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• Null reference exceptions in .net

  - by Carlo

  Hello, we're having this big problem with our application. It's a rather large application with several modules, and thousands and thousands lines of code. A lot of parts of the application are designed to exist only with a reference to another object, for example a Person object can never exists without a House object, so if you at any point in the app say: bool check = App.Person.House == null; check should always be false (by design), so, to keep using that example, while creating modules, testing, debugging, App.Person.House is never null, but once we shipped the application to our client, they started getting a bunch of NullReferenceException with the objects that by design, should never have a null reference. They tell us the bug, we try to reproduce it here, but 90% of the times we can't, because here it works fine. The app is being developed with C# and WPF, and by design, it only runs on Windows XP SP 3, and the .net framework v3.5, so we KNOW the user has the same operative system, service pack, and .net framework version as we do here, but they still get this weird NullReferenceExceptions that we can't reproduce. So, I'm just wondering if anyone has seen this before and how you fixed it, we have the app running here at least 8 hours a day in 5 different computers, and we never see those exceptions, this only happens to the client for some reason. ANY thought, any clue, any solution that could get us closer to fixing this problem will be greatly appreciated. Thanks!

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• Why "Not an ARRAY reference" error?

  - by Sandra Schlichting

  I have this script #!/usr/bin/perl use strict; use warnings; use yy; my $data = [ ["aax", "ert", "ddd"], ["asx", "eer", "kkk"], ["xkk", "fff", "lll"], ["xxj", "vtt", "lle"], ]; use Test::More tests => 4; is(yy::type1_to_type2(\$data, 'aax'), 'ert'); is(yy::type1_to_type3(\$data, 'asx'), 'kkk'); is(yy::type2_to_type3(\$data, 'fff'), 'lll'); is(yy::type3_to_type1(\$data, 'lle'), 'xxj'); which uses this module package yy; sub typeX_to_typeY { my ($x, $y, $data, $str) = @_; foreach (@$data) { if ($_->[$x - 1] eq $str) { return $_->[$y - 1]; } } return; } sub type1_to_type2 { typeX_to_typeY(1, 2, @_) } sub type1_to_type3 { typeX_to_typeY(1, 3, @_) } sub type2_to_type1 { typeX_to_typeY(2, 1, @_) } sub type2_to_type3 { typeX_to_typeY(2, 3, @_) } sub type3_to_type1 { typeX_to_typeY(3, 1, @_) } sub type3_to_type2 { typeX_to_typeY(3, 2, @_) } 1; and gives this error Not an ARRAY reference at yy.pm line 6. # Looks like your test died before it could output anything. The line it complains about is foreach (@$data) { Isn't this the way to pass an array reference? What am I doing wrong?

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• Google Maps in Drupal: reference to gmap object from JavaScript

  - by user280817

  Is there a way to obtain JavaScript references to the Google maps that are embedded into Drupal pages by the GMap module? I want to be able to manipulate the maps in these pages. I want to pan and zoom them. But I cannot find a reference to an embedded map object. I've dissected the relevant JavaScript objects Drupal.gmap and Drupal.settings.gmap with no success--unless I've overlooked something. The Drupal GMap module doesn't seem to explicitly provide references (within its API) to the GMap objects that it embeds into pages. It just generates themed text which is interpolated into the page. The technique of passing the HTML ID of the map container to either the GMap2 object constructor or the similar Drupal.gmap.getMap() function in order to obtain a map reference doesn't appear to work: Both simply return an instance to a new map, one having the same dimensions and basic characteristics of the original map, but apparently sans all of its overlays (which could contain markers). And I have to call setCenter() on it before I can use it, which initializes the structure, so I know it has no overlays.

