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• NullPointerException Java help

  - by KP65

  Hello guys. I've been tearing my hair out the past few hours trying to solve this problem. Every time I click on a JButton which should open a JFrame(And it does), i get a stacktrace saying I have a null point exception at these bits of code: In class A i have: aButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { B instanceofB = new B(userSession.getBalance()); }); and Class B super.getSomeBtn().setVisible(false); This is where the stacktrace says the errors are in the two above sections. I have a line exactly the same as the one above in Class B and it works fine? Really stuck here!

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• Getting 'this' pointer inside dependency property changed callback

  - by mizipzor

  I have the following dependency property inside a class: class FooHolder { public static DependencyProperty CurrentFooProperty = DependencyProperty.Register( "CurrentFoo", typeof(Foo), typeof(FooHandler), new PropertyMetadata(OnCurrentFooChanged)); private static void OnCurrentFooChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { FooHolder holder = (FooHolder) d.Property.Owner; // <- something like this // do stuff with holder } } I need to be able to retrieve a reference to the class instance in which the changed property belongs. This is since FooHolder has some event handlers that needs to be hooked/unhooked when the value of the property is changed. The property changed callback must be static, but the event handler is not.

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• open iphone Mail from Actionsheet..

  - by totato

  hi .. I want to open Mail app from my app when the one button in actionsheet is pressed, I know this way : -(IBAtion)openClick:(id)sender { [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@”mailto:[email protected]”]]; } but can I write this method inside if statement or switch case?(in ControlView class NOT NSObject class , because I use actionsheet for this propose) like this: - (void)actionSheet:(UIActionSheet *)modalView clickedButtonAtIndex:(NSInteger)buttonIndex { switch (buttonIndex) { case 0: { [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@”mailto:[email protected]”]]; break; } I can't test my code because simulator doesn't have the Mail app.. So I need to know is this will work in controlView or must write it in NSObject class ? + seconde question : I want to open Mail app from my app and copy the content in the view to mail body,then the user choice the contact from his contacts list ! Is this way achieve my goal?

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• Force external function to be const

  - by vanna

  Here is my problem. I made a class with a member function declared as const that uses an external function that I cannot modify (declared in someone else's code) and that is not declared const. More precisely Someone else's code class B { public: void foo(); }; My code class A : public B { public: void bar() const { this->foo(); } }; I know that for member data we can force const-correctness by using mutable or const_cast. How can I 'hack' foo such that my compiler understands that I would like to use it as if it was const even if it is not declared in someone else's code ?

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• How can i see if dealloc is being called on a uikit object, or any object not created by myself

  - by Gyozo Kudor

  I think i have an UIImage that has a higher retain count than it should have and i am probably leaking memory. I use this image as a thumbnail, to set a custom background to a uibutton. So the uibutton is holding a reference to it and so do i. But instead of 2, the retainCount is 3. Do i have to create a custom UIImage derived class and override dealloc if I want to place a log message there and then change the class used from UIImage to my class, or is there an easier way. Thanks in advance.

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• How to mock WCF Web Services with Rhino Mocks.

  - by Will

  How do I test a class that utilizes proxy clients generated by a Web Service Reference? I would like to mock the client, but the generated client interface doesn't contain the close method, which is required to properly terminate the proxy. If I don't use the interface, but instead a concrete reference, I get access to the close method but loose the ability to mock the proxy. I'm trying to test a class similar to this: public class ServiceAdapter : IServiceAdapter, IDisposable { // ILoggingServiceClient is generated via a Web Service reference private readonly ILoggingServiceClient _loggingServiceClient; public ServiceAdapter() : this(new LoggingServiceClient()) {} internal ServiceAdapter(ILoggingServiceClient loggingServiceClient) { _loggingServiceClient = loggingServiceClient; } public void LogSomething(string msg) { _loggingServiceClient.LogSomething(msg); } public void Dispose() { // this doesn't compile, because ILoggingServiceClient doesn't contain Close(), // yet Close is required to properly terminate the WCF client _loggingServiceClient.Close(); } }

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• Databinding in windows forms on an object graph with possible null properties?

  - by Fredrik

  If I have an object graph like this: class Company { public Address MainAddress {...} } class Address { public string City { ... } } Company c = new Company(); c.MainAddress = new Address(); c.MainAddress.City = "Stockholm"; and databind to a control using: textBox1.DataBinding.Add( "Text", c, "MainAddress.City" ); Everything is fine, but If I bind to: Company c2 = new Company(); c2 using the same syntax it crashes since the MainAddress property is null. I wonder if there is a custom Binding class that can set up listeners for all the possible paths here and bind to the actual object dynamically when/if I sometime later in the application set the MainAddress property.

