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• Is this bad Object Oriented Design? (derived class used in base class)

  - by Earlz

  Hello, Can someone tell me if this class structure is bad? class abstract Parent{ public Child Foo(){ return new Child(); } } class Child : Parent{} I've heard that referring to a derived type from a base type is always bad and signs of bad design. Can someone tell me why this is bad or even if it is bad?

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• How to automatically execute python script when Maya first loaded

  - by tep

  Hi, I am new to Maya and trying to figure out how to use Python in Maya. I wanted to create a shelf in Maya and when I click that shelf, it will execute a file containing python code. First thing, I figured out that we can't simply "source" python script. I followed tutorial from http://www.rtrowbridge.com/blog/2008/11/maya-python-import-scripts/, so now I have a function psource(). In my shelf, I can just call psource("myPythonScript") My problem is I have to somehow register psource() when Maya first loaded. Do you have any idea how to do this? Thanks!

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• What is difference between output functions in php ?

  - by Karandeep Singh

  What is the difference between these code snippets? 1) $f = 12.044545; printf("%f",$f); vprintf("%f",$f); 2) echo("echo"); print("print"); Thanks,

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• Implementing callback functions in C

  - by robertjohn123

  Hi, I am a newbie to C.I am trying to implement callback function using function pointers. I am getting an error :test_callback.c:10: error: expected identifier or ‘(’ before ‘void’ when I try to compile the following program: #include<stdio.h> void (*callback) (void); void callback_proc () { printf ("Inside callback funtion\n"); } void register ((void (*callback) (void))) { printf ("Inside registration \n"); callback (); /* Calling an initial callback with function pointer */ } int main () { callback = callback_proc;/* Assigning function to the function pointer */ register (callback);/* Passing the function pointer */ return 0; } What is this error?Can anyone help?

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• Getting the first image elements id within an unordered list using JQuery

  - by Roland

  I'm trying to get the id of the first element of an unordered list using JQuery. Here's the list <ul class="list"> <li><img id="1" src="image1.jpg" name="image1" /></li> <li><img id="2" src="image2.jpg" name="image2" /></li> <li><img id="3" src="image3.jpg" name="image3" /></li> <li><img id="4" src="image4.jpg" name="image4" /></li> <li><img id="5" src="image5.jpg" name="image5" /></li> </ul> JQuery var id = $('.list li img'):first.attr('id');

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• Java: is Exception class thread-safe?

  - by Vilius Normantas

  As I understand, Java's Exception class is certainly not immutable (methods like initCause and setStackTrace give some clues about that). So is it at least thread-safe? Suppose one of my classes has a field like this: private final Exception myException; Can I safely expose this field to multiple threads? I'm not willing to discuss concrete cases where and why this situation could occur. My question is more about the principle: can I tell that a class which exposes field of Exception type is thread-safe? Another example: class CustomException extends Exception { ... } Is this class thread-safe?

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• In what package should a "Settings" class be?

  - by Tom

  I've in the middle of building an application but found myself too easily creating new packages without keeping the project's structure in mind. Now, I'm trying to redo the whole project structure on paper first. I am using a Settings class with public properties, accessed as settings for several other classes around the project. Now, since this Settings class applies for the whole project, I am unsure if it should be packaged and if so, in what kind of package should it exist? Or should it be in the root (the default package) with the main application class? I've been thinking about putting it in my utils package, then again I don't think it really is an utlity. Any strategies on how to decide on such package structure for example for a Settings class?

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• StructureMap - Injecting a dependency into a base class?

  - by David

  In my domain I have a handful of "processor" classes which hold the bulk of the business logic. Using StructureMap with default conventions, I inject repositories into those classes for their various IO (databases, file system, etc.). For example: public interface IHelloWorldProcessor { string HelloWorld(); } public class HelloWorldProcessor : IHelloWorldProcessor { private IDBRepository _dbRepository; public HelloWorldProcessor(IDBRepository dbRepository) { _dbRepository = dbrepository; } public string HelloWorld(){ return _dbRepository.GetHelloWorld(); } } Now, there are some repositories that I'd like to be available to all processors, so I made a base class like this: public class BaseProcessor { protected ICommonRepository _commonRepository; public BaseProcessor(ICommonRepository commonRepository) { _commonRepository = commonRepository; } } But when my other processors inherit from it, I get a compiler error on each one saying that there's no constructor for BaseProcessor which takes zero arguments. Is there a way to do what I'm trying to do here? That is, to have common dependencies injected into a base class that my other classes can use without having to write the injections into each one?

