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  • Python 3.0 - Dynamic Class Instance Naming

    - by Jon
    I want to use a while loop to initialize class objects with a simple incremented naming convention. The goal is to be able to scale the number of class objects at will and have the program generate the names automatically. (ex. h1...h100...h1000...) Each h1,h2,h3... being its own instance. Here is my first attempt... have been unable to find a good example. class Korker(object): def __init__(self,ident,roo): self.ident = ident self.roo = roo b = 1 hwinit = 'h' hwstart = 0 while b <= 10: showit = 'h' + str(b) print(showit) #showit seems to generate just fine as demonstrated by print str(showit) == Korker("test",2) #this is the line that fails b += 1 The errors I get range from a string error to a cannot use function type error.... Any help would be greatly appreciated.

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  • How to display panel which is of Singleton class in two different frames at a time?

    - by Sriku
    I am trying to display a singleton obj on two different Jframe, but it is displayed only in the Jframe in which the object is added at last ( in example Frame2). Other Jframe is empty. This Singleton class is inherited from Panel and contains a label in it. Can anybody please tell me how can i display this singleton object in two different frame ? public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { NewJFrame inst = new NewJFrame(); inst.setTitle("Frame1"); inst.setSize(300, 300); inst.setLocationRelativeTo(null); inst.setVisible(true); singltonpanel _sin = singltonpanel.instance(); inst.add(_sin); inst.repaint(); JFrame frame = new JFrame("Frame2"); frame.setSize(300, 300); frame.setVisible(true); singltonpanel _sin1 = singltonpanel.instance(); frame.add(_sin1); frame.repaint(); } });

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  • Perl - Calling subclass constructor from superclass (OO)

    - by Emmel
    This may turn out to be an embarrassingly stupid question, but better than potentially creating embarrassingly stupid code. :-) This is an OO design question, really. Let's say I have an object class 'Foos' that represents a set of dynamic configuration elements, which are obtained by querying a command on disk, 'mycrazyfoos -getconfig'. Let's say that there are two categories of behavior that I want 'Foos' objects to have: Existing ones: one is, query ones that exist in the command output I just mentioned (/usr/bin/mycrazyfoos -getconfig`. Make modifications to existing ones via shelling out commands. Create new ones that don't exist; new 'crazyfoos', using a complex set of /usr/bin/mycrazyfoos commands and parameters. Here I'm not really just querying, but actually running a bunch of system() commands. Affecting changes. Here's my class structure: Foos.pm package Foos, which has a new($hashref-{name = 'myfooname',) constructor that takes a 'crazyfoo NAME' and then queries the existence of that NAME to see if it already exists (by shelling out and running the mycrazyfoos command above). If that crazyfoo already exists, return a Foos::Existing object. Any changes to this object requires shelling out, running commands and getting confirmation that everything ran okay. If this is the way to go, then the new() constructor needs to have a test to see which subclass constructor to use (if that even makes sense in this context). Here are the subclasses: Foos/Existing.pm As mentioned above, this is for when a Foos object already exists. Foos/Pending.pm This is an object that will be created if, in the above, the 'crazyfoo NAME' doesn't actually exist. In this case, the new() constructor above will be checked for additional parameters, and it will go ahead and, when called using -create() shell out using system() and create a new object... possibly returning an 'Existing' one... OR As I type this out, I am realizing it is perhaps it's better to have a single: (an alternative arrangement) Foos class, that has a -new() that takes just a name -create() that takes additional creation parameters -delete(), -change() and other params that affect ones that exist; that will have to just be checked dynamically. So here we are, two main directions to go with this. I'm curious which would be the more intelligent way to go.

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  • Ruby execute code in class getting inherited to

    - by AdamB
    I'm trying to be able to have a global exception capture where I can add extra information when an error happens. I have two classes, "crawler" and "amazon". What I want to do is be able to call "crawl", execute a function in amazon, and use the exception handling in the crawl function. Here are the two classes I have: require 'mechanize' class Crawler Mechanize.html_parser = Nokogiri::HTML def initialize @agent = Mechanize.new end def crawl puts "crawling" begin #execute code in Amazon class here? rescue Exception => e puts "Exception: #{e.message}" puts "On url: #{@current_url}" puts e.backtrace end end def get(url) @current_url = url @agent.get(url) end end class Amazon < Crawler #some code with errors def stuff page = get("http://www.amazon.com") puts page.parser.xpath("//asldkfjasdlkj").first['href'] end end a = Amazon.new a.crawl Is there a way I can call "stuff" inside of "crawl" so I can use that exception handling over the entire stuff function? Is there a better way to accomplish this?