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• Remove pointer object whose reference is mantained in three different lists

  - by brainydexter

  I am not sure how to approach this problem: 'Player' class mantains a list of Bullet* objects: class Player { protected: std::list< Bullet* > m_pBullet_list; } When the player fires a Bullet, it is added to this list. Also, inside the constructor of bullet, a reference of the same object is updated in CollisionMgr, where CollisionMgr also mantains a list of Bullet*. Bullet::Bullet(GameGL*a_pGameGL, Player*a_pPlayer) : GameObject( a_pGameGL ) { m_pPlayer = a_pPlayer; m_pGameGL->GetCollisionMgr()->AddBullet(this); } class CollisionMgr { void AddBullet(Bullet* a_pBullet); protected: std::list< Bullet*> m_BulletPList; } In CollisionMgr.Update(); based on some conditions, I populate class Cell which again contain a list of Bullet*. Finally, certain conditions qualify a Bullet to be deleted. Now, these conditions are tested upon while iterating through a Cell's list. So, if I have to delete the Bullet object, from all these places, how should I do it so that there are no more dangling references to it? std::list< Bullet*>::iterator bullet_it; for( bullet_it = (a_pCell->m_BulletPList).begin(); bullet_it != (a_pCell->m_BulletPList).end(); bullet_it++) { bool l_Bullet_trash = false; Bullet* bullet1 = *bullet_it; // conditions would set this to true if ( l_Bullet_Trash ) // TrashBullet( bullet1 ); continue; } Also, I was reading about list::remove, and it mentions that it calls the destructor of the object we are trying to delete. Given this info, if I delete from one list, the object does not exist, but the list would still contain a reference to it..How do I handle all these problems ? Can someone please help me here ? Thanks PS: If you want me to post more code or provide explanation, please do let me know.

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• Add webservice reference, the classes in different file

  - by ArunDhaJ

  Hi, When I add webservice as service reference in my .Net project, it creates a service folder within "Service References". All the interfaces and classes are contained within that service folder. I wanted to know how to split the interface's method and classes. Actually I wanted the web service reference to import classes defined in different dll. I wanted to define this way because of my design constraints. I've 3 layered application. Of which third layer is communication layer which holds all web service references. second is business layer and first is presentation layer. If the class declarations are in layer-3 and I'm accessing those classes from presentation layer, it is logically a cross-layer-access-violation. Instead, I wanted a separate project which holds only the class declarations and this would be used in all 3 layers. I didn't faced any problems to achieve this with layer-1 and layer-2. But, I'm not sure how to make communication layer to use this common declaration dll. Your suggestion would help me to design my application better. Thanks in advance Regards ArunDhaJ

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• c#3.5 Deserialization error - object reference not set

  - by BBR

  I am trying to deserialize an xml string in c#3.5, the code below does work in c# 4.0. When I try to run in the code in c#3.5 I get an Object reference not set to an instance of an object exception when the code tries in initialize the XmlSerializer. Any help would be appreciated. string xml = "<boolean xmlns=\"http://schemas.microsoft.com/2003/10/serialization/\">false</boolean>"; var xSerializer = new XmlSerializer(typeof(bool), null, null, new XmlRootAttribute("boolean"), "http://schemas.microsoft.com/2003/10/serialization/"); using (var sr = new StringReader(xml)) using (var xr = XmlReader.Create(sr)) { var y = xSerializer.Deserialize(xr); } System.NullReferenceException was unhandled Message="Object reference not set to an instance of an object." Source="System.Xml" StackTrace: at System.Xml.Serialization.XmlSerializer..ctor(Type type, XmlAttributeOverrides overrides, Type[] extraTypes, XmlRootAttribute root, String defaultNamespace, String location, Evidence evidence) at System.Xml.Serialization.XmlSerializer..ctor(Type type, XmlAttributeOverrides overrides, Type[] extraTypes, XmlRootAttribute root, String defaultNamespace) .... at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() InnerException:

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• SWIG interface to receive an opaque struct reference in Java through function argument

  - by Beeo

  I am trying to use SWIG in order to use the Spotify API (libspotify) for Android: https://developer.spotify.com/technologies/libspotify/ I am having trouble defining the SWIG interface file to be able to successfully call the following native C function: sp_error sp_session_create(const sp_session_config * config, sp_session ** sess); Which in C would be called like this: //config struct defined previously sp_session *sess; sp_session_create(&config, &sess); But in Java I would need to call it like this: //config object defined previously sp_session javaSess = new sp_session(); sp_session_create(config, javaSess); sp_session is an opaque struct and is only defined in libspotify's API.h file as: typedef struct sp_session sp_session; I'm expecting the libspotify library to create it and give me a reference to it. The only thing I need that reference for then is to pass to other functions in the API. I believe the answer lies within the SWIG interface and typemaps, but I have been unsuccessful in trying to apply the examples I found in the documentation: http://www.swig.org/Doc2.0/SWIGDocumentation.html#Java_struct_pointer_pointer `http://www.swig.org/Doc2.0/SWIGDocumentation.html#Java_using_typemaps_return_arguments Help!