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• My AES encryption/decryption functions don't work with random ivecs

  - by Brendan Long

  I was bored and wrote a wrapper around openSSL to do AES encryption with less work. If I do it like this: http://pastebin.com/V1eqz4jp (ivec = 0) Everything works fine, but the default ivec is all 0's, which has some security problems. Since I'm passing the data back as a string anyway, I figured, why not generate a random ivec and stick it to the front, the take it back off when I decrypt the string? For some reason it doesn't work though. With random ivec: http://pastebin.com/MkDBFcn6 Well actually, it almost works. It seems to decrypt the middle of the string, but not the beginning or end: String is: 0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF Encrypting.. ???l%%1u???B! ?????`pN)?????[l????{?Q???2?/?H??y"?=Z?Cu????l%%1u???B! Decrypting.. String is: ?%???G*?5J?0??0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF!-e????V?5 I honestly have no idea what's going wrong. Maybe some stupid mistake, or maybe I'm missing something about AES?

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• JavaFX - reduce() function to show how to pass functions as parameters

  - by Helper Method

  At the moment I'm writing a JavaFX guide for Java developers. In order to show how to pass a function to another funtion i adopted the reduce() function found in Effective Java: function reduce(seq: Integer[], f: function(: Integer, : Integer): Integer, init: Integer) { var result = init; for (i in seq) { result = f(i, result); } result } def nums = [1 .. 10]; println(reduce(nums, function(a: Integer, b: Integer) { a + b }, 0)); // prints 55 println(reduce(nums, function(a: Integer, b: Integer) { a * b }, 0)); // prints 3628800 Now I wonder if this example is not to hard for someone starting to learn JavaFX. The tutorial is targeted to programmers with a solid understanding of Java, yet I'm not quite sure about the usefulness of the example. Any ideas?

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• Formating with printf in using two functions

  - by user317203

  I am trying to output a document that looks like this. http://pastebin.com/dpBAY8Sb my issue is that I cannot find how to format the output I have to have a floating poing and format the distance between columns. My current code looks something like this. if (defined $longitude){ printf FILE ("%-8s %.6f","",$longitude); }else{ $longitude = ""; printf FILE ("%-20s ",$longitude); } but the extra "" throws off the whole column and it looks like this. pastebin.com/kcwHyNwb

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• String Vector program exits before input

  - by kylepayne

  So, I have a project that must add, delete, and print the contents of a vector... the problem is that, when run the program exits before I can type in the string to add to the vector. I commented the function that that portion is in. Thanks! #include <iostream> #include <cstdlib> #include <vector> #include <string> using namespace std; void menu(); void addvector(vector<string>& vec); void subvector(vector<string>& vec); void vectorsize(const vector<string>& vec); void printvec(const vector<string>& vec); void printvec_bw(const vector<string>& vec); int main() { vector<string> svector; menu(); return 0; } //functions definitions void menu() { vector<string> svector; int choice = 0; cout << "Thanks for using this program! \n" << "Enter 1 to add a string to the vector \n" << "Enter 2 to remove the last string from the vector \n" << "Enter 3 to print the vector size \n" << "Enter 4 to print the contents of the vector \n" << "Enter 5 ----------------------------------- backwards \n" << "Enter 6 to end the program \n"; cin >> choice; switch(choice) { case 1: addvector(svector); break; case 2: subvector(svector); break; case 3: vectorsize(svector); break; case 4: printvec(svector); break; case 5: printvec_bw(svector); break; case 6: exit(1); default: cout << "not a valid choice \n"; // menu is structured so that all other functions are called from it. } } void addvector(vector<string>& vec) { string line; int i = 0; cout << "Enter the string please \n"; getline(cin, line); // doesn't prompt for input! vec.push_back(line); } void subvector(vector<string>& vec) { vec.pop_back(); return; } void vectorsize(const vector<string>& vec) { if (vec.empty()) { cout << "vector is empty"; } else { cout << vec.size() << endl; } return; } void printvec(const vector<string>& vec) { for(int i = 0; i < vec.size(); i++) { cout << vec[i] << endl; } return; } void printvec_bw(const vector<string>& vec) { for(int i = vec.size(); i > 0; i--) { cout << vec[i] << endl; } return; }

