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  • Object relationships

    - by Hammerstein
    This stems from a recent couple of posts I've made on events and memory management in general. I'm making a new question as I don't think the software I'm using has anything to do with the overall problem and I'm trying to understand a little more about how to properly manage things. This is ASP.NET. I've been trying to understand the needs for Dispose/Finalize over the past few days and believe that I've got to a stage where I'm pretty happy with when I should/shouldn't implement the Dispose/Finalize. 'If I have members that implement IDisposable, put explicit calls to their dispose in my dispose method' seems to be my understanding. So, now I'm thinking maybe my understanding of object lifetimes and what holds on to what is just wrong! Rather than come up with some sample code that I think will illustrate my point, I'm going to describe as best I can actual code and see if someone can talk me through it. So, I have a repository class, in it I have a DataContext that I create when the repository is created. I implement IDisposable, and when my calling object is done, I call Dispose on my repository and explicitly call DataContext.Dispose( ). Now, one of the methods of this class creates and returns a list of objects that's handed back to my front end. Front End - Controller - Repository - Controller - Front End. (Using Redgate Memory Profiler, I take a snapshot of my software when the page is first loaded). My front end creates a controller object on page load and then makes a request to the repository sending back a list of items. When the page is finished loading, I call Dispose on the controller which in turn calls dispose on the context. In my mind, that should mean that my connection is closed and that I have no instances of my controller class. If I then refresh the page, it jumps to two 'Live' instances of the controller class. If I look at the object retention graph, the objects I created in my call to the list are being held onto ultimately by what looks like Linq. The controller/repository aside, if I create a list of objects somewhere, or I create an object and return it somewhere, am I safe to just assume that .NET will eventually come and clean things up for me or is there a best practice? The 'Live' instances suggest to me that these are still in memory and active objects, the fact that RMP apparently forces GC doesn't mean anything?

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  • @Unique doesn't have any effect in DataNucleus w/ NeoDatis

    - by David Parks
    Using JDO / DataNucleus / NeoDatis datastore I added @Unique to a field of a persistable object, however I am allowed to create multiple objects which violate the unique constraint. The docs for DataNucleus/NeoDatis suggest that Unique fields are supported. @PersistenceCapable public class User { @Persistent @Unique private String username; //... } If I add multiple objects to the DB with the same username there's no problem doing so. :(

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  • JLabel wont change color twice

    - by Aly
    Hi, I have the following code: public class Test extends JFrame implements ActionListener{ private static final Color TRANSP_WHITE = new Color(new Float(1), new Float(1), new Float(1), new Float(0.5)); private static final Color TRANSP_RED = new Color(new Float(1), new Float(0), new Float(0), new Float(0.1)); private static final Color[] COLORS = new Color[]{ TRANSP_RED, TRANSP_WHITE}; private int index = 0; private JLabel label; private JButton button; public Test(){ super(); setLayout(new BoxLayout(getContentPane(), BoxLayout.Y_AXIS)); label = new JLabel("hello world"); label.setOpaque(true); label.setBackground(TRANSP_WHITE); getContentPane().add(label); button = new JButton("Click Me"); button.addActionListener(this); getContentPane().add(button); pack(); setVisible(true); } @Override public void actionPerformed(ActionEvent e) { if(e.getSource().equals(button)){ label.setBackground(COLORS[index % (COLORS.length - 1)]); } } public static void main(String[] args) { new Test(); } } When I run it I get the label with the TRANSP_WHITE background and then when I click the button this color changes to TRANSP_RED but when I click it again I see no change in color. Does anyone know why? Thanks

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  • Dilemma with two types and operator +

    - by user35443
    I have small problem with operators. I have this code: public class A { public string Name { get; set; } public A() { } public A(string Name) { this.Name = Name; } public static implicit operator B(A a) { return new B(a.Name); } public static A operator+(A a, A b) { return new A(a.Name + " " + b.Name); } } public class B { public string Name { get; set; } public B() { } public B(string Name) { this.Name = Name; } public static implicit operator A(B b) { return new A(b.Name); } public static B operator +(B b, B a) { return new B(b.Name + " " + a.Name); } } Now I want to know, which's conversion operator will be called and which's addition operator will be called in this operation: new A("a") + new B("b"); Will it be operator of A, or of B? (Or both?) Thanks....