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• Copy constructor called even when returning by reference?

  - by Johnyy

  Hi, I am testing the return of local objects by reference. My original test went well but something else happens unexpected. #include <iostream> using namespace std; class MyInt { public: MyInt(int i){ value = new int(i); } ~MyInt(){ delete value; } int getValue(){ return *value; } MyInt(const MyInt &b){ cout<<"Copy"<<endl; } private: int* value; }; MyInt& returnref(){ MyInt a(10); cout<<"Returning from returnref()"<<endl; return a; } int main(){ MyInt a = returnref(); cout<<a.getValue()<<endl; return 0; } My console prints "Returning from ..." then "Copy" then a random value. My understanding of pass by reference is that it does not need to make any copy. Why is it not doing what I expected?

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• Reference to the Main Form whilst trying to Serialize objects in C#

  - by Paul Matthews

  I have a button on my main form which calls a method to serialize some objects to disk. I am trying to add these objects to an ArrayList and then serialize them using a BinaryFormatter and a FileStream. public void SerializeGAToDisk(string GenAlgName) { // Let's make a list that includes all the objects we // need to store a GA instance ArrayList GAContents = new ArrayList(); GAContents.Add(GenAlgInstances[GenAlgName]); // Structure and info for a GA GAContents.Add(RunningGAs[GenAlgName]); // There may be several running GA's using (FileStream fStream = new FileStream(GenAlgName + ".ga", FileMode.Create, FileAccess.Write, FileShare.None)) { BinaryFormatter binFormat = new BinaryFormatter(); binFormat.Serialize(fStream, GAContents); } } When running the above code I get the following exception: System.Runtime.Serialization.SerializationException was unhandled Message=Type 'WindowsFormsApplication1.Form1' in Assembly 'GeneticAlgApp, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' is not marked as serializable. So that means that somewhere in the objects I'm trying to save there must be a reference to the main form. The only possible references I can see are 3 delegates which all point to methods in the main form code. Do delegates get serialized as well? I can't seem to apply the [NonSerialized] attribute to them. Is there anything else I might be missing? Even better, is there a quick method to find the reference(s) that are causing the problem?

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• Web Reference Code generator template.

  - by Bluephlame

  I Have an internal SOAP Web service that is being called from an external REST service in .NET it works fine however I am simply passing through the SOAP objects of the REST Layer but the automatic generation of the WebReference Code in Visual Studio adds the 'field' to the end of every attribute. basically it makes my XML look all nasty. Everything works I just want to clean up my XML. Any ideas how i can change the template for the reference.cs or to make the XML generate nicely from the Web Service Objects. Here is an example of the reference.cs public int HeadLeft { get { return this.headLeftField; } set { this.headLeftField = value; } } /// <remarks/> public int HeadTop { get { return this.headTopField; } set { this.headTopField = value; } } /// <remarks/> public int HeadWidth { get { return this.headWidthField; } set { this.headWidthField = value; } } Here is an examle of the XML <a:headHeightField>208</a:headHeightField> <a:headLeftField>316</a:headLeftField> <a:headTopField>103</a:headTopField> <a:headWidthField>161</a:headWidthField>

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• How to reference var from frame on timeline in an object class

  - by brybam

  I'm using Flash Professional cs5/AS3 I'll try and describe this the best I can. I'm new to ActionScript. So, in my timeline I have a var on a frame that represents "lives" and i have some code in the timeline that takes down the number of lives depending on certain events, which all works great. so, now i wanted to make a constructor class that I could reuse for a bunch of movie clip objects and I only want these objects to be able to move if the lives variable is greater than certain number. So now, building my constructor class for these objects i just wanted put an if statement that is looking to see if the lives are greater than a certain number, which if it is then should make these objects do what i want...But, when i run the project I get "1120: Access of undefined property lives." lives is the var I made obviously like I said, and it works fine being referenced everyone else except when I make a new .as file for these objects then try and reference it. I get the same error when I try and establish "lives" in the main project class too. I'm not sure where I should put this var or how I can make it so i can reference it from an object class. I'm not really sure how to word or describe my issue which has made it hard to search for a tutorial. Any suggestions i'm sure this has to be a simple task.

