define SDD(System Sequence Diagram) operations System->Actor?

    - by devoured elysium
    I am having some trouble understanding how to make System Sequence Diagrams, as I don't fully grasp why in some cases one should define operations for System - Actor and in others don't. Here is an example: Let's assume the System is a Cinema Ticket Store and the Actor is a client that wants to buy a ticket. 1) The User tells the System that wants to buy some tickets, stating his client number. 2) The System confirms that the given client number is valid. 3) The User tells the System the movie that wants to see. 4) The System shows the set of available sessions and seats for that movie. 5) The System asks the user which session/seat he wants. 6) The User tells the System the chosen session/seat. This would be converted to: a) -----> tellClientNumber(clientNumber) b) <----- validClientNumber c) -----> tellMovieToSee(movie) d) <----- showsAvailableSeatsHours e) -----> tellSystemChosenSessionSeat(session, seat) I know that when we are dealing with SDD's we are still far away from coding. But I can't help trying to imagine how it how it would have been had I to convert it right away to code: I can understand 1) and 2). It's like if it was a C#/Java method with the following signature: boolean tellClientNumber(clientNumber) so I put both on the SDD. Then, we have the pair 3) 4). I can imagine that as something as: SomeDataStructureThatHoldsAvailableSessionsSeats tellSystemMovieToSee(movie) Now, the problem: From what I've come to understand, my lecturer says that we shouldn't make an operation on the SDD for 5) as we should only show operations from the Actor to the System and when the System is either presenting us data (as in c)) or validating sent data (such as in b)). I find this odd, as if I try to imagine this like a DOS app where you have to put your input sequencially, it makes sense to make an arrow even for 5). Why is this wrong? How should I try to visualize this? Thanks

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  • Why did the C# designers attach three different meanings to the 'using' keyword?

    - by gWiz
    The using keyword has three disparate meanings: type/namespace aliasing namespace import syntactic sugar for ensuring Dispose is called The documentation calls the first two definitions directives (which I'm guessing means they are preprocessing in nature), while the last is a statement. Regardless of the fact that they are distinguished by their syntaxes, why would the language developers complicate the semantics of the keyword by attaching three different meanings to it? For example, (disclaimer: off the top of my head, there may certainly be better examples) why not add keywords like alias and import? Technical, theoretical, or historical reasons? Keyword quota? ;-) Contrived sample: import System.Timers; alias LiteTimer=System.Threading.Timer; alias WinForms=System.Windows.Forms; public class Sample { public void Action { var elapsed = false; using(var t = new LiteTimer.Timer(_ => elapsed = true) { while (!elapsed) CallSomeFinickyApi(); } } } "Using" is such a vague word.

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  • How to represent a 3-way relation with JPA?

    - by simpatico
    A user may have several labels, and links. Then, a user associates a label (or more) to a link. How does one represent the later relationship? A solution could be a many-to-many relationship btw user and link with the optional attribute label. http://en.wikibooks.org/wiki/Java_Persistence/ManyToMany#Mapping_a_Join_Table_with_Additional_Columns In this case the relationship btw user and label may better be 'virtual'. Any alternative I'm not seeing? PS: I've used google bookmarks terminology, as it matches my case quite well.

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  • Phonegap: Will my mobile app 'feel' faster or slower once ported to phonegap?

    - by user15872
    So I'm designing everything in mobile Safari and I know that phonegap is essentially a stripped webview but... Question: Will my application will run better in phonegap? (revised below) a)I imagine my navigation and core app will load faster as the scripts and images are on the hard drive. Is this True? b)I assume since they've been working on it for 2 years now that they may have made some optimizations to make it quicker than just an average safari window. Is this true? (Assuming both html5/js/css code bases are pretty much the same and app is running on iOS.) Update: Sorry, I meant to compare apples to slightly different apples. Question 1 revised: Will my app see any performance benefits running with in a phonegap environment vs standard mobile safari? (compare mobile - to mobile) 1b) In what ways, other than loading time has phonegap optimized performance over standard mobile safari? Follow ups: 1) Are there any pitfalls, other than large libraries, that may cause phonegap to suffer a serious performance hit vs stand mobile safari? 2) Can I mix native and webview rendering? (i.e the top half of my app is rendered in with html/css/js and the bottom half native)

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  • suggestions on syntax to express mathematical formula concisely

