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  • Alternative to singleton for unique resources

    - by user1320881
    I keep reading over and over again that one should avoid using singletons for various reasons. I'm wondering how to correctly handle a situation where a class represents a unique system resource. For example, a AudioOutput class using SDL. Since SDL_OpenAudio can only be open once at a time it makes no sense having more then one object of this type and it seems to me preventing accidentally making more then one object would actually be good. Just wondering what experienced programmers think about this, am i missing another option ?

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  • How much to put in a Repository class?

    - by chobo
    When using the repository pattern is it recommended to have one Repository class for each database table? Would I also map one service layer class to one repository class. I'm having a hard time trying to understand how much stuff one repository or service layer class should have. Thanks!

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  • How can I get a property as an Entity in Action of Asp.Net Mvc ?

    - by Felipe
    Hi all, i'd like to know how can I get a property like an entity, for example: My Model: public class Product { public int Id { get; set; } public string Name { get; set; } public Category Category { get; set; } } View: Name: <%=Html.TextBoxFor(x => x.Name) %> Category: <%= Html.DropDownList("Category", IEnumerable<SelectListItem>)ViewData["Categories"]) %> Controller: public ActionResult Save(Product product) { /// produtct.Category ??? } and how is the category property ? It's fill by the view ? ASP.Net MVC know how to fill this object by ID ? Thanks!

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  • MVC alternatives: examples of MVA & AVC?

    - by Phillip Oldham
    I'm interested in learning about the alternative patterns to Model-View-Controller, specifically the Model-View-Adapter and Application-View-Controller patterns. Google results tend to be either a high-level overview or Java-based. Can anyone either provide, or point me to, an example of these patterns in either PHP, Python or JavaScript?

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  • Locking DB w/ Large Reads (Ruby-on-Rails/Heroku)

    - by Splashlin
    Currently I have a Web API running on Heroku that is constantly writing information we're collecting from other data sources (currently theres about half a GB of data and it's growing very quickly). We're looking to add a reporting system on top of the current database that we can use to extract useful information out of the DB. The problem is that when we're running reports we're locking the DB and any other sites communicating with the DB are timing out. Does anyone have any solutions on how to solve this type of issue? Amazon RDS seems to have some interesting stuff with database replication but I don't know if that will solve my problems. Any advice would be greatly appreciated. Thanks

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  • Organizing development teams

    - by Patrick
    A long time ago, when my company was much smaller, dividing the development work over teams was quite easy: the 'application' team developed the applications-specific logic, often requiring a deep insight of specific industry problems) the 'generic' team developed the parts that were common/generic for all applications (user interface related stuff, database access, low-level Windows stuff, ...) Over the years the boundaries between the teams have become fuzzy: the 'application' teams often write application-specific functionality with a 'generic' part, so instead of asking the 'generic' team to write that part for them, they write it themselves to speed up the developments; then donate it to the 'generic' team the 'generic' team's focus seems to be more 'maintenance oriented'. All of the 'very generic' code has already been written, so no new developments are needed in it, but instead they continuously have to support all the functionality donated by the application teams. All this seems to indicate that it's not a good idea anymore to have this split in teams. Maybe the 'generic' team should evolve into a 'software quality' team (defining and guarding the rules for writing good quality software), or into a 'software deployment' team (defining how software should be deployed, installed, ...). How do you split up the work in different teams if you have different applications? everybody can write generic code and donates it to a central 'generic' team? everybody can write generic code, but nobody 'manages' this generic code (everybody is the owner) generic code is written by a 'generic' team only and the applications have to wait until the 'generic' team delivers the generic part (via a library, via a DLL) there is no overlap in code between the different applications some other way? Notice that thee advantage of having the mix (allowing everybody to write everywhere in the code) is that: code is written in a more flexible way it's easier to debug the code since you can easily step into the 'generic' code in the debugger But the big (and maybe only) disadvantage is that this generic code may become nobody's responsibility if there is no clear team that manages it anymore. What is your vision?

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  • I built my rails app with sqlite and without specifying any db field sizes, Is my app now foobared for production?

