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  • Does Qt support virtual pure slots ?

    - by ereOn
    Hi, My GUI project in Qt has a lot of "configuration pages" classes which all inherit directly from QWidget. Recently, I realized that all these classes share 2 commons slots (loadSettings() and saveSettings()). Regarding this, I have two questions: Does it make sense to write a intermediate base abstract class (lets name it BaseConfigurationPage) with these two slots as virtual pure methods ? (Every possible configuration page will always have these two methods, so I would say "yes") Before I do the heavy change in my code (if I have to) : does Qt support virtual pure slots ? Is there anything I should be aware of ? Here is a code example describing everything: class BaseConfigurationPage : public QWidget { // Some constructor and other methods, irrelevant here. public slots: virtual void loadSettings() = 0; virtual void saveSettings() = 0; }; class GeneralConfigurationPage : public BaseConfigurationPage { // Some constructor and other methods, irrelevant here. public slots: void loadSettings(); void saveSettings(); };

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  • Check if CSS Class exists in StyleSheet using javascript/jQuery

    - by Akhil Sekharan
    Is there a way to check if there is a class named 'some-class-name' in css? For example, I have: <style type="text/css"> .box { position: absolute; left: 150%; } </style> My intention is to randomly assign a class to a div on certain event: var classList = []; //Need to populate this array $('#updateClass').on('click', function() { $('#resultDiv').attr('class',classList[Math.floor((Math.random()*classList.length)+1)]); }); Is it possible to check by JS/jQuery whether a class named 'box' exists in the stylesheet? Thanks.

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  • OpenGL and layouts

    - by Hnefi
    I'm using OpenGL to render a game view in my android application. The game is turn based and I wish to add some buttons to the interface. I'd prefer to use standard Android widgets, structured in an XML-generated layout (or, if I have to, a hardcoded layout) and put the OpenGL view in its own window as part of that layout. So in regards to this, I have 3 questions: 1: Is such a thing possible? I've done a few half-hearted tries, but have had no luck so far. 2: Is such a thing advisable? Does it carry a significant performance penalty, for example, over using OpenGL-based homebrew widgetry? 3: Is it possible to pass particular arguments to instances created in XML layouts? For example, my current OpenGL view has three arguments in its constructor; is it somehow possible for me to invoke that particular constructor with particular parameters when it's part of a layout?

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  • To "null" or not to "null" my class's attributes

    - by Helper Method
    When I write a class in Java, I like to initialize the attributes which are set to a default value directly and attributes which are set by the caller in the constructor, something like this: public class Stack<E> { private List<E> list; private size = 0; public Stack(int initialCapacity) { list = new ArrayList<E>(initialCapacity); } // remainder omitted } Now suppose I have a Tree class: public class Tree<E> { private Node<E> root = null; // no constructor needed, remainder omitted } Shall I set the root attribute to null, to mark that it is set to null by default, or omit the null value?

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  • Is c++ explicit conversion really that bad?

    - by LoudNPossiblyRight
    My knowledge in c++ at this point is more academic than anything else and in all my reading thus far, the use of explicit conversion with named casts (const_cast, static_cast, reinterpret_cast, dynamic_cast) has come with a big warning label (and it's easy to see why) that pretty much implies explicit conversion is symptomatic of bad design and should only be used as a last resort in desperate circumstances. So i have to ask: Is explicit conversion with named casts really just jury rigging code or is there a more graceful and positive application to this feature? Is there a good example of the latter? Thanks in advance.

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  • problem with update the counter value

    - by Edan
    Hello, I having problem to update the counter (integer value). this is the definitions of the class: public class Item_Actions { private final int MAX_ITEMS = 100; private Item myItem[]; private int counter; public Item_Actions() { myItem = new Item[MAX_ITEMS]; counter++; } //Constructor add item into the menu (Description, type & price of Item) public void addItem(Item itm) { myItem[counter] = itm; counter++; }....... Now everytime I call the addItem constructor from another class, the counter always stays on zero. What causing it and how do I save the data inside? thanks

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  • Why the compiler doesn't complain about this error ?

