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  • JUnit confusion: use 'extend Testcase' or '@Test' ?

    - by Rabarberski
    I've found the proper use (or at least the documentation) of JUnit very confusing. This question serves both as a future reference and as a real question. If I've understood correctly, there are two main approaches to create and run a JUnit test: Approach A: create a class that extends TestCase, and start test methods with the word test. When running the class as a JUnit Test (in Eclipse), all methods starting with the word test are automatically run. import junit.framework.TestCase; public class DummyTestA extends TestCase { public void testSum() { int a = 5; int b = 10; int result = a + b; assertEquals(15, result); } } Approach B: create a 'normal' class and prepend a @Test annotation to the method. Note that you do NOT have to start the method with the word test. import org.junit.*; import static org.junit.Assert.*; public class DummyTestB { @Test public void Sum() { int a = 5; int b = 10; int result = a + b; assertEquals(15, result); } } Mixing the two seems not to be a good idea, see e.g. this stackoverflow question: Now, my questions(s): What is the preferred approach, or when would you use one instead of the other? Approach B allows for testing for exceptions by extending the @Test annotation like in @Test(expected = ArithmeticException.class). But how do you test for exceptions when using approach A? When using approach A, you can group a number of test classes in a test suite. TestSuite suite = new TestSuite("All tests");<br/> suite.addTestSuite(DummyTestA.class); suite.addTestSuite(DummyTestAbis.class);` But this can't be used with approach B (since each testclass should subclass TestCase). What is the proper way to group tests for approach B?

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  • general learning methodology

    - by momo
    just wanted to hear on the different general learning paths people embark on when learning a new language/framework. the one i currently use, which is how i learned bash and am currently learning python, is: instant hacking tutorial (very short tutorial introducing the basic syntax, variable declaration, loops, data types, etc. and how they are generally used) in depth tutorial with good programming style and slightly topic-specific (e.g. Mark Pilgrim's Dive into Python), important topics for me personally are regex methods, file IO, and ways the different data types are utilized best (i wrote a very primitive bayesian spam filter using python's dictionaries to keep track of word occurrences) spaced-repition of syntax or short recipes (i use anki, with questions like 'create dictionary with filename and filesize metadata, human-readable' or simpler ones like 'match 0 - 3 occurences of the letter M in a string', or 'return/create an iterator from two sequences') the use of spaced-repitition has been invaluable, and i credit it with the ease that i can recall/create python algorithms. however, i've recently started looking into django, and i've found that spaced-repitition, at least in my case, doesn't work very well for learning a framework, it works best with short code recipes (either that or i should start looking into more basic django framework tutorials). the problem i'm encountering is that since framework programming is not only algorithms, but actually learning the API, which can be quite complex since you have to learn all the methods, modules, the places where they are stored, and the sequence of which things have to be done. for ex. in django to start a project that deals with polls (from the django tutorial), one has to create the project, edit the settings.py file, create the polls app, edit the models.py file (which requires knowing the classes that are present in the module models), edit the urls.py file, etc. i found that my spaced-repition method didn't work very well for this type of learning, so i wanted to ask you guys what method(s) you use for learning the different frameworks/APIs.

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  • Problem detecting installed application on Win Svr 2003 x64

    - by PD
    I have an x86 Windows application that consists of a couple of services and a client ui. Due to various issues with persuading the various MSIs to upgrade properly, the installation process is now governed by a wizard-style program that detects what is currently installed and handles upgrades by storing the user's current settings, uninstalling the existing software and installing the new version(s). The basic process is: Look in HKLM\Software\Classes\Installer\Products Loop through the GUID keys therein looking for ProductName="(my app name)" If not found, repeat starting from HKCU\Software\Microsoft\Installer\Products instead If found, offer the user an upgrade (as described earlier) else a clean install (i.e. user is asked various questions by the wizard) Now, this works just fine on pretty much any Windows platform you care to mention, from XP up. It fails only on Windows Server 2003 x64, in that an existing installation is not detected by the wizard - despite the exact same registry keys being present as are on any other platform I test on. It's fine on: XP x32 Vista x32, x64 Server 2003 x86 Server 2008 x86, x64 Server 2008 R2 x64 Windows 7 x86, x64 It's only Server 2003 x64 that seems to exhibit this issue.

