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  • Why does Java think my object is a variable?

    - by user2896898
    Ok so I'm trying to make a simple pong game. I have a paddle that follows the mouse and a ball that bounces around. I wrote a method collidesWith(Sprite s) inside of my Sprite class that checks if the ball collides with the paddle (this works and isn't the problem). I have two objects extending my sprite class, a ball and a paddle object. So inside of my ball class I'm trying to check if it collides with the paddle. So I've tried if(this.collidesWith(paddle) == true){ System.out.println("They touched"); } I've also tried ball.collidesWith(paddle) and other combinations but it always says the same thing about the paddle (and the ball when I use ball.collidesWith) "Cannot find symbol. Symbol: variable paddle(or ball). Location: class Ball" So if I'm reading this right, it thinks that the paddle (and ball) are variables and it's complaining because it can't find them. How can I make it understand I am passing in objects, not variables? For extra information, an earlier assignment had me make two boxes and for them to change colors when they were colliding. In that assignment I used very similar code to above with if(boxOne.collidesWith(boxTwo) == true){ System.out.println("yes"); } And in this code it worked just fine. The program knew that boxOne and boxTwo were child classes of my Sprite class. Anyone know why they wouldn't work the same?

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  • Integration testing - can it be done right?

    - by Max
    I used TDD as a development style on some projects in the past two years, but I always get stuck on the same point: how can I test the integration of the various parts of my program? What I am currently doing is writing a testcase per class (this is my rule of thumb: a "unit" is a class, and each class has one or more testcases). I try to resolve dependencies by using mocks and stubs and this works really well as each class can be tested independently. After some coding, all important classes are tested. I then "wire" them together using an IoC container. And here I am stuck: How to test if the wiring was successfull and the objects interact the way I want? An example: Think of a web application. There is a controller class which takes an array of ids, uses a repository to fetch the records based on these ids and then iterates over the records and writes them as a string to an outfile. To make it simple, there would be three classes: Controller, Repository, OutfileWriter. Each of them is tested in isolation. What I would do in order to test the "real" application: making the http request (either manually or automated) with some ids from the database and then look in the filesystem if the file was written. Of course this process could be automated, but still: doesn´t that duplicate the test-logic? Is this what is called an "integration test"? In a book i recently read about Unit Testing it seemed to me that integration testing was more of an anti-pattern?

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  • (Java) Get value of string loaded into dynamic-type object?

    - by Michael
    I'm very new to Java (~10 days), so my code is probably pretty bad, but here's what I've got: ArgsDataHolder argsData = new ArgsDataHolder(); // a class that holds two // ArrayList's where each element // representing key/value args Class thisArgClass; String thisArgString; Object thisArg; for(int i=2; i< argsString.length; i++) { thisToken = argsString[i]; thisArgClassString = getClassStringFromToken(thisToken).toLowerCase(); System.out.println("thisArgClassString: " + thisArgClassString); thisArgClass = getClassFromClassString(thisArgClassString); // find closing tag; concatenate middle Integer j = new Integer(i+1); thisArgString = getArgValue(argsString, j, "</" + thisArgClassString + ">"); thisArg = thisArgClass.newInstance(); thisArg = thisArgClass.valueOf(thisArgString); argsData.append(thisArg, thisArgClass); } The user basically has to input a set of key/value arguments into the command prompt in this format: <class>value</class>, e.g. <int>62</int>. Using this example, thisArgClass would be equal to Integer.class, thisArgString would be a string that read "62", and thisArg would be an instance of Integer that is equal to 62. I tried thisArg.valueOf(thisArgString), but I guess valueOf(<String>) is only a method of certain subclasses of Object. For whatever reason, I can't seem to be able to cast thisArg to thisArgClass (like so: thisArg = (thisArgClass)thisArgClass.newInstance();, at which point valueOf(<String>) should become accessible. There's got to be a nice, clean way of doing this, but it is beyond my abilities at this point. How can I get the value of the string loaded into a dynamically-typed object (Integer, Long, Float, Double, String, Character, Boolean, etc.)? Or am I just overthinking this, and Java will do the conversion for me? :confused:

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  • Container of Generic Types in java

    - by Cyker
    I have a generic class Foo<T> and parameterized types Foo<String> and Foo<Integer>. Now I want to put different parameterized types into a single ArrayList. What is the correct way of doing this? Candidate 1: public class MMM { public static void main(String[] args) { Foo<String> fooString = new Foo<String>(); Foo<Integer> fooInteger = new Foo<Integer>(); ArrayList<Foo<?> > list = new ArrayList<Foo<?> >(); list.add(fooString); list.add(fooInteger); for (Foo<?> foo : list) { // Do something on foo. } } } class Foo<T> {} Candidate 2: public class MMM { public static void main(String[] args) { Foo<String> fooString = new Foo<String>(); Foo<Integer> fooInteger = new Foo<Integer>(); ArrayList<Foo> list = new ArrayList<Foo>(); list.add(fooString); list.add(fooInteger); for (Foo foo : list) { // Do something on foo. } } } class Foo<T> {} In a word, it is related to the difference between Foo<?> and the raw type Foo. Update: Grep What is the difference between the unbounded wildcard parameterized type and the raw type? on this link may be helpful.

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  • Null reference but it's not?

    - by Clint Davis
    This is related to my previous question but it is a different problem. I have two classes: Server and Database. Public Class Server Private _name As String Public Property Name() As String Get Return _name End Get Set(ByVal value As String) _name = value End Set End Property Private _databases As List(Of Database) Public Property Databases() As List(Of Database) Get Return _databases End Get Set(ByVal value As List(Of Database)) _databases = value End Set End Property Public Sub LoadTables() Dim db As New Database(Me) db.Name = "test" Databases.Add(db) End Sub End Class Public Class Database Private _server As Server Private _name As String Public Property Name() As String Get Return _name End Get Set(ByVal value As String) _name = value End Set End Property Public Property Server() As Server Get Return _server End Get Set(ByVal value As Server) _server = value End Set End Property Public Sub New(ByVal ser As Server) Server = ser End Sub End Class Fairly simple. I use like this: Dim s As New Server s.Name = "Test" s.LoadTables() The problem is in the LoadTables in the Server class. When it hits Databases.Add(db) it gives me a NullReference error (Object reference not set). I don't understand how it is getting that, all the objects are set. Any ideas? Thanks.

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  • How to check if TypeIdenitifier(T) is an Object?

    - by John
    I'm creating a generic list class that has a member of type Array(Array of ). The problem is the class descruction,because the class is supposed to be used for types from byte to types inheriting TObject. Specifically: destructor Destroy; var elem:T; begin /*if(T is Tobject) then //Check if T inherits TObject {Compiler error!} for elem in FData do TObject(elem).Free;*/ // do not know how to do it SetLength(FItems,0); //FItems : Array of T inherited Destroy; end; How do I check if T is TObject so I can free every member if the typeidenitifier is a class,for example?

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  • Singelton restricted to instance of dll

    - by codeySmurf
    If I create a singleton class in the context of a dll, the singleton class is instantiated once and used by all instances of the dll. I am using a dll as a plug-in for an application. Now the following thing came to my mind: If I use a singleton Class, it will be shared across multiple instances of the plug-in. However, this makes it difficult to manage the lifetime of the singleton class efficiently. The only way I could think of would be to use a reference count and to make the singleton delete its self when the reference count is 0. Does anyone have any better ideas on that? Is there any good way to restrict the singleton object to one instance of the dll? Language is c++

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  • "Add another item" form functionality

