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  • c++ polymorphism and other function question

    - by aharont
    i have got this code: class father{ public: virtual void f() { cout<<1;} }; class son:public father{ public: void f() {cout<<2;} }; void test (father x){x.f();} int main(){ son s; test(s); } the question says: the output is '1', what is the rule about polymorphism that the programmer forgot and how can i fix it so the output would be '2'? there is another rule that the programmer forgot when he wrote the father class, and he need to add an empty function to avoid problems from other sons of the father class. what is the rule and what is the missing function? another question write the g function so the next code would run with no crashes int x=11; g(x)=22;

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  • Using an empty column as a divider in a JTable.

    - by Catalina Island
    I'm trying to use an empty column as a divider between pairs of columns in a JTable. Here's a picture and code for what I have so far. I know I can change the look using a custom TableCellRenderer. Before I go down that road, is there a better way to do this? Any ideas appreciated. import javax.swing.*; import javax.swing.table.*; public class TablePanel extends JPanel { public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { JFrame f = new JFrame("TablePanel"); f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); f.add(new TablePanel()); f.pack(); f.setVisible(true); } }); } public TablePanel() { TableModel dataModel = new MyModel(); JTable table = new JTable(dataModel); table.getColumnModel().getColumn(MyModel.DIVIDER).setMaxWidth(0); JScrollPane jsp = new JScrollPane(table); jsp.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS); this.add(jsp); } private static class MyModel extends AbstractTableModel { private static final int DIVIDER = 2; private final String[] names = { "A1", "A2", "", "B1", "B2" }; @Override public int getRowCount() { return 32; } @Override public int getColumnCount() { return names.length; } @Override public String getColumnName(int col) { if (col == DIVIDER) return ""; return names[col]; } @Override public Object getValueAt(int row, int col) { if (col == DIVIDER) return ""; return (row + 1) / 10.0; } @Override public Class<?> getColumnClass(int col) { if (col == DIVIDER) return String.class; return Number.class; } } }

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  • Html.EditorFor Global Template?

    - by Grant Trevor
    Is there any way to define a global template for the Html.EditorFor helper? I would like to alter the markup that is output so that for example instead of rendering <div class="editor-label"> <label .../> </div> <div class="editor-field"> <input .../> </div> It would render: <div> <div class="label"><label..../></div> <div class="field"><input..../></div> </div> This is for when I'm using Html.EditorFor with an object instance not just an object property.

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  • Purpose of singletons in programming

    - by thecoshman
    This is admittedly a rather loose question. My current understanding of singletons is that they are a class that you set up in such a way that only one instance is ever created. This sounds a lot like a static class to me. The main differnce being that with a static class you don't / can't instance it, you just use it such as Math.pi(). With a singletong class, you would still need to do something like singleton mySingleton = new singleton(); mysingleton.set_name("foo"); singleton otherSingleton = new singleton(); // correct me if i am wrong, but mysingleton == othersingleton right now, yes? // this the following should happen? otherSingleston.set_name("bar"); mysingleton.report_name(); // will output "bar" won't it? Please note, I am asking this language independently, more about the concept. So I am not so worried about actually how to coed such a class, but more why you would wan't to and what thing you would need to consider.

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  • Override jre_lib classes

    - by Filip
    What is the best way to override jre_lib classes? Let's say I need to store all ArrayLists not in RAM but on disk or anywhere else. I wanna write my own ArrayList class to code this functionality and make sure that every instantiations of ArrayList use my class. I thought about class loading mechanism to change order of classpath, but as I see java checks standard classes first.

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  • where is "create instance" menu in visual studio 2010?

    - by austin powers
    Hi, in visual studio 2008 there is a sub-menu called "create instance" which is resides in class designer. Today I've opened VS.net 2010 and then opened class designer and create my class over there and when I wanted to test my class with the help of "create instance" option there was no such option available in vs.net 2010. and I've googled about it a little bit but no answer at all so I decided to mention about it here. where can I find this menu in vs.net 2010? regards.

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  • allocator with no template

    - by Merni
    Every stl container take an allocator as a second object, template < class T, class Allocator = allocator<T> > class vector; If you write your own class It is possible to use your own allocator. But is it possible to write your own allocator without using templates? For example, writing this function is not easy if you are not allowed to use templates pointer allocate(size_type n, const_pointer = 0) { void* p = std::malloc(n * sizeof(T)); if (!p) throw std::bad_alloc(); return static_cast<pointer>(p); } Because how could you know the size of T?