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  • ASP.NET MVC Newbie: why isn't my model available when creating a strongly-typed view?

    - by Rax Olgud
    I'm starting with ASP.NET MVC, and working with NerdDinner as reference. I did the following: Created a new project Added a couple of tables Created LINQ to SQL for them Created a new controller My Models directory now contains MyModel.dbml, under which I have MyModel.designer.cs, that contains classes for models relating to both of my tables (let's call them Categories and Products). Now, under my new controller, I would like to create a strongly typed view. So for example I have the following code in my controller (for my application I must work by name, and the "Name" field is unique): public ActionResult Details(string name) { MyModelDataContext db = new MyModelDataContext(); Product user = db.Products.Single(t => t.Name == name); return View(user); } I would like to create a strongly-typed view. So I right-click the line "return View(user)", and choose "Add View...". I click "Create a strongly-typed view". When I click the dropdown of "View data class", I don't see my models, but only: MyProject.Controllers.AccountMembershipService MyProject.Controllers.FormsAuthenticationService What am I missing?

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  • How can I get all content within <td> tag using a HTML Agility Pack?

    - by Bob Dylan
    So I'm writing an application that will do a little screen scrapping. I'm using the HTML Agility Pack to load an entire HTML page into an instance of HtmlDocoument called doc. Now I want to parse that doc, looking for this: <table border="0" cellspacing="3"> <tr><td>First rows stuff</td></tr> <tr> <td> The data I want is in here <br /> and it's seperated by these annoying <br /> 's. No id's, classes, or even a single <p> tag. </p> Just a bunch of <br /> tags. </td> </tr> </table> So I just need to get the data within the 2nd row. How can I do this? Should I use a regex or something else?

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  • Write a program which works out which is the lowest priced computer in an ArrayList of computer obje

    - by Eoin
    Hello everybody! I am trying to study some java and cannot get my head around this question! Any help would be really appreciated and would help me in further studies! Thank you so much in advance! Eoin from Dublin, Ireland. ArrayList of Objects Write a program which works out which is the lowest priced computer in an ArrayList of computer objects. You should have two classes, one called ComputerTest, and the other called Computer. In the ComputerTest class you should: Have a main method which declares an ArrayList of type Computer called computerList, each element of which represents a computer. Initialise the first three entries of the ArrayList Call a static method which prints out the lowest price computer, called lowestPrice The parameter of this method is (i) an ArrayList of type Computer i.e. ArrayList data Sample output: The lowest priced computer is the Cheapo400 at 399 euro. The Computer class should have: Private instance variables: manufacturer, model, price and quality. Quality is a rating from 1 to 10. public get and set methods to retrieve and set/change the value of the four instance variables a default constructor a constructor that takes four parameters

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  • OO vs Simplicity when it comes to user interaction

    - by Oetzi
    Firstly, sorry if this question is rather vague but it's something I'd really like an answer to. As a project over summer while I have some downtime from Uni I am going to build a monopoly game. This question is more about the general idea of the problem however, rather than the specific task I'm trying to carry out. I decided to build this with a bottom up approach, creating just movement around a forty space board and then moving on to interaction with spaces. I realised that I was quite unsure of the best way of proceeding with this and I am torn between two design ideas: Giving every space its own object, all sub-classes of a Space object so the interaction can be defined by the space object itself. I could do this by implementing different land() methods for each type of space. Only giving the Properties and Utilities (as each property has unique features) objects and creating methods for dealing with the buying/renting etc in the main class of the program (or Board as I'm calling it). Spaces like go and super tax could be implemented by a small set of conditionals checking to see if player is on a special space. Option 1 is obviously the OO (and I feel the correct) way of doing things but I'd like to only have to handle user interaction from the programs main class. In other words, I don't want the space objects to be interacting with the player. Why? Errr. A lot of the coding I've done thus far has had this simplicity but I'm not sure if this is a pipe dream or not for larger projects. Should I really be handling user interaction in an entirely separate class? As you can see I am quite confused about this situation. Is there some way round this? And, does anyone have any advice on practical OO design that could help in general?