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  • How do you return draggable content to their original positions in iPhone dev?

    - by Matt Thomas
    I am wanting to create a button in my iPhone app that when touched will return other draggable elements to their original position. I have looked at the Apple "MoveMe' example, but that returns the button to the center of the screen. I want to be able to position draggable objects around the screen, drag the objects within the app, and then return them to their original starting positions by pressing a designated button. Any help appreciated!

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  • Efficiently get the size of a parameter pack up to a certain index

    - by NmdMystery
    I want to be able to determine the number of bytes that are in a subset of a parameter pack from 0 to a given index. Right now I'm using a non-constexpr way of doing this. Below is my code: template <size_t index, typename... args> struct pack_size_index; template <size_t index, typename type_t, typename... args> struct pack_size_index <index, type_t, args...> { static const size_t index_v = index; static const size_t value(void) { if (index_v > 0) { return sizeof(type_t) + pack_size_index<index - 1, args...>::value(); } return 0; } }; template <size_t index> struct pack_size_index <index> { static const size_t index_v = index; static const size_t value(void) { return 0; } }; Usage: //output: 5 (equal to 1 + 4) std::cout << pack_size_index<2, bool, float, int, double>::value() << std::endl; //output: 20 (equal to 8 + 8 + 4) std::cout << pack_size_index<3, double, double, float, int>::value() << std::endl; This gets the job done, but this uses runtime comparison and the resulting executable increases in size rapidly whenever this is used. What's a less expensive way of doing this?

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  • Threads syncronization with ThreadPoolExecutor

    - by justme1
    I'm trying to implement some logic when I create main(father) thread witch executes several other threads. Then it waits for some condition which child threads creates. After condition is meet the father executes some more child threads. The problem that when I use wait/notify I have java.lang.IllegalMonitorStateException exception. Here is the code: public class MyExecutor { final static ArrayBlockingQueue<Runnable> queue = new ArrayBlockingQueue<Runnable>(10); final static ExecutorService svc = Executors.newFixedThreadPool(1); static final ThreadPoolExecutor threadPool = new ThreadPoolExecutor(5, 8, 10, TimeUnit.SECONDS, queue); public static void main(String[] args) throws InterruptedException { final MyExecutor me = new MyExecutor(); svc.execute(new Runnable() { public void run() { try { System.out.println("Main Thread"); me.execute(threadPool, 1); System.out.println("Main Thread waiting"); wait(); System.out.println("Main Thread notified"); me.execute(threadPool, 2); Thread.sleep(100); threadPool.shutdown(); threadPool.awaitTermination(20000, TimeUnit.SECONDS); } catch (InterruptedException e) { e.printStackTrace(); } } }); svc.shutdown(); svc.awaitTermination(10000, TimeUnit.SECONDS); System.out.println("Main Thread finished"); } public void execute(ThreadPoolExecutor tpe, final int id) { tpe.execute(new Runnable() { public void run() { try { System.out.println("Child Thread " + id); Thread.sleep(2000); System.out.println("Child Thread " + id + " finished"); notify(); } catch (InterruptedException e) { e.printStackTrace(); } } }); } } When I comment wait and notify line I have the following output: Main Thread Main Thread waiting Main Thread notified Child Thread 1 Child Thread 2 Child Thread 1 finished Child Thread 2 finished Main Thread finished

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  • Input In Java- How does it work?

