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• Retrieving license type (linux/windows/windows+sqlserver) for an Amazon EC2 instance via the API?

  - by Geir

  I need to calculate the hourly running costs for my Amazon EC2 instances. This varies even between instances with same hardware configs (instance types) because I use different amazon images (AMIs): some plain windows server and some windows server with sql server (both of them have additional costs compared with plain linux instances) The EC2 Java API has a describeInstances() method which returns Instance objects with metadata such as instance id, instance type (m1.small/large...), state (running,stopped..) public ip, etc. This Instance object also has a .getLicense().getPool() which according to the Java API should return "The license pool from which this license was used (ex: 'windows')." I thought this is were it may also give 'windows+sqlserver' or something to that effect. The getLicense() method does however return null.. I've navigated around the EC2 web console, not being able to find this information, but I'm hoping that it is possible - otherwise it would mean that you cannot identify the true hourly cost of an particular instance unless you know which AMI was used to create it in the first place (plain windows server or windows server with sql server). Anyone? Thanks :) /Geir

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• How to store and remove dynamically and automatic variable of generic data type in custum list data

  - by Vineel Kumar Reddy

  Hi I have created a List data structure implementation for generic data type with each node declared as following. struct Node { void *data; .... .... } So each node in my list will have pointer to the actual data(generic could be anything) item that should be stored in the list. I have following signature for adding a node to the list AddNode(struct List *list, void* eledata); the problem is when i want to remove a node i want to free even the data block pointed by *data pointer inside the node structure that is going to be freed. at first freeing of datablock seems to be straight forward free(data) // forget about the syntax..... But if data is pointing to a block created by malloc then the above call is fine....and we can free that block using free function int *x = (int*) malloc(sizeof(int)); *x = 10; AddNode(list,(void*)x); // x can be freed as it was created using malloc what if a node is created as following int x = 10; AddNode(list,(void*)&x); // x cannot be freed as it was not created using malloc Here we cannot call free on variable x!!!! How do i know or implement the functionality for both dynamically allocated variables and static ones....that are passed to my list.... Thanks in advance...

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• What corresponds to the Unity 'registration name' in the unity configuration section?

  - by unanswered

  When registering and resolving types in a Unity Container using code you can use 'Registration Names' to disambiguate your references that derive from an interface or base class hierarchy. The 'registration name' text would be provided as a parameter to the register and resolve methods: myContainer.RegisterType<IMyService, CustomerService>("Customers"); and MyServiceBase result = myContainer.Resolve<MyServiceBase>("Customers"); However when I register types in the configuration files I do not see where the 'registration name' can be assigned I register an Interface: <typeAlias alias="IEnlistmentNotification" type="System.Transactions.IEnlistmentNotification, System.Transactions, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /> Then two types that I happen to know implement that interface: <typeAlias alias="PlaylistManager" type="Sample.Dailies.Grid.Workers.PlaylistManager, Sample.Dailies.Grid.Workers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" /> <typeAlias alias="FlexAleManager" type="Sample.Dailies.Grid.Workers.FlexAleManager, Sample.Dailies.Grid.Workers, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" /> Then I provide mappings between the interface and the two types: <type type="IEnlistmentNotification" mapTo="FlexAleManager"><lifetime type="singleton"/></type> <type type="IEnlistmentNotification" mapTo="PlaylistManager"><lifetime type="singleton"/></type> That seems to correspond to this code: myContainer.RegisterType<IEnlistmentNotification, FlexAleManager>(); myContainer.RegisterType<IEnlistmentNotification, PlaylistManager>(); but clearly what I need is a disambiguating config entry that corresponds to this code: myContainer.RegisterType<IEnlistmentNotification, FlexAleManager>("Flex"); myContainer.RegisterType<IEnlistmentNotification, PlaylistManager>("Play"); Then when I get into my code I could do this: IEnlistmentNotification flex = myContainer.Resolve<IEnlistmentNotification>("Flex"); IEnlistmentNotification play = myContainer.Resolve<IEnlistmentNotification>("Play"); See what I mean? Thanks, Kimball

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• C++ design related question

