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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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  • Nested pound sign problem

    - by Ray Buechler
    I'm having an issue when I try to nest pound signs in my ColdFusion code. I keep getting the following error message: Invalid CFML construct found on line 57 at column 26. ColdFusion was looking at the following text: # Here is the code: <cfloop index="i" from="1" to="12"> <cfset needRecord.setNeed#i#(#form["need#i#"]#) /> </cfloop> If I run the loop outside the cfset tag like this: <cfloop index="i" from="1" to="12"> needRecord.setNeed#i#(#form["need#i#"]#) </cfloop> The code runs and generates what I would like to generate within the cfset tag. Any idea what I'm doing wrong? Any help would be greatly appreciated.

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  • Get all descendants types of base class

    - by user1260827
    I have a base class called BaseEvent and several descendants classes: public class BaseEvent { // the some properties ... } [MapInheritance(MapInheritanceType.ParentTable)] public class Film : BaseEvent { // the some properties ... } [MapInheritance(MapInheritanceType.ParentTable)] public class Concert : BaseEvent { // the some properties ... } I have a code which create the BaseEvent instance at runtime: BaseEvent event = new BaseEvent(); //assign values for a properties ... baseEvent.XPObjectType = Database.XPObjectTypes.SingleOrDefault(t => t.TypeName == "MyApp.Module.BO.Events.BaseEvent"); Now, this event will be shows in BaseEvent list view. I want to do the following: when a user click Edit button then show in list view lookup field with all descendants types. And when user saves record change ObjectType to selected value. How can I do this? Thanks. PS. this is asp.net app.

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  • How does array class work in Java?

    - by oks16
    In Java, array is a class and extends Object. I am curious to know about this special array class. I don't find the class definition anywhere. Doing a getClass().getName() gives strange result. String[] array = new String[]{"one","two"}; System.out.println(array.getClass().getName()); // prints [Ljava.lang.String; I want to understand how array works under the hood. Is the array class definition hardcoded in the JVM? Any resources, books, links on this will be helpful. Thank you.

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  • static thread function access non-static class member in C++

    - by user397390
    Class Test{ int value; static void* thread_func(void* args){ value++; } void newthread(){ pthread_create(&thread_func,...); } } I'm trying to create a thread in Class Test. Therefore compiler forces me to make thread_func static. However I cannot access the non-static member "value" anymore. It says: invalid use of member 'Class::value' in static member function Is there a way around it?

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  • How to control manager class in Blackberry

    - by Keng
    Dear All, I have a problem when creating a UI on Blackberry. First, i try to create a ChatLayoutManager class extended from Manager class. My layout has three component: topfield, mainfield and bottom field. public class ChatLayoutManager extends Manager { private Field bottomField; private Field mainField; private Field titleField; public ChatLayoutManager(long style) { super(style); } protected void sublayout(int width, int height) { setExtent(width, height); int y = 0; if (bottomField != null) { layoutChild(bottomField, width, height); // This goes at the bottom of the screen setPositionChild(bottomField, 0, height-bottomField.getHeight()); height -= bottomField.getHeight(); } if (titleField != null) { layoutChild(titleField, width, height); // This goes at the top of the screen setPositionChild(titleField, 0, 0); height -= titleField.getHeight(); y += titleField.getHeight(); } if (mainField != null) { layoutChild(mainField, width, height); // This goes just below the title field (if any) setPositionChild(mainField, 0, y); } } public void setMainField(Field f) { mainField = f; add(f); } public void setBottomField(Field f) { bottomField = f; add(f); } public void setTitleField(Field f) { titleField = f; add(f); } Then i create another field (ChatField) extended from manager to add to mainfield in the ChatLayoutManager class which i have created above. public class ChatField extends Manager{ private Field _contentField[]; protected ChatField(){ super(Manager.HORIZONTAL_SCROLL | Manager.VERTICAL_SCROLL); } // TODO Auto-generated constructor stub} protected synchronized void sublayout(int width, int height) { // TODO Auto-generated method stub setExtent(width, height); int x = 0; int y = 0; if(_contentField.length > 0){ for(int i = 0 ;i<_contentField.length; i++){ //if(getManager() == this){ this.layoutChild(_contentField[i], _contentField[i].getWidth(), _contentField[i].getHeight()); this.setPositionChild(_contentField[i], x, y); if(_contentField[i++]!= null){ if ((_contentField[i].getWidth() + _contentField[i].getWidth()) >= width){ x = 0; y += _contentField[i].getHeight(); } else{ x += _contentField[i].getWidth(); } } //} } } } public void setContentField(Field field[]){ _contentField = field; } } And now, when i create some fields(such as TextField, BitmapField ...) added to ChatField, the program has an error "Field is not a child of this manager". The reason is when the framework invokes the sublayout function of the ChatField class , when sublayout starts calling layoutChild function the manager of field is not ChatField but ChatlayoutManager. I've experience hard time trying to resolve this problem, still I have no solution. Anybody can give me some suggestions? I really appreciate.

