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• Is there a difference between Perl's shift versus assignment from @_ for subroutine parameters?

  - by cowgod

  Let us ignore for a moment Damian Conway's best practice of no more than three positional parameters for any given subroutine. Is there any difference between the two examples below in regards to performance or functionality? Using shift: sub do_something_fantastical { my $foo = shift; my $bar = shift; my $baz = shift; my $qux = shift; my $quux = shift; my $corge = shift; } Using @_: sub do_something_fantastical { my ($foo, $bar, $baz, $qux, $quux, $corge) = @_; } Provided that both examples are the same in terms of performance and functionality, what do people think about one format over the other? Obviously the example using @_ is fewer lines of code, but isn't it more legible to use shift as shown in the other example? Opinions with good reasoning are welcome.

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• How to test method call order with Moq

  - by Finglas

  At the moment I have: [Test] public void DrawDrawsAllScreensInTheReverseOrderOfTheStack() { // Arrange. var screenMockOne = new Mock<IScreen>(); var screenMockTwo = new Mock<IScreen>(); var screens = new List<IScreen>(); screens.Add(screenMockOne.Object); screens.Add(screenMockTwo.Object); var stackOfScreensMock = new Mock<IScreenStack>(); stackOfScreensMock.Setup(s => s.ToArray()).Returns(screens.ToArray()); var screenManager = new ScreenManager(stackOfScreensMock.Object); // Act. screenManager.Draw(new Mock<GameTime>().Object); // Assert. screenMockOne.Verify(smo => smo.Draw(It.IsAny<GameTime>()), Times.Once(), "Draw was not called on screen mock one"); screenMockTwo.Verify(smo => smo.Draw(It.IsAny<GameTime>()), Times.Once(), "Draw was not called on screen mock two"); } But the order in which I draw my objects in the production code does not matter. I could do one first, or two it doesn't matter. However it should matter as the draw order is important. How do you (using Moq) ensure methods are called in a certain order? Edit I got rid of that test. The draw method has been removed from my unit tests. I'll just have to manually test it works. The reversing of the order though was taken into a seperate test class where it was tested so it's not all bad. Thanks for the link about the feature they are looking into. I sure hope it gets added soon, very handy.

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• design using a readonly class in c#

  - by edosoft

  Hi Small design question here. I'm trying to develop a calculation app in C#. I have a class, let's call it InputRecord, which holds 100s of fields (multi dimensional arrays) This InputRecordclass will be used in a number of CalculationEngines. Each CalculcationEngine can make changes to a number of fields in the InputRecord. These changes are steps needed for it's calculation. Now I don't want the local changes made to the InputRecord to be used in other CalculcationEngine's classes. The first solution that comes to mind is using a struct: these are value types. However I'd like to use inheritance: each CalculationEngine needs a few fields only relevant to that engine: it's has it's own InputRecord, based on BaseInputRecord. Can anyone point me to a design that will help me accomplish this?

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• Is there a naming convention for a method that should set the properties of the passed object.

  - by Genady Sergeev

  Hello, I am writing a method that will set the properties of an object passed as a parameter. The method accepts one parameter of type interface and the return type of the method is the same interface. I was wondering if there is some kind of a naming convention for such methods. I was thinking of something like: FillInInterfaceTypeData or InitInterfaceTypeData but both sound clumsy to me. How do you think?

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• If handcoded webpage displays the same as WYSIWYG generated page, what did I gain? Can I compete wit

  - by CrazyJugglerDrummer

  My friend uses DreamWeaver to create web pages and doesn't know any HTML at all. I know HTML inside and out and can hand code from the ground up. But our web pages look similar and he can get paid for his WYSIWYG generated sites. What have I gained from learning HTML and hand-coding? Can I compete with people using DreamWeaver or other WYSIWYG editors? I know that for something like JavaScript or PHP the only way to go is to hand-code the whole thing yourself, no tools can do that for you, but is HTML in the same position?

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• Would you rather use a Singleton or dispatch another class' event through a Chain of Responsibility?

  - by Pup

  In general, what would make your program more maintainable? I know a lot of folks that make heavy use of Singletons, but that seems like a cop-out, which creates a kind of global junk drawer organization.

