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  • WPF Databinding With A Collection Object

    - by Randster
    Argh, although I've been googling, I really would appreciate it if someone could break my problem down as all the code examples online are confusing me more than assisting (perhaps it's just late)... I have a simple class as defined below: public class Person { int _id; string _name; public Person() { } public int ID { get { return _id; } set { _id = value; } } public string Name { get { return _name; } set { _name = value; } } } that is stored in a database, and thru a bit more code I put it into an ObservableCollection object to attempt to databind in WPF later on: public class People : ObservableCollection<Person> { public People() : base() { } public void Add(List<Person> pListOfPeople) { foreach (Person p in pListOfPeople) this.Add(p); } } In XAML, I have myself a ListView that I would like to populate a ListViewItem (consisting of a textblock) for each item in the "People" object as it gets updated from the database. I would also like that textblock to bind to the "Name" property of the Person object. I thought at first that I could do this: lstPeople.DataContext = objPeople; where lstPeople is my ListView control in my XAML, but that of course does nothing. I've found TONS of examples online where people through XAML create an object and then bind to it through their XAML; but not one where we bind to an instantiated object and re-draw accordingly. Could someone please give me a few pointers on: A) How to bind a ListView control to my instantiated "People" collection object? B) How might I apply a template to my ListView to format it for the objects in the collection? Even links to a decent example (not one operating on an object declared in XAML please) would be appreciated. Thanks for your time.

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  • CArray doesn't call copy constructors on memory reallocations, now what?

    - by MMx
    Suppose I have a class that requires copy constructor to be called to make a correct copy of: struct CWeird { CWeird() { number = 47; target = &number; } CWeird(const CWeird &other) : number(other.number), target(&number) { } void output() { printf("%d %d\n", *target, number); } int *target, number; }; Now the trouble is that CArray doesn't call copy constructors on its elements when reallocating memory (only memcpy from the old memory to the new), e.g. this code CArray<CWeird> a; a.SetSize(1); a[0].output(); a.SetSize(2); a[0].output(); results in 47 47 -572662307 47 I don't get this. Why is it that std::vector can copy the same objects properly and CArray can't? What's the lesson here? Should I use only classes that don't require explicit copy constructors? Or is it a bad idea to use CArray for anything serious?

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  • AS3 colorTransform over multiple frames?

    - by user359519
    (Flash Professional, AS3) I'm working on a custom avatar system where you can select various festures and colors. For example, I have 10 hairstyles, and a colorPicker to change the color. mc_myAvatar has 10 frames. Each frame has a movieclip of a different hairstyle (HairStyle1, HairStyle2, etc.) Here's my code: var hairColor:ColorTransform; hairColor = mc_myAvatar.hair.colorLayer.transform.colorTransform; hairColor.color = 0xCCCC00; mc_myAvatar.hair.colorLayer.transform.colorTransform = hairColor; This correctly changes the initial color. I have a "nextHair" button to advance mc_myAvatar.hair to the next frame. When I click the button, I get an error message saying that I have a null object reference. I added a trace, and mc_myAvatar.hair.colorLayer is null on frame 2. Why??? I've clearly named HairStyle2 as "colorLayer" in frame 2. I think the problem is related to me using the same name for different classes/movieclips, but I don't know how to fix the problem... I added a square movieclip below my hairStyle movieclips, named the square "colorLevel", and deleted the name from my hairStyle clips. When I click the next button, the square correctly maintains the color from frame to frame. However, having a square doesn't do me much good. :( I tried converting the hairStyle layer to a mask. Doing this, however, results in yet another "null object" error - mc_myAvatar.hair.colorLayer is null after frame 1. I even tried "spanning" my colorLevel across all frames (no keyframes), thinking that this would give me just one movieclip to work with. No luck. Same error! What's going on, here? Why am I getting these null objects, when they are clearly defined in my movieclip? I'm also open to suggestions on a better way to do multiple frames and colors.

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  • How to enforce jsf to create new instance of bean instead of throwing NullPointerException?

