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  • How do you code up a pattern matching block in scala?

    - by egervari
    How do you code a function that takes in a block of code that contains case statements? For instance, in my block of code, I don't want to code a match or a default case... looking something like this myApi { case Whatever() => // code for case 1 case SomethingElse() => // code for case 2 } And inside of my myApi(), it'll actually do the matches. Help?

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  • How do you code up a pattern matching code block in scala?

    - by egervari
    How do you code a function that takes in a block of code as a parameter that contains case statements? For instance, in my block of code, I don't want to do a match or a default case explicitly. I am looking something like this myApi { case Whatever() => // code for case 1 case SomethingElse() => // code for case 2 } And inside of my myApi(), it'll actually execute the code block and do the matches. Help?

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  • Good case for a Null Object Pattern? (Provide some service with a mailservice)

    - by fireeyedboy
    For a website I'm working on, I made an Media Service object that I use in the front end, as well as in the backend (CMS). This Media Service object manipulates media in a local repository (DB); it provides the ability to upload/embed video's and upload images. In other words, website visitors are able to do this in the front end, but administrators of the site are also able to do this in the backend. I'ld like this service to mail the administrators when a visitor has uploaded/embedded a new medium in the frontend, but refrain from mailing them when they upload/embed a medium themself in the backend. So I started wondering whether this is a good case for passing a null object, that mimicks the mail funcionality, to the Media Service in the backend. I thought this might come in handy when they decide the backend needs to have implemented mail functionality as well. In simplified terms I'ld like to do something like this: Frontend: $mediaService = new MediaService( new MediaRepository(), new StandardMailService() ); Backend: $mediaService = new MediaService( new MediaRepository(), new NullMailService() ); How do you feel about this? Does this make sense? Or am I setting myself up for problems down the road?

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  • ASP.NET MVC - How to Unit Test boundaries in the Repository pattern?

    - by JK
    Given a basic repository interface: public interface IPersonRepository { void AddPerson(Person person); List<Person> GetAllPeople(); } With a basic implementation: public class PersonRepository: IPersonRepository { public void AddPerson(Person person) { ObjectContext.AddObject(person); } public List<Person> GetAllPeople() { return ObjectSet.AsQueryable().ToList(); } } How can you unit test this in a meaningful way? Since it crosses the boundary and physically updates and reads from the database, thats not a unit test, its an integration test. Or is it wrong to want to unit test this in the first place? Should I only have integration tests on the repository? I've been googling the subject and blogs often say to make a stub that implements the IRepository: public class PersonRepositoryTestStub: IPersonRepository { private List<Person> people = new List<Person>(); public void AddPerson(Person person) { people.Add(person); } public List<Person> GetAllPeople() { return people; } } But that doesnt unit test PersonRepository, it tests the implementation of PersonRepositoryTestStub (not very helpful).

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  • Is context inheritance, as shown by Head First Design Patterns' Duck example, irrelevant to strategy pattern?

    - by Korey Hinton
    In Head First Design Patterns it teaches the strategy pattern by using a Duck example where different subclasses of Duck can be assigned a particular behavior at runtime. From my understanding the purpose of the strategy pattern is to change an object's behavior at runtime. Emphasis on "an" meaning one. Could I further simplify this example by just having a Duck class (no derived classes)? Then when implementing one duck object it can be assigned different behaviors based on certain circumstances that aren't dependent on its own object type. For example: FlyBehavior changes based on the weather or QuackBehavior changes based on the time of day or how hungry a duck is. Would my example above constitute the strategy pattern as well? Is context inheritance (Duck) irrelevant to the strategy pattern or is that the reason for the strategy pattern? Here is the UML diagram from the Head First book:

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  • ObjectDataSource typename of a singleton Business object