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  • Resolve php endless recursion issue

    - by Matt
    Hey all, I'm currently running into an endless recursion situation. I'm implementing a message service that calls various object methods.. it's quite similar to observer pattern.. Here's whats going on: Dispatcher.php class Dispatcher { ... public function message($name, $method) { // Find the object based on the name $object = $this->findObjectByName($name); // Slight psuedocode.. for ease of example if($this->not_initialized($object)) $object = new $object(); // This is where it locks up. } return $object->$method(); ... } class A { function __construct() { $Dispatcher->message("B", "getName"); } public function getName() { return "Class A"; } } class B { function __construct() { // Assume $Dispatcher is the classes $Dispatcher->message("A", "getName"); } public function getName() { return "Class B"; } } It locks up when neither object is initialized. It just goes back and forth from message each other and no one can be initialized. I'm looking for some kind of queue implementation that will make messages wait for each other.. One where the return values still get set. I'm looking to have as little boilerplate code in class A and class B as possible Any help would be immensely helpful.. Thanks! Matt Mueller

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  • Rails: Getting rid of "X is invalid" validation errors

    - by DJTripleThreat
    I have a sign-up form that has nested associations/attributes whatever you want to call them. My Hierarchy is this: class User < ActiveRecord::Base acts_as_authentic belongs_to :user_role, :polymorphic => true end class Customer < ActiveRecord::Base has_one :user, :as => :user_role, :dependent => :destroy accepts_nested_attributes_for :user, :allow_destroy => true validates_associated :user end class Employee < ActiveRecord::Base has_one :user, :as => :user_role, :dependent => :destroy accepts_nested_attributes_for :user, :allow_destroy => true validates_associated :user end I have some validation stuff in these classes as well. My problem is that if I try to create and Customer (or Employee etc) with a blank form I get all of the validation errors I should get plus some Generic ones like "User is invalid" and "Customer is invalid" If I iterate through the errors I get something like: user.login can't be blank User is invalid customer.whatever is blah blah blah...etc customer.some_other_error etc etc Since there is at least one invalid field in the nested User model, an extra "X is invalid" message is added to the list of errors. This gets confusing to my client and so I'm wondering if there is a quick way to do this instead of having to filer through the errors myself.

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  • How does the PHP IteratorIterator class work?

    - by WilliamMartin
    Try as I might I cannot get my head around what the IteratorIterator class actually does. I understand that classes can implement Traversable so the engine knows it can loop using foreach and I realise that IteratorIterator is supposed to convert anything that is Traversable into an Iterator but I cannot for the life of me understand how. Take for example, the PDOStatement class; how would the standard Iterator methods (next, key, rewind, etc) be implemented to allow iteration over a PDOStatement? Sorry if my question is unclear, I am just struggling to grasp the exact reason for this class and the documentation on it is scant. Thanks, Will Update: Going through the phpt files, I found one test which uses IteratorIterator: <?php $root = simplexml_load_string('<?xml version="1.0"?> <root> <child>Hello</child> <child>World</child> </root> '); foreach (new IteratorIterator($root->child) as $child) { echo $child."\n"; } ?> The expected output is: Hello World I don't really follow how the IteratorIterator construct takes $root-child as an argument and how it manages to iterate over the child elements.

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  • Database nesting layout confusion

    - by arzon
    I'm no expert in databases and a beginner in Rails, so here goes something which kinda confuses me... Assuming I have three classes as a sample (note that no effort has been made to address any possible Rails reserved words issue in the sample). class File < ActiveRecord::Base has_many :records, :dependent => :destroy accepts_nested_attributes_for :records, :allow_destroy => true end class Record < ActiveRecord::Base belongs_to :file has_many :users, :dependent => :destroy accepts_nested_attributes_for :users, :allow_destroy => true end class User < ActiveRecord::Base belongs_to :record end Upon entering records, the database contents will appear as such. My issue is that if there are a lot of Files for the same Record, there will be duplicate record names. This will also be true if there will be multiple Records for the same user in the the Users table. I was wondering if there is a better way than this so as to have one or more files point to a single Record entry and one or more Records will point to a single User. BTW, the File names are unique. Files table: id name 1 name1 2 name2 3 name3 4 name4 Records table: id file_id record_name record_type 1 1 ForDaisy1 ... 2 2 ForDonald1 ... 3 3 ForDonald2 ... 4 4 ForDaisy1 ... Users table: id record_id username 1 1 Daisy 2 2 Donald 3 3 Donald 4 4 Daisy Is there any way to optimize the database to prevent duplication of entries, or this should really the correct and proper behavior. I spread out the database into different tables to be able to easily add new columns in the future.