    - by aaa
    hello. I am developing functional domain specific embedded language within C++ to translate formulas into working code as concisely and accurately as possible. I post prototype in the comment, it is about 2 hundred lines long. Right now my language looks something like this (well, actually is going to look like): // implies two nested loops j=0:N, i=0,j (range(i) < j < N)[T(i,j) = (T(i,j) - T(j,i))/e(i+j)]; // implies summation over above expression sum(range(i) < j < N))[(T(i,j) - T(j,i))/e(i+j)]; I am looking for possible syntax improvements/extensions or just different ideas about expressing mathematical formulas as clearly and precisely as possible (in any language, not just C++). Can you give me some syntax examples relating to my question which can be accomplished in your language of choice which consider useful. In particular, if you have some ideas about how to translate the above code segments, I would be happy to hear them. Thank you just to clarify and give actual formula, my short-term goal is to express the following expression concisely where values in <> are already computed as 4-dimensional array

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  • Would it be useful to change java to support both static and dynamic types?

    - by James A. N. Stauffer
    What if a Java allow both static and dynamic types. That might allow the best of both worlds. i.e.: String str = "Hello"; var temp = str; temp = 10; temp = temp * 5; Would that be possible? Would that be beneficial? Do any languages currently support both and how well does it work out? Here is a better example (generics can't be used but the program does know the type): var username = HttpServletRequest.getSession().getAttribute("username");//Returns a String if(username.length() == 0) { //Error }

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  • What do you call a generalized (non-GUI-related) "Model-View-Controller" architecture?

    - by dcuccia
    I am currently refactoring code that coordinates multiple hardware components for data acquisition, and feeling a bit like I'm recreating the wheel. In particular, an MVC-like pattern seems to be emerging. Except, this has nothing to do with a GUI and I'm worried that I'm forcing this particular pattern where another might be more appropriate. Here's my scenario: Individual hardware "component" classes obey interface contracts for each hardware type. Previously, component instances were orchestrated by a single monolithic InstrumentController class, which relied heavily on configuration + branching logic for executing a specific acquisition sequence. After an iteration, I have a separate controller for each component, with these controllers all managed by a small InstrumentControllerBase (or its derivatives). The composite system will receive "input" either programmatically or via inter-hardware component triggering - in either case these interactions are routed to, and handled by, the appropriate controller. So, I have something that feels MVC-esque, but I don't know if that's because I'm forcing the point. With little direct MVC experience in application development, it's hard to know if I'm just trying to make my scenario fit MVC, where another pattern might be a good alternative or complimentary. My problem is, search results and wiki documentation of these family of patterns seems to immediately drop me into GUI-specific discussions. I understand "M means Model data and the V means View" - but do you call the superset pattern? Component-Commander-Controller? Whence can I exhume examples exemplary?

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  • Is there anything wrong with having a few private methods exposing IQueryable<T> and all public meth

    - by Nate Bross
    I'm wondering if there is a better way to approach this problem. The objective is to reuse code. Let’s say that I have a Linq-To-SQL datacontext and I've written a "repository style" class that wraps up a lot of the methods I need and exposes IQueryables. (so far, no problem). Now, I'm building a service layer to sit on top of this repository, many of the service methods will be 1<-1 with repository methods, but some will not. I think a code sample will illustrate this better than words. public class ServiceLayer { MyClassDataContext context; IMyRepository rpo; public ServiceLayer(MyClassDataContext ctx) { context = ctx; rpo = new MyRepository(context); } private IQueryable<MyClass> ReadAllMyClass() { // pretend there is some complex business logic here // and maybe some filtering of the current users access to "all" // that I don't want to repeat in all of the public methods that access // MyClass objects. return rpo.ReadAllMyClass(); } public IEnumerable<MyClass> GetAllMyClass() { // call private IQueryable so we can do attional "in-database" processing return this.ReadAllMyClass(); } public IEnumerable<MyClass> GetActiveMyClass() { // call private IQueryable so we can do attional "in-database" processing // in this case a .Where() clause return this.ReadAllMyClass().Where(mc => mc.IsActive.Equals(true)); } #region "Something my class MAY need to do in the future" private IQueryable<MyOtherTable> ReadAllMyOtherTable() { // there could be additional constrains which define // "all" for the current user return context.MyOtherTable; } public IEnumerable<MyOtherTable> GetAllMyOtherTable() { return this.ReadAllMyOtherTable(); } public IEnumerable<MyOtherTable> GetInactiveOtherTable() { return this.ReadAllMyOtherTable.Where(ot => ot.IsActive.Equals(false)); } #endregion } This particular case is not the best illustration, since I could just call the repository directly in the GetActiveMyClass method, but let’s presume that my private IQueryable does some extra processing and business logic that I don't want to replicate in both of my public methods. Is that a bad way to attack an issue like this? I don't see it being so complex that it really warrants building a third class to sit between the repository and the service class, but I'd like to get your thoughts. For the sake of argument, lets presume two additional things. This service is going to be exposed through WCF and that each of these public IEnumerable methods will be calling a .Select(m => m.ToViewModel()) on each returned collection which will convert it to a POCO for serialization. The service will eventually need to expose some context.SomeOtherTable which wont be wrapped into the repository.