    - by M.H
    Hi I am writing some java questions to help my friends in the java exam. I wrote a question and I supposed that three errors will occurred in the code but the compiler complained only about two. the code is : class MyClass { static MyClass() { System.out.println("I am The First Statement here!"); this(); } } I expected the following errors : the constructor can't be static this can't be in a static function (since the constructor isn't valid) this here should be the first statement. NetBeans isn't complaining about the second error here. why ?

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  • Locate Database File in SQLITE

    - by Nagendra Baliga
    I have created a file named "MyFile.db" using SQLite3 from my C#.net application. This file got created in my "D:\MyProject\bin" folder. I have created a table named "MyTable" inside "MyFile.db" from same C# app. Now I am running sqlite3.exe from my "C:\" drive to get Command Line Shell For SQLite. How can I get the file "D:\MyProject\bin\MyFile.db" in the SQLite Command Line Shell i.e, how can I locate the file "MyFile.db" in the command shell to get the data from "MyTable".

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  • Hierarchy of modules in guice

    - by Niko
    Hi, I'd like to run a unit test where a constant is slightly different than in the standard version. That is, in my default module, the following is bindConstant().annotatedWith(Names.named("number of players")).to(4); but in testing, I'd like to try this line instead: bindConstant().annotatedWith(Names.named("number of players")).to(2); Id like to achieve that without copying all of the rest of the module. What I really want is a "default" module that is "below" a more specialized module, such that in case of conflict, the specialized module wins (instead of throwing an exception, which is what guice does). In essence, my question is: how does anybody arrange for more than one module without lots of code duplication?

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  • Wierdness debugging Visual Studio C++ 2008

    - by Jeff Dege
    I have a legacy C++ app, that in its most incarnation we've been building with makefiles and VS2003's command-line tool. I'm trying to get it to build using VS2008 and MsBuild. The build is working OK, but I'm getting errors where I'd never seen errors, before, and stepping through in VS2008's debugger only confuses me. The app links a number of static libraries, which fall into two categories: those that are part of the same application suite, and those that are shared between a number of application suites. Originally, I had a .csproj file for each static library, and two .sln files, one for the application suite (including the suite-specific libraries) and one for the non-suite-specific shared libraries. The shared libraries were included in the link, their projects were not included in the application suite .sln. The application instantiates an object from a class that is defined in one of the shared libraries. The class has a member object of a class that wraps a linked list. The constructor of the linked list class sets its "head" pointer to null. When I run the app, and try to add an element to the linked list, I get an error - the head pointer contains the value 0xCCCCCCCC. So I step through with the debugger. And see weirdness. When the current line in the debugger is in a source file belonging to the static library, the head pointer contains 0x00000000. When I step into the constructor, I can see the pointer being set to that value, and when I'm stepped into any other method of the class, I can see that the head pointer still contains 0x00000000. But when I step out into methods that are defined in the application suite .sln, it contains 0xCCCCCCCC. It's not like it's being overwritten. It changes back and forth depending upon which source file I am currently debugging. So I included the shared library's project in the application suite .sln, and now I see the head pointer containing 0xCCCCCCCC all the time. It looks like the constructor of the linked list class is not being called. So now, I'm entirely confused. Anyone have any ideas?

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  • How does a Java Arraylist contains() method evaluate objects?

    - by mvid
    Say i create one object and add it to my ArrayList. If I then create another object with exactly the same constructor input, will the contain() method evaluate the two objects to be the same? Assume the constructor doesn't do anything funny with the input, and the variables stored in both objects are identical. ArrayList<Thing> basket = new ArrayList<Thing>(); Thing thing = new Thing(100); basket.add(thing); Thing another = new Thing(100); basket.contains(another); // true or false?

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  • Cannot use String.Empty as a default value for an optional parameter in C# - then what's the point?