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  • ConfigurationSection with multiple projects

    - by shivesh
    In my asp.net solution i have a couple of class library-projects that act as modules of the site. In main project I have SiteConfigurationSection class that derives from ConfigurationSection. I want all projects to be able to access and use this SiteConfigurationSection. But class library projects can't access it because they obviously don't have a reference to the website itself. Should create a special library-project for SiteConfigurationSection of maybe it's better to create a mini SiteConfigurationSection class in every project and encapsulate only the needed values?

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  • Spring FactoryBean and scopes working together

    - by TTar
    I'd like to use FactoryBeans and scopes together. Specifically, I'd like the object created and returned by a FactoryBean to be placed into a specified (perhaps custom) scope. The issue is that doing the following: <bean class="x.y.z.TestFactoryBean" scope="test" /> Results in the FactoryBean itself being scoped, and has somewhat unpredictable behaviour on the object created by the factory. I understand why this is; the factory itself is a first-class spring-managed bean, and has its own lifecycle. However, I can't find a way to specify that the object returned from the factory should itself be scoped. On the other hand, this does exactly what I want (as long as TestFactoryBean does NOT implement the FactoryBean interface): <bean class="x.y.z.TestFactoryBean" name="testFactory"> <bean class="x.y.z.TestBean" factory-bean="testFactory" factory-method="getObject" scope="test" /> So the real question is, how can I make Spring behave like it does for the 2nd example above, but using real FactoryBeans?

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  • Multiple instance_of?

    - by c00lryguy
    How would I make Object#instance_of? accept multiple arguments so that something like the below example would work? class Foo; end class Bar; end class Baz; end my_foo = Foo.new my_bar = Bar.new my_baz = Baz.new my_foo.instance_of?(Foo, Bar) # => true my_bar.instance_of?(Foo, Bar) # => true my_baz.instance_of?(Foo, Bar) # => false

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  • Grails Unique Constraint for Groups

    - by WaZ
    Hi there, I have the following requirement I have 3 domains namely: class Product { String productName static constraints = { productName(unique:true,blank:false) } class SubType { String subTypeName static constraints = { subTypeName(unique:true,blank:false) } String toString() { "${subTypeName}" } } class CLType { String TypeName static belongsTo = Car static hasMany = [car:Cars] static constraints = { } String toString() { "${TypeName}" } class CLines implements Serializable { Dealer dealer CLType clType SubType subType Product product static constraints = { dealer(nullable:false,blank:false,unique:['subType','product','clType']) clType(blank:false,nullable:false) subType(nullable:true) product(nullable:true) } } I want to achieve this combination: A user can assign dealer a CLType. But cannot have duplicates. As an example consider this scenario Please let me know what to mention in my unqiue constraint to make this possible? Thanks, Much Appreciated.

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  • C++ and Dependency Injection in unit testing

    - by lhumongous
    Suppose I have a C++ class like so: class A { public: A() { } void SetNewB( const B& _b ) { m_B = _b; } private: B m_B; } In order to unit test something like this, I would have to break A's dependency on B. Since class A holds onto an actual object and not a pointer, I would have to refactor this code to take a pointer. Additionally, I would need to create a parent interface class for B so I can pass in my own fake of B when I test SetNewB. In this case, doesn't unit testing with dependency injection further complicate the existing code? If I make B a pointer, I'm now introducing heap allocation, and some piece of code is now responsible for cleaning it up (unless I use ref counted pointers). Additionally, if B is a rather trivial class with only a couple of member variables and functions, why introduce a whole new interface for it instead of just testing with an instance of B? I suppose you could make the argument that it would be easier to refactor A by using an interface. But are there some cases where two classes might need to be tightly coupled?