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• Returning a reference from a Class member?

  - by nebukadnezzar

  Hi, I've a class that basically looks like this: class App { public function newTemplate($filename, $vars=array()) { $smarty = new Smarty; $smarty->compile_dir = $this->template_compile_path; if(count($vars) > 0) { foreach($vars as $v_key => $v_name) { $smarty->assign($v_key, $v_name); } } return $smarty; } } However, when I create a Instance of 'App', the reference to $smarty seems broken, as every call to the membermethods don't seem to do anything: $app = new App; $tpl = $app->newTemplate("index.tmpl"); $tpl->assign("foo", "bar"); // {$foo} does not appear with "bar" in the template Now I wonder why? Of course I tried to use references: ... public function &newTemplate() ... ... But that doesn't work. Variable references don't seem to work either: ... $tpl = &$app->newTemplate("index.tmpl"); ... What is causing PHP here not to return a proper reference? Help is very appreciated!

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• Flex Tree Properties, Null Reference?

  - by mvrak

  I am pulling down a large XML file and I have no control over it's structure. I used a custom function to use the tag name to view the tree structure as a flex tree, but then it breaks. I am guessing it has something to do with my other function, one that calls attribute values from the selected node. See code. <mx:Tree x="254" y="21" width="498" height="579" id="xmllisttree" labelFunction="namer" dataProvider="{treeData}" showRoot="false" change="treeChanged(event)" /> //and the Cdata import mx.rpc.events.ResultEvent; [Bindable] private var fullXML:XMLList; private function contentHandler(evt:ResultEvent):void{ fullXML = evt.result.page; } [Bindable] public var selectedNode:Object; public function treeChanged(event:Event):void { selectedNode=Tree(event.target).selectedItem; } public function namer(item:Object):String { var node:XML = XML(item); var nodeName:QName = node.name(); var stringtest:String ="bunny"; return nodeName.localName; } The error is TypeError: Error #1009: Cannot access a property or method of a null object reference. Where is the null reference?

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• java array pass by reference does not work?

  - by stdnoit

  guys i thought almost all language including java pass array into function as reference (modifiable) but somehow it does not work here. and the testArray is still 1,2,3 with size of 3 strange enough, when if i change result[i] = 2 to a[1] =2; it work . it did pass by reference what is wrong with this code? at the end, i had a = result; (which update the a). did result get removed from stack. that is why a still get to the original a ? i am confused. thanks class Test { public static void main(String[] args) { int[] testArray = {1,2,3}; equalize(testArray, 6); System.out.println("test Array size :" + testArray.length); for(int i = 0; i < testArray.length; i++) System.out.println(testArray[i]); } public static void equalize(int[] a, int biggerSize) { if(a.length > biggerSize) throw new Error("Array size bigger than biggerSize"); int[] result = new int[biggerSize]; // System.arraycopy(a, 0, result, 0, a.length); // int array default value should be 0 for(int i = 0; i < biggerSize; i++) result[i] = 2; a = result; } }

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• How reference popup object when opener page changes?

  - by achairapart

  This is driving me crazy! Scenario: The main page opens a pop-up window and later calls a function in it: newWin = window.open(someurl,'newWin',options); ...some code later... newWin.remoteFunction(options); and it's ok. Now, popup is still open and Main Page changes to Page 2. In Page 2 newWin doesn't exist anymore and I need to recreate the popup window object reference in order to call again the remote function (newWin.remoteFunction) I tried something like: newWin = open('','newWin', options); if (!newWin || newWin.closed || !newWin.remoteFunction) { newWin = window.open(someurl,'newWin',options); } And it works, I can call newWin.remoteFunction again BUT Safari for some reason gives Focus() to the popup window everytime the open() method is called breaking the navigation (I absolutely need the popup working in the background). Only workaround I can think to solve this is to create an interval in the popup with: if(window.opener && !window.opener.newWin) window.opener.newWin = self; and then set another interval in the opener Page with some try/catch but it is inelegant and very inefficient. so, I wonder, it's really so hard to get the popup object reference between different pages in the opener window?