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• Obtaining reference to Class instance by string name - VB.NET

  - by Jeff Williams

  Is it possible using Reflection or some other method to obtain a reference to a specific class instance from the name of that class instance? For example the framework for the applications i develop heavily uses public class instances such as: Public bMyreference as MyReference = new MyReference Then throughout the application bMyReference is used by custom controls and code. One of the properties of the custom controls is the "FieldName" which references a Property in these class instances (bMyReference.MyField) as a string. What i would like to be able to do is analyze this string "bMyReference.MyField" and then refer back to the actual Instance/Property. In VB6 I would use an EVAL or something simular to convert the string to an actual object but this obviously doesn't work in VB.net What I'm picturing is something like this Dim FieldName as String = MyControl.FieldName ' sets FielName to bMyReference.MyField Dim FieldObject() as String = FieldName.Split(".") ' Split into the Object / Property Dim myInstance as Object = ......... ' Obtain a reference to the Instance and set as myInstance Dim myProperty = myInstance.GetType().GetProperty(FieldObject(1))

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• Java - Calling all methods of a class

  - by Thomas Eschemann

  I'm currently working on an application that has to render several Freemarker templates. So far I have a Generator class that handles the rendering. The class looks more or less like this: public class Generator { public static void generate(…) { renderTemplate1(); renderTemplate2(); renderTemplate3(); } private static void render(…) { // renders the template } private static void renderTemplate1() { // Create config object for the rendering // and calls render(); }; private static void renderTemplate1() { // Create config object for the rendering // and calls render(); }; … } This works, but it doesn't really feel right. What I would like to do is create a class that holds all the renderTemplate...() methods and then call them dynamically from my Generator class. This would make it cleaner and easier to extend. I was thinking about using something like reflection, but it doesn't really feel like a good solution either. Any idea on how to implement this properly ?

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• MATLAB: Automatic detection of relations between workspace variables through functions

  - by Peterstone

  Hi all, I´m trying to write a function what detect this relation between the variables I have got in the workspace: v1 - fft(v2) = 0 Where v1, v2 are variables of my workspace. Sometimes I need to know which variables have a certain numerical relation. If I have thirty, I don´t want to be looking for this relation in "manual way", just itroducing a sentence for each pair of different variables. I would like a function in which I introuce (or I modify this function every time I need it) the sentence (for instance what I wrote before) and the function show me the pair of variables a I am looking for. Does anyone know how to do it? Thank you so much!

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• selenium cannot find element with class in IE

  - by Rob

  I'm using selenium_client with cucumber, webrat + IE As you'd expect, Firefox works fine. I've tried the following: selenium.is_visible("css=#flash .flash_notice") selenium.is_visible("xpath=//*[@id='flash']/*[@class='flash_notice]") selenium.is_visible("xpath=//*[@id='flash']/*[contains(@class,'flash_notice]')") both cannot find the element. I think it must be something to do with IE, looking closer at the html selenium returns from IE... It looks like this: <UL id=flash> <LI className=flash_notice>Deleted</LI> </UL> Notice IE returns the class attribute as className, is this confusing selenium? How can I get round this so that I can use the same statement for selenium using IE and Firefox Just to confuse us even more, this example works, confirming its something to do with checking the class attribute selenium.is_visible("xpath=//*[@id='flash']/*[. =\'Deleted\']")

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• Python: Is there a way to reflectivly list all attributes of a class

  - by hhafez

  Given a class such as def MyClass text = "hello" number = 123 Is there a way in python to inspect MyClass an determine that it has the two attributes text and number. I can not use something like inspect.getSource(object) because the class I am to get it's attributes for are generate using SWIG (so they are hidden in .so :) ). So I am really looking for something equivalant to Java's [Class.getDeclardFields][1] Any help would be appreciated, otherwise I'll have to solve this problem with SWIG + JAVA instead of SWIG + Python.