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  • Elements of a Java Object Array are created but without correct names

    - by Greenhouse Gases
    Hi all Im having rather an annoying problem. I have a class called Person and a class called Event which serve to create objects to be used for competitors that compete in a certain event. When I add a competitor thats fine and the GUI list updates accordingly, however when I add an event the element in the array does not take on the value of the instance variable name in the class Event and so the GUI does not show the event name, though it is being added in the array correctly. How can I make it so that the event object in each element of the listOfEvents array (which is an array of event objects) has the name of the event. I should add this is for university though this isnt the part for which we will be assessed, it is somethign i have come across and due to not being able to see the code for the GUI, I've hit the proverbial brick wall. I wont include the whole load of code Ive been writing but hopefully my description and snippets below will suffice. Any advice I would appreciate greatly. No doubt I have overlooked something simple! Many thanks. listOfEvents is declared as: Event[] listOfEvents = new Event[20]; A snippet from the Event class: public class Event { String name; Person[] participants = new Person[10]; // array of competitors for the event public Event(String name) { this.name = name; } } and its use in the addEvent method (p is a global variable): public void addEvent(String eventName) { listOfEvents[p] = new Event(eventName); p++; }

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  • Multiple datepicker problem with same ID

    - by namezero
    hi, here is my problem: <input type="text" class="datepick1" id="date" /> <input type="text" class="datepick2" id="date" /> <input type="text" class="datepick3" id="date" /> then i apply datepicker on dom (by classname) $('.datepick1').datepicker(); $('.datepick2').datepicker(); $('.datepick3').datepicker(); = the three dom have datepicker but, onselect date, it change automatically the first one (datepick1) HELP

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  • Undefined behaviour with non-virtual destructors - is it a real-world issue?

    - by Roddy
    Consider the following code: class A { public: A() {} ~A() {} }; class B: public A { B() {} ~B() {} }; A* b = new B; delete b; // undefined behaviour My understanding is that the C++ standard says that deleting b is undefined behaviour - ie, anything could happen. But, in the real world, my experience is that ~A() is always invoked, and the memory is correctly freed. if B introduces any class members with their own destructors, they won't get invoked, but I'm only interested in the simple kind of case above, where inheritance is used maybe to fix a bug in one class method for which source code is unavailable. Obviously this isn't going to be what you want in non-trivial cases, but it is at least consistent. Are you aware of any C++ implementation where the above does NOT happen, for the code shown?

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  • Is there a way to deserialize an object into "$this"?

    - by Andreas Bonini
    I'm writing a class to handle a memcached object. The idea was to create abstract class Cachable and all the cachable objects (such as User, Post, etc) would be subclasses of said class. The class offers some method such as Load() which calls the abstract function LoadFromDB() if the object is not cached, functions to refresh/invalidate the cache, etc. The main problem is in Load(); I wanted to do something similar: protected function Load($id) { $this->memcacheId = $id; $this->Connect(); $cached = $this->memcache->get(get_class($this) . ':' . $id); if($cached === false) { $this->SetLoaded(LoadFromDB($id)); UpdateCache(); } else { $this = $cached; $this->SetLoaded(true); } } Unfortunately I need $this to become $cached (the cached object); is there any way to do that? Was the "every cachable object derives from the cachable class" a bad design idea?

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  • Putting a thread to sleep until event X occurs

    - by tipu
    I'm writing to many files in a threaded app and I'm creating one handler per file. I have HandlerFactory class that manages the distribution of these handlers. What I'd like to do is that thread A requests and gets foo.txt's file handle from the HandlerFactory class thread B requests foo.txt's file handler handler class recognizes that this file handle has been checked out handler class puts thread A to sleep thread B closes file handle using a wrapper method from HandlerFactory HandlerFactory notifies sleeping threads thread B wakes and successfully gets foo.txt's file handle This is what I have so far, def get_handler(self, file_path, type): self.lock.acquire() if file_path not in self.handlers: self.handlers[file_path] = open(file_path, type) elif not self.handlers[file_path].closed: time.sleep(1) self.lock.release() return self.handlers[file_path][type] I believe this covers the sleeping and handler retrieval successfully, but I am unsure how to wake up all threads, or even better wake up a specific thread.

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  • How do I configure encodings (UTF-8) for code executed by Quartz scheduled Jobs in Spring framework