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• Obtain reference to View in ActionScript class within ViewNavigatorApplication

  - by chb

  I've got a very simple project in FlashBuilder 4.5. It's a mobile application of type ViewNavigatorApplication with a single view, MapView. In the MapView.mxml file, I've got a Flex component of type Map declared in xml. <?xml version="1.0" encoding="utf-8"?> <s:View xmlns:fx="http://ns.adobe.com/mxml/2009" name="CatBusMapView"> <fx:Script> <![CDATA[ import com.esri.ags.Map; .... ]]> </fx:Script> <fx:Declarations> .... </fx:Declarations> <esri:Map id="cbm"> ... </esri:Map> </s:View> In this same project, I've an actionscript class called UserGeolocation. In this class, I'm attempting to get a reference to this map component. So far, I can get a reference to the top-level application, its ViewNavigator and the NavigationStack of said ViewNavigator. However, I cannot find a way to access the MapView, much less the map I've declared within it. I'm aware of methods like firstView() and activeView(), but I want an absolute solution, one that retrieves the view regardless of whether or not it's first or active. I've tried navigator.getChildByName("MapView") with no luck.

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• Reference - What does this error mean in PHP?

  - by hakre

  On Stackoverflow you can see a lot of questions popping up about errors. Some users do not even know that error messages exists, others are asking about code that gives an error message but they do not understand the error message. If the error message is common, many questions about the same kind of error appears, but it is hard to find existing Q&A about the topic. Please add "your favorite" error message, one per answer, a short description what it means (even if it is only highlighting terms to their manual page) and a listing of existing Q&A that are of value. This will create a list. The question is a community wiki, so you are not answering for reputation but for creating a reference list for new users. It's based on error messages. Compare with the existing Reference - What does this symbol mean in PHP? question, which works pretty well. What are common errors in PHP and what are their Solutions. Index of Errors Just starting, but there are already some: Warning: Cannot modify header information - headers already sent Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in ... on line Parse error: syntax error, unexpected T_XXX in YYY on line ZZZ Fatal Error: Call to a member function ... on a non-object

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• Need help getting parent reference to child view controller

  - by Andy

  I've got the following code in one of my view controllers: - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { switch (indexPath.section) { case 0: // "days" section tapped { DayPicker *dayPicker = [[DayPicker alloc] initWithStyle:UITableViewStylePlain]; dayPicker.rowLabel = self.activeDaysLabel; dayPicker.selectedDays = self.newRule.activeDays; [self.navigationController pushViewController:dayPicker animated:YES]; [dayPicker release]; break; ... Then, in the DayPicker controller, I do some stuff to the dayPicker.rowLabel property. Now, when the dayPicker is dismissed, I want the value in dayPicker.rowLabel to be used as the cell.textLabel.text property in the cell that called the controller in the first place (i.e., the cell label becomes the option that was selected within the DayPicker controller). I thought that by using the assignment operator to set dayPicker.rowLabel = self.activeDaysLabel, the two pointed to the same object in memory, and that upon dismissing the DayPicker, my first view controller, which uses self.activeDaysLabel as the cell.textLabel.text property for the cell in question, would automagically pick up the new value of the object. But no such luck. Have I missed something basic here, or am I going about this the wrong way? I originally passed a reference to the calling view controller to the child view controller, but several here told me that was likely to cause problems, being a circular reference. That setup worked, though; now I'm not sure how to accomplish the same thing "the right way." As usual, thanks in advance for your help.

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• Cached data accessed by reference?

  - by arthurdent510

  I am running into an odd problem, and this is the only thing I can think of. I'm storing a list in cache, and I am randomly losing items from my list as users use the site. I have a class that is called that either goes to cache and returns the list from there, or if the cache is over a certain time frame old, it goes to the database and refreshes the cache. So when I pull the data from cache, this is what it looks like.... results = (List<Software>)cache["software"]; And then I return results and do some processing, filter for security, and eventually it winds up on the screen. For each Software record, there can be multiple resources attached to it, and based on how the security goes they may see some, all, or none of the records. So in the security check it will remove some of those resources from the software record. So my question is.... when I return my results list, is it a reference directly to the cache object? So when I remove a resource from the software object, it is really removing from cache as well? If that is the case, is there any way to not return it as a reference? Thanks!