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• How can I access and change elements in this private readonly property?

  - by CrimsonX

  I'm trying to figure out how I am able to successfully change a "readonly" array. I have this: namespace ConsoleApplication1 { class Program { static void Main(string[] args) { MyClass myClass = new MyClass(); myClass.Time[5] = 5; // How is this legal? } } public class MyClass { private readonly uint[] time; public IList<uint> Time { get { return time; } } public MyClass() { time = new uint[7]; } } } As I Note above, I would expect that Time[5] would be illegal due to the fact that public IList Time does not have a setter. Additionally, how can I create an array in the constructor which is read-only and unchangeable outside of this class?

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• Why isn't the "this." command needed in this constructor? (java)

  - by David

  I'm reading a book about java. It just got to explaining how you create a class called "deck" which contains an array of cards as its instance variable(s). Here is the code snippit: class Deck { Card[] cards; public Deck (int n) { cards = new Card[n]; } } why isn't the this. command used? for example why isn't the code this: class Deck { Card[[] cards; public Deck (int n) { this.cards = new Card[n]; } }

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• Using a delegate to populate a listbox

  - by Leroy Jenkins

  Ive been playing around with delegates trying to learn and I ran into one small problem Im hoping you can help me with. class myClass { OtherClass otherClass = new OtherClass(); // Needs Parameter otherClass.SendSomeText(myString); } class OtherClass { public delegate void TextToBox(string s); TextToBox textToBox; public OtherClass(TextToBox ttb) // ***Problem*** { textToBox = ttb; } public void SendSomeText(string foo) { textToBox(foo); } } the form: public partial class MainForm : Form { OtherClass otherClass; public MainForm() { InitializeComponent(); otherClass = new OtherClass(this.TextToBox); } public void TextToBox(string aString) { listBox1.Items.Add(aString); } } Obviously this doesnt compile because the OtherClass constructor is looking for TextToBox as a parameter. How would you recommend getting around the issue so I can get an object from myClass into the textbox in the form?

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• Implementing operator< in C++

  - by Vulcan Eager

  I have a class with a few numeric fields such as: class Class1 { int a; int b; int c; public: // constructor and so on... bool operator<(const Class1& other) const; }; I need to use objects of this class as a key in an std::map. I therefore implement operator<. What is the simplest implementation of operator< to use here?

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• Hibernate Bi-Directional ManyToMany Updates with Second Level cache

  - by DD

  I have a bidirectional many-to-many class: public class A{ @ManyToMany(mappedBy="listA") private List<B> listB; } public class B{ @ManyToMany private List<A> listA; } Now I save a listA into B: b.setListA(listA); This all works fine until I turn on second-level caching on the collection a.ListB. Now, when I update the list in B, a.listB does not get updated and remains stale. How do you get around this? Thanks, Dwayne

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• C# listbox,params

  - by Oyeme

  As Andrew Hare suggested in his answer: Create a field to store all the ListBox instances and then change the constructor to accept an arbitrary number of them: by I tried the following class scaner { readonly IEnumerable<ListBox> listBoxes; public IEnumerable<ListBox> ListBoxes { get { return this.listBoxes; } } public scaner(params ListBox[] listBoxes) { this.listBoxes = listBoxes; } } This will allow you to do this: scaner Comp = new scaner(listBox1, listBox2); How can i access listbox1? In class scaner i'm trying to call this.listBoxes. (I need to call the listbox1 in scaner class.How can i do/call it? Thanks for answers.

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• Reverse Expression.Like criterion

  - by Joel Potter

  How should I go about writing a backwards like statement using NHibernate criteria? WHERE 'somestring' LIKE [Property] + '%' Sub Question: Can you access the abstract root alias in a SQLCriterion expression? This is somewhat achievable using the SQLCriterion expression Expression.Sql("? like {alias}.[Property] + '.%'", value, NHibernateUtil.String); However, in the case of class inheritance, {alias} is replaced with the incorrect alias for the column. Example (these classes are stored in separate tables): public abstract class Parent { public virtual string Property { get; set; } } public class Child : Parent { } The above query executed with Child as the root type will replace {alias} with the alias to the Child table rather than the Parent table. This results in an invalid column exception. I need to execute a like statement as above where the property exists on the parent table rather than on the root type table.

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• Question regarding C++ Templates

  - by Isuru

  I used a simple class for a test program about templates, this is what I did: template <typename T> class test { public: test<T>::test(); T out(); }; template <typename T> test<T>::test() { } T test<T>::out() { } int main() { //test<int> t; } But when I try to compile it says 'T' : undeclared identifier and use of class template requires template argument list , pointing to the same line, where I have implemented the method out() . Can anyone please explain what the problem is?? I'm using visual studio 2008.