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  • C# Design a class with interface?

    - by Haroon
    I am having a bit of trouble understanding how I will design a class. My class will have 3 methods ICollection<Field> GetFields(); //perform validation internally - return back the object T UpdateFields(ICollection<Field> fields); //pass in model object with values on it, set up fields, then pass back all fields ICollection<Field> GetFieldsWithValues(T object); What is the best way to construct/design such a class keeping in mind: 1. The model object I pass in will be one of 3 or 4 tables, however when I call GetFIelds - internally for each object I know what fields will be there i.e. list.add(new Field{name = "id", value = "5"}); list.add(new Field{name = "nameofcompany", value = "super guys"});

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  • How to initialise a STL vector/list with a class without invoking the copy constructor

    - by Warpspace
    I have a C++ program that uses a std::list containing instances of a class. If I call e.g. myList.push_back(MyClass(variable)); it goes through the process of creating a temporary variable, and then immediately copies it to the vector, and afterwards deletes the temporary variable. This is not nearly as efficient as I want, and sucks when you need a deep copy. I would love to have the constructor of my class new something and not have to implement a copy constructor just to allocate my memory for the second time and waste runtime. I'd also rather not have to immediately find the class instance from the vector/list and then manually allocate the memory (or do something horrible like allocate the memory in the copy constructor itself). Is there any way around this (I'm not using Visual Studio BTW)?

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  • Make Java parent class not part of the interface

    - by Bart van Heukelom
    (This is a hypothetical question for discussion, I have no actual problem). Say that I'm making an implementation of SortedSet by extending LinkedHashMap: class LinkedHashSortedMapThing extends LinkedHashMap implements SortedSet { ... } Now programmers who use this class may do LinkedHashMap x = new LinkedHashSortedMapThing(); But what if I consider the extending of LinkedHashMap an implementation detail, and do not want it to be a part of the class' contract? If people use the line above, I can no longer freely change this detail without worrying about breaking existing code. Is there any way to prevent this sort of thing, other than favouring composition over inheritance (which is not always possible due to private/protected members)?

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  • How to use the vtable to determine class type

    - by Alex Silverman
    I was recently on an interview for a position where C/C++ is the primary language and during one question I was told that it's possible to use the vtable to determine which class in a hierarchy a base pointer actually stores. So if, for example you have class A { public: A() {} virtual ~A() {} virtual void method1() {} }; class B : public A { public: B() {} virtual ~B() {} virtual void method1() {} }; and you instantiate A * pFoo = new B(), is it indeed possible to use the vtable to determine whether pFoo contains a pointer to an instance of A or B?

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  • Are raw C++ pointers first class objects?

    - by Shailesh Kumar
    According to Wikipedia: An object is first-class when it: can be stored in variables and data structures can be passed as a parameter to a subroutine can be returned as the result of a subroutine can be constructed at runtime has intrinsic identity (independent of any given name) Somebody had once told me that raw pointers are not first class objects while smart pointers like std::auto_ptr are. But to me, a raw pointer (to an object or to a function) in C++ does seem to me to satisfy the conditions stated above to qualify as a first class object. Am I missing something?

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  • Returning a static array without using a class field

    - by Bart Friederichs
    I have the following base and derived (partial, for sake of brevity) classes: class Base { public abstract int[] someArray { get; } } class Derived : Base { private readonly static int[] _someArray = new int[] { 1,2,3,4 }; public override int[] someArray { get { return _someArray; } } } What I would like now, is put the new int[] { 1,2,3,4 } in the return part of the getter. But, that would create a new array every time the getter is called. Is it possible to directly return some kind of object, which stays the same for all objects of class Derived ? Something along the lines of (I know this is invalid C#): get { return (int[]) { 1, 2, 3, 4 }; }

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  • Access parent class from custom attribute

