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  • How to handle too many files in Qt

    - by mree
    I'm not sure how to ask this, but here goes the question: I'm migrating from J2SE to Qt. After creating some small applications in Qt, I noticed that I've created way too many files compared to what I would've create if I was developing in Java (I use Netbeans). For an example, for a GUI to Orders, I'd have to create Main Order Search Window Edit Order Dialog Manage Order Dialog Maybe some other dialogs... For Java, I don't have to create a new file for every new Dialog, the Dialog will be created in the JFrame class itself. So, I will only be seeing 1 file for Orders which has other Dialogs in it. However, in Qt, I'd have to create 1 ui file, 1 header file, 1 cpp file for each of the Dialog (I know I can just put the cpp in the header, but it's easier to view codes in seperate files). So, in the end, I might end up with 3 (if there are 3 dialogs) x3 files = 9 files for the GUI in Qt, compared to Java which is only 1 file. I do know that I can create a GUI by coding it manually. But it seems easy on small GUIs but not some on complicated GUIs with lots of inputs, tabs and etc. So, is there any suggestion on how to minimize the file created in Qt?

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  • C# Linq: Can you merge DataContexts?

    - by Andreas Grech
    Say I have one database, and this database has a set of tables that are general to all Clients and some tables that are specific to certain clients. Now what I have in mind is creating a primary DataContext that includes only the tables that are general to all the clients, and then create separate DataContexts that contain only the tables that are specific to the client. Is there a way to kind of "merge" DataContexts so that it becomes one context? So for Client A, I need one DataContext that includes both the general tables and also the tables for that specific client (retrieved from two different DataContexts) ? [Update] What I think I can do is, from the Partial Class of the DataContext instead of letting my DataContext inherit from DataContext I make it inherit from MyDataContext; that way, the tables from MyDataContext and the other DataContext will be available in one DataContext class. What do you think about this approach? Of course with something like this you can only merge two datacontexts at once though...

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  • Why cast null before checking if object is equal to null?

    - by jacerhea
    I was looking through the "Domain Oriented N-Layered .NET 4.0 Sample App" project and ran across some code that I do not understand. In this project they often use syntax like the following to check arguments for null: public GenericRepository(IQueryableContext context,ITraceManager traceManager) { if (context == (IQueryableContext)null) throw new ArgumentNullException("context", Resources.Messages.exception_ContainerCannotBeNull); Why would you cast null to the type of the object you are checking for null?

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  • C++ Headers/Source Files

    - by incrediman
    (Duplicate of C++ Code in Header Files) What is the standard way to split up C++ classes between header and source files? Am I supposed to put everything in the header file? Or should I declare the classes in the header file and define them in a .cpp file (source file)? Sorry if I'm shaky on the terminology here (declare, define, etc). So what's the standard?

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  • What's the preferred way to use helper methods in Ruby?

    - by DR
    Disclaimer: Although I'm asking in context of a Rails application, I'm not talking about Rails helpers (i.e. view helpers) Let's say I have a helper method/function: def dispatch_job(job = {}) #Do something end Now I want to use this from several places (mostly controllers, but also a few BackgrounDRb workers) What's the preferred way to do this? I can think of two possibilities: 1. Use a class and make the helper a static method: class MyHelper def self.dispatch_job(job = {}) end end class MyWorker def run MyHelper.dispatch_job(...) end end 2. Use a module and include the method into whatever class I need this functionality module MyHelper def self.dispatch_job(job = {}) end end class MyWorker include MyHelper def run dispatch_job(...) end end 3. Other possibilities I don't know yet ... The first one is more Java-like, but I'm not sure if the second one is really an appropriate use of Ruby's modules.

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  • Technical non-terminating condition in a loop