    - by luppi
    My singleton business object is defined in Global: public class Global : HttpApplication { public static BusinessForm BusinessFormLayer; void Application_Start(object sender, EventArgs e) { FormDalProvider concreteProvider = FormDalProvider.Instance; BusinessForumLayer = new BusinessForum(concreteProvider); } } My page: <asp:ObjectDataSource ID="objThreads" runat="server" SelectMethod="GetForms" SelectCountMethod="GetFormsCount" TypeName="Global.BusinessFormLayer" EnablePaging="true" SortParameterName="sortExpression">

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  • Java : Singleton class instances in a Web based Application

    - by Preethi Jain
    I have this Singleton class inside a Web Application . public class MyDAO { private static MyDAO instance; private MyDAO() { } public static MyDAO getInstance() { if (instance == null) { instance = new MyDAO(); } return instance; } I will access it this way public void get_Data() { MyDAO dao = MyDAO.getInstance(); } How many Objects of MyDAO class will be created if there are 3 Users accessing the Application ?? Will there be one instance of MyDAO per User ??

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  • Session vs singleton pattern

    - by chobo
    Hi, I have a web application where I would like to pull user settings from a database and store them for Global access. Would it make more sense to store the data in a Singleton, or a Session object? What's the difference between the two? Is it better to store the data as an object reference or break it up into value type objects (ints and strings)? Thanks!

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  • Spring singleton lifecycle

    - by EugeneP
    Reading this When a bean is a singleton, only one shared instance of the bean will be managed and all requests for beans with an id or ids matching that bean definition will result in that one specific bean instance being returned. Will be managed... What does that mean? If there's only one object, than any modification to this object will result in that every another attempt to get this bean will return a modified instance??

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  • Servlet mapping url patterns

    - by Scobal
    I have the following urls that need mapping to two different servlets. Can anyone suggest a working url-pattern please? vehlocsearch-ws: /ws/vehlocsearch/vehlocsearch /ws/vehavailrate/vehavailratevehlocsearch /ws/vehavailrate/vehavailratevehlocsearch.wsdl vehavailrate-ws: /ws/vehavailrate/vehavailrate /ws/vehavailrate/vehavailratevehavailrate /ws/vehavailrate/vehavailratevehavailrate.wsdl So far I have this, which feels right, but isn't: <servlet-mapping> <servlet-name>vehlocsearch-ws</servlet-name> <url-pattern>*.vehlocsearch*</url-pattern> </servlet-mapping> <servlet-mapping> <servlet-name>vehavailrate-ws</servlet-name> <url-pattern>*.vehavailrate*</url-pattern> </servlet-mapping> Note: I have no control over the incoming urls

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  • 'Singleton' application - or let the user only launch one instance of a program at the time

    - by Disco
    I'm running a few linux desktops; mainly for kids (yeah, trying to teach them the right OS at early stage) (running Ubuntu 10.10, Gnome) The problem is that they found very funny to make their workstations (actually, old 512 Mb pentium 4) by launching thousands of firefox instances. I'm looking for a way to restrict them to launch 'N' instances of a particular application. Haven't figured yet how. Thought of a monitoring daemon but I think that would be too ressources hungry. Any idea of a script/trick to achieve this ? Note: i might have 1-2 level of users (the kids, and the more grown up kids) so i have also to limit per user; something like user1: 3firefox, user2: 2firefox instances.

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  • Pass variable to regular expression pattern string in jquery

    - by phil
    Is that possible to pass variable into regular expression pattern string in jquery ( or javascript)? For example, I want to validate a zip code input field every time while user type in a character by passing variable i to the regular expression pattern. How to do it right? $('#zip').keyup( function(){ var i=$('#zip').val().length for ( i; i<=5; i++){ var pattern=/^[0-9]{i}$/; if ( !pattern.test( $('#zip').val() ) ) {$('#zip_error').css('display','inline');} else {$('#zip_error').css('display','none');} } })

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  • java.util.regex.Pattern matching the beginning of a String

    - by Pierre
    Hi all, Is it possible to know if a stream/string contains an input that could match a regular expression. For example String input="AA"; Pattern pat=Pattern.compile("AAAAAB"); Matcher matcher=pat.matcher(input); //<-- something here returning true ? or String input="BB"; Pattern pat=Pattern.compile("AAAAAB"); Matcher matcher=pat.matcher(input); //<-- something here returning false ? Thanks

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  • How does the following regex pattern work?