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  • Which is the better C# class design for dealing with read+write versus readonly

    - by DanM
    I'm contemplating two different class designs for handling a situation where some repositories are read-only while others are read-write. (I don't foresee any need to a write-only repository.) Class Design 1 -- provide all functionality in a base class, then expose applicable functionality publicly in sub classes public abstract class RepositoryBase { protected virtual void SelectBase() { // implementation... } protected virtual void InsertBase() { // implementation... } protected virtual void UpdateBase() { // implementation... } protected virtual void DeleteBase() { // implementation... } } public class ReadOnlyRepository : RepositoryBase { public void Select() { SelectBase(); } } public class ReadWriteRepository : RepositoryBase { public void Select() { SelectBase(); } public void Insert() { InsertBase(); } public void Update() { UpdateBase(); } public void Delete() { DeleteBase(); } } Class Design 2 - read-write class inherits from read-only class public class ReadOnlyRepository { public void Select() { // implementation... } } public class ReadWriteRepository : ReadOnlyRepository { public void Insert() { // implementation... } public void Update() { // implementation... } public void Delete() { // implementation... } } Is one of these designs clearly stronger than the other? If so, which one and why? P.S. If this sounds like a homework question, it's not, but feel free to use it as one if you want :)

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  • How do I POST/GET from rails to API with either ActiveResource or rest-client (preferred)?

    - by Angela
    Hi, this is a pretty basic question but I'm not entirely clear how to do this. I am trying to use a third-party service that has RESTful service. The service is called Postful. But I'm not clear what exactly to do? I've looked at ActiveResource (http://api.rubyonrails.org/classes/ActiveResource/Base.html) and rest-client, but I'm still not clear exactly what steps, code, and files to create. http://www.postful.com/service/mail is one of the services (details found http://www.postful.com/developer/guide#rest ), but to upload an image I have to post the following (but I'm not sure how I actually do this?). Thanks! > http://www.postful.com/service/upload > > Be sure to include the Content-Type > and Content-Length headers and the > image itself as the body of the > request. > > POST /upload HTTP/1.0 Content-Type: > application/octet-stream > Content-Length: 301456 > > ... file content here ... > > If the upload is successful, you will > receive a response like the following: > > <?xml version="1.0" encoding="UTF-8"?> > <upload> > <id>290797321.waltershandy.2</id> > </upload>

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  • Stop Child Elements from Inheriting Parent Style, Broken Tabs Javascript

    - by WillingLearner
    I am using the flowplayer jquery tabs plugin: http://flowplayer.org/tools/tabs/index.html Im having mucho difficulty when placing my child elements inside the panes divs, and stopping them from inheriting the style of the container pane div. Its breaking my layout to pieces and i need to know how to override the style and just keep the container panes div only to itself. Also, im having a devil of a time trying to call 2 different sets of tabs and panes. Im not getting the classes and IDs right, the javascript, or something along those lines. How would i set this up so i can call (tabs A / panes A) and then (tabs B / panes B), css wise, and javascript wise? My current javascript is: <!-- This JavaScript snippet activates the tabs --> <script> // perform JavaScript after the document is scriptable. $(function() { // setup ul.tabs to work as tabs for each div directly under div.panes $("ul.tabs").tabs("div.panes1 > div"); //$("ul.tabs.myprofile").tabs("div.panes > div"); }); </script> This only works for 1 set of tabs and panes on a page. Dosent help me much if i want to call 2 totally different sets. Ive gone over the documentation many times but im still not getting it. Please help me find a solution to BOTH of my problems. Thanks.

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  • Use .bat file to recursively loop through folders and get hold of .class files