    - by Snarfblam
    Most of us know that a loop should not have a non-terminating condition. For example, this C# loop has a non-terminating condition: any even value of i. This is an obvious logic error. void CountByTwosStartingAt(byte i) { // If i is even, it never exceeds 254 for(; i < 255; i += 2) { Console.WriteLine(i); } } Sometimes there are edge cases that are extremely unlikeley, but technically constitute non-exiting conditions (stack overflows and out-of-memory errors aside). Suppose you have a function that counts the number of sequential zeros in a stream: int CountZeros(Stream s) { int total = 0; while(s.ReadByte() == 0) total++; return total; } Now, suppose you feed it this thing: class InfiniteEmptyStream:Stream { // ... Other members ... public override int Read(byte[] buffer, int offset, int count) { Array.Clear(buffer, offset, count); // Output zeros return count; // Never returns -1 (end of stream) } } Or more realistically, maybe a stream that returns data from external hardware, which in certain cases might return lots of zeros (such as a game controller sitting on your desk). Either way we have an infinite loop. This particular non-terminating condition stands out, but sometimes they don't. A completely real-world example as in an app I'm writing. An endless stream of zeros will be deserialized into infinite "empty" objects (until the collection class or GC throws an exception because I've exceeded two billion items). But this would be a completely unexpected circumstance (considering my data source). How important is it to have absolutely no non-terminating conditions? How much does this affect "robustness?" Does it matter if they are only "theoretically" non-terminating (is it okay if an exception represents an implicit terminating condition)? Does it matter whether the app is commercial? If it is publicly distributed? Does it matter if the problematic code is in no way accessible through a public interface/API? Edit: One of the primary concerns I have is unforseen logic errors that can create the non-terminating condition. If, as a rule, you ensure there are no non-terminating conditions, you can identify or handle these logic errors more gracefully, but is it worth it? And when? This is a concern orthogonal to trust.

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  • Lock thread using somthing other than a object

    - by Scott Chamberlain
    when using a lock does the thing you are locking on have to be a object. For example is this legal static DateTime NextCleanup = DateTime.Now; const TimeSpan CleanupInterval = new TimeSpan(1, 0, 0); private static void DoCleanup() { lock ((object)NextCleanup) { if (NextCleanup < DateTime.Now) { NextCleanup = DateTime.Now.Add(CleanupInterval); System.Threading.ThreadPool.QueueUserWorkItem(new System.Threading.WaitCallback(cleanupThread)); } } return; } EDIT-- From reading SLaks' responce I know the above code would be not valid but would this be? static MyClass myClass = new MyClass(); private static void DoCleanup() { lock (myClass) { // } return; }

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  • Pattern for database-wrapper in java

    - by Space_C0wb0y
    I am currently writing a java-class that wraps an SQLite database. This class has two ways to be instantiated: Open an existing database. Create a new database. This is what I cam up with: public class SQLiteDatabaseWrapper { public static SQLiteDatabaseWrapper openExisting(File PathToDB) { return new SQLiteDatabaseWrapper(PathToDB); } public static SQLiteDatabaseWrapper createNew(File PathToDB) { CreateAndInitializeNewDatabase(PathToDB); return new SQLiteDatabaseWrapper(PathToDB); } private SQLiteDatabaseWrapper(File PathToDB) { // Open connection and setup wrapper } } Is this the way to go in Java, or is there any other best practice for this situation?

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  • Lazy loading? Better avoiding it?

    - by Charlie Pigarelli
    I just read about this design pattern: Lazy Load. And, since in the application i'm working on i have all the classes in one folder, i was wondering if this pattern could just make me avoiding the include() function for every class. I mean: It's nice to know that if i forgot to include a class, PHP, before falling into an error, trough an __autoload() function try to get it. But is it fine enough to just don't care about including classes and let PHP do it by your own every time? Or we should write __autoload() just in case it is needed?

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  • How should I handle expected errors? eg. "username already exists"

    - by Pheter
    I am struggling to understand how I should design the error handling parts of my code. I recently asked a similar question about how I should go about returning server error codes to the user, eg. 404 errors. I learnt that I should handle the error from within the current part of the application; seem's simple enough. However, what should I do when I can't handle the error from the current link in the chain? For example, I may have a class that is used to manage authentication. One of it's methods could be createUser($username, $password). Within that function, I need to determine if the username already exists. If this is true, how should I alert the calling code about this? Returning null instead of a user object is one way. But how do I then know what caused the error? How should I handle errors in such a way that calling code can easily find out what caused the error? Is there a design pattern commonly used for this kind of situation?

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  • Continuous integration with multiple branch development

    - by ryanprayogo
    In the project that I'm working on, we are using SVN with 'Stable Trunk' strategy. What that means is that for each bug that is found, QA opens a bug ticket and assigns it to a developer. Then, a developer fixes that bug and checks it in a branch (off trunk, let's call this the bug branch) and that branch will only contain fixes for that particular bug ticket When we decided to do a release, for each bug fixes that we want to release to the customer, a developer will merge all the fixes from several bug branch to trunk and proceed with the normal QA cycle. The problem is that we use trunk as the codebase for our CI job (Hudson, specifically), and therefore, for all commits to the bug branch, it will miss the daily build until it gets merged to trunk when we decided to release the new version of the software. Obviously, that defeats the purpose of having CI. What is the proper way to fix this issue?