  - by Kotti

  Hi! Here is the question's plot: suppose I have some abstract classes for objects, let's call it Object. It's definition would include 2D position and dimensions. Let it also have some virtual void Render(Backend& backend) const = 0 method used for rendering. Now I specialize my inheritance tree and add Rectangle and Ellipse class. Guess they won't have their own properties, but they will have their own virtual void Render method. Let's say I implemented these methods, so that Render for Rectangle actually draws some rectangle, and the same for ellipse. Now, I add some object called Plane, which is defined as class Plane : public Rectangle and has a private member of std::vector<Object*> plane_objects; Right after that I add a method to add some object to my plane. And here comes the question. If I design this method as void AddObject(Object& object) I would face trouble like I won't be able to call virtual functions, because I would have to do something like plane_objects.push_back(new Object(object)); and this should be push_back(new Rectangle(object)) for rectangles and new Circle(...) for circles. If I implement this method as void AddObject(Object* object), it looks good, but then somewhere else this means making call like plane.AddObject(new Rectangle(params)); and this is generally a mess because then it's not clear which part of my program should free the allocated memory. ["when destroying the plane? why? are we sure that calls to AddObject were only done as AddObject(new something).] I guess the problems caused by using the second approach could be solved using smart pointers, but I am sure there have to be something better. Any ideas?

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• What, if any, printable character did a user type based on the values in a given System.Windows.Form

  - by Corey Trager

  As a workaround for a problem, I think I have to handle KeyDown events to get the printable character the user actually typed. KeyDown supplies me with a KeyEventArgs object with the properities KeyCode, KeyData, KeyValue, Modifiers, Alt, Shift, Control. My first attempt was just to consider the KeyCode to be the ascii code, but KeyCode on my keyboard is 46, a period ("."), so I end up printing a period when the user types the delete key. So, I know my logic is inadequate. (For those who are curious, the problem is that I have my own combobox in a DataGridView's control collection and somehow SOME characters I type don't produce the KeyPress and TextChanged ComboBox events. These letters include Q, $, %.... This code will reproduce the problem. Generate a Form App and replace the ctor with this code. Run it, and try typing the letter Q into the two comboxes. public partial class Form1 : Form { ComboBox cmbInGrid; ComboBox cmbNotInGrid; DataGridView grid; public Form1() { InitializeComponent(); grid = new DataGridView(); cmbInGrid = new ComboBox(); cmbNotInGrid = new ComboBox(); cmbInGrid.Items.Add("a"); cmbInGrid.Items.Add("b"); cmbNotInGrid.Items.Add("c"); cmbNotInGrid.Items.Add("d"); this.Controls.Add(cmbNotInGrid); this.Controls.Add(grid); grid.Location = new Point(0, 100); this.grid.Controls.Add(cmbInGrid); }

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• Self referencing userdata and garbage collection

  - by drtwox

  Because my userdata objects reference themselves, I need to delete and nil a variable for the garbage collector to work. Lua code: obj = object:new() -- -- Some time later obj:delete() -- Removes the self reference obj = nil -- Ready for collection C Code: typedef struct { int self; // Reference to the object // Other members and function references removed } Object; // Called from Lua to create a new object static int object_new( lua_State *L ) { Object *obj = lua_newuserdata( L, sizeof( Object ) ); // Create the 'self' reference, userdata is on the stack top obj->self = luaL_ref( L, LUA_REGISTRYINDEX ); // Put the userdata back on the stack before returning lua_rawgeti( L, LUA_REGISTRYINDEX, obj->self ); // The object pointer is also stored outside of Lua for processing in C return 1; } // Called by Lua to delete an object static int object_delete( lua_State *L ) { Object *obj = lua_touserdata( L, 1 ); // Remove the objects self reference luaL_unref( L, LUA_REGISTRYINDEX, obj->self ); return 0; } Is there some way I can set the object to nil in Lua, and have the delete() method called automatically? Alternatively, can the delete method nil all variables that reference the object? Can the self reference be made 'weak'?

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• How can I get swig to wrap a linked list-type structure?