    - by Mikeyg36
    I am reading Effective C# by Bill Wagner. In Item 14 - Minimize Duplicate Initialization Logic, he shows the following example of using the new optional parameters feature in a constructor: public MyClass(int initialCount = 0, string name = "") Notice that he used "" instead of string.Empty. He comments: You'll note [in an example above] that the second constructor specified "" for the default value on the name parameter, rather than the more customary string.Empty. That's because string.Empty is not a compile-time constant. It is a static property defined in the string class. Because it is not a compile constant, you cannot use it for the default value for a parameter. If we cannot use the string.Empty static in all situations, then doesn't that defeat the purpose of it? I thought that we would use it to be sure that we have a system-independent means of referring to the empty string. Is my understanding wrong? Thanks.

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  • Porting C++-code from Windows to Unix: systemcalls colliding with name of functions

    - by marvin2k
    Hi I'm porting some crufty C++ Windows-code to Linux, which uses functions called "open" and "close" inside every class... Very bad style, or? Luckily that wasn't a problem in windows, since their systemcalls are named different. When I try to call the systemcalls open() or close() I'm getting some compiler error about "no matching function for call for class:open()". I can't rename all our functions named "class::open" and "class::close" in the whole code, and I have to use open() and close() since I'm working with serial ports. So my question is: How can I tell the compiler, which open I mean? How can I escape or hide the namespace of a class in C++?

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  • Regarding Authlogic and page redirection.

    - by Paddy
    I am using authlogic for authentication in my Rails app. Have named routes for the frequent actions, viz: map.login "login", :controller = "user_sessions", :action = "new" map.logout "logout", :controller = "user_sessions", :action = "destroy" map.register "register", :controller = "users", :action = "new" map.edit 'user/edit/:id', :controller = "users", :action = "edit" But also in my routes.rb i have these automatically created REST routes too: map.resources :user_sessions map.resources :users The problem now is that a user can login from two different routes. Ex: From, http://localhost/login and also from http ://localhost/user_sessions/new. How do i restrict access only from the named route i have defined and not allow from user_sessions/new?

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  • How do I change my current directory from a python script?

    - by misterloogs
    I'm trying to implement my own version of the 'cd' command that presents the user with a list of hard-coded directories to choose from, and the user has to enter a number corresponding to an entry in the list. The program, named my_cd.py for now, should then effectively 'cd' the user to the chosen directory. Example of how this should work: /some/directory $ my_cd.py 1) ~ 2) /bin/ 3) /usr Enter menu selection, or q to quit: 2 /bin $ Currently, I'm trying to 'cd' using os.chdir('dir'). However, this doesn't work, probably because my_cd.py is kicked off in its own child process. I tried wrapping the call to my_cd.py in a sourced bash script named my_cd.sh: #! /bin/bash function my_cd() { /path/to/my_cd.py } /some/directory $ . my_cd.sh $ my_cd ... shows list of dirs, but doesn't 'cd' in the interactive shell Any ideas on how I can get this to work? Is it possible to change my interactive shell's current directory from a python script?

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  • How to solve 'Badly constructed integrity constraints' in doctrine

    - by Carson
    When I execute the command './doctrine build-all-reload' It comes out the following output: build-all-reload - Are you sure you wish to drop your databases? (y/n) y build-all-reload - Successfully dropped database for connection named 'doctrine' build-all-reload - Generated models successfully from YAML schema build-all-reload - Successfully created database for connection named 'doctrine' Badly constructed integrity constraints. Cannot define constraint of different f ields in the same table. Here is the source code of Doctrine that outputs the error: here What causes the error? How can I debug where the error comes from?

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  • Design question - loading info from DB

    - by eriks
    I need to build a class that will represent a row in some table in DB (lets say the table is 'Subscriber' and so is the class). I can have the class Subscriber which constructor receives the Objectkey of subscriber, retrieves info from DB and initializes its members. I add another class - SubscriberLoader which have a static method 'LoadSubscriber'. This method will receive the subscriber objectkey, retrieve info from DB, crate a Subscriber object and initialize its members. Subscriber constructor will be private and SubscirberLoader will be friend class of Subscriber - this way, client could build a Subscriber only using the loader. which of the two in better? any other suggestions?

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  • Qt: any way to automatically generate QSharedData-based structures?