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  • C++ allocate objects on heap of base class with protected constructors via inheritance

    - by KRao
    I have a class with protected constructor: class B { protected: B(){}; }; Now I derive from it and define two static functions and I manage to actually create objects of the class B, but not on the heap: class A : public B { public: static B createOnStack() {return B();} //static B* createOnHeap() {return new B;} //Compile time Error on VS2010 }; B b = A::createOnStack(); //This works on VS2010! The question is: 1) Is VS2010 wrong in allowing the first case? 2) Is it possible to create objects of B without modifying B in any way (no friendship and no extra functions). I am asking, because it is possible to make something similar when dealing with instances of B and its member functions, see: http://accu.org/index.php/journals/296 Thank you in advance for any suggestion! Kind regards

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  • shared_ptr as class member

    - by idimba
    It's common to declared contained objects as a pointers to that class, while "forward declarating" them in header file. This in order to reduce physical dependencies in code. For example class B; // forward declaration class A { private: B* pB; }; Would it be good idea to declare such a member as shared_ptr, instead of naked pointer? I would prefer scoped_ptr, but AFAIKit it won't be in standard.

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  • Undefined / Uninitialized default values in a class

    - by Jir
    Let's suppose you have this class: class A { public: A () {} A (double val) : m_val(val) {} ~A () {} private: double m_val; }; Once I create an instance of A, how can I check if m_val has been initialized/defined? Put it in other words, is there a way to know if m_val has been initialized/defined or not? Something along the lines of the defined operator in Python, I suppose. (But correct me if I'm wrong.) I thought of modifying the class and the c-tors the following way: class A { public: A () : defined(false) {} A (double val) : m_val(val), defined(true) {} ~A () {} private: double m_val; bool defined; }; How do you rate this solution? Any suggestion? TIA, Chris

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  • Posting form using javascript and json with nested objects

    - by Tim
    I have an html form that has the following structure: <input type="text" name="title" /> <input type="text" name="persons[0].name" /> <input type="text" name="persons[0].color" /> <input type="text" name="persons[1].name" /> <input type="text" name="persons[1].color" /> I would like to serialize this into the following json: { "title":"titlecontent", "persons":[ { "name":"person0name", "color":"red" }, { "name":"person1name", "color":"blue" } ] } Notice that the number of persons can vary from case to case. The structure of the html form can change, but the structure of the submitted json can't. How is this done the easiest?

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  • Can C# make my class look like another class?

    - by Vaccano
    I have a class that look like this: public class BasePadWI { public WorkItem WorkItemReference { get; set; } .... Other stuff ...... } I then have a dictionary that is defined like this: public Dictionary<BasePadWI, Canvas> Pad { get; set; } I would then like to make a call like this: List<WorkItem> workItems = Pad.Keys.ToList(); (Note: WorkItem is a sealed class, so I cannot inherit.) Is there some trickery that I could do in the class to make it look like a WorkItem? I have done this in the mean time: List<WorkItem> workItems = Pad.Keys.ToList().ConvertAll(x=>x.WorkItem);

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  • C#: Basic Reflection Class

    - by Mike
    I'm trying to find a basic reflection abstract class that will generate basic information about a class. I have a template of how I would like it to work: class ThreeList<string,Type,T> { string Name {get; set;} Type Type {get; set;} T Value {get; set;} } abstract class Reflect<T> { List<ThreeList<string, Type, T> list; ReturnType MethodName() { foreach (System.Reflection.PropertyInfo prop in this.GetType().GetProperties()) { object value = prop.GetValue(this, new object[] { }); list.Add(prop.Name, prop.DeclaringType, value); } } } I'd like it to be infinitely deep, recursively calling Reflect. Something like this has to exist. I'm not really opposed to coding it myself, I just don't want to go through the hassle if its already been done.