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  • Getting up to speed on modern architecture

    - by Matt Thrower
    Hi, I don't have any formal qualifications in computer science, rather I taught myself classic ASP back in the days of the dotcom boom and managed to get myself a job and my career developed from there. I was a confident and, I think, pretty good programmer in ASP 3 but as others have observed one of the problems with classic ASP was that it did a very good job of hiding the nitty-gritty of http so you could become quite competent as a programmer on the basis of relatively poor understanding of the technology you were working with. When I changed on to .NET at first I treated it like classic ASP, developing stand-alone applications as individual websites simply because I didn't know any better at the time. I moved jobs at this point and spent the next several years working on a single site whose architecture relied heavily on custom objects: in other words I gained a lot of experience working with .NET as a middle-tier development tool using a quite old-fashioned approach to OO design along the lines of the classic "car" class example that's so often used to teach OO. Breaking down programs into blocks of functionality and basing your classes and methods around that. Although we worked under an Agile approach to manage the work the whole setup was classic client/server stuff. That suited me and I gradually got to grips with .NET and started using it far more in the manner that it should be, and I began to see the power inherent in the technology and precisely why it was so much better than good old ASP 3. In my latest job I have found myself suddenly dropped in at the deep end with two quite young, skilled and very cutting-edge programmers. They've built a site architecture which is modelling along a lot of stuff which is new to me and which, in truth I'm having a lot of trouble understanding. The application is built on a cloud computing model with multi-tenancy and the architecture is all loosely coupled using a lot of interfaces, factories and the like. They use nHibernate a lot too. Shortly after I joined, both these guys left and I'm now supposedly the senior developer on a system whose technology and architecture I don't really understand and I have no-one to ask questions of. Except you, the internet. Frankly I feel like I've been pitched in at the deep end and I'm sinking. I'm not sure if this is because I lack the educational background to understand this stuff, if I'm simply not mathematically minded enough for modern computing (my maths was never great - my approach to design is often to simply debug until it works, then refactor until it looks neat), or whether I've simply been presented with too much of too radical a nature at once. But the only way to find out which it is is to try and learn it. So can anyone suggest some good places to start? Good books, tutorials or blogs? I've found a lot of internet material simply presupposes a level of understanding that I just don't have. Your advice is much appreciated. Help a middle-aged, stuck in the mud developer get enthusastic again! Please!

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  • How should I ethically approach user password storage for later plaintext retrieval?

    - by Shane
    As I continue to build more and more websites and web applications I am often asked to store user's passwords in a way that they can be retrieved if/when the user has an issue (either to email a forgotten password link, walk them through over the phone, etc.) When I can I fight bitterly against this practice and I do a lot of ‘extra’ programming to make password resets and administrative assistance possible without storing their actual password. When I can’t fight it (or can’t win) then I always encode the password in some way so that it at least isn’t stored as plaintext in the database—though I am aware that if my DB gets hacked that it won’t take much for the culprit to crack the passwords as well—so that makes me uncomfortable. In a perfect world folks would update passwords frequently and not duplicate them across many different sites—unfortunately I know MANY people that have the same work/home/email/bank password, and have even freely given it to me when they need assistance. I don’t want to be the one responsible for their financial demise if my DB security procedures fail for some reason. Morally and ethically I feel responsible for protecting what can be, for some users, their livelihood even if they are treating it with much less respect. I am certain that there are many avenues to approach and arguments to be made for salting hashes and different encoding options, but is there a single ‘best practice’ when you have to store them? In almost all cases I am using PHP and MySQL if that makes any difference in the way I should handle the specifics. Additional Information for Bounty I want to clarify that I know this is not something you want to have to do and that in most cases refusal to do so is best. I am, however, not looking for a lecture on the merits of taking this approach I am looking for the best steps to take if you do take this approach. In a note below I made the point that websites geared largely toward the elderly, mentally challenged, or very young can become confusing for people when they are asked to perform a secure password recovery routine. Though we may find it simple and mundane in those cases some users need the extra assistance of either having a service tech help them into the system or having it emailed/displayed directly to them. In such systems the attrition rate from these demographics could hobble the application if users were not given this level of access assistance, so please answer with such a setup in mind. Thanks to Everyone This has been a fun questions with lots of debate and I have enjoyed it. In the end I selected an answer that both retains password security (I will not have to keep plain text or recoverable passwords), but also makes it possible for the user base I specified to log into a system without the major drawbacks I have found from normal password recovery. As always there were about 5 answers that I would like to have marked correct for different reasons, but I had to choose the best one--all the rest got a +1. Thanks everyone!

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  • Why is 'virtual' optional for overridden methods in derived classes?

