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  • C++ design with static methods

    - by user231536
    I would like to define as class X with a static method: class X { static string get_type () {return "X";} //other virtual methods } I would like to force classes which inherit from X to redefine the get_type() method and return strings different from "X" (I am happy if they just redefine get_type for now). How do I do this? I know that I cannot have virtual static methods. Edit: The question is not about the type_id, but in general about a static method that should be overriden. For example class X { static int getid() {return 1;} }

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  • When is it safe to do a Response.Redirect() without throwing an exception?

    - by DDechant
    I have an intermediary class extending System.Web.UI.Page for all of my pages that require authentication. The class mostly does custom authentication handling. When a user with insufficient access attempts to visit a page, I try to redirect the user back to the login page while preventing any further page events from being executed (ie. Page_load). The first solution that came to mind was the default implementation of Response.Redirect. Of course the downside to this is the possibility of ThreadAbortExceptions being thrown. So my question is this: When (if at all) during the page life cycle is it actually safe to execute Response.Redirect() without ThreadAbortException ever being thrown? public class CustomPage : System.Web.UI.Page { protected override void OnInit(EventArgs e) { base.OnInit(e); if (!IsValid()) Response.Redirect("login.aspx", true); } }

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  • Best way to test instance methods without running __init__

    - by KenFar
    I've got a simple class that gets most of its arguments via init, which also runs a variety of private methods that do most of the work. Output is available either through access to object variables or public methods. Here's the problem - I'd like my unittest framework to directly call the private methods called by init with different data - without going through init. What's the best way to do this? So far, I've been refactoring these classes so that init does less and data is passed in separately. This makes testing easy, but I think the usability of the class suffers a little. EDIT: Example solution based on Ignacio's answer: import types class C(object): def __init__(self, number): new_number = self._foo(number) self._bar(new_number) def _foo(self, number): return number * 2 def _bar(self, number): print number * 10 #--- normal execution - should print 160: ------- MyC = C(8) #--- testing execution - should print 80 -------- MyC = object.__new__(C) MyC._bar(8)

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  • Parallelizing a serial algorithm

    - by user643813
    Hej folks, I am working on porting a Text mining/Natural language application from single-core to a Map-Reduce style system. One of the steps involves a while loop similar to this: Queue<Element>; while (!queue.empty()) { Element e = queue.next(); Set<Element> result = calculateResultSet(e); if (!result.empty()) { queue.addAll(result); } } Each iteration depends on the result of the one before (kind of). There is no way of determining the number of iterations this loop will have to perform. Is there a way of parallelizing a serial algorithm such as this one? I am trying to think of a feedback mechanism, that is able to provide its own input, but how would one go about parallelizing it? Thanks for any help/remarks

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  • bulk update/delete entities of different kind in db.run_in_transaction

    - by Ray Yun
    Here goes pseudo code of bulk update/delete entities of different kind in single transaction. Note that Album and Song entities have AlbumGroup as root entity. class AlbumGroup: pass class Album: group = db.ReferenceProperty(reference_class=AlbumGroup,collection_name="albums") class Song: album = db.ReferenceProperty(reference_class=Album,collection_name="songs") def bulk_update_album_group(album_group): updated = [album_group] deleted = [] for album in album_group.albums: updated.append(album) for song in album.songs: if song.is_updated: updated.append(song) if song.is_deleted: deleted.append(song) db.put(updated) db.delete(deleted) a = AlbumGroup.all().filter("...").get() # bulk update/delete album group. for simplicity, album cannot be deleted. db.run_in_transaction(bulk_update_album_group,a) But I met a famous "Only Ancestor Queries in Transactions" error at the iterating reference properties like album.songs or album_group.albums. I guess ancestor() filter does not help because those entities are modified in memory. Should I not to iterate reference property in transaction function and always provide them as function parameters like def bulk_update_album_group(updated,deleted): ??? Is there any good coding pattern for this situation?