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  • Pass parameters to Flash Main (Document) class

    - by loto
    In Flash CSn/AS3 you associate a Main class with a flash file which when loaded in the flash player "automatically creates an instance of the program's main class." I'd like to know how to pass arguments to the main class, since you don't write it yourself (you put its name in the Document textfield in the IDE).

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  • File::Find and $_ in nested subroutines.

    - by zedoo
    When running the following code, the filenames of all files below C:\Test are printed. Why doesn't it print just Hello (n times, depending on how many files are processed)? Does this imply that I cannot rely on shift to reliably assign to $_? Imagine a coworker implements the wtf function and doesn't know that it's called from a File::Find wanted sub. I run this code with Strawberry Perl 5.12 use strict; use warnings; use File::Find; find(\&wanted, "C:\\test"); sub wanted{ wtf("Hello"); } sub wtf { shift; print; #expecting Hello }

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  • Member variable in C++ class that is always constant for all objects of that class?

    - by user1799323
    I'm constructing a class where I have three member variables that I want to always be the same value NO MATTER WHAT. I have class foo{ public: double var_1, var_2, var_3; double x=1, y=2, z=3; [functions go here] }; that gave me an error since I can't initialize a variable like that. But I want x, y and z to always be 1, 2 and 3 respectively. I tried defining them outside the class but that doesn't work since I want them to be member variables of the class. How do I do this?

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  • Multiple/nested "select where" with Zend_Db_Select

    - by DJRayon
    Hi there I need to create something like this: select name from table where active = 1 AND (name LIKE 'bla' OR description LIKE 'bla') The first part is easy: $sqlcmd = $db->select() ->from("table", "name") ->where("active = ?", 1) Now comes the tricky part. How can I nest? I know that I can just write ->orWhere("name LIKE ? OR description LIKE ?", "bla") But thats wron, because I need to dynamically change all the parts. The query will be built all the time the script runs. Some parts get deleted, some altered. In this example I need to add those OR-s because sometimes I need to search wider. "My Zend Logic" tells me that the correct way is like this: $sqlcmd = $db->select() ->from("table", "name") ->where("active = ?", 1) ->where(array( $db->select->where("name LIKE ?", "bla"), $db->select->orWhere("description LIKE ?", "bla") )) But that doesn't work (atleast I dont remember it working). Please. Can someone help me to find a object oriented way for nesting "where"-s

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  • Model class is not found in zend framework project (quickstart) ,please help

    - by Dumindu
    The things I did is zf create project demo1 in command prompt add the lines to application.ini appnamespace = "Application" resources.layout.layoutPath = APPLICATION_PATH "/layouts/scripts" add a layout with header and footer using partial() (They are perfectly worked) create Data.php in models directory and add this simple class <?php class Application_Model_Data{ }//Application for appnamespace then I tried to load this class(by creating instance)from index controller index action $data = new Application_Model_Data(); but when I test it even in this level it gives an error Fatal error: Class 'Application_Model_Data' not found in C:\Zend\...\IndexController.php Question Do I want to add a autoloader to load models in the application( I'm not used modules) if not what was I missed to add please help I'm stuck in the beginning,Thank you

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  • nested list comprehension using intermediate result

    - by KentH
    I am trying to grok the output of a function which doesn't have the courtesy of setting a result code. I can tell it failed by the "error:" string which is mixed into the stderr stream, often in the middle of a different conversion status message. I have the following list comprehension which works, but scans for the "error:" string twice. Since it is only rescanning the actual error lines, it works fine, but it annoys me I can't figure out how to use a single scan. Here's the working code: errors = [e[e.find('error:'):] for e in err.splitlines() if 'error:' in e] The obvious (and wrong) way to simplify is to save the "find" result errors = [e[i:] for i in e.find('error:') if i != -1 for e in err.splitlines()] However, I get "UnboundLocalError: local variable 'e' referenced before assignment". Blindly reversing the 'for's in the comprehension also fails. How is this done? THanks. Kent

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  • Reference variable to an object instantiated/initialized in another class in Java

    - by Alex
    The reason I'm asking is because I'm getting NullPointerException. I now this is very easy but I'm pretty new programming and find this a bit confusing. So say I have initialized an object in a class and want to access that same object from another class. Like now for instance I'm working on a small Chess game, in my model Game class I have an instance of Board, an object. Board, in turn, has an array of Squares. Square[][]. Game has board, board has Square[][]. Now if I want to access the Square[][] through the object board (in Game) of type Board. Do I just declare a variable with the same name and type or do I have to initialize it again? Board board OR Board board = new Board(); Note, I have already initialized board in the class Game so if I do it again, won't they be two totally different Board objects?