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  • Creating DB views in Ruby on Rails

    - by Zigu
    Hey guys, I'm building a "reports" functionality to a project. 3 roles here: 1) Volunteers (they report what hours they volunteered) 2) Supervisors (they look at the reported stuff, note: one supervisor can view all projects) 3) Projects (Represents a work project that some collection of volunteers work on) To explain what it does: A report will be specified by the supervisor to generate based on a query of what he needs. These could be plausible reports: 1) The total number of volunteers, and the total amount of volunteer hours on this project 2) All the volunteer's names and emails associated with a project 3) The number of active projects vs. the total number of projects I was thinking maybe that creating a view in rails and storing the name of that view so Rails will just check the view whenever a supervisor wants to pull up the "report". Is a view really the answer or is it better to just save a query? Can Rails do this or is there an even better or more simple way of achieving this functionality? Cheers, -Jeremiah Tantongco

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  • Is there a best practice for maintaining history in a database?

    - by Pete
    I don't do database work that often so this is totally unfamiliar territory for me. I have a table with a bunch of records that users can update. However, I now want to keep a history of their changes just in case they want to rollback. Rollback in this case is not the db rollback but more like revert changes two weeks later when they realized that they made a mistake. The distinction being that I can't have a transaction do the job. Is the current practice to use a separate table, or just a flag in the current table? It's a small database, 5 tables each with < 6 columns, < 1000 rows total.

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  • Android & Web: What is the equivalent style for the web?

    - by Legend
    I am quite impressed by the workflow I follow when developing Android applications: Define a layout in an xml file and then write all the code in a code-behind style. Is there an equivalent style for the web? I mean, with a predefined list of widgets that can be defined using a markup language and then control them using code? I have come across Google's Web Toolkit that does something like this but I'd like to hear what other's think as well.

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  • calling database driver in java app [basically a swing app]

    - by user993250
    I have made a java application that allows a user to choose from certain standards and then allows him to customize those standards according to his needs. Now, the customization [via a swing application] that has been made needs to be persistent. For this we use a database [mysql/access] and hook it to the application so that with each customization made, a table [if non-existent] is created [thus making it runtime and we can not pre-determine the table names or the keys of table etc] and an appropriate entry in the table is made. I have written the driver for this connection. How do I call it in the java application and what approach should I take? I would much appreciate that if somebody can refer me some example that not only shows a sample connection being made via driver but its appropriate calls to the database as well so that i can use it as a guide.

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  • Instantiating and referencing models in MVC

    - by fig-gnuton
    In MVC, should each model be a globally accessible singleton accessible to any view/controller? Or should the models be singletons that are dependency injected into any component that requires them? Or should a new model instance be created for each component that needs one, in which case events would be used to propagate changes across model instances of the same class?

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  • Best way to have common class shared by both C++ and Ruby?

    - by shuttle87
    I am currently working on a project where a team of us are designing a game, all of us are proficient in ruby and some (but not all) of us are proficient in c++. Initially we made the backend in ruby but we ported it to c++ for more speed. The c++ port of the backend has exactly the same features and algorithms as the original ruby code. However we still have a bunch of code in ruby that does useful things but we want it to now get the data from the c++ classes. Our first thought was that we could save some of the data structures in something like XML or redis and call that, but some of the developers don't like that idea. We don't need anything particularly complex data structures to be passed between the different parts of the code, just tuples, strings and ints. Is there any way of integrating the ruby code so that it can call the c++ stuff natively? Will we need to embed code? Will we have to make a ruby extension? If so are there any good resources/tutorials you could suggest? For example say we have this code in the c++ backend: class The_game{ private: bool printinfo; //print the player diagnostic info at the beginning if true int numplayers; std::vector<Player*> players; string current_action; int action_is_on; // the index of the player in the players array that the action is now on //more code here public: Table(std::vector<Player *> in_players, std::vector<Statistics *> player_stats ,const int in_numplayers); ~Table(); void play_game(); History actions_history; }; class History{ private: int action_sequence_number; std::vector<Action*> hand_actions; public: void print_history(); void add_action(Action* the_action_to_be_added); int get_action_sequence_number(){ return action_sequence_number;} bool history_actions_are_equal(); int last_action_size(int street,int number_of_actions_ago); History(); ~History(); }; Is there any way to natively call something in the actions_history via The_game object in ruby? (The objects in the original ruby code all had the same names and functionality) By this I mean: class MyRubyClass def method1(arg1) puts arg1 self.f() # ... but still available puts cpp_method.the_current_game.actions_history.get_action_sequence_number() end # Constructor: def initialize(arg) puts "In constructor with arg #{arg}" #get the c++ object here and call it cpp_method end end Is this possible? Any advice or suggestions are appreciated.