    - by Martin
    I wonder how to configure Quartz scheduled job threads to reflect proper encoding. Code which otherwise executes fine within Springframework injection loaded webapps (java) will get encoding issues when run in threads scheduled by quartz. Is there anyone who can help me out? All source is compiled using maven2 with source and file encodings configured as UTF-8. In the quartz threads any string will have encoding errors if outside ISO 8859-1 characters: Example config <bean name="jobDetail" class="org.springframework.scheduling.quartz.JobDetailBean"> <property name="jobClass" value="example.ExampleJob" /> </bean> <bean id="jobTrigger" class="org.springframework.scheduling.quartz.SimpleTriggerBean"> <property name="jobDetail" ref="jobDetail" /> <property name="startDelay" value="1000" /> <property name="repeatCount" value="0" /> <property name="repeatInterval" value="1" /> </bean> <bean class="org.springframework.scheduling.quartz.SchedulerFactoryBean"> <property name="triggers"> <list> <ref bean="jobTrigger"/> </list> </property> </bean> Example implementation public class ExampleJob extends QuartzJobBean { private Log log = LogFactory.getLog(ExampleJob.class); protected void executeInternal(JobExecutionContext ctx) throws JobExecutionException { log.info("ÅÄÖ"); log.info(Charset.defaultCharset()); } } Example output 2010-05-20 17:04:38,285 1342 INFO [QuartzScheduler_Worker-9] ExampleJob - vÖvÑvñ 2010-05-20 17:04:38,286 1343 INFO [QuartzScheduler_Worker-9] ExampleJob - UTF-8 The same lines of code executed within spring injected beans referenced by servlets in the web-container will output proper encoding. What is it that make Quartz threads encoding dependent?

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  • How to pass a method as callback to a Windows API call?

    - by Heinrich Ulbricht
    Hi, I'd like to pass a method of a class as callback to a WinAPI function. Is this possible and if yes, how? Example case for setting a timer: TMyClass = class public procedure TimerProc(Wnd:HWND; uMsg:DWORD; idEvent:PDWORD; dwTime:DWORD); procedure DoIt; end; [...] procedure TMyClass.DoIt; begin SetTimer(0, 0, 8, @TimerProc); // <-???- that's what I want to do (last param) end; Thanks for your help! Edit: The goal is to specify a method of this class as callback. No procedure outside the class.

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  • When does logic belong in the Business Object/Entity, and when does it belong in a Service?

    - by Casey
    In trying to understand Domain Driven Design I keep returning to a question that I can't seem to definitively answer. How do you determine what logic belongs to a Domain entity, and what logic belongs to a Domain Service? Example: We have an Order class for an online store. This class is an entity and an aggregate root (it contains OrderItems). Public Class Order:IOrder { Private List<IOrderItem> OrderItems Public Order(List<IOrderItem>) { OrderItems = List<IOrderItem> } Public Decimal CalculateTotalItemWeight() //This logic seems to belong in the entity. { Decimal TotalWeight = 0 foreach(IOrderItem OrderItem in OrderItems) { TotalWeight += OrderItem.Weight } return TotalWeight } } I think most people would agree that CalculateTotalItemWeight belongs on the entity. However, at some point we have to ship this order to the customer. To accomplish this we need to do two things: 1) Determine the postage rate necessary to ship this order. 2) Print a shipping label after determining the postage rate. Both of these actions will require dependencies that are outside the Order entity, such as an external webservice to retrieve postage rates. How should we accomplish these two things? I see a few options: 1) Code the logic directly in the domain entity, like CalculateTotalItemWeight. We then call: Order.GetPostageRate Order.PrintLabel 2) Put the logic in a service that accepts IOrder. We then call: PostageService.GetPostageRate(Order) PrintService.PrintLabel(Order) 3) Create a class for each action that operates on an Order, and pass an instance of that class to the Order through Constructor Injection (this is a variation of option 1 but allows reuse of the RateRetriever and LabelPrinter classes): Public Class Order:IOrder { Private List<IOrderItem> OrderItems Private RateRetriever _Retriever Private LabelPrinter _Printer Public Order(List<IOrderItem>, RateRetriever Retriever, LabelPrinter Printer) { OrderItems = List<IOrderItem> _Retriever = Retriever _Printer = Printer } Public Decimal GetPostageRate { _Retriever.GetPostageRate(this) } Public void PrintLabel { _Printer.PrintLabel(this) } } Which one of these methods do you choose for this logic, if any? What is the reasoning behind your choice? Most importantly, is there a set of guidelines that led you to your choice?

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  • jQuery: Getting value from input array

    - by betacar
    We have the following form: <form> ... <table width="100%" cellspacing="0" class="datagrid_ppal"> <tbody> <tr> <th scope="row">Area 1 <input name="config_line" type="hidden" value="0,5,50" /></th> <td class="gantt"> </td> <td class="gantt"> </td> <td class="gantt"> </td> ... </tr> </tbody> </table width="100%" cellspacing="0" class="datagrid_ppal"> ... <form> What we need is to get the first, second or third from the hidden input value. We have tried this and didn't work: var value = $('th').children('input:hidden').val(); Can anyone help us? We would really appreciate it.