    - by GSTAR
    I have a form that lets a user enter their career history - it's a very simple form with only 3 fields - type (dropdown), details (textfield) and year (dropdown). Basically I want to include some dynamic functionality whereby the user can enter multiple items on the same page and then submit them all in one go. I had a search on Google and found some examples but they were all based on tables - my markup is based on DIV tags: <div class="form-fields"> <div class="row"> <label for="type">Type</label> <select id="type" name="type"> <option value="Work">Work</option> </select> </div> <div class="row"> <label for="details">Details</label> <input id="details" type="text" name="details" /> </div> <div class="row"> <label for="year">Year</label> <select id="year" name="year"> <option value="2010">2010</option> </select> </div> </div> So basically the 3 DIV tags with class "row" need to be duplicated, or to simplify things - the div "form-fields" could just be duplicated. I am also aware that the input names would have to converted to array format. Additionally each item will require a "remove" button. There will be a main submit button at the bottom which submits all the data. Anyone got an elegant solution for this?

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  • How do I write a Guice Provider that doesn't explicitly create objects?

    - by ripper234
    Say I have a ClassWithManyDependencies. I want to write a Guice Provider for this class, in order to create a fresh instance of the class several times in my program (another class will depend on this Provider and use it at several points to create new instances). One way to achieve this is by having the Provider depend on all the dependencies of ClassWithManyDependencies. This is quite ugly. Is there a better way to achieve this? Note - I certainly don't want the Provider to depend on the injector. Another option I considered is having ClassWithManyDependencies and ClassWithManyDependenciesProvider extend the same base class, but it's butt ugly.

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  • Trying to change img src if another element is visible with jQuery

    - by R.J.
    I have a div ("panel" class) on my page that toggles open/closed on the click of a paragraph element ("flip" class), which has an image inside of it. Here's the HTML: <div class="panel">Contact info</div> <p class="flip"><img src="images/contactExpand.png" />Expand</p> And the jQuery: $(".flip").click(function(){ $(".panel").slideToggle("slow"); }); Everything works fine so far, but I want the image src to change to "contactCollapse.png" when the panel div is visible. This doesn't seem to do anything (image just stays the same): if ($(".panel").is(":visible") == true) { $(".flip img").attr("src","../images/contactCollapse.png") } else { $(".flip img").attr("src","../images/contactExpand.png") } Am I missing something? Thanks for any help!

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  • Problems with capturing an event in child object in Actionscript

    - by Raigomaru
    I have two classes. The first one (the starting class): package { import flash.display.Sprite; import flash.events.KeyboardEvent; import tetris.*; public class TetrisGame extends Sprite { private var _gameWell:Well; public function TetrisGame() { _gameWell = new Well(); addChild(_gameWell); } } } The second: package tetris { import flash.display.Sprite; import flash.events.KeyboardEvent; public class Well extends Sprite { public function Well() { super(); addEventListener(KeyboardEvent.KEY_DOWN, onKeyboard); } private function onKeyboard():void { //some code is here } } } But when I press any buttons on my keyboard, the child class Well doesn't have any reaction. What's the problem?

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  • Inferring type from method generics

    - by ng
    I am from a Java background and I am looking from the equivalent in c# for the following. public interface Reader { <T> T read(Class<? extends T> type); } Such that I can do the following, constraining the parameter and inferring the return type. Cat cat = reader.read(Cat.class); Dog dog = reader.read(Dog.class); I was hoping something like this would work in c# but I am not sure it will. public interface Reader { T Read<T>(); } And and do this. public class TypeReader : Reader { public T Read<T>() { Type type = T.GetType(); ... } } Is something like this even possible in c#?

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  • How can I use the HTML5 <button> tag in Drupal 6

    - by Frankie Yale
    I have the following HTML which I'd like to use in my Drupal 6 theme. It needs to replace the search-box code. <fieldset class="search"> <input type="text" class="box font-myriad" /> <button class="btn" title="Submit Search">Search</button> </fieldset> I'm trying stuff like $vars['form']['button']['#attributes'] = array('class' => 'btn'); in template.php, but no luck so far. Couldn't find much help on drupal.org.