    - by Roman
    I'm almost sure that I do something wrong and thus the question's title is a bit incorrect. I have a form with several fields for creating a new User-objects (fields like login, password, birthday etc). And I have 2 buttons - Cancel and Create. I didn't finish Create yet :) , but when I press Cancel I see NullPointerException. Here is simplified code: <f:view> <h:form> <h:panelGroup layout="block"> <h:inputText id="add_login" value="#{userSupport.user.login}"/> <h:inputSecret id="add_password" value="#{userSupport.user.password}"/> <h:inputText id="add_name" value="#{userSupport.user.name}"/> <h:inputText id="add_surname" value="#{userSupport.user.surname}"/> <h:commandButton value="Cancel" action="cancel"/> </h:panelGroup> </h:form> </f:view> UserSupport class has field user with getter and setter and some other methods. It's a Spring bean with Session scope. When I press cancel, I see NPE because jsf tries to save values from inputs in user-object, but user-object is null. What is the correct way of doing this?

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  • Which Java debugger do *you* use.

    - by mikevdg
    I spend a lot of time debugging applications in Eclipse using JPDA. There are a few issues with the Eclipse debugger which really annoy me. Can anybody recommend plug-ins, better debuggers or perhaps tricks that I don't know of yet? In the "Variables" tab, you can type in and execute bits of Java code. However, you first need to click on something (I usually click on "this") to give it some context. Then, after you've typed in a lengthy Java expression to debug something and "execute" it, your expression gets replaced with the result, so you need to type it in all over again. Is there some better way, such as a console or something that I'm missing? When you're poking through data structures, the presentation in the debugger leaves much to be desired. You see the internal representation of Lists, Maps, StringBuilders etc. What I want to see is what these objects conceptually contain. Is there a way of doing this, perhaps using some other debugger, or an extension or something? When an Exception is thrown, is there some way of inspecting the state of the application where the Exception was thrown? Currently I need to set breakpoints just before the Exception occurs and then try to reproduce it. When I'm stepping over a line with many statements on it, I can't actually see which of those statements is being executed, except by "stepping in" to each one to see where it takes me. If no source code is found, Eclipse just stares blankly at you. You get a helpful screen saying "Class File Editor / Source code not found" which is completely useless. I'd much prefer to be able to step through the bytecodes so I can at least see what is going on. Does anybody know of a Java debugger that does this better than Eclipse?

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  • XNA, C# - Check if a Vector2 path crosses another Vector2 path.

    - by Nick
    Hello all, I have an XNA question for those with more experience in these matters than myself (maths). Background: I have a game that implements a boundary class, this simply hosts 2 Vector2 objects, a start and an end point. The current implementation crudely handles collision detection by assuming boundaries are always vertical or horizontal, i.e. if start.x and end.x are the same check I am not trying to pass x etc. Ideally what I would like to implement is a method that accepts two Vector2 parameters. The first being a current location, the second being a requested location (where I would like to move it to assuming no objections). The method would also accept a boundary object. What the method should then do is tell me if I am going to cross the boundry in this move. this could be a bool or ideally something representing how far I can actually move. This empty method might explain better than I can in words. /// <summary> /// Checks the move. /// </summary> /// <param name="current">The current.</param> /// <param name="requested">The requested.</param> /// <param name="boundry">The boundry.</param> /// <returns></returns> public bool CheckMove(Vector2 current, Vector2 requested, Boundry boundry) { //return a bool that indicated if the suggested move will cross the boundry. return true; }

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  • how to reverse an angle

    - by MissHalberd
    I am no mathematician, but I somehow got into game development as a hobby. Having never studied anything beyond basic math, I have a lot of trouble figuring out how to reverse the angle of something, facing to the opposite direction, among the X axis. One image says more than 1000 words though (specially uneducated words): http://img156.imageshack.us/i/wihwin.png/ I basically want to reverse the direction of cannon objects adhered to a robot. When the robot changes from facing right to facing left, I do (180 - angle) as everyone suggested me, but it reverses the angle...literally, making the cannons aim up when they are aiming down. So, I need to do something else, but it escapes my knowledge. Anyone would be so kind to help me with this? Oh, I use regular C by the way, in case there's something built-in specific to it. To put it in other words, I work in 2D, so I want an angle that is facing right to face left. 0 being "totally to the right", 180 "left", 90 "up" and 270 "down". I want something that is aiming with an angle of 91 to turn into 89 when reversed, literally. There's no Z axis present. EDIT: Thanks for the answers! Trying them out now. I'll post which one worked in a minute!