    - by user320550
    HI all, This is what i'm trying to do. I have a .bat file which takes in a argument which is nothing but a folder name. What i do first is go one level up (cd ..). Now in this directory i have 3 folders and each folders have sub-folders and have .class files in them. What i want to do is recursively loop through the folders and get hold of the .class files. Once this is done i want to echo the target folder of the .class file as well as echo the name of the.class file. So c:\temp\potter\myclass.class. I would echo out c:\temp\potter\ and myclass. I'm able to do this by writing a separate bat file which works. But when i integrate this with the recursive function it seems to break. This is what i'm doing: :: call the junit classes... and save the results echo step 3... cd %1 cd .. for /r %%a in (*.class) do set Var=%%a echo Full file location %Var% for %%i in ("%Var%") do Set CF=%%~dpi Set CF=%CF:~0,-1% :LOOP If "%CF:~-1,1%"=="\" GoTo :DONE Set CF=%CF:~0,-1% GoTo :LOOP :DONE Set CF=%CF:~0,-1% echo Folder Location %CF% ::cd %CF% For %%j in ("%Var%") Do Set name=%%~nxj :: -6 because of Quotations Set name=%name:~0,-6% echo File Name %name% echo step 3 complete... However i only get the output of one directory, while i have multiple directories having .class files. This is the output i get: step 3... Full file location C:\NKCV\Project\MyActivities\6_Selenium\htmlTestCasesConve rted2JUnit\iexplore\flow2\testCase_app2.class Folder Location C:\NKCV\Project\MyActivities\6_Selenium\htmlTestCasesConverte d2JUnit\iexplore\flow2 File Name testCase_app2 step 3 complete... missing argument! usage htmltestCaseLocation for eg., "C:\NKCV\Project\MyActivities\6_Selenium\htmlTestCases" Could anyone please let me know whats wrong here? Thanks.

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  • Java semaphore to syncronize printing to screen

    - by Travis Griswald
    I'm currently stuck on a bit of homework and was wondering if anyone could help - I have to use semaphores in java to syncronize printing letters from 2 threads - one printing "A" and one printing "B". I cannot print out more than 2 of the same character in a row, so output should look like AABABABABABBABABABABAABBAABBABABA At the moment I have 3 semaphores, a binary mutex set to 1, and a counting semaphore, and my thread classes look something like this - public void run() { while (true) { Time.delay(RandomGenerator.integer(0,20)); Semaphores.mutex.down (); System.out.println (produce()); if (printCount > 1) { printCount = 0; Semaphores.mutex.up (); Semaphores.printB.up(); } } } public String produce() { printCount++; return "A"; } public void run() { while (true) { Time.delay(RandomGenerator.integer(0,20)); Semaphores.mutex.down (); System.out.println (produce()); if (printCount > 1) { printCount = 0; Semaphores.mutex.up (); Semaphores.printA.up(); } } } public String produce() { printCount++; return "B"; } Yet whatever I try it either deadlocks, or it seems to be working only printing 2 in a row at most, but always seems to print 3 in a row every now and again! Any help is much appreciated, not looking code or anything just a few pointers if possible :)

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  • Free utility which runs in Linux to create a UML class diagram from Java source files

    - by DeletedAccount
    I prefer to jot down UML-diagrams on paper and then implement them using Java. It would be nice to have a utility which could create UML-diagrams for me which I may share on-line and include in the digital documentation. In other words: I want to create UML diagrams from Java source code. The utility must be able to: Run in Linux. Handle Generics, i.e show List<Foo correctly in parameters and return type. Show class inheritance and interface implementations. It's nice if the utility is able to: Run in Windows and Mac OS X. Display enums in some nice manner. Generate output in a diagram format which I may modify using some other utility. Run from the command line. Restrict the UML generation to a set of packages which I may specify. Handle classes/interfaces which are not part of my source code. It could include the first class/interface which is external in the UML diagram. Perhaps in another color to indicate it being a library/framework created by someone else. Focuses on this task and doesn't try to solve the whole issue of documentation.

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  • New Rails deployment half working...not sure why?

    - by Meltemi
    I'm in the final stages of going round trip through the entire Rails cycle: development - test - production (on an external server). I'm very close...but seeing some errors with the production version and don't know enough about Rails' "magic" to troubleshoot it yet... all seems well and I can load my app by going to www.mydomain.com/rails and it seems to work...I can interact with my app and create new objects in my database. However, when I go to www.mydomain.com/rails/ (difference is the trailing slash) i get a webpage that just says "Index from public" on it?!? I don't know where that's coming from? index.html is long removed from public. this may or may not be related to why I can't access, say, the first record in one of my classes by calling its controller like so: www.mydomain.com/rails/mycontroller/1 . and yes, there are records in the database. anyway, something's askew. it works fine on development box. but, only half working on production server. anyone know what might be causing this? this app is running on the server box (not development) Installed Passenger on server to serve app via Apache modified my httpd.conf with Passenger's stuff (headache but finally got it to respond) loaded schema into the production database: rake db:schema:load RAILS_ENV=production

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  • Different EF Property DataType than Storage Layer Possible?