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  • PHP: How do I access child properties from a method in a base object?

    - by Nick
    I'd like for all of my objects to be able to return a JSON string of themselves. So I created a base class for all of my objects to extend, with an AsJSON() method: class BaseObject { public function AsJSON() { $JSON=array(); foreach ($this as $key = $value) { if(is_null($value)) continue; $JSON[$key] = $value; } return json_encode($JSON); } } And then extend my child classes from that: class Package extends BaseObject { ... } So in my code, I expect to do this: $Box = new Package; $Box-SetID('123'); $Box-SetName('12x8x6'); $Box-SetBoxX('12'); $Box-SetBoxY('8'); $Box-SetBoxZ('6'); echo $Box-AsJSON(); But the JSON string it returns only contains the BaseClass's properties, not the child properties. How do I modify my AsJSON() function so that $this refers to the child's properties, not the parent's?

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  • Frame sizing of tableview within nested child controllers/subviews

    - by jwoww
    I'm a bit confused by the proper frame sizing of a table view to fit within my screen. Here's my setup of view controllers within view controllers: UITabBarController UINavigationController as one of the tab bar viewcontrollers; title bar hidden ViewController - a container view controller because I need the option to place some controls beneath the UITableView, sometimes (but not in the current scenario) UITableViewController Now, my question is what the proper frame dimensions of the UITableview should be. Here's what I've got in the ViewController viewDidLoad method. I used subtracted 49.0 (the size of the tab bar) from 480.0. However, this leaves a black bar at the bottom. 20.0 appears to do it (coincidentally?) the size of the status bar, but I don't understand why that would be. Wouldn't the true pixel dimensions of the tableview be 480-49? // MessageTableViewController is my subclass of UITableViewController MessagesTableViewController *vcMessagesTable = [[MessagesTableViewController alloc] init]; CGRect tableViewFrame = CGRectMake(0, 0, 320.0, 480.0 - 49.0); [[vcMessagesTable view] setFrame:tableViewFrame]; self.tableViewController = vcMessagesTable; [self addChildViewController:vcMessagesTable]; [[self view] addSubview:vcMessagesTable.view]; Here's how it looks:

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  • 1.8.x Ruby on Rails RESTful nested admin page and form_for problems

    - by Loomer
    So I am creating a website that I want to have an admin directory in rails 1.8.x and I'm struggling a bit to get the form_for to link to the right controller. I am trying to be RESTful. What I basically want is an admin page that has a summary of actions which can then administer sub models such as: /admin (a summary of events) /admin/sales (edit sales on the site) /admin/sales/0 (the normal RESTful stuff) I can't use namespaces since they were introduced in Rails 2.0 (production site that I don't want to mess with updating rails and all that). Anyway, what I have in the routes.rb is: map.resource :admin do |admin| admin.resources :sales end I am using the map.resource as a singleton as recommended by another site. The problem comes in when I try to use the form_for to link to the subresource RESTfully. If i do : form_for(:sales, @sale) it never links to the right controller no matter what I try. I have also tried: form_for [@admin, @sale] do |f| and that doe not work either (I am guessing since admin is a singleton which does not have a model, it's just a placeholder for the admin controller). Am I supposed to add a prefix or something? Or something into the sales controller to specify that it is a subcontroller to admin? Is there an easier way to do this without manually creating a bunch of routes? Thanks for any help.

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  • Why isn't the eigenclass equivalent to self.class, when it looks so similar?

    - by The Wicked Flea
    I've missed the memo somewhere, and I hope you'll explain this to me. Why is the eigenclass of an object different from self.class? class Foo def initialize(symbol) eigenclass = class << self self end eigenclass.class_eval do attr_accessor symbol end end end My train of logic that equates the eigenclass with class.self is rather simple: class << self is a way of declaring class methods, rather than instance methods. It's a shortcut to def Foo.bar. So within the reference to the class object, returning self should be identical to self.class. This is because class << self would set self to Foo.class for definition of class methods/attributes. Am I just confused? Or, is this a sneaky trick of Ruby meta-programming?

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