  - by bk

  Here's what I take to be a pretty standard header for a list. Because the struct points to itself, we need this two-part declaration. Call it listicle.h: typedef struct _listicle listicle; struct _listicle{ int i; listicle *next; }; I'm trying to get swig to wrap this, so that the Python user can make use of the listicle struct. Here's what I have in listicle.i right now: %module listicle %{ #include "listicle.h" %} %include listicle.h %rename(listicle) _listicle; %extend listicle { listicle() {return malloc (sizeof(listicle));} } As you can tell by my being here asking, it doesn't work. All the various combinations I've tried each fail in their own special way. [This one: %extend defined for an undeclared class listicle. Change it to %extend _listicle (and fix the constructor) and loading in Python gives type object '_listicle' has no attribute '_listicle_swigregister'. And so on.] Suggestions?

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• how to change type of value in an php array and sorting it..is it possible ?

  - by justjoe

  hi, i got problem with my code and hopefully someone able to figure it out. The main purpose is to sort array based on its value (then reindex its numerical key). i got this sample of filename : $filename = array("index 198.php", "index 192.php", "index 144.php", "index 2.php", "index 1.php", "index 100.php", "index 111.php"); $alloutput = array(); //all of index in array foreach ($filename as $name) { preg_match('#(\d+)#', $name, $output); // take only the numerical from file name array_shift($output); // cleaned. the last code create duplicate numerical in $output, if (is_array($hasilku)) { $alloutput = array_merge($alloutput, $output); } } //try to check the type of every value in array foreach ($alloutput as $output) { if (is_array($hasil)) { echo "array true </br>"; } elseif (is_int($hasil)) { echo "integer true </br>"; } elseif (is_string($hasil)) { //the numerical taken from filename always resuld "string". echo "string true </br>"; } } the output of this code will be : Array ( [0] = 198 [1] = 192 [2] = 144 [3] = 2 [4] = 1 [5] = 100 [6] = 111 ) i have test every output in array. It's all string (and not numerical), So the question is how to change this string to integer, so i can sort it from the lowest into the highest number ? the main purpose of this code is how to output array where it had been sort from lowest to highest ?

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• Symfony2 entity field type alternatives to "property" or "__toString()"?

  - by Polmonino

  Using Symfony2 entity field type one should specify property option: $builder->add('customers', 'entity', array( 'multiple' => true, 'class' => 'AcmeHelloBundle:Customer', 'property' => 'first', )); But sometimes this is not sufficient: think about two customers with the same name, so display the email (unique) would be mandatory. Another possibility is to implement __toString() into the model: class Customer { public $first, $last, $email; public function __toString() { return sprintf('%s %s (%s)', $this->first, $this->last, $this->email); } } The disadvances of the latter is that you are forced to display the entity the same way in all your forms. Is there any other way to make this more flexible? I mean something like a callback function: $builder->add('customers', 'entity', array( 'multiple' => true, 'class' => 'AcmeHelloBundle:Customer', 'property' => function($data) { return sprintf('%s %s (%s)', $data->first, $data->last, $data->email); }, ));

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• How to map oracle timestamp to appropriate java type in hibernate?

  - by jschoen

  I am new to hibernate and I am stumped. In my database I have tables that have a columns of TIMESTAMP(6). I am using Netbeans 6.5.1 and when I generate the hibernate.reveng.xml, hbm.xml files, and pojo files it sets the columns to be of type Serializable. This is not what I expected, nor what I want them to be. I found this post on the hibernate forums saying to place: in the hibernate.reveng.xml file. In Netbeans you are not able to generate the mappings from this file (it creates a new one every time) and it does not seem to have the ability to re-generate them from the file either (at least according to this it is slated to be available in version 7). So I am trying to figure out what to do. I am more inclined to believe I am doing something wrong since I am new to this, and it seems like it would be a common problem for others. So what am I doing wrong? If I am not doing anything wrong, how do I work around this? I am using Netbeans 6.5, Oracle 10G, and I believe Hibernate 3 (it came with my netbeans). Edit: Meant to say I found this stackoverflow question, but it is really a different problem.