    - by squelart
    When a method is declared as virtual in a class, its overrides in derived classes are automatically considered virtual as well, and the C++ language makes this keyword virtual optional in this case: class Base { virtual void f(); }; class Derived : public Base { void f(); // 'virtual' is optional but implied. }; My question is: What is the rationale for making virtual optional? I know that it is not absolutely necessary for the compiler to be told that, but I would think that developers would benefit if such a constraint was enforced by the compiler. E.g., sometimes when I read others' code I wonder if a method is virtual and I have to track down its superclasses to determine that. And some coding standards (Google) make it a 'must' to put the virtual keyword in all subclasses.

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  • Access of private field of another object in copy constructors - Really a problem?

    - by DR
    In my Java application I have some copy-constructors like this public MyClass(MyClass src) { this.field1 = src.field1; this.field2 = src.field2; this.field3 = src.field3; ... } Now Netbeans 6.9 warns about this and I wonder what is wrong with this code? My concerns: Using the getters might introduce unwanted side-effects. The new object might no longer be considered a copy of the original. If it is recommended using the getters, wouldn't it be more consistent if one would use setters for the new instance as well?

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  • How to face observable object containing an observable field

    - by iseek
    Hello, I need a hint concerning MVC and Observer-Pattern. For example a model contains the classes "Address" and "Person". The Address class contains the fields street:String, zipcode:String, location:String. Whereas the Person class contains the fields name:String, firstName:String, address:Address. My approach so far looks something like this: Both, Address and Person are observable. If one of their setters is being called, I validate whether the current value and new value differ. Only in this case an update event is fired. The event contains the source, the name of the changed field, the old and the new value. The class for the view contains text fields to display and edit the information of a person: name, firstname, street, zipcode, location. It knows the Person model and is an subscribed observer for the person. So it gets the update events from the person object. My questions concerns the address field from type Address in the person class, since an address is observable on its own. If the view gets an update event from person when a new address has been set, I can update all of the address related fields in the view. But what if a field of the address changes? Should the view also register for update events from the address? Any hints about common design approaches would be appreciated. Greetings.

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  • Alternative to jQuery .data()?

    - by thebossman
    I'm a big fan of jQuery's .data() method, but I can't always use it. Often times I am rendering html templates that I pass via AJAX and I need to attach metadata to each of the elements in the template. For example: <ul> {% for item in itemlist %} <li metadata="{{ item.metadata }}">{{ item.name }}</li> {% endfor %} </ul> I know attaching attributes to store data is bad practice (and it might not even work in older versions of IE). What is the best practice? Is there a good alternative to this method?

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  • Is there a design pattern that expresses objects (an their operations) in various states?

    - by darren
    Hi I have a design question about the evolution of an object (and its state) after some sequence of methods complete. I'm having trouble articulating what I mean so I may need to clean up the question based on feedback. Consider an object called Classifier. It has the following methods: void initialise() void populateTrainingSet(TrainingSet t) void pupulateTestingSet(TestingSet t) void train() void test() Result predict(Instance i) My problem is that these methods need to be called in a certain order. Futher, some methods are invalid until a previous method is called, and some methods are invalid after a method has been called. For example, it would be invalid to call predict() before test() was called, and it would be invalid to call train() after test() was called. My approach so far has been to maintain a private enum that represents the current stateof the object: private static enum STATE{ NEW, TRAINED, TESTED, READY}; But this seems a bit cloogy. Is there a design pattern for such a problem type? Maybe something related to the template method.

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  • Sending object C from class A to class B

    - by user278618
    Hi, I can't figure out how to design classes in my system. In classA I create object selenium (it simulates user actions at website). In this ClassA I create another objects like SearchScreen, Payment_Screen and Summary_Screen. # -*- coding: utf-8 -*- from selenium import selenium import unittest, time, re class OurSiteTestCases(unittest.TestCase): def setUp(self): self.verificationErrors = [] self.selenium = selenium("localhost", 5555, "*chrome", "http://www.someaddress.com/") time.sleep(5) self.selenium.start() def test_buy_coffee(self): sel = self.selenium sel.open('/') sel.window_maximize() search_screen=SearchScreen(self.selenium) search_screen.choose('lavazza') payment_screen=PaymentScreen(self.selenium) payment_screen.fill_test_data() summary_screen=SummaryScreen(selenium) summary_screen.accept() def tearDown(self): self.selenium.stop() self.assertEqual([], self.verificationErrors) if __name__ == "__main__": unittest.main() It's example SearchScreen module: class SearchScreen: def __init__(self,selenium): self.selenium=selenium def search(self): self.selenium.click('css=button.search') I want to know if there is anything ok with a design of those classes?

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