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• Why null reference exception in SetMolePublicInstance?

  - by OldGrantonian

  I get a "null reference" exception in the following line: MoleRuntime.SetMolePublicInstance(stub, receiverType, objReceiver, name, null); The program builds and compiles correctly. There are no complaints about any of the parameters to the method. Here's the specification of SetMolePublicInstance, from the object browser: SetMolePublicInstance(System.Delegate _stub, System.Type receiverType, object _receiver, string name, params System.Type[] parameterTypes) Here are the parameter values for "Locals": + stub {Method = {System.String <StaticMethodUnitTestWithDeq>b__0()}} System.Func<string> + receiverType {Name = "OrigValue" FullName = "OrigValueP.OrigValue"} System.Type {System.RuntimeType} objReceiver {OrigValueP.OrigValue} object {OrigValueP.OrigValue} name "TestString" string parameterTypes null object[] I know that TestString() takes no parameters and returns string, so as a starter to try to get things working, I specified "null" for the final parameter to SetMolePublicInstance. As already mentioned, this compiles OK. Here's the stack trace: Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object. at Microsoft.ExtendedReflection.Collections.Indexable.ConvertAllToArray[TInput,TOutput](TInput[] array, Converter`2 converter) at Microsoft.Moles.Framework.Moles.MoleRuntime.SetMole(Delegate _stub, Type receiverType, Object _receiver, String name, MoleBindingFlags flags, Type[] parameterTypes) at Microsoft.Moles.Framework.Moles.MoleRuntime.SetMolePublicInstance(Delegate _stub, Type receiverType, Object _receiver, String name, Type[] parameterTypes) at DeqP.Deq.Replace[T](Func`1 stub, Type receiverType, Object objReceiver, String name) in C:\0VisProjects\DecP_04\DecP\DeqC.cs:line 38 at DeqPTest.DecCTest.StaticMethodUnitTestWithDeq() in C:\0VisProjects\DecP_04\DecPTest\DeqCTest.cs:line 28 at Starter.Start.Main(String[] args) in C:\0VisProjects\DecP_04\Starter\Starter.cs:line 14 Press any key to continue . . . To avoid the null parameter, I changed the final "null" to "parameterTypes" as in the following line: MoleRuntime.SetMolePublicInstance(stub, receiverType, objReceiver, name, parameterTypes); I then tried each of the following (before the line): int[] parameterTypes = null; // if this is null, I don't think the type will matter int[] parameterTypes = new int[0]; object[] parameterTypes = new object[0]; // this would allow for various parameter types All three attempts produce a red squiggly line under the entire line for SetMolePublicInstance Mouseover showed the following message: The best overloaded method match for 'Microsoft.Moles.Framework.Moles.MoleRuntime.SetMolePublicInstance(System.Delegate, System.Type, object, string, params System.Type[])' has some invalid arguments. I'm assuming that the first four arguments are OK, and that the problem is with the params array.

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• Cannot make a static reference to the non-static type MyRunnable

  - by kaiwii ho

  Here is the whole code : import java.util.ArrayList; public class Test{ ThreadLocal<ArrayList<E>>arraylist=new ThreadLocal<ArrayList<E>>(){ @Override protected ArrayList<E> initialValue() { // TODO Auto-generated method stub //return super.initialValue(); ArrayList<E>arraylist=new ArrayList<E>(); for(int i=0;i<=20;i++) arraylist.add((E) new Integer(i)); return arraylist; } }; class MyRunnable implements Runnable{ private Test mytest; public MyRunnable(Test test){ mytest=test; // TODO Auto-generated constructor stub } @Override public void run() { System.out.println("before"+mytest.arraylist.toString()); ArrayList<E>myarraylist=(ArrayList<E>) mytest.arraylist.get(); myarraylist.add((E) new Double(Math.random())); mytest.arraylist.set(myarraylist); System.out.println("after"+mytest.arraylist.toString()); } // TODO Auto-generated method stub } public static void main(String[] args){ Test test=new Test<Double>(); System.out.println(test.arraylist.toString()); new Thread(new MyRunnable(test)).start(); new Thread(new MyRunnable(test)).start(); System.out.println(arraylist.toString()); } } my questions are: 1\ why the new Thread(new MyRunnable(test)).start(); cause the error: Cannot make a static reference to the non-static type MyRunnable ? 2\ what is the static reference refer to right here? thx in advanced

