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  • Is it advisable to have an interface as the return type?

    - by wb
    I have a set of classes with the same functions but with different logic. However, each class function can return a number of objects. It is safe to set the return type as the interface? Each class (all using the same interface) is doing this with different business logic. protected IMessage validateReturnType; <-- This is in an abstract class public bool IsValid() <-- This is in an abstract class { return (validateReturnType.GetType() == typeof(Success)); } public IMessage Validate() { if (name.Length < 5) { validateReturnType = new Error("Name must be 5 characters or greater."); } else { validateReturnType = new Success("Name is valid."); } return validateReturnType; } Are there any pitfalls with unit testing the return type of an function? Also, is it considered bad design to have functions needing to be run in order for them to succeed? In this example, Validate() would have to be run before IsValid() or else IsValid() would always return false. Thank you.

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  • How to separate model and view with Core Data?

    - by andrewebling
    I have a subclass of UIView which draws itself based on data held in a corresponding model class, which is a subclass of NSManagedObject. The problem is, some fields in the data model (e.g. the position of the view) are already held in the view (i.e. the frame property in this case). I then have a data duplication/synchronization problem to solve. To complicate matters further, the view needs to update in response to changes made to the data model and the data model needs to be updated in responses made to the view (e.g. the user dragging it to a new location). What's the best way to solve this? Using KVO and references in both directions? Or is there a better approach?

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  • Can I use an abstract class instead of a private __construct() when creating a singleton in PHP?

    - by Pheter
    When creating a Singleton in PHP, I ensure that it cannot be instantiated by doing the following: class Singleton { private function __construct() {} private function __clone() {} public static function getInstance() {} } However, I realised that defining a class as 'abstract' means that it cannot be instantiated. So is there anything wrong with doing the following instead: abstract class Singleton { public static function getInstance() {} } The second scenario allows me to write fewer lines of code which would be nice. (Not that it actually makes much of a difference.)

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  • commad design pattern usage

    - by sagie
    Hi. I've read 3 descriptions of the command design pattern: wikipedia, dofactory and source making. In all of them, the UML shows a relation between the client to the receiver & the concrete command, but no relation to the invoker. But in all 3 examples the client is the one that initiates the invoker and call its Execute method. I think that should be a relation to the invoker as well. Am I missing somthing in here? Maybe even a basic UML knowladge?

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  • How to proxy calls to the instance of an object

    - by mr.b
    Edit: Changed question title from "Does C# allow method overloading, PHP style (__call)?" - figured out it doesn't have much to do with actual question. Also edited question text. What I want to accomplish is to proxy calls to a an instance of an object methods, so I could log calls to any of its methods. Right now, I have code similar to this: class ProxyClass { static logger; public AnotherClass inner { get; private set; } public ProxyClass() { inner = new AnotherClass(); } } class AnotherClass { public void A() {} public void B() {} public void C() {} // ... } // meanwhile, in happyCodeLandia... ProxyClass pc = new ProxyClass(); pc.inner.A(); // need to write log message like "method A called" pc.inner.B(); // need to write log message like "method B called" // ... So, how can I proxy calls to an object instance in extensible way? Method overloading would be most obvious solution (if it was supported in PHP way). By extensible, meaning that I don't have to modify ProxyClass whenever AnotherClass changes. In my case, AnotherClass can have any number of methods, so it wouldn't be appropriate to overload or wrap all methods to add logging. I am aware that this might not be the best approach for this kind of problem, so if anyone has idea what approach to use, shoot. Thanks!

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  • How to design the application to conform to the n-tier architecture? (Winform sample in .net with li

    - by AlexRednic
    Rather a simple question. But the implications are vast. Over the last few weeks I've been reading a lot of material about n-tier architecture and it's implementation in the .NET world. The problem is I couldn't find a relevant sample for Winforms with Linq (linq is the way to go for BLL right?). How did you guys manage to grasp the n-tier concept? Books, articles, relevant samples etc.

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  • effective counter for unique number of visits in PHP & MySQL

    - by Adnan
    Hello, I am creating a counter for unique number of visits on a post, so what I have until now is a table for storing data like this; cvp_post_id | cvp_ip | cvp_user_id In cases a registered user visits a post, for the first time a record is inserted with cpv_post_id and cvp_user_id, so for his next visit I query the table and if the record is available I do not count him as a new visitor. In cases of an anonymous user the same happens but now the cvp_ip and cpv_post_id are used. My concerns is that I do a query every time anyone visits a post for checking if there has been a visit, what would be a more effective way for doing this?

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  • C++ Iterator Pipelining Designs

    - by Kirakun
    Suppose we want to apply a series of transformations, int f1(int), int f2(int), int f3(int), to a list of objects. A naive way would be SourceContainer source; TempContainer1 temp1; transform(source.begin(), source.end(), back_inserter(temp1), f1); TempContainer2 temp2; transform(temp1.begin(), temp1.end(), back_inserter(temp2), f2); TargetContainer target; transform(temp2.begin(), temp2.end(), back_inserter(target), f3); This first solution is not optimal because of the extra space requirement with temp1 and temp2. So, let's get smarter with this: int f123(int n) { return f3(f2(f1(n))); } ... SourceContainer source; TargetContainer target; transform(source.begin(), source.end(), back_inserter(target), f123); This second solution is much better because not only the code is simpler but more importantly there is less space requirement without the intermediate calculations. However, the composition f123 must be determined at compile time and thus is fixed at run time. How would I try to do this efficiently if the composition is to be determined at run time? For example, if this code was in a RPC service and the actual composition--which can be any permutation of f1, f2, and f3--is based on arguments from the RPC call.