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• Recursive Iterators

  - by soandos

  I am having some trouble making an iterator that can traverse the following type of data structure. I have a class called Expression, which has one data member, a List<object>. This list can have any number of children, and some of those children might be other Expression objects. I want to traverse this structure, and print out every non-list object (but I do want to print out the elements of the list of course), but before entering a list, I want to return "begin nest" and after I just exited a list, I want to return "end nest". I was able to do this if I ignored the class wherever possible, and just had List<object> objects with List<object> items if I wanted a subExpression, but I would rather do away with this, and instead have an Expressions as the sublists (it would make it easier to do operations on the object. I am aware that I could use extension methods on the List<object> but it would not be appropriate (who wants an Evaluate method on their list that takes no arguments?). The code that I used to generate the origonal iterator (that works) is: public IEnumerator GetEnumerator(){ return theIterator(expr).GetEnumerator(); } private IEnumerable theIterator(object root) { if ((root is List<object>)){ yield return " begin nest "; foreach (var item in (List<object>)root){ foreach (var item2 in theIterator(item)){ yield return item2; } } yield return " end nest "; } else yield return root; } A type swap of List<object> for expression did not work, and lead to a stackOverflow error. How should the iterator be implemented? Update: Here is the swapped code: public IEnumerator GetEnumerator() { return this.GetEnumerator(); } private IEnumerable theIterator(object root) { if ((root is Expression)) { yield return " begin nest "; foreach (var item in (Expression)root) { foreach (var item2 in theIterator(item)) yield return item2; } yield return " end nest "; } else yield return root; }

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• How to support comparisons for QVariant objects containing a custom type?

  - by Tyler McHenry

  According to the Qt documentation, QVariant::operator== does not work as one might expect if the variant contains a custom type: bool QVariant::operator== ( const QVariant & v ) const Compares this QVariant with v and returns true if they are equal; otherwise returns false. In the case of custom types, their equalness operators are not called. Instead the values' addresses are compared. How are you supposed to get this to behave meaningfully for your custom types? In my case, I'm storing an enumerated value in a QVariant, e.g. In a header: enum MyEnum { Foo, Bar }; Q_DECLARE_METATYPE(MyEnum); Somewhere in a function: QVariant var1 = QVariant::fromValue<MyEnum>(Foo); QVariant var2 = QVariant::fromValue<MyEnum>(Foo); assert(var1 == var2); // Fails! What do I need to do differently in order for this assertion to be true? I understand why it's not working -- each variant is storing a separate copy of the enumerated value, so they have different addresses. I want to know how I can change my approach to storing these values in variants so that either this is not an issue, or so that they do both reference the same underlying variable. It don't think it's possible for me to get around needing equality comparisons to work. The context is that I am using this enumeration as the UserData in items in a QComboBox and I want to be able to use QComboBox::findData to locate the item index corresponding to a particular enumerated value.

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• C#. Saving information about events and event handlers and removing handlers using this information

  - by Philipp

  I have an object which is creating several event handlers using lambda expressions, and I need to remove all handlers created in that object in one time. I'm trying to create some unified static object which will 'know' which handler relates to which object and event if event handler was created through this static object. I tried something like code below, but I don't understand how to save events and event handlers objects, to be able remove handlers in one time. class Program { static void Main(string[] args) { var EventSender = new EventSender(); var EventReceiver = new EventReceiver(EventSender); EventSender.Invoke(" some var "); LinkSaver.RemoveEvent(EventReceiver); // ?? Console.ReadKey(); } } public class ObjLink{ public object Event; public object Action; } public static class LinkSaver { public static void SetEvent<T>(object obj, Action<T> Event, T Action) { Event(Action); var objLink = new ObjLink{Event = Event, Action = Action}; if (!Links.ContainsKey(obj)) Links.Add(obj, new List<ObjLink>{objLink}); else Links[obj].Add(objLink); } static Dictionary<object,List<ObjLink>> Links = new Dictionary<object, List<ObjLink>>(); public static void RemoveEvent(object obj){ foreach(var objLink in Links[obj]){ // objLink.Event -= objLink.Action; ??? } } } public class EventReceiver { public EventReceiver(EventSender obj) { LinkSaver.SetEvent<EventSender.TestDelegate>(this, obj.SetEvent, str => Console.WriteLine(str + " test event!")); } } public class EventSender { public void Invoke(string var) { if (eventTest != null) eventTest(var); } public void SetEvent(TestDelegate Action) { eventTest += Action; } public delegate void TestDelegate(string var); private event TestDelegate eventTest; // by the way public void RemoveFromEvent() { foreach (var handler in eventTest.GetInvocationList()) eventTest -= (TestDelegate)handler; } }