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• Perl help dereferencing a reference to an array of hash references, containing record set data

  - by user1724150

  I'm using the a Amazon Perl module that returns a reference to an array of hash references as $record_sets, containing record set data and I'm having a hard time dereferencing it. I can print the data using data dumper but I need to be able to manipulate the data. Below is the documentation provided for the module Thanks In Advance: #list_resource_record_sets #Lists resource record sets for a hosted zone. #Called in scalar context: $record_sets = $r53->list_resource_record_sets(zone_id => '123ZONEID'); #Returns: A reference to an array of hash references, containing record set data. Example: $record_sets = [ { name => 'example.com.', type => 'MX' ttl => 86400, records => [ '10 mail.example.com' ] }, { name => 'example.com.', type => 'NS', ttl => 172800, records => [ 'ns-001.awsdns-01.net.', 'ns-002.awsdns-02.net.', 'ns-003.awsdns-03.net.', 'ns-004.awsdns-04.net.' ]

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• How to reference {{outlet}} in Ember.CollectionView's itemView

  - by ceed

  I am new to ember and ran into a problem and could not find an answer online. I have a collectionView App.MyView = Ember.CollectionView.extend({ itemViewClass: 'App.MyViewItem', contentBinding: 'controller' }); and the itemViewClass App.MyViewItem = Ember.View.extend({ templateName: 'mytemplate' }); the template looks like that: <div {{action 'select' view.content}}>{{view.content.name}}</div> {{outlet detail}} </div> This produces the content list just fine. In the controller, I have an action: select: function(evt){ this.transitionToRoute('item', evt); } What I want to do is to transition to a nested route when selecting the item (which works fine) and also load more data of the selected item into {{outlet detail}}. While I can load the content of the "item" route into an outlet of e.g. application.hbs, I don't know how to reference the outlet of the selected collectionView item so that the detailed contents are displayed within the existing view. I tried to use: this.render('item', { outlet: 'detail', into: '????' }); within the item Route, but I don't know how to reference the collectionview item template. Maybe there's also a much easier way of loading more data from an item in the item's view (while changing the route at the same time). Any help would be appreciated.

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• C++ const-reference semantics?

  - by Kristoffer

  Consider the sample application below. It demonstrates what I would call a flawed class design. #include <iostream> using namespace std; struct B { B() : m_value(1) {} long m_value; }; struct A { const B& GetB() const { return m_B; } void Foo(const B &b) { // assert(this != &b); m_B.m_value += b.m_value; m_B.m_value += b.m_value; } protected: B m_B; }; int main(int argc, char* argv[]) { A a; cout << "Original value: " << a.GetB().m_value << endl; cout << "Expected value: 3" << endl; a.Foo(a.GetB()); cout << "Actual value: " << a.GetB().m_value << endl; return 0; } Output: Original value: 1 Expected value: 3 Actual value: 4 Obviously, the programmer is fooled by the constness of b. By mistake b points to this, which yields the undesired behavior. My question: What const-rules should you follow when designing getters/setters? My suggestion: Never return a reference to a member variable if it can be set by reference through a member function. Hence, either return by value or pass parameters by value. (Modern compilers will optimize away the extra copy anyway.)

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• Reference a GNU C (POSIX) DLL built in GCC against Cygwin, from C#/NET