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• How to remove class Conditionally ?

  - by Wazdesign

  $("li").hoverIntent({ sensitivity: 3, interval: 200, over: addOver, timeout: 500, out: removeOver }); function addOver(){ $(this).addClass('over').children('a:first').addClass('active');} function removeOver(){ $(this).removeClass('over').children('a:first').removeClass('active');} alert ('version 2 menu'); }); On mouseout I want to remove class of " li a" if it already dont have class. I want to remove the class of the children.

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• Encapsulating user input of data for a class (C++)

  - by Dr. Monkey

  For an assignment I've made a simple C++ program that uses a superclass (Student) and two subclasses (CourseStudent and ResearchStudent) to store a list of students and print out their details, with different details shown for the two different types of students (using overriding of the display() method from Student). My question is about how the program collects input from the user of things like the student name, ID number, unit and fee information (for a course student) and research information (for research students): My implementation has the prompting for user input and the collecting of that input handled within the classes themselves. The reasoning behind this was that each class knows what kind of input it needs, so it makes sense to me to have it know how to ask for it (given an ostream through which to ask and an istream to collect the input from). My lecturer says that the prompting and input should all be handled in the main program, which seems to me somewhat messier, and would make it trickier to extend the program to handle different types of students. I am considering, as a compromise, to make a helper class that handles the prompting and collection of user input for each type of Student, which could then be called on by the main program. The advantage of this would be that the student classes don't have as much in them (so they're cleaner), but also they can be bundled with the helper classes if the input functionality is required. This also means more classes of Student could be added without having to make major changes to the main program, as long as helper classes are provided for these new classes. Also the helper class could be swapped for an alternative language version without having to make any changes to the class itself. What are the major advantages and disadvantages of the three different options for user input (fully encapsulated, helper class or in the main program)?

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• PDO using singleton stored as class properity

  - by Misiur

  Hi again. OOP drives me crazy. I can't move PDO to work. Here's my DB class: class DB extends PDO { public function &instance($dsn, $username = null, $password = null, $driver_options = array()) { static $instance = null; if($instance === null) { try { $instance = new self($dsn, $username, $password, $driver_options); } catch(PDOException $e) { throw new DBException($e->getMessage()); } } return $instance; } } It's okay when i do something like this: try { $db = new DB(DB_TYPE.':host='.DB_HOST.';dbname='.DB_NAME, DB_USER, DB_PASS); } catch(DBException $e) { echo $e->getMessage(); } But this: try { $db = DB::instance(DB_TYPE.':host='.DB_HOST.';dbname='.DB_NAME, DB_USER, DB_PASS); } catch(DBException $e) { echo $e->getMessage(); } Does nothing. I mean, even when I use wrong password/username, I don't get any exception. Second thing - I have class which is "heart" of my site: class Core { static private $instance; public $db; public function __construct() { if(!self::$instance) { $this->db = DB::instance(DB_TYPE.':hpost='.DB_HOST.';dbname='.DB_NAME, DB_USER, DB_PASS); } return self::$instance; } private function __clone() { } } I've tried to use "new DB" inside class, but this: $r = $core->db->query("SELECT * FROM me_config"); print_r($r->fetch()); Return nothing. $sql = "SELECT * FROM me_config"; print_r($core->db->query($sql)); I get: PDOStatement Object ( [queryString] => SELECT * FROM me_config ) I'm really confused, what am I doing wrong?

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• how to get $form_state outside of FAPI's functions?