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  • c++ compilation error

    - by clamp
    hello, i got a compile error which i do not understand. i have a h/cpp file combination that does not contain a class but just defines some utility functions. when i try to use a struct that is defined in another class i get the error: error C2027: use of undefined type so, stripped down to the problem, the h file looks like this namespace A { void foo(B::C::SStruct const & Var); } the definition of SStruct is in a class which is in another h-file, that is of course included. namespace B { Class C { struct SStruct { }; } } what am i missing here? thanks!

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  • A strange error in java generic.

    - by ???
    This is ok: Class<? extends String> stringClass = "a".getClass(); But this gets error: <T> void f(T obj) { Class<? extends T> objClass = obj.getClass(); } I know I can cast it like: <T> void f(T obj) { @SuppressWarnings("unchecked") Class<? extends T> objClass = (Class<? extends T>) obj.getClass(); } But why the previous error? Will the next release of Java 7 will support such usage?

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  • Avoiding sub-type selection in view code

    - by John Donoghue
    Hi, I have some code where the model contains some classes like (vb.net pseudocode, but could be any OO language): Enum AttributeType Boolean Date String End Enum MustInherit Class Attibute Must Override Function Type As AttributeType End Class Class BooleanAttribute: Attribute Function Type As AttributeType Return AttributeType.Boolean End Function End Class And the view contains some code like: Select Case AttributeType Case Boolean //Display checkbox control Case Date //Display date picker control Case String //Display textbox control End Select I don't really like the code in the view, for the hopefully obvious reasons (what happens when I get a new attribute type etc). My question is, how should I replace it? I could easily add a method to the concrete classes, but that pollutes the model with UI stuff so that's a horrible idea. I could move the select into a factory, but that seems to be just hiding the problem. Can anybody advise a better approach?

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  • PyQt4 plugin in c++ application

    - by veverica17
    How is it posible to load python script as plugin in qt based application? The basic idea would be to make a class in c++ class b { virtual void method1(); virtual void method2(); } and 'somehow' inherit it in python like class c(b): def method1: #do something def method2: #do something I need to be able to modify the gui from python( add buttons to some widgets made in c++ with qt ). Basicaly something similiar to (gedit, blender, etc) plugin architecture with qt

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  • What is a truly empty std::vector in C++?

    - by RyanG
    I've got a two vectors in class A that contain other class objects B and C. I know exactly how many elements these vectors are supposed to hold at maximum. In the initializer list of class A's constructor, I initialize these vectors to their max sizes (constants). If I understand this correctly, I now have a vector of objects of class B that have been initialized using their default constructor. Right? When I wrote this code, I thought this was the only way to deal with things. However, I've since learned about std::vector.reserve() and I'd like to achieve something different. I'd like to allocate memory for these vectors to grow as large as possible because adding to them is controlled by user-input, so I don't want frequent resizings. However, I iterate through this vector many, many times per second and I only currently work on objects I've flagged as "active". To have to check a boolean member of class B/C on ever iteration is silly. I don't want these objects to even BE there for my iterators to see when I run through this list. Is reserving the max space ahead of time and using push_back to add a new object to the vector a solution to this?

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  • Strange C++ thread function invocation

    - by Tony
    I have the following: class DThread { virtual void run()=0; _beginthreadex(NULL,0,tfunc,this,0,&m_UIThreadID); // class itself being passed as param to thread function... static unsigned int __stdcall tfunc(void* thisptr) { static_cast<DThread*>(thisptr)->run(); return 0; } //other stuff } The run function is implemented in a derived class. Why is the function that's being called in the thread being called through a cast this pointer? Is this good practise? Can't it just be called directly? The actual function needing to run is in the derived class. My question is

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  • how to get something to display only once in a while loop