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• C# Property Access vs Interface Implementation

  - by ehdv

  I'm writing a class to represent a Pivot Collection, the root object recognized by Pivot. A Collection has several attributes, a list of facet categories (each represented by a FacetCategory object) and a list of items (each represented by a PivotItem object). Therefore, an extremely simplified Collection reads: public class Collection { private List<FacetCategory> categories; private List<PivotItem> items; // other attributes } What I'm unsure of is how to properly grant access to those two lists. Because declaration order of both facet categories and items is visible to the user, I can't use sets, but the class also shouldn't allow duplicate categories or items. Furthermore, I'd like to make the Collection object as easy to use as possible. So my choices are: Have Collection implement IList<PivotItem> and have accessor methods for FacetCategory: In this case, one would add an item to Collection foo by writing foo.Add(bar). This works, but since a Collection is equally both kinds of list making it only pass as a list for one type (category or item) seems like a subpar solution. Create nested wrapper classes for List (CategoryList and ItemList). This has the advantage of making a consistent interface but the downside is that these properties would no longer be able to serve as lists (because I need to override the non-virtual Add method I have to implement IList rather than subclass List. Implicit casting wouldn't work because that would return the Add method to its normal behavior. Also, for reasons I can't figure out, IList is missing an AddRange method... public class Collection { private class CategoryList: IList<FacetCategory> { // ... } private readonly CategoryList categories = new CategoryList(); private readonly ItemList items = new ItemList(); public CategoryList FacetCategories { get { return categories; } set { categories.Clear(); categories.AddRange(value); } } public ItemList Items { get { return items; } set { items.Clear(); items.AddRange(value); } } } Finally, the third option is to combine options one and two, so that Collection implements IList<PivotItem> and has a property FacetCategories. Question: Which of these three is most appropriate, and why?

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• Facade controller, is it efficient?

  - by Berlioz

  Using a facade controller pattern in .net. It seems as if though it is not efficient BECAUSE, for every event that happens in a domain object(Sales, Register, Schedule, Car) it has to be subscribed to by the controller(use case controller) and then the controller in turn has to duplicate that same event to make it available for the presentation, so that the presentation can show it to the user. Does this make sense? Please comment!

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• One executable with cmd-line params or just many satellite executables?

  - by Nikos Baxevanis

  I design an application back-end. For now, it is a .NET process (a Console Application) which hosts various communication frameworks such as Agatha and NServiceBus. I need to periodically update my datastore with values (coming from the application while it's running). I found three possible ways: Accept command line arguments, so I can call my console app with -update. On start up a background thread will periodically invoke the update method. Create an updater.exe app which will do the updates, but I will have code duplication since in some way it will need to query the data from the source in order to save it to the datastore. Which one is better?

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• How to allow for modular development while still running in same JVM?

  - by Marcus

  Our current app runs in a single JVM. We are now splitting up the app into separate logical services where each service runs in its own JVM. The split is being done to allow a single service to be modified and deployed without impacting the entire system. This reduces the need to QA the entire system - just need to QA the interaction with the service being changed. For interservice communication we use a combination of REST, an MQ system bus, and database views. What I don't like about this: REST means we have to marshal data to/from XML DB views couple the systems together which defeats the whole concept of separate services MQ / system bus is added complexity There is inevitably some code duplication between services You have set up n JBoss server configurations, we have to do n number of deployments, n number of set up scripts, etc, etc. Is there a better way to structure an internal application to allow modular development and deployment while allowing the app to run in a single JVM (and achieving the associated benefits)?

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• Building a minimal plugin architecture in Python.

  - by dF

  I have an application, written in Python, which is used by a fairly technical audience (scientists). I'm looking for a good way to make the application extensible by the users, i.e. a scripting/plugin architecture. I am looking for something extremely lightweight. Most scripts, or plugins, are not going to be developed and distributed by a third-party and installed, but are going to be something whipped up by a user in a few minutes to automate a repeating task, add support for a file format, etc. So plugins should have the absolute minimum boilerplate code, and require no 'installation' other than copying to a folder (so something like setuptools entry points, or the Zope plugin architecture seems like too much.) Are there any systems like this already out there, or any projects that implement a similar scheme that I should look at for ideas / inspiration?

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• How should I implement items that are normalized in the Database, in Object Oriented Design?

  - by Jonas

  How should I implement items that are normalized in the Database, in Object Oriented classes? In the database I have a big table of items and a smaller of groups. Each item belong to one group. This is how my database design look like: +----------------------------------------+ | Inventory | +----+------+-------+----------+---------+ | Id | Name | Price | Quantity | GroupId | +----+------+-------+----------+---------+ | 43 | Box | 34.00 | 456 | 4 | | 56 | Ball | 56.50 | 3 | 6 | | 66 | Tin | 23.00 | 14 | 4 | +----+------+-------+----------+---------+ Totally 3000 lines +----------------------+ | Groups | +---------+------+-----+ | GroupId | Name | VAT | +---------+------+-----+ | 4 | Mini | 0.2 | | 6 | Big | 0.3 | +---------+------+-----+ Totally 10 lines I will use the OOP classes in a GUI, where the user can edit Items and Groups in the inventory. It should also be easy to do calculations with a bunch of items. The group information like VAT are needed for the calculations. I will write an Item class, but do I need a Group class? and if I need it, should I keep them in a global location or how do I access it when I need it for Item-calculations? Is there any design pattern for this case?