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  • Python, lambda, find minimum

    - by qba
    I have foreach function which calls specified function on every element which it contains. I want to get minimum from thise elements but I have no idea how to write lambda or function or even a class that would manage that. Thanks for every help. I use my foreach function like this: o.foreach( lambda i: i.call() ) or o.foreach( I.call ) I don't like to make a lists or other objects. I want to iterate trough it and find min. I manage to write a class that do the think but there should be some better solution than that: class Min: def __init__(self,i): self.i = i def get_min(self): return self.i def set_val(self,o): if o.val < self.i: self.i = o.val m = Min( xmin ) self.foreach( m.set_val ) xmin = m.get_min() Ok, so I suppose that my .foreach method is non-python idea. I should do my Class iterable because all your solutions are based on lists and then everything will become easier. In C# there would be no problem with lambda function like that, so I though that python is also that powerful.

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  • An issue on object orientation in php

    - by rabidmachine9
    Hello people, I have come up to issues while I'm trying to write some classes, here is an example: I have this class called TwitterGrub and I cant call it like that: $c = new TwitterGrub(); $c->twitterDisplay(); here is the class itself: <?php class TwitterGrub{ function twitterCapture($user = 'username',$password = 'pass') { $ch = curl_init("https://twitter.com/statuses/user_timeline.xml"); curl_setopt($ch, CURLOPT_HEADER, 1); curl_setopt($ch,CURLOPT_TIMEOUT, 30); curl_setopt($ch,CURLOPT_USERPWD,$user . ":" . $password); curl_setopt($ch,CURLOPT_RETURNTRANSFER,1); curl_setopt ($ch, CURLOPT_SSL_VERIFYPEER, 0); curl_setopt ($ch, CURLOPT_SSL_VERIFYHOST, 0); $result=curl_exec ($ch); $data = strstr($result, '<?'); $xml = new SimpleXMLElement($data); return $xml; } function twitterDisplay($twitNum = 2){ $xml = $this::twitterCapture(); for($i= 0; $i<$twitNum; $i++){ echo "<div class= 'curvebox'>".$xml->status[$i]->text."</div>"; } } } ?> The problem is that everytime I want to change the username or password I have to jump back to class definition and that makes things not modular... and in many ways it feels wrong. So the question is what would be the proper way to chance my username and password through the objects interface and then call twitterDisplay() method with the new data?Hope that makes sense. Thanks in advance

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  • Silverlight ~ MVVM ~ Dynamic setting of Style property based on model value

    - by eponymous23
    I have a class called Question that represents a question and it's answer. I have an application that renders an ObservableCollection of Question objects. Each Question is rendered as a StackPanel that contains a TextBlock for the question verbiage, and a TextBox for the user to enter in an answer. The questions are rendered using an ItemsControl, and I have initially set the Style of the Questions's StackPanel using a StaticResource key called 'IncorrectQuestion' (defined in UserControl.Resources section of the page). In the UserControl.Resources section, I've also defined a key calld 'CorrectQuestion' which I need to somehow apply to the Question's StackPanel when the user correctly answers the question. My problem is I'm not sure how to dynamically change the Style of the StackPanel, specifically within the constraints of a ViewModel class (i.e. I don't want to put any style selection code in the View's code-behind). My Question class has an IsCorrect property which is accurately being set when the correction is answered. I'd like to somehow reflect the IsCorrect value in the form of a Style selection. How do I do that?