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• problems getting HTTPRiot working

  - by bwizzy

  I've got an iphone app where I'm trying to use HTTPRiot to make some API calls to a web app. Problem is I can't see that none of the HTTPRiot delegate methods are being called. I've got a log in all the delegate methods, and I'm also looking at the webserver log. I see that the URL is being hit. //API.h #import <Foundation/Foundation.h> #include <HTTPRiot/HTTPRiot.h> @interface API : HRRestModel { } +(void)runTest; @end //API.m #import "API.h" @implementation API + (void)initialize { NSLog(@"api initialize"); [self setDelegate:self]; [self setBaseURL:[NSURL URLWithString:@"http://localhost:3000/api"]]; [self setBasicAuthWithUsername:@"demo" password:@"123456"]; NSDictionary *params = [NSDictionary dictionaryWithObject:@"1234567" forKey:@"api_key"]; [self setDefaultParams:params]; }//end initialize +(void)runTest { NSLog(@"api run test"); // Would send a request to http://localhost:1234/api/people/1?api_key=1234567 [self getPath:@"/save_diet" withOptions:nil object:nil]; } +(void)restConnection:(NSURLConnection *)connection didReturnResource:(id)resource object:(id)object { NSLog(@"didReturnResource"); } +(void)restConnection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse *)response object:(id)object { NSLog(@"didReceiveResponse"); } +(void)restConnection:(NSURLConnection *)connection didReceiveParseError:(NSError *)error responseBody:(NSString *)body object:(id)object { NSLog(@"didReceiveParseError"); } +(void)restConnection:(NSURLConnection *)connection didReceiveError:(NSError *)error response:(NSHTTPURLResponse *)response object:(id)object { NSLog(@"didReceiveError"); } +(void)restConnection:(NSURLConnection *)connection didFailWithError:(NSError *)error object:(id)object { NSLog(@"didFailWithError"); } @end //test code [API runTest]; //log output

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• Undefined javascript function?

  - by user74283

  Working on a google maps project and stuck on what seems to be a minor issue. When i call displayMarkers function firebug returns: ReferenceError: displayMarkers is not defined [Break On This Error] displayMarkers(1); <script type="text/javascript"> function initialize() { var center = new google.maps.LatLng(25.7889689, -80.2264393); var map = new google.maps.Map(document.getElementById('map'), { zoom: 10, center: center, mapTypeId: google.maps.MapTypeId.ROADMAP }); //var data = [[25.924292, -80.124314], [26.140795, -80.3204049], [25.7662857, -80.194692]] var data = {"crs": {"type": "link", "properties": {"href": "http://spatialreference.org/ref/epsg/4326/", "type": "proj4"}}, "type": "FeatureCollection", "features": [{"geometry": {"type": "Point", "coordinates": [25.924292, -80.124314]}, "type": "Feature", "properties": {"industry": [2], "description": "hosp", "title": "shaytac hosp2"}, "id": 35}, {"geometry": {"type": "Point", "coordinates": [26.140795, -80.3204049]}, "type": "Feature", "properties": {"industry": [1, 2], "description": "retail", "title": "shaytac retail"}, "id": 48}, {"geometry": {"type": "Point", "coordinates": [25.7662857, -80.194692]}, "type": "Feature", "properties": {"industry": [2], "description": "hosp2", "title": "shaytac hosp3"}, "id": 36}]} var markers = []; for (var i = 0; i < data.features.length; i++) { var latLng = new google.maps.LatLng(data.features[i].geometry.coordinates[0], data.features[i].geometry.coordinates[1]); var marker = new google.maps.Marker({ position: latLng, title: console.log(data.features[i].properties.industry[0]), map: map }); marker.category = data.features[i].properties.industry[0]; marker.setVisible(true); markers.push(marker); } function displayMarkers(category) { var i; for (i = 0; i < markers.length; i++) { if (markers[i].category === category) { markers[i].setVisible(true); } else { markers[i].setVisible(false); } } } } google.maps.event.addDomListener(window, 'load', initialize); </script> <div id="map-container"> <div id="map"></div> </div> <input type="button" value="Retail" onclick="displayMarkers(1);">

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• ADO.NET Data Services Media type requires a ';' character before a parameter definition.