    - by Tim Santeford
    I've been following a lot of good tutorials on building rails apps but I seem to be missing the whole specifying and validating db field sizes part. I love not needing to have to think about it when roughing out an app (I would have never done this with a PHP or ASP.net app). However, now that I'm ready to go to production, I think I might have done myself a disservice by not specifying field sizes as I went. My production db will be MySQL. What is the best practice here? Do I need to go through all of my migration files and specify sizes, update all the models with validation, and update all my form partial views with input max widths? or am I missing a critical step in my development process?

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  • Can't declare an abstract method private....

    - by Zombies
    I want to do this, yet I can't. Here is my scenario and rational. I have an abstract class for test cases that has an abstract method called test(). The test() method is to be defined by the subclass; it is to be implemented with logic for a certain application, such as CRMAppTestCase extends CompanyTestCase. I don't want the test() method to be invoked directly, I want the super class to call the test() method while the sub class can call a method which calls this (and does other work too, such as setting a current date-time right before the test is executed for example). Example code: public abstract class CompanyTestCase { //I wish this would compile, but it cannot be declared private private abstract void test(); public TestCaseResult performTest() { //do some work which must be done and should be invoked whenever //this method is called (it would be improper to expect the caller // to perform initialization) TestCaseResult result = new TestCaseResult(); result.setBeginTime(new Date()); long time = System.currentTimeMillis(); test(); //invoke test logic result.setDuration(System.currentTimeMillis() - time); return result; } } Then to extend this.... public class CRMAppTestCase extends CompanyTestCase { public void test() { //test logic here } } Then to call it.... TestCaseResult result = new CRMAppTestCase().performTest();

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  • Which database should I use for best performance

    - by _simon_
    Hello, I am working in Visual Studio 2005, .NET 2.0. I need to write an application, which listens on COM port and saves incoming data to a database. Main feature: save incoming data (series of 13-digits numbers), if this number allready exists, then mark it as double. For example, there could be these records in database: 0000000000001 OK 0000000000002 OK 0000000000002 Double 0000000000003 OK 0000000000004 OK I could use SQL database, but I don't know if it is fast enough... Database should be able to store up to 10.000.000 records and write up to 100 records per minute (so it needs to check 100 times per minute if this record allready exists). Which database should I use? Maybe the whole database would need to be in RAM. Where could I learn more about this? Thanks

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  • Is throwing an exception a healthy way to exit?

    - by ramaseshan
    I have a setup that looks like this. class Checker { // member data Results m_results; // see below public: bool Check(); private: bool Check1(); bool Check2(); // .. so on }; Checker is a class that performs lengthy check computations for engineering analysis. Each type of check has a resultant double that the checker stores. (see below) bool Checker::Check() { // initilisations etc. Check1(); Check2(); // ... so on } A typical Check function would look like this: bool Checker::Check1() { double result; // lots of code m_results.SetCheck1Result(result); } And the results class looks something like this: class Results { double m_check1Result; double m_check2Result; // ... public: void SetCheck1Result(double d); double GetOverallResult() { return max(m_check1Result, m_check2Result, ...); } }; Note: all code is oversimplified. The Checker and Result classes were initially written to perform all checks and return an overall double result. There is now a new requirement where I only need to know if any of the results exceeds 1. If it does, subsequent checks need not be carried out(it's an optimisation). To achieve this, I could either: Modify every CheckN function to keep check for result and return. The parent Check function would keep checking m_results. OR In the Results::SetCheckNResults(), throw an exception if the value exceeds 1 and catch it at the end of Checker::Check(). The first is tedious, error prone and sub-optimal because every CheckN function further branches out into sub-checks etc. The second is non-intrusive and quick. One disadvantage is I can think of is that the Checker code may not necessarily be exception-safe(although there is no other exception being thrown anywhere else). Is there anything else that's obvious that I'm overlooking? What about the cost of throwing exceptions and stack unwinding? Is there a better 3rd option?