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  • How to make a piece of WPF content take up the entire application window

    - by Bojin Li
    I'm working on an application that contains a number of content areas. I want to implement a behavior such that in response to user input, any of these content areas can be toggled to fit the entire application window, and optionally back to its original position again. I experimented with several approaches and none of them seem optimal for me. Here's what I tried to do: Use the ClipToBoundsProperty on the content I want to make "Full Screen": Doesn't work because only the CanvasPanel seems to fully respect this property. The application need to be localized so I would really like to avoid the CanvasPanel. Use a Grid and collapse the other content areas, such that only the one I want to see is visible, hence taking up the entire screen: This will probably work but doesn't seem easy to implement nor maintain. The "Full Screen" content area could be several levels deep, for example residing inside a Tabcontrol, so I would have to hide the tab headers too etc. Reconstruct the content area in a separate view and display it while hiding the rest: Seems easy enough to do with DataTemplates and my ViewModel objects, but any GUI/View only states are not preserved using this approach. Somehow "lift" the GUI/View I want to "Full Screen" into the separate view and display it while hiding the rest: I don't know how to do this or even if this is possible. Anyway if anyone knows a better approach I would love to know about it. Thanks a lot!

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  • Entityframework duplicate record on second insert

    - by Delysid
    I am building an application for recipe/meal planning, and i have come across a problem i cant seem to figure out. i have a table for units of measure, where i keep the used units in, i only want unique units in here (for grocery list calculation and so forth) but if i use a unit from the table on a recipe, the first time it is okay, nothing is inserted in units of measure, but the second time i get a "duplicate". i suspect it has something to do with entitykey, because the primary key is identity column on the sql server (2008 r2) for some reason it works to change the objectstate on some objects (courses, see code) and that does not generate a duplicate, but that does not work on the unit of measure my insert methods looks like this : public recipe Create(recipe recipe) { using (RecipeDataContext ctx = new RecipeDataContext()) { foreach (recipe_ingredient rec_ing in recipe.recipe_ingredient) { if (rec_ing.ingredient.ingredient_id == 0) { ingredient ing = (from _ing in ctx.ingredients where _ing.name == rec_ing.ingredient.name select _ing).FirstOrDefault(); if (ing != null) { rec_ing.ingredient_id = ing.ingredient_id; rec_ing.ingredient = null; } } if (rec_ing.unit_of_measure.unit_of_measure_id == 0) { unit_of_measure _uom = (from dbUom in ctx.unit_of_measure where dbUom.unit == rec_ing.unit_of_measure.unit select dbUom).FirstOrDefault(); if (_uom != null) { rec_ing.unit_of_measure_id = _uom.unit_of_measure_id; rec_ing.unit_of_measure = null; } } ctx.Recipes.AddObject(recipe); //for some reason it works to change object state of this, and not generate a duplicate ctx.ObjectStateManager.ChangeObjectState(recipe.courses[0], EntityState.Unchanged); } ctx.SaveChanges(); } return recipe; } My datamodel looks like this : http://i.imgur.com/NMwZv.png

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  • What's a good way to format AJAX responses? Or, using Django templating with AJAX

    - by synic
    In some of the code I'm working on, the author max AJAX calls to a Django view that returns JSON. Once the JSON is retrieved, it'll be injected into the page with a function that looks like this (note, this is a simplification, but I'm sure you know what I'm getting at here): function build_event_listing(events) { var html = ''; for(int i = 0; i < events.length; i++) { event = events[i]; html += "<h2>" + event.title + "</h2>\n"; html += "<p>" + event.description + "</p>"; html += "Click <a href='/event/view/" + event.id + "'>here<a> for more info."; } events_div.html(html); } I really don't like this approach. To change the look of each event listing, the designer would have to modify that ugly JS. I'd much rather make use of Django's templating system, but I'm wondering how I can do this? I had the idea of writing the view like this: def view_listings(req): events = models.Event.objects.all() html = [] for event in events: html.append( render_to_string('event/single_event.html', { 'event': event, }, context_instance=RequestContext(req)) return HttpResponse(''.join(html), mimetype='text/html') ... but it just seems like there should be a better way. Any ideas?

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  • What's wrong (or right) with this JS Object Pattern?