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  • Preprocessor Conditionals

    - by Mike
    I was wondering if it would be possible to have a define which changes values at some point in the code be used in a conditional. Basically something like this: //////////////////////////////////////////// SomeFile.cpp #define SHUTDOWN false while(window->isOpen()) { if(SHUTDOWN) window->close(); // Rest of the main loop } //////////////////////////////////////////// SomeOtherFile.cpp if(Escape.isPressed()) { #undef SHUTDOWN #define SHUTDOWN true } Thus causing the app to close. If it's not, would having a function like RenderWindow* getWindow() { return window; } and then calling if(Escape.isPressed()) getWindow()->close(); The best way to do it? I'd rather not go that route because the classes that are calling the key event are members of the class controlling the main loop and the window, so I'd have to set pointers to the containing class in the smaller classes to call getWindow() and it just seems like a more complicated method. But if I can't do it with preprocessor directives I'll just have to use pointers to the parent class.

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  • JQuery Validation Plugin not working when used on page that includes another page via AJAX

    - by droidy
    We have a long page that contains a bunch of different form elements. One part of the form is called remotely via AJAX and is populated in an empty div. This is the part which JQuery Validation plugin is not working correctly on. We have class="required" on the elements on this page, but they do not show up as required. I'm guessing it's because the Validation plugin is looking for class="required" on our main page, and since the content from the AJAX page is put into the empty div behind the scenes, it's not detected the required fields. Any help is greatly appreciated.

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  • Why my WCF Service returns xml serialized objects?

    - by user294554
    Hi, I'm new here and I hope anyonte can help me. I have WCF Service and Windows Forms working with this client written in VB.NET. The Service class started to return xml serialized objects, but all my classes on Service side are DataContract-s and the service class is DataContractFormat. I googled everywhere about serializations and I couldn't find reason why it started to do that. I checked my classes and service, app.config file, but I couldn't find anything. I checked Reference.vb class, and it's System.Xml.Serialization.XmlElementAttribute everywhere. The question may seem dummy, but I really don't know what to do. I just want to know what can cause the service to act like that. Thank you.

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  • having trouble with a mysql query

    - by chuck akers
    this keeps saying Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in directory here the error is near the login_query variable, can someone help me fix it. <?php if (isset($_POST['login_username'], $_POST['login_password'])) { $login_username = trim(mysql_real_escape_string(htmlentities($_POST['login_username']))); $login_password = md5(trim(mysql_real_escape_string(htmlentities($_POST['login_password'])))); if (!empty($login_username) && !empty($login_password)) { $login_query = mysql_query("SELECT user_id FROM username WHERE username='".$login_username."' AND password='".$login_password."'"); if (mysql_num_rows($login_query)==1) { $user_id = mysql_result($login_query, 0, 'user_id'); $_SESSION['user_id'] = $user_id; header('Location: index.php'); die(); } }} ?

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  • how to use multiple $_name using extends Zend_Db_Table_Abstract in zend frame work.

    - by karthik
    we tried to give our tables(users,messages) like this in two different abstract classes but it is not working. This is included in a file childconnect1.php ,is there any relation between the file name(childconnect1.php) and the class(Application_Model_childconnect1). class Application_Model_childconnect1 extends Zend_Db_Table_Abstract { protected $_name = 'users'; public function loginvalidation($username,$pwd) { $row = $this->fetchRow('UserName = \'' . $username . '\'and UserPW = \''. $pwd . '\''); if (!$row) { $msg="invalid"; return $msg; } else { return $row->toArray(); } } } class Application_Model_childconnect2 extends Zend_Db_Table_Abstract { protected $_name = 'messages'; public function replymessage($message) { $data=array( 'MessageText'=>$message ); $this->insert($data); } }

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  • Casting objects to Integer,string ,...