    - by madcapnmckay
    Hi, Is it possible to access a parent class from within an attribute. For example I would like to create a DropDownListAttribute which can be applied to a property of a viewmodel class in MVC and then create a drop down list from an editor template. I am following a similar line as Kazi Manzur Rashid here. He adds the collection of categories into viewdata and retrieves them using the key supplied to the attribute. I would like to do something like the below, public ExampleDropDownViewModel { public IEnumerable<SelectListItem> Categories {get;set;} [DropDownList("Categories")] public int CategoryID { get;set; } } The attribute takes the name of the property containing the collection to bind to. I can't figure out how to access a property on the parent class of the attribute. Does anyone know how to do this? Thanks

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  • C#: reflection alternative for switch on enum in order to select namespace/class

    - by Am
    Hi, I have an interface named IHarvester. There are 3 implementations of that interface, each under their own namespace: Google Yahoo Bing A HarvesterManager uses the given harvester. It knows the interface and all 3 implementations. I want some way of letting the class user say in which harvester it wants to use. And in the code select that implementation, without a switch-case implementation. Can reflection save my day? Here is the code bits: // repeat for each harvester namespace Harvester.Google { public abstract class Fetcher : BaseHarvester, IInfoHarvester {...} } public enum HarvestingSource { Google, Yahoo, Bing, } class HarvesterManager { public HarvestingSource PreferedSource {get;set;} public HarvestSomthing() { switch (PreferedSource) .... // awful... } } Thanks.

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  • Dynamically create class attributes

    - by ahojnnes
    Hi, I need to dynamically create class attributes from a DEFAULTS dictionary. defaults = { 'default_value1':True, 'default_value2':True, 'default_value3':True, } class Settings(object): default_value1 = some_complex_init_function(defaults[default_value1], ...) default_value2 = some_complex_init_function(defaults[default_value2], ...) default_value3 = some_complex_init_function(defaults[default_value3], ...) I could also achive this by having sth. like __init__ for class creation, in order to dynamically create these attributes from dictionary and save a lot of code and stupid work. How would you do this? Thank you very much in advance!

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  • consts and other animals

    - by bks
    Hello i have a cpp code wich i'm having trouble reading. a class B is defined now, i understand the first two lines, but the rest isn't clear enough. is the line "B const * pa2 = pa1" defines a const variable of type class B? if so, what does the next line do? B a2(2); B *pa1 = new B(a2); B const * pa2 = pa1; B const * const pa3 = pa2; also, i'm having trouble figuring out the difference between these two: char const *cst = “abc”; const int ci = 15; thank you

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  • Storing Object Types in Variable then Initializing

    - by Jon Mattingly
    Is there a way in Objective-C to store an object/class in a variable to be passed to alloc/init somewhere else? For example: UIViewController = foo foo *bar = [[foo alloc] init] I'm trying to create a system to dynamically create navigation buttons in a separate class based on the current view controller. I can pass 'self' to the method, but the variable that results does not allow me to alloc/init. I could always import the .h file directly, but ideally I would like to make reusing the code as simple as possible. Maybe I'm going about this the wrong way?

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  • How to Execute Page_Load() in Page's Base Class?

    - by DaveDev
    I have the following PerformanceFactsheet.aspx.cs page class public partial class PerformanceFactsheet : FactsheetBase { protected void Page_Load(object sender, EventArgs e) { // do stuff with the data extracted in FactsheetBase divPerformance.Controls.Add(this.Data); } } where FactsheetBase is defined as public class FactsheetBase : System.Web.UI.Page { public MyPageData Data { get; set; } protected void Page_Load(object sender, EventArgs e) { // get data that's common to all implementors of FactsheetBase // and store the values in FactsheetBase's properties this.Data = ExtractPageData(Request.QueryString["data"]); } } The problem is that FactsheetBase's Page_Load is not executing. Can anyone tell me what I'm doing wrong? Is there a better way to get the result I'm after? Thanks

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  • Database Error django

    - by Megan
    DatabaseError at /admin/delmarva/event/ no such column: delmarva_event.eventdate I created a class in my models.py file: from django.db import models from django.contrib.auth.models import User class Event(models.Model): eventname = models.CharField(max_length = 100) eventdate = models.DateField() eventtime = models.TimeField() address = models.CharField(max_length = 200) user = models.ForeignKey(User) def __unicode__(self): return self.eventname and now when i try to view my events in my admin or my main_page it gives me the error that there is no eventdate. I tried syncing the db again but nothing changed. Also, I hashtagged eventdate out to see if I get a different error and then it states that delmarva_event.eventtime does not exist as well. I It is weird because it does not have a problem with eventname. Any suggestions would be greatly appreciated!