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• best practice for passing many arguments to method ?

  - by Tony

  Occasionally , we have to write methods that receive many many arguments , for example : public void doSomething(Object objA , Object objectB ,Date date1 ,Date date2 ,String str1 ,String str2 ) { } When I encounter this kind of problem , I often encapsulate arguments into a map. Map<Object,Object> params = new HashMap<Object,Object>(); params.put("objA",ObjA) ; ...... public void doSomething(Map<Object,Object> params) { // extracting params Object objA = (Object)params.get("objA"); ...... } This is not a good practice , encapsulate params into a map is totally a waste of efficiency. The good thing is , the clean signature , easy to add other params with fewest modification . what's the best practice for this kind of problem ?

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• How should the Version field be used in Trac?

  - by Eric

  I use Trac to track bugs, and future changes in my software projects. Tickets in Trac have a "Version" field and I'm trying to figure out the best way to use this field. Say I find a series of bugs in version 1.0 of my software. I create tickets in track for each and assign them to version 1.0. Now say I fix some of the bugs, and add some of the new features and release version 1.1. But some of the old 1.0 bugs are still in 1.1. Should I change their corresponding tickets to version 1.1 because they also now exist in 1.1? Or should I leave them set to version 1.0 as a way of tracking what version the bug was found in, and just assume that any open tickets in older versions still exist in newer versions?

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• Immutable classes in C++

  - by ereOn

  Hi, In one of my projects, I have some classes that represent entities that cannot change once created, aka. immutable classes. Example : A class RSAKey that represent a RSA key which only has const methods. There is no point changing the existing instance: if you need another one, you just create one. My objects sometimes are heavy and I enforced the use of smart pointers to avoid copy. So far, I have the following pattern for my classes: class RSAKey : public boost::noncopyable, public boost::enable_shared_from_this<RSAKey> { public: /** * \brief Some factory. * \param member A member value. * \return An instance. */ static boost::shared_ptr<const RSAKey> createFromMember(int member); /** * \brief Get a member. * \return The member. */ int getMember() const; private: /** * \brief Constructor. * \param member A member. */ RSAKey(int member); /** * \brief Member. */ const int m_member; }; So you can only get a pointer (well, a smart pointer) to a const RSAKey. To me, it makes sense, because having a non-const reference to the instance is useless (it only has const methods). Do you guys see any issue regarding this pattern ? Are immutable classes something common in C++ or did I just created a monster ? Thank you for your advices !

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• Why should GoTos be bad?

  - by lisn

  I'm using gotos and a lot of them. C++, PHP or COBOL - I use them on nearly all occasions where everybody else would use functions or even classes. Yet my code is Clear Maintainable Bug-free Fast So why does everybody I meet tell me about how bad gotos are? Are there any facts that show that they are "bad"?

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• Combine hash values in C#

  - by Chris

  I'm creating a generic object collection class and need to implement a Hash function. I can obviously (and easily!) get the hash values for each object but was looking for the 'correct' way to combine them to avoid any issues. Does just adding, xoring or any basic operation harm the quality of the hash or am I going to have to do something like getting the objects as bytes, combining them and then hashing that? Cheers in advance

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• Is there a memory and performance hit taken from using Bloch's Builder Pattern?

  - by WolfmanDragon

  What is the memory and performance usage compared to creating a object with only a constructor? The usage here is in creating a Set<Object> or List<Object> that may contain million plus entries and I am concerned with the overhead of using Bloch's Builder Pattern. I have used it in the past, but never in this large of a scope.

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• How to save objects using Multi-Threading in Core Data?

  - by Konstantin

  I'm getting some data from the web service and saving it in the core data. This workflow looks like this: get xml feed go over every item in that feed, create a new ManagedObject for every feed item download some big binary data for every item and save it into ManagedObject call [managedObjectContext save:] Now, the problem is of course the performance - everything runs on the main thread. I'd like to re-factor as much as possible to another thread, but I'm not sure where I should start. Is it OK to put everything (1-4) to the separate thread?

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• MVC (model-view-controller) - can it be explained in simple terms?

  - by DVK

  I need to explain to a not-very-technical manager the MVC (model-view-controller) concept and ran into trouble. The problem is that the explanation needs to be on a "your grandma will get it" level - e.g. even the fairly straightforward explanation offered on MVC Wiki page didn't work, at least with my commentary. Does anyone have a reference to a good MVC explanation in simple terms? It would ideally be done with non-techie metaphor examples (e.g. similar to "Decorator pattern is like glasses") - one reason I failed was that all MVC examples I could come up with were development related. I once saw a list of pattern explanations but to the best of my memory MVC was not on it. Thanks!