    - by unsane1
    Here's an example of the pattern I'm using in my javascript objects these days (this example relies on jQuery). http://pastie.org/private/ryn0m1gnjsxdos9onsyxg It works for me reasonably well, but I'm guessing there's something wrong, or at least sub-optimal about it, I'm just curious to get people's opinions. Here's a smaller, inline example of it: sample = function(attach) { // set internal reference to self var self = this; // public variable(s) self.iAmPublic = true; // private variable(s) var debug = false; var host = attach; var pane = { element: false, display: false } // public function(s) self.show = function() { if (!pane.display) { position(); $(pane.element).show('fast'); pane.display = true; } } self.hide = function() { if (pane.display) { $(pane.element).hide('fast'); pane.display = false; } } // private function(s) function init () { // do whatever stuff is needed on instantiation of this object // like perhaps positioning a hidden div pane.element = document.createElement('div'); return self; } function position() { var h = { 'h': $(host).outerHeight(), 'w': $(host).outerWidth(), 'pos': $(host).offset() }; var p = { 'w': $(pane.element).outerWidth() }; $(pane.element).css({ top: h.pos.top + (h.h-1), left: h.pos.left + ((h.w - p.w) / 2) }); } function log () { if (debug) { console.log(arguments); } } // on-instantiation let's set ourselves up return init(); } I'm really curious to get people's thoughts on this.

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  • [SOLVED]Django - Passing variables to template based on db

    - by George 'Griffin
    I am trying to add a feature to my app that would allow me to enable/disable the "Call Me" button based on whether or not I am at [home|the office]. I created a model in the database called setting, it looks like this: class setting(models.Model): key = models.CharField(max_length=200) value = models.CharField(max_length=200) Pretty simple. There is currently one row, available, the value of it is the string True. I want to be able to transparently pass variables to the templates like this: {% if available %} <!-- Display button --> {% else %} <!-- Display grayed out button --> {% endif %} Now, I could add logic to every view that would check the database, and pass the variable to the template, but I am trying to stay DRY. What is the best way to do this? UPDATE I created a context processor, and added it's path to the TEMPLATE_CONTEXT_PROCESSORS, but it is not being passed to the template def available(request): available = Setting.objects.get(key="available") if open.value == "True": return {"available":True} else: return {} UPDATE TWO If you are using the shortcut render_to_response, you need to pass an instance of RequestContext to the function. from the django documentation: If you're using Django's render_to_response() shortcut to populate a template with the contents of a dictionary, your template will be passed a Context instance by default (not a RequestContext). To use a RequestContext in your template rendering, pass an optional third argument to render_to_response(): a RequestContext instance. Your code might look like this: def some_view(request): # ... return render_to_response('my_template.html', my_data_dictionary, context_instance=RequestContext(request)) Many thanks for all the help!

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  • Store data in tableview to NSUserDefaults

    - by Jozef Vrana
    Tricks.h file #import "Tricks.h" @implementation Tricks static NSMutableArray *trickList = nil; +(NSMutableArray *)trickList { if(!trickList){ trickList = [[NSMutableArray alloc]init]; } return trickList; } @end Tricks.m file @interface Tricks : NSObject @property(strong, nonatomic) NSString *trickName; Method for adding objects to array -(IBAction)saveAction:(id)sender { Tricks *trick = [[Tricks alloc]init]; trick.trickName = self.trickLabel.text; [[Tricks trickList]insertObject:trick atIndex:0]; [self.navigationController popViewControllerAnimated:YES]; } In .h file of UITabelview class I am making a reference to tricks class, but I am sure there is error on this line. @property (strong, nonatomic) Tricks *tricks; In cellForRow method I am storing data _trick = [[NSMutableDictionary alloc]initWithObjectsAndKeys:trick,nil]; NSUserDefaults *defaults=[NSUserDefaults standardUserDefaults]; [defaults setObject:_trick forKey:@"numberArray"]; [defaults synchronize]; NSLog(@"%@",_trick); In .m class of UITableview in viewDidLoad I want to retrieve data if([[NSUserDefaults standardUserDefaults] objectForKey:@"numberArray"] != nil) { _tricks = [[NSUserDefaults standardUserDefaults] objectForKey:@"numberArray"]; } Thanks for advices

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  • Doing a global count of an object type (like Users), best practice?

    - by user246114
    Hi, I know keeping global counters is frowned upon in app engine. I am interested in getting some stats though, like once every 24 hours. For example, I'd like to count the number of User objects in the system once every 24 hours. So how do we do this? Do we simply keep a set of admin tool functions which do something like: SELECT FROM com.me.project.server.User; and just see what the size of the returned List is? This is kind of a bummer because the datastore would have to deserialize every single User instance to create the returned list, right? I could optimize this possibly by asking for only the keys to be returned, so the whole User object doesn't have to be deserialized. Then again, a global counter for # of users probably would create too much contention, because there probably won't be hundreds of signups a minute for the service I'm creating. How should we go about doing this? Getting my total number of users once a day is probably a pretty typical operation? Thank you

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  • Why would gnu ld link order causes Signal 11 (SEGV) on startup?