  - by idahosaedokpayi

  I am experimenting with ADO.NET and I am seeing this error on the second attempt to browse the service: <?xml version="1.0" encoding="utf-8" standalone="yes" ?> <error xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata"> <code /> <message xml:lang="en-US">Media type requires a ';' character before a parameter definition.</message> </error> The first attempt is normal. I am working with an exactly identical service on an internal development network and it is fine. I am including my connection string: <add name="J4Entities" connectionString="metadata=res://*;provider=System.Data.SqlClient;provider connection string=&quot;Data Source=MNSTSQL01N;Initial Catalog=J4;Integrated Security=True;MultipleActiveResultSets=True&quot;" providerName="System.Data.EntityClient"/> and my Data service class: using System; using System.Data.Services; using System.Collections.Generic; using System.Linq; using System.ServiceModel.Web; public class Data : DataService< J4Model.J4Entities > { // This method is called only once to initialize service-wide policies. public static void InitializeService(IDataServiceConfiguration config) { // TODO: set rules to indicate which entity sets and service operations are visible, updatable, etc. // Examples: config.SetEntitySetAccessRule("*", EntitySetRights.AllRead); // config.SetServiceOperationAccessRule("MyServiceOperation", ServiceOperationRights.All); } } Is there something obvious I am not doing?

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• App Engine - Query using a class member as parameter

  - by Zach

  I have a simple class, relevant details below: @PersistenceCapable(identityType = IdentityType.APPLICATION) public class SimpleCategory implements Serializable{ ... public static enum type{ Course, Category, Cuisine } @Persistent public type t; ... } I am attempting to query all SimpleCategory objects of the same type. public SimpleCategory[] getCategories(SimpleCategory.type type) { PersistenceManager pm = PMF.get().getPersistenceManager(); try{ Query q = pm.newQuery(SimpleCategory.class); q.setFilter("t == categoryType"); q.declareParameters("SimpleCategory.type categoryType"); List<SimpleCategory> cats = (List<SimpleCategory>) q.execute(type); ... } This results in a ClassNotResolvedException for SimpleCategory.type. The google hits I've found so far recommended to: Use query.declareImports to specify the class i.e. q.declareImports("com.test.zach.SimpleCategory.type"); Specify the fully qualified name of SimpleCategory in declareParameters Neither of these suggestions has worked. By removing .type and recompiling, I can verify that declareParameters can see SimpleCategory just fine, it simply cannot see the SimpleCategory.type, despite the fact that the remainder of the method has full visibility to it. What am I missing?

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• Why would dynamically changing the stroke type of a GestureOverlayView cause unusual behaviour?

  - by Rob Kent

  I recently introduced multi-stroke gestures into my application. This is a preference so I set the StrokeType dynamically in Activity.OnCreate. What I have discovered is that if you change the StrokeType so that it is different to the setting in the layout file, it changes the behaviour of the GestureOverlayView in the following way. The normal behaviour is that you draw a gesture and it stays on the screen after it is drawn. When you change the stroke type dynamically however, any gesture drawn on the screen disappears immediately after the OnGestureEnded event has fired. I reloaded the sample GesturesBuilder application and confirmed it has the same problem if you add the second line shown here: GestureOverlayView overlay = (GestureOverlayView) findViewById(R.id.gestures_overlay); overlay.setGestureStrokeType(GestureOverlayView.GESTURE_STROKE_TYPE_SINGLE); overlay.addOnGestureListener(new GesturesProcessor()); } The default in the layout is MULTIPLE but changing it to single changes the behaviour. If you keep the above line but set it to what it already is, the behaviour is not affected. Is this a bug in the Android gestures library and does anyone know a workaround? Note that this is on an HTC Magic so it could also be a handset issue.