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  • Elegant way to add functionallity to previously defined functions

    - by Bastiaan
    How to combine two functions together I have a class controlling some hardware: class Heater() def set_power(self,dutycycle, period) ... def turn_on(self) ... def turn_off(self) And a class that connects to a database and handles all data logging fuctionallity for an experiment: class DataLogger() def __init__(self) # Record measurements and controls in a database def start(self,t) # Starts a new thread to aqcuire and reccord measuements every t secconds Now, in my program recipe.py I want to do something like: log = DataLogger() @DataLogger_decorator H1 = Heater() log.start(60) H1.set_power(10,100) H1.turn_on() sleep(10) H1.turn_off() etc Where all actions on H1 are recorded by the datalogger. I can change any of the classes involved, just looking for an elegant way to do this. Ideally the hardware functions remain separated from the database and DataLogger functions. And ideally the DataLogger is reusable for other controls and measurements.

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  • Wrapping a Flash/AS3 Sprite as a Flex MXML component

    - by John
    For my game, I am making the main game view as a plain Flash/AS3 class, something like: public class GameArena extends Sprite This is simply a big rectangle in which game objects are drawn, so no need for fancy UI and I want to keep the main game engine Flex-free so I can use Sprites rather than heavier Flex components. However for the entire game/app, I do still want to use Flex for GUI/layout. So I thought I could create a Flex class subclassing UIComponent, which has a GameView object as a child... now I can use this in MXML as a standard Flex component. e.g. public class ArenaView extends UIComponent { public var gameArena:GameArena; override protected function createChildren():void { super.createChildren(); if (!gameArena) { gameArena = new GameArena(); gameArena.width = 200; gameArena.height = 200; addChild(gameArena); } } } Then I have a simple line in my main App MXML like: <logic:Arena x="0" y="0" width="50%" height="100%" name="TestArenaPanel" /> But so far while my code compiles, the Flash class isn't getting rendered. Maybe it's something simple, but I wanted to ask if this is a reasonable approach, or there is something better? BTW: I've had the "should Flex be used" conversation many times. If you want to discuss that please do so in comments, but keep answers on topic.

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  • ProgressDialog won't show, even in onPreExecute of AsyncTask

    - by Geltrude
    In my class, Main extends Activity, I've this: @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { super.onActivityResult(requestCode, resultCode, data); switch (requestCode) { case ... case CREDENTIAL_VIEW: new SetStatusProgressBar(this).execute(); And there is this nested class: private class SetStatusProgressBar extends AsyncTask<String, Void, Boolean> { private ProgressDialog dialog; private Main ctx; public SetStatusProgressBar(Main ctx) { this.ctx = ctx; dialog = new ProgressDialog(ctx); } // progress dialog to show user that contacting server. protected void onPreExecute() { this.dialog = ProgressDialog.show(ctx, null, "Refreshing data from server...", true, false); } @Override protected void onPostExecute(final Boolean success) { //... //statements that refresh UI //... if (dialog.isShowing()) { dialog.dismiss(); timerProgressBarStop(); } } protected Boolean doInBackground(final String... args) { //... //statements to download data from server //... return true; } } In the Main class I open a second Activity, in this way: Intent myIntent = new Intent(Main.this, Credentials.class); startActivityForResult(myIntent, CREDENTIAL_VIEW); That second Activity returns to the Main activity in this way: Intent intent = new Intent(); setResult(RESULT_OK, intent); finish(); I don't understand why when I navigate from the second Activity to the Main, the ProgressDialog will show ONLY AFTER that the UI refreshes... In this way the Progress Dialog stays on the screen only for half second... and then hides! :( I'd like to see the ProgressDialog on top during all the download time! Help, please. Thank you all

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  • Simultaneous private and public inheritance in C++

    - by gspr
    Suppose a class Y publicly inherits a class X. Is it possible for a class Z to privately inherit Y while publicly inheriting X? To make this clearer, suppose X defines public methods x1 and x2. Y inherits X, overrides x1 and provides a method y. Does C++ allow for a third class Z to subclass Y in such a way that Y's implementation of x1 and y are privately available to it, while the outside world only sees it inheriting X publicly, i.e. having only a single public method x2?

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