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• How to deserialize from json to ActiveRecord objects with associations?

  - by Carmine Paolino

  In my Rails application there is a model that has some has_one associations (this is a fabricated example): class Person::Admin < ActiveRecord::Base has_one :person_monthly_revenue has_one :dude_monthly_niceness accepts_nested_attributes_for :person_monthly_revenue, :dude_monthly_niceness end class Person::MonthlyRevenue < ActiveRecord::Base belongs_to :person_admin end class Dude::MonthlyNiceness < ActiveRecord::Base belongs_to :person_admin end The application talks to a backend that computes some data and returns a piece of JSON like this: { "dude_monthly_niceness": { "february": 1.1153232569518972, "october": 1.1250217200558268, "march": 1.3965786869658541, "august": 1.6293418014601631, "september": 1.4062771500697835, "may": 1.7166279693955291, "january": 1.0086401628086725, "june": 1.5711510228365859, "april": 1.5614525597326563, "december": 0.99894169970474289, "july": 1.7263264324994585, "november": 0.95044938418509506 }, "person_monthly_revenue": { "february": 10.585596551505297, "october": 10.574823016656749, "march": 9.9125274764852787, "august": 9.2111604702328922, "september": 9.7905249446675153, "may": 9.1329712474607962, "january": 10.479614016604238, "june": 9.3710235926961936, "april": 9.5897372624830304, "december": 10.052587677671438, "july": 8.9508877843925561, "november": 10.925339756096172 }, } To deserialize it, I use ActiveRecord's from_json, but instead of a Person::Admin object with all the associations in place, I get this error: >> Person::Admin.new.from_json(json) NameError: uninitialized constant Person::Admin::DudeMonthlyNiceness Am I doing something wrong? Is there a better way to deserialize data? (I can modify the backend easily)

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• Unittest and mock

  - by user1410756

  I'm testing with unittest in python and it's ok. Now, I have introduced mock and I need to resolve a question. This is my code: from mock import Mock import unittest class Matematica(object): def __init__(self, op1, op2): self.op1 = op1 self.op2 = op2 def adder(self): return self.op1 + self.op2 def subs(self): return abs(self.op1 - self.op2) def molt(self): return self.op1 * self.op2 def divid(self): return self.op1 / self.op2 class TestMatematica(unittest.TestCase): """Test della classe Matematica""" def testing(self): """Somma""" mat = Matematica(10,20) self.assertEqual(mat.adder(),30) """Sottrazione""" self.assertEqual(mat.subs(),10) class test_mock(object): def __init__(self, matematica): self.matematica = matematica def execute(self): self.matematica.adder() self.matematica.adder() self.matematica.subs() if __name__ == "__main__": result = unittest.TextTestRunner(verbosity=2).run(TestMatematica('testing')) a = Matematica(10,20) b = test_mock(a) b.execute() mock_foo = Mock(b.execute)#return_value = 'rafa') mock_foo() print mock_foo.called print mock_foo.call_count print mock_foo.method_calls This code is functionally and result of print is: True, 1, [] . Now, I need to count how many times are called self.matematica.adder() and self.matematica.subs() . THANKS

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• Singleton constructor question

  - by gillyb

  Hi, I created a Singleton class in c#, with a public property that I want to initialize when the Singleton is first called. This is the code I wrote : public class BL { private ISessionFactory _sessionFactory; public ISessionFactory SessionFactory { get { return _sessionFactory; } set { _sessionFactory = value; } } private BL() { SessionFactory = Dal.SessionFactory.CreateSessionFactory(); } private object thisLock = new object(); private BL _instance = null; public BL Instance { get { lock (thisLock) { if (_instance == null) { _instance = new BL(); } return _instance; } } } } As far as I know, when I address the Instance BL object in the BL class for the first time, it should load the constructor and that should initialize the SessionFactory object. But when I try : BL.Instance.SessionFactory.OpenSession(); I get a Null Reference Exception, and I see that SessionFactory is null... why?

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• Working with the Objective-C/Cocoa flat namespace

  - by Stephen Blinkhorn

  I've not found anything that addresses my specific name space question as yet. I am working on some AudioUnit plug-ins featuring Cocoa based GUIs. The plug-ins use a common library of user interface classes (sliders, buttons etc) which are simply added to each Xcode project. When I recompile and distribute updates it is pretty much guaranteed that at least one user interface class will have been updated since the last release. If the user launches an older plug-in before an updated plug-in then the old Cocoa classes are already loaded into the run time and the plug-in attempts to use the older implementations - often resulting in a failure one way or another. I know frameworks are the intended solution but the overhead and backwards compatibility issues are not ideal. I prefix all class names where possible but what options do I have to ensure that each plug-in contains unique class names for the shared user interface classes?