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• Synchronize write to two collections

  - by glaz666

  I need to put some value to maps if it is not there yet. The key-value (if set) should always be in two collections (that is put should happen in two maps atomically). I have tried to implement this as follows: private final ConcurrentMap<String, Object> map1 = new ConcurrentHashMap<String, Object>(); private final ConcurrentMap<String, Object> map2 = new ConcurrentHashMap<String, Object>(); public Object putIfAbsent(String key) { Object retval = map1.get(key); if (retval == null) { synchronized (map1) { retval = map1.get(key); if (retval == null) { Object value = new Object(); //or get it somewhere synchronized (map2) { map1.put(key, value); map2.put(key, new Object()); } retval = value; } } } return retval; } public void doSomething(String key) { Object obj1 = map1.get(key); Object obj2 = map2.get(key); //do smth } Will that work fine in all cases? Thanks

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• Perl : In splice() type of arg1 must be array, cannot be scalar dereference. How to fix?

  - by Michael Mao

  I am trying to comprehend the reference/dereference system in Perl. What I am trying to do is to remove an element by using reference: my $ref= \@{$collection{$_[0]}}; # delete($$ref[$i]); # delete works, I've tested that already splice($$ref, $i, 1); # this wouldn't do. I first tried the delete() subroutine, it works; however, it doesn't shift the index after the removed elements forward by 1, so I cannot continue working on other stuff. I then Googled and found the splice() subroutine which does delete and shift in one go. But the error feedback tells me that "Type of arg 1 to splice must be array (not scalar dereference)..." I then tried something like this: splice(@{$$ref}, $i, 1); That resulted in another error like this: "Not a SCALAR reference at...(pointing at that line)" So I am a bit puzzled, how could I handle this issue? I prefer not using any CPAN or additional library for the solution, if possible.

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• Wouldn't it be nice to have a type variable referring to the class's instance.

  - by user93197

  I often have a pattern like this: class VectorBase<SubClass, Element> where SubClass : VectorBase<SubClass, Element>, new() where Element : Addable<Element> { Element[] data; public VectorBase(Element[] data) { this.data = data; } public SubClass add(SubClass second) { Element[] newData = new Element[data.Length]; for (int i = 0; i < newData.Length; i++) { newData[i] = data[i].add(second.data[i]); } SubClass result = new SubClass(); result.data = newData; return result; } } class VectorInt : VectorBase<VectorInt, Int32> { } class MyInt : Addable<MyInt> { int data; public MyInt(int data) { this.data = data; } public MyInt add(MyInt t) { return new MyInt(data + t.data); } } interface Addable<T> { T add(T t); } But I would rather just have: class VectorBase2<Element> where Element : Addable<Element> { Element[] data; public VectorBase(Element[] data) { this.data = data; } public SubClass add(SubClass second) { Element[] newData = new Element[data.Length]; for (int i = 0; i < newData.Length; i++) { newData[i] = data[i].add(second.data[i]); } SubClass result = new SubClass(data); return result; } } class VectorInt2 : VectorBase2<Int32> { } Why not make the subclass type available to all classes? Is this technically impossible?

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• How do I cast from int to generic type Integer?

  - by Rob Kent

  I'm relatively new to Java and am used to generics in C# so have struggled a bit with this code. Basically I want a generic method for getting a stored Android preference by key and this code, albeit ugly, works for a Boolean but not an Integer, when it blows up with a ClassCastException. Can anyone tell me why this is wrong and maybe help me improve the whole routine (using wildcards?)? public static <T> T getPreference(Class<T> argType, String prefKey, T defaultValue, SharedPreferences sharedPreferences) { ... try { if (argType == Boolean.class) { Boolean def = (Boolean) defaultValue; return argType.cast(sharedPreferences.getBoolean(prefKey, def)); } else if (argType == Integer.class) { Integer def = (Integer) defaultValue; return argType.cast(sharedPreferences.getInt(prefKey, def)); } else { AppGlobal.logWarning("getPreference: Unknown type '%s' for preference '%s'. Returning default value.", argType.getName(), prefKey); return defaultValue; } } catch (ClassCastException e) { AppGlobal.logError("Cast exception when reading pref %s. Using default value.", prefKey); return defaultValue; } } I've tried various ways - using the native int, casting to an Integer, but nothing works.

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• How to strongly type properties in JavaScript that map to models in C# ?