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  • C# Class Factories

    - by Andy
    I have a class called Foo that has a function that looks like the following List<Bar> LoadData(); Both Foo and Bar are in a library that I want to reuse in other projects. Now I am working on a new project and I want to subclass Bar. Let's call it NewBar. What is a simple and flexible way to get Foo.LoadData to return a list of NewBar? I think that a factory is needed or perhaps just a delegate function. Can anyone provide an example? Thanks, Andy

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  • How to have the controller change its behavior depending on the view?

    - by Ian Boyd
    If from one view a user enters some invalid data, e.g.:     E-mail: [email protected]     then i want the controller to: not place the data into the model color the text box reddish not allow the user to save But it's possible that if the user enters the same invalid data in a different view i want the controller to: place the data into the model color the text box reddish allow the user to save But it's possible that if the user enters the same invalid data in a different view i want the controller to: place the data into the model color the text box bluish allow the user to save And it's possible that another view will: place the data into the model leave the text box uncolored allow the user to save And it's possible that another view will: auto-correct the data, placing it into the model color the text-box reddish allow the user to have And it's possible for another view to: auto-correct the data, placing it into the model update the view with the new data color the text-box bluish allow the user to save [ad infinitum] Without using n-controllers for n-views, how do i do this?

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  • Request/Response pattern in SOA implementation

    - by UserControl
    In some enterprise-like project (.NET, WCF) i saw that all service contracts accept a single Request parameter and always return Response: [DataContract] public class CustomerRequest : RequestBase { [DataMember] public long Id { get; set; } } [DataContract] public class CustomerResponse : ResponseBase { [DataMember] public CustomerInfo Customer { get; set; } } where RequestBase/ResponseBase contain common stuff like ErrorCode, Context, etc. Bodies of both service methods and proxies are wrapped in try/catch, so the only way to check for errors is looking at ResponseBase.ErrorCode (which is enumeration). I want to know how this technique is called and why it's better compared to passing what's needed as method parameters and using standard WCF context passing/faults mechanisms?

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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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  • Method returns an IDisposable - Should I dispose of the result, even if it's not assigned to anythin

    - by mjd79
    This seems like a fairly straightforward question, but I couldn't find this particular use-case after some searching around. Suppose I have a simple method that, say, determines if a file is opened by some process. I can do this (not 100% correctly, but fairly well) with this: public bool IsOpen(string fileName) { try { File.Open(fileName, FileMode.Open, FileAccess.Read, FileShare.None); } catch { // if an exception is thrown, the file must be opened by some other process return true; } } (obviously this isn't the best or even correct way to determine this - File.Open throws a number of different exceptions, all with different meanings, but it works for this example) Now the File.Open call returns a FileStream, and FileStream implements IDisposable. Normally we'd want to wrap the usage of any FileStream instantiations in a using block to make sure they're disposed of properly. But what happens in the case where we don't actually assign the return value to anything? Is it still necessary to dispose of the FileStream, like so: try { using (File.Open(fileName, FileMode.Open, FileAccess.Read, FileShare.None)); { /* nop */ } } catch { return true; } Should I create a FileStream instance and dispose of that? try { using (FileStream fs = File.Open(fileName, FileMode.Open, FileAccess.Read, FileShare.None)); } ... Or are these totally unnecessary? Can we simply call File.Open and not assign it to anything (first code example), and let the GC dispose of it right away?

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  • Separating data from the UI code with Linq to SQL entities

    - by Sir Psycho
    If it's important to keep data access 'away' from business and presentation layers, what alternatives or approaches can I take so that my LINQ to SQL entities can stay in the data access layer? So far I seem to be simply duplicating the classes produced by sqlmetal, and passing those object around instead simply to keep the two layers appart. For example, I have a table in my DB called Books. If a user is creating a new book via the UI, the Book class generated by sqlmetal seems like a perfect fit although I'm tightly coupling my design by doing so.

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  • Where does the query language sit within the MVC pattern?

    - by weesilmania
    I'd assume that since the query language sits within the controller (typically) that it belongs to that component, but if I play devil's advocate I'd argue that the query language is execute within the domain of the model, and is tightly coupled to that component so it might also be a part of it. Anyone know the answer? Is there a straight answer or is it technology specific?