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  • What is the best way to expose a callback API - C++

    - by rursw1
    Hi, I have a C++ library that should expose some system\ resource calls as callbacks from the linked application. For example: the interfacing application (which uses this library) can send socket management callback functions - send, receive, open, close etc., and the library will use this implementation in stead of the library's implementation. (This way enables the application to manage the sockets by itself, can be useful). This library has to expose also more callbacks, like, for example, a password validation, so I wonder if there is a preferred method to expose the callback sending option in one API. Something like: int AddCallbackFunc (int functionCallbackType, <generic function prototype>, <generic way to pass some additional arguments>) Then within my library I will assign the callback to the appropriate function pointer according to the functionCallbackType parameter. Is there any way to implement it in a generic way which will fit ANY function prototype and ANY additional arguments? Your help will be more than appreciated... Thanks!

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  • Ignoring (serious) errors to keep the program alive?

    - by SQuirreL bites
    One of the main things I wanted to achieve in my experimental programming language was: When errors occur (Syntax, Name, Type, etc.) keep the program running, no matter how serious or devastating it is. I know that this is probably very bad, but I just wanted something that doesn't kill itself on every error - I find it interesting what happens when a serious error occurs but the program continues. Does this "paradigm" have a name? I mean expect for How bad is it to do the above? Are there programs in use out there that just follow: "Hey, this is a fatal, unexpected error - but you know what? I don't care!"?

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  • Entering large amounts of text data in HTML form

    - by MakkyNZ
    Hi I have a web page that has a requirement to allow users to paste large amounts of text data from an Excel spreadsheet directly into the input controls of the page. Typically the user would be pasting anywhere between 150 to 300 spreadsheet cells that are all in one column. What are some good ways i could use to capture this data on the web page? thanks

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  • Client-side user custom CSS single file for overriding multiple domains

    - by Cawas
    This is for using in Safari, though it could probably be used on Firefox as well. In Chrome you have to add a plugin anyway (which generally allow for custom CSS per domain), and Opera already allows this to be done without needing any CSS. But while it's for customizing on the client-side, it's also a pure CSS question. So I'm using no plugins here. So, again, I got a custom CSS code (easily) working for all domains. Now I want to get specify CSS code for each domain. All with just 1 CSS file that's being loaded by Safari. Over the web and googling, I've found two ways to supposedly do this, but none actually worked. They're both documented on userstyles.com: @-moz-document domain("your-domain.com") { }. This would be perfect, since I can have several tags like that and just choose which style will be loaded for which domain. It just doesn't work. @namespace is quite confusing and I've tried every variation I could think of. None worked.

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  • Many tables for many users?

    - by Seagull
    I am new to web programming, so excuse the ignorance... ;-) I have a web application that in many ways can be considered to be a multi-tenant environment. By this I mean that each user of the application gets their own 'custom' environment, with absolutely no interaction between those users. So far I have built the web application as a 'single user' environment. In other words, I haven't actually done anything to support multi-users, but only worked on the functionality I want from the app. Here is my problem... What's the best way to build a multi-user environment: All users point to the same 'core' backend. In other words, I build the logic to separate users via appropriate SQL queries (eg. select * from table where user='123' and attribute='456'). Each user points to a unique tablespace, which is built separately as they join the system. In this case I would simply generate ALL the relevant SQL tables per user, with some sort of suffix for the user. (eg. now a query would look like 'select * from table_ where attribute ='456'). In short, it's a difference between "select * from table where USER=" and "select * from table_USER".

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  • How value objects are saving and loading?

    - by yeraycaballero
    Since there isn't respositories for value objects. How can I load all value objects? Suppose we are modeling a blog application and we have this classes: Post (Entity) Comment (Value object) Tag (Value object) PostsRespository (Respository) I Know that when I save a new post, its tags are saving with it in the same table. But how could I load all tags of all posts. Has PostsRespository got a method to load all tags? I usually do it, but I want to know others opinions

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