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  • What is the Rule of Thumb on Exposing Encapsulated Class Methods

    - by javamonkey79
    Consider the following analogy: If we have a class: "Car" we might expect it to have an instance of "Engine" in it. As in: "The car HAS-A engine". Similarly, in the "Engine" class we would expect an instance of "Starting System" or "Cooling System" which each have their appropriate sub-components. By the nature of encapsulation, is it not true that the car "HAS-A" "radiator hose" in it as well as the engine? Therefore, is it appropriate OO to do something like this: public class Car { private Engine _engine; public Engine getEngine() { return _engine; } // is it ok to use 'convenience' methods of inner classes? // are the following 2 methods "wrong" from an OO point of view? public RadiatorHose getRadiatorHose() { return getCoolingSystem().getRadiatorHose(); } public CoolingSystem getCoolingSystem() { return _engine.getCoolingSystem(); } } public class Engine { private CoolingSystem _coolingSystem; public CoolingSystem getCoolingSystem() { return _coolingSystem; } } public class CoolingSystem { private RadiatorHose _radiatorHose; public RadiatorHose getRadiatorHose() { return _radiatorHose; } } public class RadiatorHose {//... }

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  • How to construct objects based on XML code?

    - by the_drow
    I have XML files that are representation of a portion of HTML code. Those XML files also have widget declarations. Example XML file: <message id="msg"> <p> <Widget name="foo" type="SomeComplexWidget" attribute="value"> inner text here, sets another attribute or inserts another widget to the tree if needed... </Widget> </p> </message> I have a main Widget class that all of my widgets inherit from. The question is how would I create it? Here are my options: Create a compile time tool that will parse the XML file and create the necessary code to bind the widgets to the needed objects. Advantages: No extra run-time overhead induced to the system. It's easy to bind setters. Disadvantages: Adds another step to the build chain. Hard to maintain as every widget in the system should be added to the parser. Use of macros to bind the widgets. Complex code Find a method to register all widgets into a factory automatically. Advantages: All of the binding is done completely automatically. Easier to maintain then option 1 as every new widget will only need to call a WidgetFactory method that registers it. Disadvantages: No idea how to bind setters without introducing a maintainability nightmare. Adds memory and run-time overhead. Complex code What do you think is better? Can you guys suggest a better solution?

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  • Several C# Language Questions

    - by Water Cooler v2
    1) What is int? Is it any different from the struct System.Int32? I understand that the former is a C# alias (typedef or #define equivalant) for the CLR type System.Int32. Is this understanding correct? 2) When we say: IComparable x = 10; Is that like saying: IComparable x = new System.Int32(); But we can't new a struct, right? or in C like syntax: struct System.In32 *x; x=>someThing = 10; 3) What is String with a capitalized S? I see in Reflector that it is the sealed String class, which, of course, is a reference type, unlike the System.Int32 above, which is a value type. What is string, with an uncapitalized s, though? Is that also the C# alias for this class? Why can I not see the alias definitions in Reflector? 4) Try to follow me down this subtle train of thought, if you please. We know that a storage location of a particular type can only access properties and members on its interface. That means: Person p = new Customer(); p.Name = "Water Cooler v2"; // legal because as Name is defined on Person. but // illegal without an explicit cast even though the backing // store is a Customer, the storage location is of type // Person, which doesn't support the member/method being // accessed/called. p.GetTotalValueOfOrdersMade(); Now, with that inference, consider this scenario: int i = 10; // obvious System.object defines no member to // store an integer value or any other value in. // So, my question really is, when the integer is // boxed, what is the *type* it is actually boxed to. // In other words, what is the type that forms the // backing store on the heap, for this operation? object x = i; Update Thank you for your answers, Eric Gunnerson and Aaronought. I'm afraid I haven't been able to articulate my questions well enough to attract very satisfying answers. The trouble is, I do know the answers to my questions on the surface, and I am, by no means, a newbie programmer. But I have to admit, a deeper understanding to the intricacies of how a language and its underlying platform/runtime handle storage of types has eluded me for as long as I've been a programmer, even though I write correct code.

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  • How do I manipulate a tree of immutable objects?