  - by Roberto Sebestyen

  I'm not even sure if I worded the question right, but I'll try and explain as clearly as possible with an example: In the following example scenario: 1) Take a class such as this: public class foo { public string firstName {get;set;} public string lastName {get;set} } 2) Serialize that into JSON, pass it over the wire to the Browser. 3) Browser de-serializes this and turns the JSON into a JavaScript object so that you can then access the properties like this: var foo = deSerialize("*******the JSON from above**************"); alert(foo.firstName); alert(foo.lastName); What if now a new developer comes along working on this project decides that firstName is no longer a suitable property name. Lets say they use ReSharper to rename this property, since ReSharper does a pretty good job at finding (almost) all the references to the property and renaming them appropriately. However ReSharper will not be able to rename the references within the JavaScript code (#3) since it has no way of knowing that these also really mean the same thing. Which means the programmer is left with the responsibility of manually finding these references and renaming those too. The risk is that if this is forgotten, no one will know about this error until someone tests that part of the code, or worse, slip through to the customer. Back to the actual question: I have been trying to think of a solution to this to some how strongly type these property names when used in javascript, so that a tool like ReSharper can successfully rename ALL usages of the property? Here is what I have been thinking for example (This would obviously not work unless i make some kind of static properties) var foo = deSerialize("*******the JSON from above**************"); alert(foo.<%=foo.firstName.GetPropertyName()%>) alert(foo.<%=foo.lastName.GetPropertyName()%>) But that is obviously not practical. Does anyone have any thoughts on this? Thanks, and kudos to all of the talented people answering questions on this site.

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• The type or namespace name 'WebControls' could not be found (are you missing a using directive or an assembly reference?)

  - by user1467175

  I encountered this error: The type or namespace name 'WebControls' could not be found (are you missing a using directive or an assembly reference?) Source Error: Line 28: Login Login1 = (WebControls.Login)LoginView1.FindControl("Login1"); // here the error code Line 29: TextBox UserName = (TextBox)Login1.FindControl("UserName"); Line 30: TextBox FailureText = (TextBox)Login1.FindControl("FailureText"); I did some research and the solution was to add this into the source code: System.Web.UI.WebControls.Login but I have no idea where this code can be add into. At first I tried putting it as a namespace, but it was wrong. Anyone can tell me where should I place this code at?? EDIT protected void Login1_LoginError(object sender, System.EventArgs e) { //Login Login1 = (WebControls.Login).LoginView1.FindControl("Login1"); Login Login1 = (System.Web.UI.WebControls.Login)LoginView1.FindControl("Login1"); TextBox UserName = (TextBox)Login1.FindControl("UserName"); TextBox FailureText = (TextBox)Login1.FindControl("FailureText"); //There was a problem logging in the user //See if this user exists in the database MembershipUser userInfo = Membership.GetUser(UserName.Text); if (userInfo == null) { //The user entered an invalid username... FailureText.Text = "There is no user in the database with the username " + UserName.Text; } else { //See if the user is locked out or not approved if (!userInfo.IsApproved) { FailureText.Text = "When you created your account you were sent an email with steps to verify your account. You must follow these steps before you can log into the site."; } else if (userInfo.IsLockedOut) { FailureText.Text = "Your account has been locked out because of a maximum number of incorrect login attempts. You will NOT be able to login until you contact a site administrator and have your account unlocked."; } else { //The password was incorrect (don't show anything, the Login control already describes the problem) FailureText.Text = string.Empty; } } }

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• Acessing a struct member, using a pointer to a vector of structs. Error:base operand of '->' has non-pointer type

  - by Matt Munson

  #include <iostream> #include <vector> using namespace std; struct s_Astruct { vector <int> z; }; int main () { vector <s_Astruct> v_a; for(int q=0;q<10;q++) { v_a.push_back(s_Astruct()); for(int w =0;w<5;w++) v_a[q].z.push_back(8); } vector <s_Astruct> * p_v_a = & v_a; cout << p_v_a[0]->z[4]; //error: base operand of '->' has non-pointer type //'__gnu_debug_def::vector<s_Astruct, std::allocator<s_Astruct> >' } There seems to be some issue with this sort of operation that I don't understand. In the code that I'm working on I actually have things like p_class-vector[]-vector[]-int; and I'm getting a similar error.

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