  - by logii

  I'm writing a custom module and I'd like to use $form_state of the current form in another non-form api function - custom_facet_view_build(). any help is appreciated :) <?php /** * Implementation of hook_perm(). */ function custom_facet_perm() { return array( 'access foo content', 'access baz content', ); } /** * Implementation of hook_menu(). */ function custom_facet_menu() { $items['faceted-search'] = array( 'title' => 'Faceted Search', 'page callback' => 'drupal_get_form', 'access arguments' => array(), ); $items['facet-search-test'] = array( 'page callback' => 'drupal_get_form', 'page arguments' => array('custom_facet_form'), 'access callback' => TRUE, 'type' => MENU_CALLBACK, ); return $items; } /** * Form definition; ahah_helper_demo form. */ function custom_facet_form($form_state) { $form = array(); ahah_helper_register($form, $form_state); if (isset($form_state['storage']['categories'])) { $categories_default_value = $form_state['storage']['categories']["#value"]; } $form['facet_search_form'] = array( '#type' => 'fieldset', '#title' => t('Faceted Search'), '#prefix' => '<div id="billing-info-wrapper">', // This is our wrapper div. '#suffix' => '</div>', '#tree' => TRUE, // Don't forget to set #tree! ); $form['facet_search_form']['categories'] = array( '#type' => 'select', '#title' => t('Category'), '#options' => _custom_facet_taxonomy_query(1), '#multiple' => TRUE, '#default_value' => $categories_default_value, ); $form['save'] = array( '#type' => 'submit', '#value' => t('Save'), ); return $form; } /** * Validate callback for the form. */ function custom_facet_form_validate($form, &$form_state) { } /** * Submit callback for the form. */ function custom_facet_form_submit($form, &$form_state) { drupal_set_message('nothing done'); $form_state['storage']['categories'] = $form['facet_search_form']['categories']; // dpm($form_state); // There's a value returned in form_state['storage] within this function } /** * Implementation of hook_views_api(). */ function custom_facet_views_api() { return array( 'api' => 2, ); } function custom_facet_view_build(&$view) { dpm($form_state); // form_state['storage] remains NULL even though there's a value on previous submission }

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• Choosing a design pattern for a class that might change it's internal attributes

  - by the_drow

  I have a class that holds arbitrary state and it's defined like this: class AbstractFoo { }; template <class StatePolicy> class Foo : public StatePolicy, public AbstractFoo { }; The state policy contains only protected attributes that represent the state. The state might be the same for multiple behaviors and they can be replaced at runtime. All Foo objects have the same interface to abstract the state itself and to enable storing Foo objects in containers. I would like to find the least verbose and the most maintainable way to express this.

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• creative way for implementing Data object with its corresponding business logic class in java

  - by ekeren

  I have a class that need to be serialized (for both persistentcy and client-server communication) for simplicity's sake let's call the classes Business a BusinessData and I prefix for their Interfaces. All the getter and setter are delegated from Business class to BusinessData class. I thought about implementing IBusinessData interface that will contain all the getter and setters and IBusiness interface that will extend it. I can either make Business extend BuisnessData so I will not need to implement all getter and setter delegates, or make some abstract class ForwardingBusinessData that will only delegate getter and setters. Any of the above option I lose my hierarchy freedom, do any of you have any creative solutions for this problem... I also reviewed DAO pattern: http://java.sun.com/blueprints/patterns/DAO.html

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• Base class with abstract subclasses in C# ?

  - by Nick Brooks

  public abstract class Request { public class Parameters { //Threre are no members here //But there should be in inherited classes } public Request() { parameters = new Parameters(); } public Parameters parameters; } Two questions: How do I make it so I can add stuff to the constructor but the original constructor will still be executed? How do I make it so the subclasses can add members to the Parameters class?

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• How to show login screen only for the first time when app launches

  - by Jaw Ali

  I want to launch the login screen when first time app launches other wise app work simple but problem is that again again it goes to login screen. here is the code which i am using in didFininsh I want the user show go to login screen first time only and next time it should show splitViewController [[NSUserDefaults standardUserDefaults] registerDefaults:[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES],@"firstLaunch",nil]]; if ([[NSUserDefaults standardUserDefaults] boolForKey:@"firstLaunch"]) { [self.window addSubview:[splitViewController view]]; LoginViewController *targetController = [[LoginViewController alloc] initWithNibName:@"LoginViewController" bundle:nil]; targetController.modalPresentationStyle = UIModalPresentationFullScreen; [self.splitViewController presentViewController:targetController animated:YES completion:nil]; } else { [self.window addSubview:[splitViewController view]]; } // my comment[window addSubview:splitViewController.view]; [window makeKeyAndVisible]; return YES;

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