    - by Frederik
    I'm building an entire application out of immutable objects so that multi-threading and undo become easier to implement. I'm using the Google Collections Library which provides immutable versions of Map, List, and Set. My application model looks like a tree: Scene is a top-level object that contains a reference to a root Node. Each Node can contain child Nodes and Ports. An object graph might look like this: Scene | +-- Node | +-- Node | +- Port +-- Node | +- Port +- Port If all of these objects are immutable, controlled by a top-level SceneController object: What is the best way to construct this hierarchy? How would I replace an object that is arbitrarily deep in the object tree? Is there a way to support back-links, e.g. a Node having a "parent" attribute?

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  • Sharing logic across different platforms

    - by Pranz
    Hello all, We have a business logic that works with the file systems on OS that we want to implement on both Linux and Windows platforms. The language we have selected is Python for Linux and C# for Windows. GUI is not a priority for now. We were looking for ways to abstract the business logic in a way that we dont have to repeat the business logic (ofcourse I understand since it is related to file system, some code will differ from platform to platform). Any ideas on how to implement it? Is C/C++ the only option. We dont want to use Java. Thanks, Pranz

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  • What CSS do I need to make my site more responsive?

    - by user2938757
    My site is: http://library.skybundle.com I feel like I almost have a responsive site. I did all the CSS styling myself. It is a Wordpress site but I completely edited the CSS of the original theme, so it is night-and-day different than it used to be. The original theme was mostly just for a canvas for me to work with, since I am not an expert in PHP and we wanted a Wordpress site for easy editing later on. Thanks to stackoverflow, I now have a footer that sticks to the bottom of every page and everything mostly looks good -- the way we want it anyway. The only thing missing now is the we want browser windows on MOBILE devices, such as on an iPhone, to automatically adjust the layout of the content in the body (wrapper). For example, on the main page (library.skybundle.com), I would like those two big icons two become vertically aligned as soon as the browser window sizes to a small, mostly vertical size, like that of a mobile phone. Take this site, for example: http://freedomsoundproductions.securesb.net/ This is what we would like it to do. So one a page with a sidebar, the content to the right of the sidebar should basically jump into the same "column" as the left sidebar and form one single long column. Just like in the example site above. This should all be possible via CSS. People in other forums seem to want me to use jQuery and stuff, but I can only use CSS, and I know that this must be possible without having to resort to jQuery, HTML, or other code.

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  • I need to create a contest....

    - by creocare
    I'm working on a contest where users vote for contestants. Each contestant will have a bio. I was wondering what would be the best way to approach this? Should I do this in php or javascript? Should I use a database to collect data? Should I use sqlite3? If I use sqlite3 how do i install that on my mac? I'm very new to all this but I'm a quick learner. Thanks for any advice.

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  • How to write this in better way?

    - by dario
    Hi all. Let's look at this code: IList<IHouseAnnouncement> list = new List<IHouseAnnouncement>(); var table = adapter.GetData(); //get data from repository object -> DataTable if (table.Rows.Count >= 1) { for (int i = 0; i < table.Rows.Count-1; i++) { var anno = new HouseAnnouncement(); anno.Area = float.Parse(table.Rows[i][table.powierzchniaColumn].ToString()); anno.City = table.Rows[i][table.miastoColumn].ToString(); list.Add(anno); } } return list; Is it better way to write this in less code and better fashion (must be :-) )? Maybe using labda (but let mi know how)? Thanks in advance!

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  • Static selection and Ruby on Rails objects

    - by Dave
    Hi all- I have a simple problem, but am having trouble wrapping my head around it. I have an video object that should have one or more "genres". This list of genres should be prepopulated and then the user should just select one or more using autocomplete or some such. Here is the question: Is it worth creating a table with genres for the static selection? Or should it just be included in the presentation layer? If there is a static table, how do we name it correctly. I envision something like this class Video < ActiveRecord::Base has_many :genres ... end class Genre < ... belongs_to :video ... end But then we get a table called genre, that basically maps all the selected genres to their parent videos. There would need to be some static table to reference the static genres. Is this the best way to do it? Sorry if this was rambl-y a little stream of conciousness. Thanks!

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