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  • PHP Classes: parent/child communication

    - by Fffff
    Hi all, I'm having some trouble extending Classes in PHP. Have been Googling for a while. $a = new A(); $a->one(); $a->b1(); // something like this, or... class A { public $test1; public function one() { echo "this is A-one"; $this->two(); $parent->two(); $parent->B->two(); // ...how do i do something like this (prepare it for using in instance $a)? } } class B extends A { public $test2; public function two($test) { echo "this is B-two"; } } I'm ok at procedural PHP.

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  • How do you resolve the common collsision between type name and object name?

    - by Catskul
    Since the convention is to capitalize the first letter of public properties, the old c++ convention of initial capital for type names, and initial lowercase for non-type names does not prevent the classic name collision class FooManager { public BarManager BarManager { get; set; } // Feels very wrong. // Recommended naming convention? public int DoIt() { return Foo.Blarb + Foo.StaticBlarb; // 1st and 2nd Foo are two // different symbols } } class BarManager { public int Blarb { get; set; } public static int StaticBlarb { get; set; } } It seems to compile, but feels so wrong. Is there a recommend naming convention to avoid this?

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  • Add UserControl To Page From Another Class

    - by Raika
    I have page and call method inside my page. I want to add some control to my page Control (not page itself) inside that method. namespace Program { public partail class Default : Page { protected void Page_Load(object sender, Eventargs e) { MyClass.Calling(this); } } } in another class namespace Program { public class MyClass { public static void Calling(Page page) { Textbox txt = new Textbox() // I want somthing like this. // page.PlaceHolder1.Controls.Add(txt); } } } Is this possible? My Default.aspx : <%@ Page Title="Home Page" MasterPageFile="~/Site.master" ... %> <asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent"> <asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder> </asp:Content> Update: thanks to The King for help. his suggest work correctly if control is inside page not Content of master page like my defualt sample code.

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  • Find images that have a certain HTML class name

    - by Frederik Vig
    I have some markup that contains certain HTML image tags with the class featured. What I need is to find all those images, add an anchor tag around the image, set the href attribute of the anchor to the images src value (the image path), and lastly replace the images src value with a new value (I call a method that will return this value). <p>Some text here <img src="/my/path/image.png" alt="image description" class="featured" />. Some more text and another image that should not be modified <img src="/my/path/image2.png" alt="image description" /></p> Should become. <p>Some text here <a href="/my/path/image.png"><img src="/new/path/from/method.png" alt="image description" class="featured" /></a>. Some more text and another image that should not be modified <img src="/my/path/image2.png" alt="image description" /></p>

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  • C++: Overload != When == Overloaded

    - by Mark W
    Say I have a class where I overloaded the operator == as such: Class A { ... public: bool operator== (const A &rhs) const; ... }; ... bool A::operator== (const A &rhs) const { .. return isEqual; } I already have the operator == return the proper Boolean value. Now I want to extend this to the simple opposite (!=). I would like to call the overloaded == operator and return the opposite, i.e. something of the nature bool A::operator!= (const A &rhs) const { return !( this == A ); } Is this possible? I know this will not work, but it exemplifies what I would like to have. I would like to keep only one parameter for the call: rhs. Any help would be appreciated, because I could not come up with an answer after several search attempts.

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  • Why baseclass calls method of subclass?

    - by twlkyao
    I encounter some code like the following: BaseClass: public class BaseClass { String name = "Base"; public BaseClass() { printName(); } public void printName() { System.out.println(name + "——Base"); } } DrivedClass: public class SubClass extends BaseClass { String name = "Sub"; public SubClass() { printName(); } public void printName() { System.out.println(name + "——Sub"); } public static void main(String[] args) { new SubClass(); } } When run the code, the output is: null——Sub Sub——Sub while it should be: Base——Base Sub——Sub I wonder why the BaseClass constructor calls the SubClass method, can anybody explain this? Thanks in advance.

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