    - by Nir Avnon
    Hey guys, with a lot of help from you i was managed to write this nice code (I'm new in it, so kind of exciting.. :) ) And still I have not understand how can I input this code. first of all, I get an this error in the console line (I'm using Eclipse): Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0 at NumberConverter.main(NumberConverter.java:5). What does that mean? I just want to chack whether it works, and I can't call the function/program any how. I used to call in an "old fashion way", like in scheme, to the function that I wrote and see if something happens. How does it work in java? Do we call the program itself? function? what and where do we write? -I want to chack if it works, doesn't matter how, and I'll be glad to know how can I plugin input. Thank you so much! public class NumberConverter{ public static void main(String[] args) { int i = Integer.parseInt(args[0]); toBinary(i); toOctal(i); toHex(i); } public static void toBinary(int int1){ System.out.println(int1 + " in binary is"); System.out.println(Integer.toBinaryString(int1)); } public static void toOctal(int int1){ System.out.println(int1 + " in octal is"); System.out.println(Integer.toOctalString(int1)); } public static void toHex(int int1){ System.out.println(int1 + " in hex is"); System.out.println(Integer.toHexString(int1)); } }

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  • ref and out parameters in C# and cannot be marked as variant.

    - by Water Cooler v2
    What does the statement mean? From here ref and out parameters in C# and cannot be marked as variant. 1) Does it mean that the following can not be done. public class SomeClass<R, A>: IVariant<R, A> { public virtual R DoSomething( ref A args ) { return null; } } 2) Or does it mean I cannot have the following. public delegate R Reader<out R, in A>(A arg, string s); public static void AssignReadFromPeonMethodToDelegate(ref Reader<object, Peon> pReader) { pReader = ReadFromPeon; } static object ReadFromPeon(Peon p, string propertyName) { return p.GetType().GetField(propertyName).GetValue(p); } static Reader<object, Peon> pReader; static void Main(string[] args) { AssignReadFromPeonMethodToDelegate(ref pReader); bCanReadWrite = (bool)pReader(peon, "CanReadWrite"); Console.WriteLine("Press any key to quit..."); Console.ReadKey(); } I tried (2) and it worked.

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  • HibernateTemplate alwaysUseNewSession

    - by DD
    Hi, I had a problem where I was using the hibernate template to do most of my DB work but I had a part of the system that directly accessed the session to do batch persisting. I noticed that the hibernate template session was old and would be storing cached values which didnt take into account the objects save with the session directly. What are the drawbacks of using alwaysUseNewSession? This fixes the problem as I always get up-to-date objects. Thanks.

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  • difference between -> and . for member selection operator.

    - by TimothyTech
    in this book i have I'm learning pointers, and i just got done with the chapter about OOP (spits on ground) anyways its telling me i can use a member selection operator like this ( - ). it sayd that is is like the "." except points to objects rather than member objects. whats the difference, it looks like it is used the same way...

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  • Maximize/Minimize is causing Close Button to be re-enabled after disabling it -- Why?

    - by Brainsick
    I have used P/Invoke to call GetSystemMenu and EnableMenuItem (win32api) to disable the close functionality. However, after minimizing or maximizing my Windows Forms application the button is re-enabled. Obviously minimizing or maximizing is causing the behavior, but how? I'm not sure where to look to prevent this behavior. Should I be preventing the maximize and minimize behavior or is there something particularly wrong with the way in which I P/Invoked the calls? Once the application (main form) has loaded, I call the static method from a button click. class PInvoke { // P/Invoke signatures [DllImport("user32.dll")] static extern IntPtr GetSystemMenu(IntPtr hWnd, bool bRevert); [DllImport("user32.dll")] static extern bool EnableMenuItem(IntPtr hMenu, uint uIDEnableItem, uint uEnable); // SysCommand (WM_SYSCOMMAND) constant internal const UInt32 SC_CLOSE = 0xF060; // Constants used with Add/Check/EnableMenuItem internal const UInt32 MF_BYCOMMAND = 0x00000000; internal const UInt32 MF_ENABLED = 0x00000000; internal const UInt32 MF_GRAYED = 0x00000001; internal const UInt32 MF_DISABLED = 0x00000002; /// <summary> /// Sets the state of the Close (X) button and the System Menu close functionality. /// </summary> /// <param name="window">Window or Form</param> /// <param name="bEnabled">Enabled state</param> public static void EnableCloseButton(IWin32Window window, bool bEnabled) { IntPtr hSystemMenu = GetSystemMenu(window.Handle, false); EnableMenuItem(hSystemMenu, SC_CLOSE, MF_BYCOMMAND | (bEnabled ? MF_ENABLED : MF_GRAYED)); } }

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  • Copy values from one object to another.