    - by Milan
    Hello everybody! I have one small problem. I have list of types(int,string,..) ArrayList<Class> typeList; and I have some input values; ArrayList<Object> values; How to cast some value to some type if I know which type from the typeList is the values; typeList.get(i).cast(values.get(i)); <- this is not working??? Actualy I generate dynamic form in runtime. With Java reflection I get parameterTypes from methods from some class, I generate form with input fields and then i want to cast the text from the input fields to specific types from the paramterTypes that I got with Java reflection from some class.

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  • Confused about "override" vs. "new" in C#

    - by iTayb
    I'm having the following classes: class Base { public virtual void Print() { Console.WriteLine("Base"); } } class Der1 : Base { public new virtual void Print() { Console.WriteLine("Der1"); } } class Der2 : Der1 { public override void Print() { Console.WriteLine("Der2"); } } This is my main method: Base b = new Der2(); Der1 d1 = new Der2(); Der2 d2 = new Der2(); b.Print(); d1.Print(); d2.Print(); The output is Base, Der2, Der2. As far as I know, Override won't let previous method to run, even if the pointer is pointing to them. So the first line should output Der2 as well. However Base came out. How is it possible? How the override didn't work there?

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  • Buffering db inserts in multithreaded program

    - by Winter
    I have a system which breaks a large taks into small tasks using about 30 threads as a time. As each individual thread finishes it persists its calculated results to the database. What I want to achieve is to have each thread pass its results to a new persisance class that will perform a type of double buffering and data persistance while running in its own thread. For example, after 100 threads have moved their data to the buffer the persistance class then the persistance class swaps the buffers and persists all 100 entries to the database. This would allow utilization of prepared statements and thus cut way down on the I/O between the program and the database. Is there a pattern or good example of this type of multithreading double buffering?

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  • Can't run the ActionBarCompat sample

    - by David Miler
    I am having trouble compiling and running the ActionBarCompat sample of Android 16. I have API level 16 as the build target selected, which seems to build fine, but when I try to debug these errors pop up. Of course I could change the min API level in the manifest, but what would be the point of that? I have made no changes to the sample, so how come it is not working properly? Class requires API level 14 (current min is 3): android.view.ActionProvider SimpleMenuItem.java /ActionBarCompat/src/com/example/android/actionbarcompat line 129 Android Lint Problem Class requires API level 14 (current min is 3): android.view.ActionProvider SimpleMenuItem.java /ActionBarCompat/src/com/example/android/actionbarcompat line 134 Android Lint Problem Class requires API level 14 (current min is 3): android.view.MenuItem.OnActionExpandListener SimpleMenuItem.java /ActionBarCompat/src/com/example/android/actionbarcompat line 155 Android Lint Problem I am thoroughly confused, any help would be appreciated.

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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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  • what the java command's -jar option really does

    - by JBoy
    Does the -jar option of the java command also compile the sources before running the main method? I believe so but i would like to have a better understanding of the internal process, from the man page you can clearly see a small workflow sequence: -jar Execute a program encapsulated in a JAR file. The first argument is the name of a JAR file instead of a startup class name. In order for this option to work, the manifest of the JAR file must contain a line of the form Main-Class: classname. Here, classname identifies the class having the public static void main(String[] args) method that serves as your application's starting point. See the Jar tool reference page and the Jar trail of the Java Tutorial @ But it does not mention that it compiles the sources.

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  • Correct handling of return data

    - by Serhiy
    Hello, I have a question related to correct handling of returns of the DAO library I'm writing for one project. This library probably is going to be used by another people and I want to do it correctly. So I would like to know, how I should deal with return statements of the functions of my DAO. Example 1 I have function to getCustomer which should return String. In case query doesn't return any result should I return null, empty string or throw some kind of Exception? Example 2 I have function getCutomerList which return ArrayList. In case query doesn't return any result should I return null, empty ArrayList or throw some Exception? Example 3 Some sql exception was detected, what should I do: throw exception or do try..catch of the block where it can occur? What is the "good" practice or "best" practice to apply in my case? Thanks on advance, Serhiy.