    - by Benoit
    We are building a large application in C++ that includes the use of many (static) libraries. We have a problem where the application crashes on startup with a Signal 11, before we even reach main. After much debugging, we have observed that if we explicitly reference an object file so its link order is early, the program crashes on startup. If the file is referenced later (or not referenced at all), the program does not crash. To be clear, there is NO code invoked directly from this object file. However, as it is C++, there might be static objects that do get constructed (it's a CORBA IDL generated file). We use the -Wl,--start-group ... --end-group arguments to multi-pass link the symbols since the libraries are interdependent. Here is a representation of what I mean. This is what the linker's object file order is: Order 1 Order 2 Order 3 foo.o foo.o foo.o ... ... ... main.o main.o main.o crasher.o libA.o libA.o libA.o LibB.o LibB.o LibB.o LibC.o LibC.o LibC.o crasher.o Results: NO CRASH NO CRASH CRASH Does any one have an idea why the linkage order has an effect on the crash? It would be nice if we could force the crasher.o to link later, but we're really after an explanation. Also, is there a way to force the linker to place crasher.o towards the end? Just to add to the fun, in actuality, crasher.o is part of a Library in the --start/--end-group.

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  • Java - multithreaded access to a local value store which is periodically cleared

    - by Telax
    I'm hoping for some advice or suggestions on how best to handle multi threaded access to a value store. My local value storage is designed to hold onto objects which are currently in use. If the object is not in use then it is removed from the store. A value is pumped into my store via thread1, its entry into the store is announced to listeners, and the value is stored. Values coming in on thread1 will either be totally new values or updates for existing values. A timer is used to periodically remove any value from the store which is not currently in use and so all that remains of this value is its ID held locally by an intermediary. Now, an active element on thread2 may wake up and try to access a set of values by passing a set of value IDs which it knows about. Some values will be stored already (great) and some may not (sadface). Those values which are not already stored will be retrieved from an external source. My main issue is that items which have not already been stored and are currently being queried for may arrive in on thread1 before the query is complete. I'd like to try and avoid locking access to the store whilst a query is being made as it may take some time.

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  • C++ Instantiate class and add name to array/vector then cycle through update functions from the array

    - by SD42
    I have a bunch of classes in a basic (and badly coded!) game engine that are currently instantiated in the code and have to have their individual update functions called. What I want to do is be able to create an instance of a class, pass the name to an array, and then subsequently cycle through the array to call the update functions of each class. I'm unsure as to whether or not this is an impossible or spectacularly stupid way of trying to manage objects, so please tell me if it is. So currently I might have manually instantiated Enemy class a couple of times: Enemy enem1; Enemy enem2; I then have to update them manually in the game loop: enem1.update(); enem2.update(); What method should I use to be able to spawn and destroy instances of the enemy class during gametime? Is it possible to populate an array with instantiated names and then do something like (and i'm aware this doesn't work); array[x].update(); Then iterate through the names in the array? Anything that even points me in the right direction would be greatly appreciated!

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  • How do I make this Java code operate properly? [Multi-threaded, race condition]

    - by Fixee
    I got this code from a student, and it does not work properly because of a race condition involving x++ and x--. He added synchronized to the run() method trying to get rid of this bug, but obviously this only excludes threads from entering run() on the same object (which was never a problem in the first place) but doesn't prevent independent objects from updating the same static variable x at the same time. public class DataRace implements Runnable { static volatile int x; public synchronized void run() { for (int i = 0; i < 10000; i++) { x++; x--; } } public static void main(String[] args) throws Exception { Thread [] threads = new Thread[100]; for (int i = 0; i < threads.length; i++) threads[i] = new Thread(new DataRace()); for (int i = 0; i < threads.length; i++) threads[i].start(); for (int i = 0; i < threads.length; i++) threads[i].join(); System.out.println(x); // x not always 0! } } Since we cannot synchronize on x (because it is primitive), the best solution I can think of is to create a new static object like static String lock = ""; and enclose the x++ and x-- within a synchronized block, locking on lock. But this seems really awkward. Is there a better way?