    - by BrokeMyLegBiking
    Anyone have a suggestion for a good utility class that maps values from one object to another? I want a utility class that uses reflection and takes two objects and copies values from the 1st object to the second if there is a public property with the same name. I have two entities that are generated from a web service proxy, so I can't change the parent class or impliment an interface or anything like that. But I know that the two objects have the same public properties.

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  • binary quicksort

    - by davit-datuashvili
    hi i want implement Binary quicksort algorithm from robert sedgewick book it looks like this public class quickb{ public static final int bitsword=32; public static void quicksortB(int a[],int l,int r,int d){ int i=l; int j=r-1; if (r<=l || d>bitsword) return ; while (j!=i) { while (digit(a[i],d)==0 && (i<j)) i++; while (digit(a[j],d)==1 && (j>i)) j++; int t=a[i]; a[i]=a[j]; a[j]=t; } if (digit(a[r-1],d)== 0) j++; quicksortB(a,l,j-1,d+1); quicksortB(a,j,r,d+1); } public static void main(String[]args){ int a[]=new int[]{4,7,3,9,8,2}; quicksortB(a,0,a.length-1,0); for (int i=0;i<a.length;i++){ System.out.println(a[i]); } } public static int digit(int m,int d){ return (m>>d)&1; } } but it show me error: java.lang.ArrayIndexOutOfBoundsException: 6 at quickb.quicksortB(quickb.java:13) at quickb.main(quickb.java:32) what is wrong?

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  • Hibernate - how to create list of pojos?

    - by AspNewbie
    I am very new to Hibernate. I have MySQL database and mapped pojos. What should I do next? I know little bit LINQ to SQL from .NET, and it generates me List of mapped objects. So basically, what are my next steps after creating POJOS if I want to have List of them and do CRUD operations upon them and data will be also saved in DB not only in java objects ? kthx

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  • how to get memory address

    - by levirg
    hey Folks, Is there any way in ruby to get the memory address of objects.. say.. (i = 5) is that possible to get the mem address of that object 5.. 'object_id_' is not that satisfying.. I just wanted to know how referencing to objects work on ruby, so i thought address will be useful, to get things done plugin memprof doesnt work on x_32bit, so is there any better way pls help me..., Any answer would be really appreciated... thanks, Regards levirg

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  • .net - invoke methods from classes from a certain namespace via reflection

    - by Kristian Hildebrandt
    SPL and PHP allows you to create objects on the fly from classes, that fulfill certain conditions, such as implementing certain interfaces and stuff like that. However, I would like to do something similar in c# and automatically create objects from all classes in a namespace and invoke a particular method from those classes that implement a certain interface. My experience developing desktop apps is very limited. I am not quite sure if I should use delegates to archive this or if reflection is really the way to go.

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  • Resource allocation and automatic deallocation

    - by nabulke
    In my application I got many instances of class CDbaOciNotifier. They all share a pointer to only one instance of class OCIEnv. What I like to achieve is that allocation and deallocation of the resource class OCIEnv will be handled automatically inside class CDbaOciNotifier. The desired behaviour is, with the first instance of class CDbaOciNotifier the environment will be created, after that all following notifiers use that same environment. With the destruction of the last notifier, the environment will be destroyed too (call to custom deleter). What I've got so far (using a static factory method to create notifiers): #pragma once #include <string> #include <memory> #include "boost\noncopyable.hpp" class CDbaOciNotifier : private boost::noncopyable { public: virtual ~CDbaOciNotifier(void); static std::auto_ptr<CDbaOciNotifier> createNotifier(const std::string &tnsName, const std::string &user, const std::string &password); private: CDbaOciNotifier(OCIEnv* envhp); // All notifiers share one environment static OCIEnv* m_ENVHP; // Custom deleter static void freeEnvironment(OCIEnv *env); OCIEnv* m_envhp; }; CPP: #include "DbaOciNotifier.h" using namespace std; OCIEnv* CDbaOciNotifier::m_ENVHP = 0; CDbaOciNotifier::~CDbaOciNotifier(void) { } CDbaOciNotifier::CDbaOciNotifier(OCIEnv* envhp) :m_envhp(envhp) { } void CDbaOciNotifier::freeEnvironment(OCIEnv *env) { OCIHandleFree((dvoid *) env, (ub4) OCI_HTYPE_ENV); *env = null; } auto_ptr<CDbaOciNotifier> CDbaOciNotifier::createNotifier(const string &tnsName, const string &user, const string &password) { if(!m_ENVHP) { OCIEnvCreate( (OCIEnv **) &m_ENVHP, OCI_EVENTS|OCI_OBJECT, (dvoid *)0, (dvoid * (*)(dvoid *, size_t)) 0, (dvoid * (*)(dvoid *, dvoid *, size_t))0, (void (*)(dvoid *, dvoid *)) 0, (size_t) 0, (dvoid **) 0 ); } //shared_ptr<OCIEnv> spEnvhp(m_ENVHP, freeEnvironment); ...got so far... return auto_ptr<CDbaOciNotifier>(new CDbaOciNotifier(m_ENVHP)); } I'd like to avoid counting references (notifiers) myself, and use something like shared_ptr. Do you see an easy solution to my problem?

