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  • How to start coding the "Dining Philosophers" simulation?

    - by GrizzlyGuru
    I'm not a beginner at C# but I really need to increase my understanding, so I've picked a classic deadlock problem to code to help teach myself some of the more advanced concepts of C#. The Dining Philosophers Problem seems like a good one, but I need a little help to get started. I know I need to approach the "diners" as objects, but to simulate the random delays between eating, should I look to threading with each diner in a separate thread? Do I need some kind of "master" to monitor all the actions? Any general design concept advice is welcome, but I'd like to do the grunt programming as an exercise. Thanks!

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  • Avoid Circular Reference in Swing GUI

    - by drhorrible
    Maybe it's not worth worrying about in this scenario, but lets say you have two classes, a JFrame with all its components, and a server-like class that handles requests from remote clients. The user is able to start and stop server objects through the GUI, and is shown various events that happen to each server object. Whether or not I use an explicit pattern (like MVC), it seems like the JFrame needs a reference to the server class (to call start and stop) and the server needs a reference to the JFrame (to notify of it of certain events). Is this a problem, or am I looking at this situation in the wrong way?

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  • Not found in protocol

    - by Alex
    I've subclassed MKAnnotation so that i can assign objects to annotations and then assign this object to a view controller like so: - (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control { PlaceDetailView *detailView = [[PlaceDetailView alloc] initWithStyle:UITableViewStyleGrouped]; detailView.place = [view.annotation place]; [self.navigationController pushViewController:detailView animated:YES]; [detailView release]; } This is working great but i'm having the following issues: If i try and access the place getter method like so view.annotation.place i recieve an error: Accessing unknown place getter method If i acces the place getter method like so [view.annotation place] i receive a warning: place not found in protocol From my understanding this is because the place object is not defined in the MKAnnotation protocol, although i'm aware of this i'm not sure how to tell the complier that place does exist and it's not calling it blind.

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  • Question about memory usage

    - by sudo rm -rf
    Hi there. I have the following method: +(NSMutableDictionary *)getTime:(float)lat :(float)lon { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] init]; [dictionary setObject:hour forKey:@"hour"]; [dictionary setObject:minute forKey:@"minute"]; [dictionary setObject:ampm forKey:@"ampm"]; return dictionary; } A lot of the method is chopped off, so I think I need the pool for some other stuff in the method. Here's my question. I know that I need to release the following objects: [dictionary release]; [pool release]; However, I can't release the dictionary before I return it, but as soon as I return it the rest of the method isn't performed. What should I do?

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  • Java - Optimize finding a string in a list

    - by Mark
    I have an ArrayList of objects where each object contains a string 'word' and a date. I need to check to see if the date has passed for a list of 500 words. The ArrayList could contain up to a million words and dates. The dates I store as integers, so the problem I have is attempting to find the word I am looking for in the ArrayList. Is there a way to make this faster? In python I have a dict and mWords['foo'] is a simple lookup without looping through the whole 1 million items in the mWords array. Is there something like this in java? for (int i = 0; i < mWords.size(); i++) { if ( word == mWords.get(i).word ) { mLastFindIndex = i; return mWords.get(i); } }

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  • DataContractAttribute with Shared Assembly

    - by Sanju
    Hi All, Is it necessary to decorate custom objects with [DataContract] and [DataMember] when using shared assemblies (as opposed to auto proxy generation)? The reason I ask is that I have encountered the following scenario: Suppose the following object is implemented in my service: public class baseClass { Guid _guid; public baseClass() { _guid = Guid.NewGuid() } public Guid ReturnGuid { get {return _guid;}} } public class newClass : baseClass { int _someValue; public newClass {} public int SomeValue { get {return _someValue;} set {_someValue = value;} } } [ServiceContract] public IService { [OperationContract] newClass SomeOperation(); } In my client (with shared assemblie) I can happily recieve and use a serialized newClass when SomeOperation is called - even though I have not marked it as a DataContract. However, as soon as I do mark it with DataContract and use DataMember then it complains that set is not implemented on ReturnGuid in the base class. Could somebody explain why it works fine when I do not decorate with DataContract and DataMember. Many thanks.