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  • java class that simulates a simple database table

    - by ericso
    I have a collection of heterogenous data that I pull from a database table mtable. Then, for every unique value uv in column A, I compute a function of (SELECT * FROM mtable WHERE A=uv). Then I do the same for column B, and column C. There are rather a lot of unique values, so I don't want to hit the db repeatedly - I would rather have a class that replicates some of the functionality (most importantly some version of SELECT WHERE). Additionally, I would like to abstract the column names away from the class definition, if that makes any sense - the constructor should take a list of names as a parameter, and also, I suppose, a list of types (right now this is just a String[], which seems hacky). I'm getting the initial data from a RowSet. I've more or less done this by using a hashmap that maps Strings to lists/arrays of Objects, but I keep getting bogged down in comparisons and types, and am thinking that my current implementation really isn't as clean and clear as it could be. I'm pretty new to java, also, and am not sure if I'm not going down a completely incorrect path. Does anyone have any suggestions?

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  • An Array returned by a model association is not an Array?

    - by Warren
    We have a model association that looks something like this: class Example < ActiveRecord::Base has_many :others, :order => 'others.rank' end The rank column is an integer type. The details of these particular models are not really important though as we have found the same problem with other has_many associations between other models. We have also added to the Enumerable module: module Enumerable def method_missing(name) super unless name.to_s[0..7] == 'collect_' method = name.to_s[8..-1] collect{|element| element.send(method)} end end This adds a collect_id method that we can use to get an array of record ids from an array of ActiveRecord objects. So if we use a normal ActiveRecord find :all, we get a nice array which we can then use collect_id on but if we use Example.others.collect_id, we get NoMethodError: undefined method `collect_id' for #<Class:0x2aaaac0060a0> Example.others.class returns "Array" so is it lying or confused? Our solution thus far has been to use it this way: Example.others.to_a.collect_id This works but this seems a bit strange. Why would you have to do that? We are on Ruby 1.8.7 and Rails 2.3.4

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  • Calling a class method within a method definition in the same class

    - by user1786288
    So I'm writing a program for an intro Java class. I'm defining a method to add two fractions together within the class Fraction. Fraction has 2 variables, numerator and denominator. Each of these variables has a setter and a getter. Anyway, I have a problem with my addition method, which is shown below. I've just sort of tried to implement it in a way that made sense, but I'm sure I did something with calling methods/using objects that doesn't work. public void add(Fraction fraction1, Fraction fraction2) { Fraction fraction3 = new Fraction(); int a = fraction1.getNumerator; int b = fraction1.getDenominator; int c = fraction2.getNumerator; int d = fraction2.getDenominator; fraction3.setNumerator((a * d) + (b * c)); fraction3.setDenominator(b * d); } I don't know if the problem is in the method definition, if I can use the object type that way, or if there's something else wrong. any help would be appreciated, and if I need to provide any information, I'll do so ASAP.

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  • scala 2.8 CanBuildFrom

    - by oxbow_lakes
    Following on from another question I asked, I wanted to understand a bit more about the Scala method TraversableLike[A].map whose signature is as follows: def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That Notice a few things about this method: it takes a function turning each A in the traversable into a B it returns That and takes an implicit argument of type CanBuildFrom[Repr, B, That] I can call this as follows: > val s: Set[Int] = List("Paris", "London").map(_.length) s: Set[Int] Set(5,6) What I cannot quite grasp is how the fact that That is bound to B (i.e. it is some collection of B's) is being enforced by the compiler. The type parameters look to be independent in both the signature above and in the signature of the trait CanBuildFrom itself: trait CanBuildFrom[-From, -Elem, +To] How is the scala compiler ensuring that That cannot be forced into something which does not make sense? > val s: Set[String] = List("Paris", "London").map(_.length) //will not compile EDIT - this question of course boils down to: How does the compiler decide what implicit CanBuildFrom objects are in scope for the call?

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