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  • C#: How to implement a smart cache

    - by Svish
    I have some places where implementing some sort of cache might be useful. For example in cases of doing resource lookups based on custom strings, finding names of properties using reflection, or to have only one PropertyChangedEventArgs per property name. A simple example of the last one: public static class Cache { private static Dictionary<string, PropertyChangedEventArgs> cache; static Cache() { cache = new Dictionary<string, PropertyChangedEventArgs>(); } public static PropertyChangedEventArgs GetPropertyChangedEventArgsa(string propertyName) { if (cache.ContainsKey(propertyName)) return cache[propertyName]; return cache[propertyName] = new PropertyChangedEventArgs(propertyName); } } But, will this work well? For example if we had a whole load of different propertyNames, that would mean we would end up with a huge cache sitting there never being garbage collected or anything. I'm imagining if what is cached are larger values and if the application is a long-running one, this might end up as kind of a problem... or what do you think? How should a good cache be implemented? Is this one good enough for most purposes? Any examples of some nice cache implementations that are not too hard to understand or way too complex to implement?

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  • Force calling the derived class implementation within a generic function in C#?

    - by Adam Hardy
    Ok so I'm currently working with a set of classes that I don't have control over in some pretty generic functions using these objects. Instead of writing literally tens of functions that essentially do the same thing for each class I decided to use a generic function instead. Now the classes I'm dealing with are a little weird in that the derived classes share many of the same properties but the base class that they are derived from doesn't. One such property example is .Parent which exists on a huge number of derived classes but not on the base class and it is this property that I need to use. For ease of understanding I've created a small example as follows: class StandardBaseClass {} // These are simulating the SMO objects class StandardDerivedClass : StandardBaseClass { public object Parent { get; set; } } static class Extensions { public static object GetParent(this StandardDerivedClass sdc) { return sdc.Parent; } public static object GetParent(this StandardBaseClass sbc) { throw new NotImplementedException("StandardBaseClass does not contain a property Parent"); } // This is the Generic function I'm trying to write and need the Parent property. public static void DoSomething<T>(T foo) where T : StandardBaseClass { object Parent = ((T)foo).GetParent(); } } In the above example calling DoSomething() will throw the NotImplemented Exception in the base class's implementation of GetParent(), even though I'm forcing the cast to T which is a StandardDerivedClass. This is contrary to other casting behaviour where by downcasting will force the use of the base class's implementation. I see this behaviour as a bug. Has anyone else out there encountered this?

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  • How can I access the "through" object of a Django ManyToManyField?

    - by Macha
    I have the following models in my Django app. How can I from the Team model find all the User objects who have accepted as True in the Membership model? I know I need to use Team.objects.filter(), but I'm not sure how to check the value of the accepted field. from django.contrib.auth.models import User class Team(models.Model): members = models.ManyToManyField(User, through="Membership") class Membership(models.Model): user = models.ForeignKey(User) team = models.ForeignKey(Team) accepted = models.BooleanField(default=False)

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