    - by Eye of Hell
    Hello. Qt has a build-in supprt for creating objects with integrated reference counting via QSharedData and QSharedDataPointer. All wordks great, but for each such object i need to write a lot of code: QSharedData-based implementation class with constructor and copy constructor, object class itsef with accessor methods for each filed. For a simple structures with 5-10 fields this requires really lot of near same code. Is it some ways to automate such classes generation? Maybe it's some generators exists that take a short description and automatically generates implementation class and object class with all accessors?

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  • Getter/Setter from separate class file in Java

    - by Crystal
    I'm new to Java and for a HW assignment, we had to create a Person class that has a constructor, getter/setter for the attributes of firstName, lastName, phone. That is in a separate file from an old HW assignment (Person.java). Now we have to use that Person class in our new HW assignment (LoanApplication.java). So if one of the attributes is private Person client do I need to create getter/setters or a constructor again? Otherwise, how does each LoanApplicaiton instance know which Person attribute it is to go with? How does the JVM know that it can use the Person.class even though my LoanApplicaiton.class does not extend Person.class? Thanks.

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  • C# Dynamic From Components (Performance problem)

    - by Svisstack
    Hello, I have a problem with performance of my code under Windows Forms. Have a form, her layout is depending on constructor data, because he layout must be OnLoad or in Constructor generated. I generation is simple, base FlowLayoutPanel have other FlowLayoutPanels, for each have a Label and TextBox with DataBinding. Problem is this is VERY SLOW, up to 20 seconds, i drawing less than 100 controls, from Performace Session i know a problem is on 70% procesing functions: System.Windows.Forms.Control.ControlCollection.Add(class System.Windows.Forms.Control) System.Windows.Forms.ControlBindingsCollection.Add(class System.Windows.Forms.Binding) How i can do with this? Anyone help me in this problem? How solve the dynamic form layout problem?

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  • Manage bad_alloc exception in C++ construtor

    - by Jimmy zhang
    I have Java experience and recently am doing some C++ coding. My question is that if I have class A, in which I have to instantiate class B and class C as two of the member variables of A. If in the constructor of A, should I assume that allocations of class B and C never fail, and handle the bad allocation exception in the destructor of A? If I don't make that assumption, meaning that I add some try catch block to catch bad_alloc of class B and class C, then if the allocation exception occurs, should I do clean up in the constructor of A? What are the recommended practices? If "new" generates a bad allocation, what value does the pointer carry?

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  • debugging c# silverlight projects from vb web application

    - by dave lowe
    Hi, I have a problem whereby I cannot debug a c# silverlight application project that is hosted from within a visual basic web application. I add breakpoints to the main App constructor and the symbols are loaded ok but my breakpoints are never hit. I have concluded that it is a vb/c# interop problem as to test i did the following. Created a new c# web application project Added a c# silverlight application Added a new vb web application project Added references to the silverlight project from both web apps set a breakpoint in App.xaml.cs constructor if i run the c# webapp the break points are hit whereas if i run the vb webapp they are not. has anyone come across this before or can anyone suggest a solution please? Many Thanks

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  • Shell script variable problem

    - by user280288
    Hi all, I'm trying to write a shell script to automate a job for me. But i'm currently stuck. Here's the problem : I have a variable named var1 (a decreasing number from 25 to 0 and another variable named var${var1} and this equals to some string. then when i try to call var${var1} in anywhere in script via echo it fails. I have tried $[var$var1], ${var$var} and many others but everytime it fails and gives the value of var1 or says operand expected error. Thanks for your help

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  • C++: retrieve map values and insert into second map

    - by donalmg
    Hi, I have one map within one header file class: class One { // code typedef map<string, int> MapStrToInt inline MapStrToInt& GetDetails(unsigned long index) { return pData[index]; } // populate pData.... private: MapStrToInt *pData; }; And a second class which implements another map and wants to get the first 10 details from the class One's map. class Two { // code One::MapStrToInt pDataTen; int function1() { for (int i =0; i < 10; i ++) { One::MapStrToInt * pMap = &(One::GetDetails(i)); pDataTen.insert(pair<string, int>(pMap->first,pMap->second)); } } When I compile this, it states that pMap: has no member named 'first' has no member named 'second' Any suggestions? Thanks..

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