    - by dj_kyron
    Hi, I am putting together a WCF Data Service for PatientEntities using Entity Framework. My solution needs to address these requirements: Property DateOfBirth of entity Patient is stored in SQL Server as string. It would be ideal if the entity class did not also use the "string" type but rather a DateTime type. (I would expect this to be possible since we're abstracting away from the storage layer). Where could a conversion mechanism be put in place that would convert to and from DateTime/string so that the entity and SQL Server are in sync?. I cannot change the storage layer's structure, so I have to work around it. WCF Data Services (Read-only, so no need for saving changes) need to be used since clients will be able to use LINQ expressions to consume the service. They can generate results based on any given query scenario they need and not be constrained by a single method such as GetPatient(int ID). I've tried to use DTOs, but run into problem of mapping the ObjectContext to a DTO, I don't think that is theoretically possible...or too complicated if it is. I've tried to use Self Tracking Entities but they require the metadata from the .edmx file if I'm correct, and this isn't allowing a different property data type. I also want to add customizations to my Entity getter methods so that a property "MRN" of type "string" needs to have .Replace("MR~", string.Empty) performed before it is returned. I can add this to the getter methods but the problem with that is Entity Framework will overwrite that next time it refreshes the entity classes. Is there a permanent place I can put these? Should I use POCO instead? How would that work with WCF Data Services? Where would the service grab the metadata?

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  • Should a setter return immediately if assigned the same value?

    - by Andrei Rinea
    In classes that implement INotifyPropertyChanged I often see this pattern : public string FirstName { get { return _customer.FirstName; } set { if (value == _customer.FirstName) return; _customer.FirstName = value; base.OnPropertyChanged("FirstName"); } } Precisely the lines if (value == _customer.FirstName) return; are bothering me. I've often did this but I am not that sure it's needed nor good. After all if a caller assigns the very same value I don't want to reassign the field and, especially, notify my subscribers that the property has changed when, semantically it didn't. Except saving some CPU/RAM/etc by freeing the UI from updating something that will probably look the same on the screen/whatever_medium what do we obtain? Could some people force a refresh by reassigning the same value on a property (NOT THAT THIS WOULD BE A GOOD PRACTICE HOWEVER)? 1. Should we do it or shouldn't we? 2. Why?

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  • What is the way to go to fake my database layer in a unit test?

    - by Michel
    Hi, i have a question about unit testing. say i have a controller with one create method which puts a new customer in the database: //code a bit shortened public actionresult Create(Formcollection formcollection){ client c = nwe client(); c.Name = formcollection["name"]; ClientService.Save(c); { Clientservice would call a datalayer object and save it in the database. What i do now is create a database testscript and set my database in a know condition before testing. So when i test this method in the unit test, i know that there must be one more client in the database, and what it's name is. In short: ClientController cc = new ClientController(); cc.Create(new FormCollection (){name="John"}); //i know i had 10 clients before assert.areEqual(11, ClientService.GetNumberOfClients()); //the last inserted one is John assert.areEqual("John", ClientService.GetAllClients()[10].Name); So i've read that unit testing should not be hitting the database, i've setup an IOC for the database classes, but then what? I can create a fake database class, and make it do nothing. But then ofcourse my assertions will not work because if i say GetNumberOfClients() it will alwasy return X because it has no interaction with the fake database class used in the Create Method. I can also create a List of Clients in the fake database class, but as there will be two different instance created (one in the controller action and one in the unit test), they will have no interaction. What is the way to make this unit test work without a database?