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  • Where does the data model go in a Prism app?

    - by HawkeyeJoeS
    I'm having trouble where to put our data model in our Prism app. Most, if not all or our data will be coming from web services and the web services are unique for each module. Unfortunately, there will be objects that need to be shared (such as a person/user object). I'm really torn about whether to add these services directly to the module, so that each is truly independent, or create a separate project to house the web service proxies and business entities. The modules are being built by different teams, but will all live in the same solution (and source control, of course).

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  • Delegates vs. events in Cocoa

    - by aaronstacy
    I'm writing my first iPhone app, and I've been exploring the design patterns in Cocoa and Objective-C. I come from a background of client-side web development, so I'm trying to wrap my head around delegates. Specifically, I don't see why delegate objects are needed instead of event handlers. For instance, when the user presses a button, it is handled with an event (UITouchUpInside), but when the user finishes inputting to a text box and closes it with the 'Done' button, the action is handled by calling a method on the text box's delegate (textFieldShouldReturn). Why use a delegate method instead of an event? I also notice this in the view controller with the viewDidLoad method. Why not just use events?

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  • Deserializing only select properties of an Entity using JDOQL query string?

    - by user246114
    Hi, I have a rather large class stored in the datastore, for example a User class with lots of fields (I'm using java, omitting all decorations below example for clarity): @PersistenceCapable class User { private String username; private String city; private String state; private String country; private String favColor; } For some user queries, I only need the favColor property, but right now I'm doing this: SELECT FROM " + User.class.getName() + " WHERE username == 'bob' which should deserialize all of the entity properties. Is it possible to do something instead like: SELECT username, favColor FROM " + User.class.getName() + " WHERE username == 'bob' and then in this case, all of the returned User instances will only spend time deserializing the username and favColor properties, and not the city/state/country properties? If so, then I suppose all the other properties will be null (in the case of objects) or 0 for int/long/float? Thank you

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  • Count number of given object in a list with LINQ

    - by Aaginor
    I have a list which can contain multiple occurrences of the same object. Now I need to count, how often the given object is contained in this list. int count = 0; foreach (IMyObject item in myList) if (item == object2Count) count++; I am sure that this can be done nicer with LINQ, but LINQ is still a mystery to me. My first question is: How would I count the objects via LINQ and the second question: Will this LINQ version be slower or faster? I am using a ObservableCollection and the number of items in the list is usally rather small ... usally not more then 20. Thanks in advance, Frank

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  • PHP 5.1.6 ArrayAccess error when iterating over object

    - by kenny99
    Hi, I'm having to develop a site on PHP 5.1.6 and I've just come across a bug in my site which isn't happening on 5.2+. When using foreach() to iterate over an object, I get the following error: "Fatal error: Objects used as arrays in post/pre increment/decrement must return values by reference..." Does anyone know how to get around this issue? if (strpos($post['feeding_type'], 'comm')) { foreach ($post['commercial_brands'] as $brand) { $comm_food = new Commercial_food_Model; $comm_food->brand = $brand; $comm_food->feeding_type_id = $f_type->id; $comm_food->save(); } }

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  • WPF DrawingVisual from my own class

    - by Robbskinizer
    Hi, Im trying to create my own class which contains a DrawingVisual, something like this public class MyObject { public DrawingVisual visual; public bool faceup; public bool flipped; } I have a drag and drop from a listview to a canvas, but when I try to get the object which back from the Canvas i only get the visual, not any of the other stuff in the class. How do i save "objects" and retreive it from a canvas? Im using my own MyCanvas which inheritance from Canvas, and using the AddVisualChild & AddLogicalChild etc. // Robbin

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  • Push a variable into global scope?