    - by zSysop
    Hi all, I'm horrible with regex but i'm trying to figure out how an import function works and i came across this regex pattern. Maybe one of you can help me understand how it works. string pattern = @"^""(?<code>.*)"",""(?<last_name>.*)"",""(?<first_name>.*)"",""(?<address>.*)"",""(?<city>.*)"",""(?<state>.*)"",""(?<zip>.*)""$"; Regex re = new Regex(pattern); Match ma = re.Match(_sReader.ReadLine().Trim()); Thanks

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  • Finding a pattern within a string variable in C#

    - by lo3
    Ok i'm working on a project for a 200 level C# course, we are required to create a heads or tails project. Basically the project is setup so that the computer will guess randomly up to 5 times, but on the sixth time it will look into the playersGuessHistory variable setup as a string to see if it can find a match for a pattern of 4 entires, if there is a pattern found the computer will guess the next character after the pattern EX: [HHTT]H [HHTTH]H HHTT being the pattern then the computer would guess H for the next turn. My only problem is that i'm having difficulty setting up the project so that it will look through the playersguesshistory and find the patterns and guess the next character in the history. Any suggestions?

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  • php replace a pattern

    - by Hulk
    Suppose in a file there is a pattern as sumthing.c: and asdfg.c: and many more.. with *.c: pattern How to replace this with the text yourinput and save the file using php The pattern is *.c thanks..

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  • The IOC "child" container / Service Locator

    - by Mystagogue
    DISCLAIMER: I know there is debate between DI and service locator patterns. I have a question that is intended to avoid the debate. This question is for the service locator fans, who happen to think like Fowler "DI...is hard to understand...on the whole I prefer to avoid it unless I need it." For the purposes of my question, I must avoid DI (reasons intentionally not given), so I'm not trying to spark a debate unrelated to my question. QUESTION: The only issue I might see with keeping my IOC container in a singleton (remember my disclaimer above), is with the use of child containers. Presumably the child containers would not themselves be singletons. At first I thought that poses a real problem. But as I thought about it, I began to think that is precisely the behavior I want (the child containers are not singletons, and can be Disposed() at will). Then my thoughts went further into a philosophical realm. Because I'm a service locator fan, I'm wondering just how necessary the notion of a child container is in the first place. In a small set of cases where I've seen the usefulness, it has either been to satisfy DI (which I'm mostly avoiding anyway), or the issue was solvable without recourse to the IOC container. My thoughts were partly inspired by the IServiceLocator interface which doesn't even bother to list a "GetChildContainer" method. So my question is just that: if you are a service locator fan, have you found that child containers are usually moot? Otherwise, when have they been essential? extra credit: If there are other philosophical issues with service locator in a singleton (aside from those posed by DI advocates), what are they?

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  • Best practice for DAO pattern ?

    - by Tony
    I've seen a lot of codes use a service-dao pattern , I don't know the origin of this pattern . It force the front layer call service , then delegates some of the service task to dao. I want to ask : Does DAO layer do purely data access related task ? What about exception encapsulation ? Is there other pattern can be used to replace this ?

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  • PRG Pattern and Sticky Forms

    - by Scott Christopherson
    I'm using the PRG pattern on a form of mine. I've never used this approach before and I'm trying to figure something out: Normally, I always just displayed the posted form again when there were validation errors and displayed POST values in the form (sticky form). However with the PRG pattern, the form is displayed after a redirect, so there aren't any POST values. So my question is, how can I implement the PRG pattern and still have sticky forms?

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