    - by Matt Nathanson
    I've got a mysql query running and it checks to see if an iterator is equal to 1, then display this div title... if ($this->dliterator == 1) {echo "<div class='clientsection' id='downloads'>Downloads</div><br/>";}; The problem is, is that the dl iterator may not necessarily start at 1. (it is directly related to a downloadid from the database). How can I get this to display only for the first time through the loop ONLY? while ($row = mysql_fetch_assoc($result)) { if ($row['download'] != null){ if ($this->dliterator == 1) {echo "<div class='clientsection' id='downloads'>Downloads</div><br/>";}; if ($editDownload == 1) { echo "<div class='clientlink' style='margin-top: 15px;'>"; echo "<input name='downloads[$this->dliterator][name]' type='text' id='download$this->dliterator' value='" . $row['download'] . "'/>"; echo "<input name='downloads[$this->dliterator][title]' type='text' id='downloadtitle$this->dliterator' value='" . $row['downloadtitle'] . "'/>"; echo "<img class='removelink' src='/images/deletelink.png' width='15' />"; echo "<input id='downloadid' name='downloads[$this->dliterator][id]' type='hidden' value='".$row['downloadid']."' style='display: none'/>"; echo "<br/><img id='uploaddownload$uploaditerator' class='uploaddownload' src='../images/upload.png' width='80'/>"; echo "</div>"; }; }; $this->dliterator++; $uploaditerator++; };

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  • Django - Problem with models/manager to organise a query...

    - by user296644
    Hi, I have an application to count the number of access to an object for each website in a same database. class SimpleHit(models.Model): """ Hit is the hit counter of a given object """ content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey('content_type', 'object_id') site = models.ForeignKey(Site) hits_total = models.PositiveIntegerField(default=0, blank=True) [...] class SimpleHitManager(models.Manager): def get_query_set(self): print self.model._meta.fields qset = super(SimpleHitManager, self).get_query_set() qset = qset.filter(hits__site=settings.SITE_ID) return qset class SimpleHitBase(models.Model): hits = generic.GenericRelation(SimpleHit) objects = SimpleHitManager() _hits = None def _db_get_hits(self, only=None): if self._hits == None: try: self._hits = self.hits.get(site=settings.SITE_ID) except SimpleHit.DoesNotExist: self._hits = SimpleHit() return self._hits @property def hits_total(self): return self._db_get_hits().hits_total [...] class Meta: abstract = True And I have a model like: class Model(SimpleHitBase): name = models.CharField(max_length=255) url = models.CharField(max_length=255) rss = models.CharField(max_length=255) creation = AutoNowAddDateTimeField() update = AutoNowDateTimeField() So, my problem is this one: when I call Model.objects.all(), I would like to have one request for the SQL (not two). In this case: one for Model in order to have information and one for the hits in order to have the counter (hits_total). This is because I cannot call directly hits.hits_total (due to SITE_ID?). I have tried select_related, but it seems to do not work... Question: - How can I add column automatically like (SELECT hits.hits_total, model.* FROM [...]) to the queryset? - Or use a functional select_related with my models? I want this model could be plugable on all other existing model. Thank you, Best regards.

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  • PHP: constant as variable in function

    - by m4recek
    I'm trying to use constant as a function paramter, is it possible to check type of this constant. Example of what I want: class ApiError { const INVALID_REQUEST = 200; } class Response { public function status(ApiError $status) { //function code here } } USE: $response = new Response(); $response->status(ApiError::INVALID_REQUEST); This shoud check that given $status is constant of class ApiError. Is something like this possible?

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  • Tracking changed (unsaved) objects

    - by Eric
    I have a class which is serialized to and from an XML file when the user decided to open or save. I'm trying to add the typical functionality where when they try to close the form with un-saved changes the form warns them and gives them the option of saving before closing. I've added a HasUnsavedChanges property to my class, which my form checks before closing. However, it's a little annoying that my properties have changed from something like this .. public string Name { get; set; } to this... private string _Name; public string Name { get { return _Name; } set { this._Name = value; this.HasUnsavedChanges = true; } } Is there a better way to track changes to an instance of a class? For example is there some standard way I can "hash" an instance of a class into a value that I can use to compare the most recent version with the saved version without mucking up every property in the class?

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