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• Application Design: Single vs. Multiple Hits to the DB

  - by shyneman

  I'm building a service that performs a set of configured activities based on the type of request that it receives. Each activity involves going to the database and retrieving/updating some kind of information. The logic for each activity can be generalized and re-used across different request types. The activities may need to participate in a transaction for the duration of the servicing the request. One option, I'm considering is having each activity maintain its own access to DAL/database. This fully encapsulates the activity into a stand-alone re-usable piece, but hitting the database multiple times for one request doesn't seem like a viable option. I don't really know how to easily implement the concept of a transaction across the multiple activities here either. The second option is to encapsulate ALL the activities into one big activity and hit the database once. But this does not allow re-use and configuration of these activities for different requests. Does anyone have any suggestions and input about what should be the best way to approach my problem? Thanks for any help.

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• Dependency Injection: I don't get where to start!

  - by Andy

  I have several articles about Dependency Injection, and I can see the benefits, especially when it comes to unit testing. The units can me loosely coupled, and mocking of dependencies can be made. The trouble is - I just don't get where to start. Consider this snippet below of (much edited for the purpose of this post) code that I have. I am instantiating a Plc object from the main form, and passing in a communications mode via the Connect method. In it's present form it becomes hard to test, because I can't isolate the Plc from the CommsChannel to unit test it. (Can I?) The class depends on using a CommsChannel object, but I am only passing in a mode that is used to create this channel within the Plc itself. To use dependancy injection, I should really pass in an already created CommsChannel (via an 'ICommsChannel' interface perhaps) to the Connect method, or maybe via the Plc constructor. Is that right? But then that would mean creating the CommsChannel in my main form first, and this doesn't seem right either, because it feels like everything will come back to the base layer of the main form, where everything begins. Somehow it feels like I am missing a crucial piece of the puzzle. Where do you start? You have to create an instance of something somewhere, but I'm struggling to understand where that should be. public class Plc() { public bool Connect(CommsMode commsMode) { bool success = false; // Create new comms channel. this._commsChannel = this.GetCommsChannel(commsMode); // Attempt connection success = this._commsChannel.Connect(); return this._connected; } private CommsChannel GetCommsChannel(CommsMode mode) { CommsChannel channel; switch (mode) { case CommsMode.RS232: channel = new SerialCommsChannel( SerialCommsSettings.Default.ComPort, SerialCommsSettings.Default.BaudRate, SerialCommsSettings.Default.DataBits, SerialCommsSettings.Default.Parity, SerialCommsSettings.Default.StopBits); break; case CommsMode.Tcp: channel = new TcpCommsChannel( TCPCommsSettings.Default.IP_Address, TCPCommsSettings.Default.Port); break; default: // Throw unknown comms channel exception. } return channel; } }

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• multiple classes with same methods - best pattern

  - by Tony

  I have a few classes in my current project where validation of Email/Website addresses is necessary. The methods to do that are all the same. I wondered what's the best way to implement this, so I don't need to have these methods copy pasted everywhere? The classes themselves are not necessarily related, they only have those validation methods in common.

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• Pattern for null settings

  - by user21243

  Hi, I would like to hear your thoughts and ideas about this one. in my application i have controls that are binded to objects properties. but.. the controls always looks like that: a check box, label that explain the settings and then the edited control (for ex: text box) when unchecking the checkbox i disable the text box (using binding) when the checkbox is unchecked i want the property to contain null, and when it is checked i would like the property to contain the text box's text. Of course text box can be NumericUpDown, ComboBox, DatePicker etc.. Do you have any smart way of doing it using binding or do i have to do everything on code; I really would like to a build a control that supports that and re-use it all over Ideas? Thanks,

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• Conditional column values in NSTableView?

  - by velocityb0y

  I have an NSTableView that binds via an NSArrayController to an NSMutableArray. What's in the array are derived classes; the first few columns of the table are bound to properties that exist on the base class. That all works fine. Where I'm running into problem is a column that should only be populated if the row maps to one specific subclass. The property that column is meant to display only exists in that subclass, since it makes no sense in terms of the base class. The user will know, from the first two columns, why the third column's cell is populated/editable or not. The binding on the third column's value is on arrangedObjects, with a model path of something like "foo.name" where foo is the property on the subclass. However, this doesn't work, as the other subclasses in the hierarchy are not key-value compliant for foo. It seems like my only choice is to have foo be a property on the base class so everybody responds to it, but this clutters up the interfaces of the model objects. Has anyone come up with a clean design for this situation? It can't be uncommon (I'm a relative newcomer to Cocoa and I'm just learning the ins and outs of bindings.)

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