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  • Passing Derived Class Instances as void* to Generic Callbacks in C++

    - by Matthew Iselin
    This is a bit of an involved problem, so I'll do the best I can to explain what's going on. If I miss something, please tell me so I can clarify. We have a callback system where on one side a module or application provides a "Service" and clients can perform actions with this Service (A very rudimentary IPC, basically). For future reference let's say we have some definitions like so: typedef int (*callback)(void*); // This is NOT in our code, but makes explaining easier. installCallback(string serviceName, callback cb); // Really handled by a proper management system sendMessage(string serviceName, void* arg); // arg = value to pass to callback This works fine for basic types such as structs or builtins. We have an MI structure a bit like this: Device <- Disk <- MyDiskProvider class Disk : public virtual Device class MyDiskProvider : public Disk The provider may be anything from a hardware driver to a bit of glue that handles disk images. The point is that classes inherit Disk. We have a "service" which is to be notified of all new Disks in the system, and this is where things unravel: void diskHandler(void *p) { Disk *pDisk = reinterpret_cast<Disk*>(p); // Uh oh! // Remainder is not important } SomeDiskProvider::initialise() { // Probe hardware, whatever... // Tell the disk system we're here! sendMessage("disk-handler", reinterpret_cast<void*>(this)); // Uh oh! } The problem is, SomeDiskProvider inherits Disk, but the callback handler can't receive that type (as the callback function pointer must be generic). Could RTTI and templates help here? Any suggestions would be greatly appreciated.

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  • Can i use microsoft ajax tab controls SKIN only ?

    - by Anil Namde
    I like YUI's Tab, to use its look and feel for own tab like implementation we just have to include yui tabs CSS and use markups and css classes and done. example below, <link rel="stylesheet" type="text/css" href="http://yui.yahooapis.com/2.8.0r4/build/tabview/assets/skins/sam/tabview.css" /> <ul class="yui-nav"> <li><a href="#tab1"><em>Tab One Label</em></a></li> <li class="selected"><a href="#tab2"><em>Tab Two Label</em></a></li> <li><a href="#tab3"><em>Tab Three Label</em></a></li> </ul> Now i have a site where Microsort's tab tab controls are used and there are some which are old simple tabs. Now i would like to change these old tabs to Microsoft tab structures just by using CSS if possible as we have done above for YUI. Is that possible to do that using CSS/file? How it can be done for Microsofts tab?

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  • Avoid loading unnecessary data from db into objects (web pages)

    - by GmGr
    Really newbie question coming up. Is there a standard (or good) way to deal with not needing all of the information that a database table contains loaded into every associated object. I'm thinking in the context of web pages where you're only going to use the objects to build a single page rather than an application with longer lived objects. For example, lets say you have an Article table containing id, title, author, date, summary and fullContents fields. You don't need the fullContents to be loaded into the associated objects if you're just showing a page containing a list of articles with their summaries. On the other hand if you're displaying a specific article you might want every field loaded for that one article and maybe just the titles for the other articles (e.g. for display in a recent articles sidebar). Some techniques I can think of: Don't worry about it, just load everything from the database every time. Have several different, possibly inherited, classes for each table and create the appropriate one for the situation (e.g. SummaryArticle, FullArticle). Use one class but set unused properties to null at creation if that field is not needed and be careful. Give the objects access to the database so they can load some fields on demand. Something else? All of the above seem to have fairly major disadvantages. I'm fairly new to programming, very new to OOP and totally new to databases so I might be completely missing the obvious answer here. :)

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  • C# Hiding, overriding and calling function from base class.

    - by Lukasz Lysik
    I'm learning C# and I encountered the following problem. I have two classes: base and derived: class MyBase { public void MyMethod() { Console.WriteLine("MyBase::MyMethod()"); } } class MyDerived: MyBase { public void MyMethod() { Console.WriteLine("MyDerived::MyMethod()"); } } For now, without virtual and override key words. When I compile this I get the warning (which is of course expected) that I try to hide MyMethod from MyBase class. What I want to do is to call the method from the base class having an instance of derived class. I do this like this: MyDerived myDerived = new MyDerived(); ((MyBase)myDerived).MyMethod(); It works fine when I do not specify any virtual, etc. keywords in the methods. I tried to put combination of the keywords and I got the following results: | MyBase::MyMethod | MyDerived::MyMethod | Result printed on the console | | -----------------|---------------------|-------------------------------| | - | - | MyBase::MyMethod() | | - | new | MyBase::MyMethod() | | virtual | new | MyBase::MyMethod() | | virtual | override | MyDerived::MyMethod() | I hope the table is clear to you. I have two questions: Is it the correct way to call the function from the base class (((MyBase)myDerived).MyMethod();)? I know about base keyword, but it can be called only from the inside of the derived class. Is it right? Why in the last case (with virtual and override modifiers) the method which was called came from the derived class? Would you please explain that?

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