  - by Dale Halliwell

  Here is what I want: I have a huge legacy C/C++ codebase written for POSIX, including some very POSIX specific stuff like pthreads. This can be compiled on Cygwin/GCC and run as an executable under Windows with the Cygwin DLL. What I would like to do is build the codebase itself into a Windows DLL that I can then reference from C# and write a wrapper around it to access some parts of it programatically. I have tried this approach with the very simple "hello world" example at http://www.cygwin.com/cygwin-ug-net/dll.html and it doesn't seem to work. #include <stdio.h> extern "C" __declspec(dllexport) int hello(); int hello() { printf ("Hello World!\n"); return 42; } I believe I should be able to reference a DLL built with the above code in C# using something like: [DllImport("kernel32.dll")] public static extern IntPtr LoadLibrary(string dllToLoad); [DllImport("kernel32.dll")] public static extern IntPtr GetProcAddress(IntPtr hModule, string procedureName); [DllImport("kernel32.dll")] public static extern bool FreeLibrary(IntPtr hModule); [UnmanagedFunctionPointer(CallingConvention.Cdecl)] private delegate int hello(); static void Main(string[] args) { var path = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "helloworld.dll"); IntPtr pDll = LoadLibrary(path); IntPtr pAddressOfFunctionToCall = GetProcAddress(pDll, "hello"); hello hello = (hello)Marshal.GetDelegateForFunctionPointer( pAddressOfFunctionToCall, typeof(hello)); int theResult = hello(); Console.WriteLine(theResult.ToString()); bool result = FreeLibrary(pDll); Console.ReadKey(); } But this approach doesn't seem to work. LoadLibrary returns null. It can find the DLL (helloworld.dll), it is just like it can't load it or find the exported function. I am sure that if I get this basic case working I can reference the rest of my codebase in this way. Any suggestions or pointers, or does anyone know if what I want is even possible? Thanks. Edit: Examined my DLL with Dependency Walker (great tool, thanks) and it seems to export the function correctly. Question: should I be referencing it as the function name Dependency Walker seems to find (_Z5hellov)? Edit2: Just to show you I have tried it, linking directly to the dll at relative or absolute path (i.e. not using LoadLibrary): [DllImport(@"C:\.....\helloworld.dll")] public static extern int hello(); static void Main(string[] args) { int theResult = hello(); Console.WriteLine(theResult.ToString()); Console.ReadKey(); } This fails with: "Unable to load DLL 'C:.....\helloworld.dll': Invalid access to memory location. (Exception from HRESULT: 0x800703E6) *Edit 3: * Oleg has suggested running dumpbin.exe on my dll, this is the output: Dump of file helloworld.dll File Type: DLL Section contains the following exports for helloworld.dll 00000000 characteristics 4BD5037F time date stamp Mon Apr 26 15:07:43 2010 0.00 version 1 ordinal base 1 number of functions 1 number of names ordinal hint RVA name 1 0 000010F0 hello Summary 1000 .bss 1000 .data 1000 .debug_abbrev 1000 .debug_info 1000 .debug_line 1000 .debug_pubnames 1000 .edata 1000 .eh_frame 1000 .idata 1000 .reloc 1000 .text Edit 4 Thanks everyone for the help, I managed to get it working. Oleg's answer gave me the information I needed to find out what I was doing wrong. There are 2 ways to do this. One is to build with the gcc -mno-cygwin compiler flag, which builds the dll without the cygwin dll, basically as if you had built it in MingW. Building it this way got my hello world example working! However, MingW doesn't have all the libraries that cygwin has in the installer, so if your POSIX code has dependencies on these libraries (mine had heaps) you can't do this way. And if your POSIX code didn't have those dependencies, why not just build for Win32 from the beginning. So that's not much help unless you want to spend time setting up MingW properly. The other option is to build with the Cygwin DLL. The Cygwin DLL needs an initialization function init() to be called before it can be used. This is why my code wasn't working before. The code below loads and runs my hello world example. //[DllImport(@"hello.dll", EntryPoint = "#1",SetLastError = true)] //static extern int helloworld(); //don't do this! cygwin needs to be init first [DllImport("kernel32", CharSet = CharSet.Ansi, ExactSpelling = true, SetLastError = true)] static extern IntPtr GetProcAddress(IntPtr hModule, string procName); [DllImport("kernel32", SetLastError = true)] static extern IntPtr LoadLibrary(string lpFileName); public delegate int MyFunction(); static void Main(string[] args) { //load cygwin dll IntPtr pcygwin = LoadLibrary("cygwin1.dll"); IntPtr pcyginit = GetProcAddress(pcygwin, "cygwin_dll_init"); Action init = (Action)Marshal.GetDelegateForFunctionPointer(pcyginit, typeof(Action)); init(); IntPtr phello = LoadLibrary("hello.dll"); IntPtr pfn = GetProcAddress(phello, "helloworld"); MyFunction helloworld = (MyFunction)Marshal.GetDelegateForFunctionPointer(pfn, typeof(MyFunction)); Console.WriteLine(helloworld()); Console.ReadKey(); } Thanks to everyone that answered~~

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