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• Weak reference and Strong reference

  - by theband

  package uk.co.bigroom.utils { import flash.utils.Dictionary; /** * Class to create a weak reference to an object. A weak reference * is a reference that does not prevent the object from being * garbage collected. If the object has been garbage collected * then the get method will return null. */ public class WeakRef { private var dic:Dictionary; /** * The constructor - creates a weak reference. * * @param obj the object to create a weak reference to */ public function WeakRef( obj:* ) { dic = new Dictionary( true ); dic[obj] = 1; } /** * To get a strong reference to the object. * * @return a strong reference to the object or null if the * object has been garbage collected */ public function get():* { for ( var item:* in dic ) { return item; } return null; } } } In this Class, how they denote one as Weak Reference and one as Strong reference.

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• Java interface design

  - by Nayn

  Hi, I had an interface initially as below. public interface testMe { public Set<String> doSomething(); } public class A implements testMe { public Set<String> doSomething() { return // Set<String> } } I had similar classes implementing testMe. Now I have to add one more class which returns Set<Some Object> public class X implements testMe() { public Set<Some OBject> doSomething() { } } How could i add this mehtod in the interface without breaking existing classes? Thanks Nayn

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• Can't get Javac to work on Mac OS X

  - by elguapo-85

  I am trying to compile with javac on Snow Leopard through the command line. I have Xcode installed. I am just using a simple Hello World file, it works in Eclipse but I can't get it to work using javac. javac -version returns javac 1.6.0_17 HelloWorld.java public class HelloWorld { public static void main(String[] args) { String message = "Welcome to Java!"; System.out.println(message); } } I type: javac HelloWorld.java and get the following error. HelloWorld.java:1: class, interface, or enum expected public class HelloWorld ^ 1 error and... javac -cp . HelloWorld.java returns the same. echo $CLASSPATH just returns blank. Thanks for the help.

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• Does a C++ destructor always or only sometimes call data member destructors?

  - by Magnus

  I'm trying to validate my understanding of C++ destructors. I've read many times that C++ supplies a default destructor if I don't write one myself. But does this mean that if I DO write a destructor that the compiler WON'T still provide the default cleanup of stack-allocated class fields? My hunch is that the only sane behavior would be that all class fields are destroyed no matter what, whether I provide my own destructor or not. In which case the statement I've read so many times is actually a little misleading and could be better stated as: "Whether or not you write your own destructor, the C++ compiler always writes a default destructor-like sequence to deallocate the member variables of your class. You may then specify additional deallocations or other tasks as needed by defining your own destructor" Is this correct?

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• What's the straightforward way to implement one to many editing in list_editable in django admin?

  - by Nate Pinchot

  Given the following models: class Store(models.Model): name = models.CharField(max_length=150) class ItemGroup(models.Model): group = models.CharField(max_length=100) code = models.CharField(max_length=20) class ItemType(models.Model): store = models.ForeignKey(Store, on_delete=models.CASCADE, related_name="item_types") item_group = models.ForeignKey(ItemGroup) type = models.CharField(max_length=100) Inline's handle adding multiple item_types to a Store nicely when viewing a single Store. The content admin team would like to be able to edit stores and their types in bulk. Is there a simple way to implement Store.item_types in list_editable which also allows adding new records, similar to horizontal_filter? If not, is there a straightforward guide that shows how to implement a custom list_editable template? I've been Googling but haven't been able to come up with anything. Also, if there is a simpler or better way to set up these models that would make this easier to implement, feel free to comment.

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• Access ConfigurationSection from ConfigurationElement

  - by shivesh

  I have a configuration class that maps web.config, something like that: public class SiteConfigurationSection : ConfigurationSection { [ConfigurationProperty("defaultConnectionStringName", DefaultValue = "LocalSqlServer")] public string DefaultConnectionStringName { get { return (string)base["defaultConnectionStringName"]; } set { base["defaultConnectionStringName"] = value; } } [ConfigurationProperty("Module", IsRequired = true)] public ModuleElement Module { get { return (ModuleElement)base["Module"]; } } } public class ModuleElement : ConfigurationElement { [ConfigurationProperty("connectionStringName")] public string ConnectionStringName { get { return (string)base["connectionStringName"]; } set { base["connectionStringName"] = value; } } public string ConnectionString { get { string str; if (string.IsNullOrEmpty(this.ConnectionStringName)) { str =//GET THE DefaultConnectionStringName from SiteConfigurationSection; } else str = this.ConnectionStringName; return WebConfigurationManager.ConnectionStrings[str].ConnectionString; } } } Meaning if connection string name value is missing in Module section in web.config file, the value should be read from configurationsection. How to do that?

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