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  • Formating a date field in the Model (Codeigniter)

    - by Landitus
    Hi, I', trying to re-format a date from a table in Codeigniter. The Controller is for a blog. I was succesfull when the date conversion happens in the View. I was hoping to convert the date in the Model to have things in order. This is the Model: class Novedades_model extends Model { function getAll() { $this->db->order_by('date','desc'); $query = $this->db->get('novedades'); if($query->num_rows() > 0) { foreach ($query->result() as $row) { $data[] = $row; } } return $data; } } This is part of the controller $this->load->model('novedades_model'); $data['records'] = $this->novedades_model->getAll(); Here's the date conversion as it happens in the View. This is inside the posts loop: <?php foreach($records as $row) : ?> <?php $fdate = "%d <abbr>%M</abbr> %Y"; $dateConv = mdate($fdate, mysql_to_unix($row->date)); ?> <div class="article section"> <span class="date"><?php echo $dateConv ;?></span> ... Keeps going ... How can I convert the date in the Model? Can I access the date key and refactor it?

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  • What do you do in your source control repository when you start a rewrite of a program?

    - by Max Schmeling
    I wrote an application a while back and have been maintaining it for a while now, but it's gotten to the point where there's several major new features to be added, a ton of changes that need made, and I know quite a few things I could do better, so I'm starting a rewrite of the entire program (using bits and pieces from original). My question is, what do you do with SVN at this point? Should I put the new version somewhere else, or should I delete the files I no longer need, add the new files, and just treat it like normal development in SVN? How have you handled this in the past?

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  • Is it better for class data to be passed internally or accessed directly?

    - by AaronSzy
    Example: // access fields directly private void doThis() { return doSomeWork(this.data); } // receive data as an argument private void doThis(data) { return doSomeWork(data); } The first option is coupled to the value in this.data while the second option avoids this coupling. I feel like the second option is always better. It promotes loose coupling WITHIN the class. Accessing global class data willy-nilly throughout just seems like a bad idea. Obviously this class data needs to be accessed directly at some point. However, if accesses, to this global class data can be eliminated by parameter passing, it seems that this is always preferable. The second example has the advantage of working with any data of the proper type, whereas the first is bound to working with the just class data. Even if you don't NEED the additional flexibility, it seems nice to leave it as an option. I just don't see any advantage in accessing member data directly from private methods as in the first example. Whats the best practice here? I've referenced code complete, but was not able to find anything on this particular issue.

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  • jquery: How to deal with 'this' in ajax callbacks

    - by Svish
    I currently have code similar to this for a form: $('#some-form') .submit(function() { // Make sure we are not already busy if($(this).data('busy')) return false; $(this).data('busy', true); // Do post $.post("some/url", $(this).serialize(), function(data) { if(data.success) // Success is a boolean I set in the result on the server { // Deal with data } else { // Display error } $('#some-form') .removeData('busy'); }); return false; }); My issue is that I would like to somehow remove the need for knowing the form id in the post callback. In the end where I remove the busy data from the form, I'd like to somehow not have that hard coded. Is there any way I can do this? Is there a way I can hand whatever is in this to the post callback function? Since I know the id right now, I can get around it by doing what I have done, but I'd like to know how to not be dependant on knowing the id, since often I don't have an id. (For example if I have a link in each row in a table and all the rows have the same click handler.

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  • A cross-platform application WPF, ASP.NET, Silverlight, WP7, XAML

    - by J. Lennon
    Considering the fact that all applications will interact with the web project (which will use the cloud or web services).. Is there any way to share my class models between applications? If yes, what is the best way to do it? About sending / receiving data from the Webservice, serialize and deserialize, how can I do this in a simple way without having to manually populate the objects? Any information about this applications would be really helpful!

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  • Class.Class vs Namespace.Class for top level general use class libraries?

    - by Joan Venge
    Which one is more acceptable (best-practice)?: namespace NP public static class IO public static class Xml ... // extension methods using NP; IO.GetAvailableResources (); vs public static class NP public static class IO public static class Xml ... // extension methods NP.IO.GetAvailableResources (); Also for #2, the code size is managed by having partial classes so each nested class can be in a separate file, same for extension methods (except that there is no nested class for them) I prefer #2, for a couple of reasons like being able to use type names that are already commonly used, like IO, that I don't want to replace or collide. Which one do you prefer? Any pros and cons for each? What's the best practice for this case? EDIT: Also would there be a performance difference between the two?

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  • Double use of variables?

    - by Vaccano
    I have read that a variable should never do more than one thing. Overloading a variable to do more than one thing is bad. Because of that I end up writing code like this: (With the customerFound variable) bool customerFound = false; Customer foundCustomer = null; if (currentCustomer.IsLoaded) { if (customerIDToFind = currentCustomer.ID) { foundCustomer = currentCustomer; customerFound = true; } } else { foreach (Customer customer in allCustomers) { if (customerIDToFind = customer.ID) { foundCustomer = customer; customerFound = true; } } } if (customerFound) { // Do something } But deep down inside, I sometimes want to write my code like this: (Without the foundCustomer variable) Customer foundCustomer = null; if (currentCustomer.IsLoaded) { if (customerIDToFind = currentCustomer.ID) { foundCustomer = currentCustomer; } } else { foreach (Customer customer in allCustomers) { if (customerIDToFind = customer.ID) { foundCustomer = customer; } } } if (foundCustomer != null) { // Do something } Does this secret desires make me an evil programmer? (i.e. is the second case really bad coding practice?)

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