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  • determine from where the function being called in php

    - by Avinash
    I have one function on my code. say its xyz(). This function is being called from different files of my project. Is there any way than I can get from where the function is being called. I want below infromation: File name from where its called. Line number of that file. if call is from inside the function then that function name. Class name Class method name. I know about use of magic constants like FILE and all that. but i don't want to pass all that in function call. like below: xyz('msg',__FILE__,__CLASS__); is there any way that i have to pass just my error related data only. and it will find the above details from where the function is called. let me know if anything is not clear.

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  • has_many relation doesn't seems right or logical, some thing like belongs_to_many looks right

    - by Vijendra
    My situation is like this. Company has many users and users may belongs to many companies. And current implementation is something like below. class Company has_many :employments has_many :users, :through = :employments end class Employment belongs_to :company belongs_to :user end class User has_many :employments has_many :companies, :through = :employments #This doesn't looks correct end User has many companies doesn't looks logically meaningful.It must be some thing like belongs_to_many companies. Do I need to use has_and_belongs_to_many? But that also will gives the same meaning. Can some one please suggest the right way for representing these relationships?

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  • undefined reference to static member variable

    - by Max
    Hi. I have this class that has a static member. it is also a base class for several other classes in my program. Here's its header file: #ifndef YARL_OBJECT_HPP #define YARL_OBJECT_HPP namespace yarlObject { class YarlObject { // Member Variables private: static int nextID; // keeps track of the next ID number to be used int ID; // the identifier for a specific object // Member Functions public: YarlObject(): ID(++nextID) {} virtual ~YarlObject() {} int getID() const {return ID;} }; } #endif and here's its implementation file. #include "YarlObject.hpp" namespace yarlObject { int YarlObject::nextID = 0; } I'm using g++, and it returns three undefined reference to 'yarlObject::YarlObject::nextID linker errors. If I change the ++nextID phrase in the constructor to just nextID, then I only get one error, and if I change it to 1, then it links correctly. I imagine it's something simple, but what's going on?

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  • C++ operator overloading doubt

    - by avd
    I have a code base, in which for Matrix class, these two definitions are there for () operator: template <class T> T& Matrix<T>::operator() (unsigned row, unsigned col) { ...... } template <class T> T Matrix<T>::operator() (unsigned row, unsigned col) const { ...... } One thing I understand is that the second one does not return the reference but what does const mean in the second declaration. Also which function is called when I do say mat(i,j)

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  • scroll bar in textareas

    - by Hulk
    Int the following code, The scroll bar appears in IE and in mozilla it doesnt,how is this to be fixed,scroll bar should not appear where there is not much of data. <script> var row= '<table><tr>'; row = '<tr class="display_row"">'; row += '<td class="display_col" wrap width="75"><b><textarea rows = "8" cols = "18" border ="1" class="input" style="border: none;overflow:visible;width:95%;" readonly maxlength="5">Name selected is Tom </textarea>'; row+='</td></tr></table>'; </script>

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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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  • 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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  • DJANGO complex modelling

    - by SledgehammerPL
    Hello. I have such model now: receipt contains components. component contain product. The difference between component and product is, that component has quantity and measure unit: eg. component is 100g sugar - sugar is a product. So I need to make lots of components to satisfy different recipes - 100g sugar is not equal 200g sugar I wonder if I can remodel it to kick off components - in pure sql it's rather easy, but I'm trying to USE django - not making workarounds. class Receipt(models.Model): name = models.CharField(max_length=128) (...) components = models.ManyToManyField(Component) class Component(models.Model): quantity = models.FloatField(max_length=9) unit = models.ForeignKey(Unit) product = models.ForeignKey(Product) class Product(models.Model): name = models.CharField(max_length = 128) TIA

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