    - by Spot
    We use instantiate and put system critical objects in $GLOBALS for easy access from anywhere (e.g. DB, Cache, User, etc.). We use $GLOBALS so much that it would (yes, really) drop the amount of code quite a bit if I could reference it like $G = &$GLOBALS for a shorthand call. The problem is that, per my experience and several hours of Googling, I have not found any construct in PHP which allows you to 'flag' a var as global, making $GLOBALS first class, and everything else second class. Am I missing something? Is this possible?

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  • Keeping historic of modification in a database.

    - by mada
    Hi, Im a j2ee developper & we are using hibernatne mapping with a postgres databasae. We have to keep track of any changes occurs in the databse , in others words alls previous & current value of any field should be saved & field can be various types (bytea, int, char...) With a simple table it is easy but we a graph of objets things are more difficult So we have , speaking in a UML point of view, a graph of objects to store in the database with every changes & the user. Any idea or pattern how to do that ? Thanks in advance.

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  • How do I get characters common to two vectors in C++?

    - by Sam Phelps
    I am trying to compare two vector objects, and return a single vector containing all the chars which appear in both vectors. How would I go about this without writing some horribly complex manual method which compares every char in the first vector to every char in the second vector and using an if to add it to a third vector (which would be returned) if they match. Maybe my lack of real experience with vectors is making me imagine this will be harder than it really is, but I suspect there is some simplier way which I have been unable to find through searching.

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  • How can I bind an Enum to a DbType of bit or int?

    - by uriDium
    Hi I am using Linq2Sql and want to bind an objects field (which is enum) to either a bit or a int type in the database. For example I want have a gender field in my model. I have already edited the DBML and changed the Type to point to my enum. I want to create Radio buttons (which I think I have figured out) for gender and dropdown lists for other areas using the same idea. My enum looks like this public enum Gender { Male, Female } Mapping between DbType 'int' and Type 'Project.Models.Gender' in Column 'Gender' of Type 'Candidate' is not supported. Any ideas on how to do this mapping. Am I missing something on the enums.

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  • Objective C memory leaking

    - by Jakub Lédl
    Hi everyone, I'm creating one Cocoa application for myself and I found a problem. I have two NSTextFields and they're connected to each other as nextKeyViews. When I run this app with memory leaks detection tool and tab through those 2 textboxes for a while, enter some text etc., I start to leak memory. It shows me that the AppKit library is responsible, the leaked objects are NSCFStrings and the responsible frames are [NSEvent charactersIgnoringModifiers] and [NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:]. I know this is quite a brief and incomplete description, but does anyone have any ideas what could be the problem? Also, I don't use GC, so I release my instance variables in the controllers dealloc. What about the outlets? Since IBOutlet is just a mark for Interface Builder and doesn't actually mean anything, should I release them too?

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  • How SqlDataAdapter works internally?

    - by tigrou
    I wonder how SqlDataAdapter works internally, especially when using UpdateCommand for updating a huge DataTable (since it's usually a lot faster that just sending sql statements from a loop). Here is some idea I have in mind : It creates a prepared sql statement (using SqlCommand.Prepare()) with CommandText filled and sql parameters initialized with correct sql types. Then, it loops on datarows that need to be updated, and for each record, it updates parameters values, and call SqlCommand.ExecuteNonQuery(). It creates a bunch of SqlCommand objects with everything filled inside (CommandText and sql parameters). Several SqlCommands at once are then batched to the server (depending of UpdateBatchSize). It uses some special, low level or undocumented sql driver instructions that allow to perform an update on several rows in a effecient way (rows to update would need to be provided using a special data format and a the same sql query (UpdateCommand here) would be executed against each of these rows).

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  • WPF: Best method for printing paginated datagrids

    - by FauxReal
    Boy did I get an education looking into this. I guess I've been spoiled by Powerbuilder, which has fantastic functionality for this out of the box. Does anyone seriously write custom documentpaginator objects to handle reporting needs for their LOB apps? I want to be able to print "for free" and not have to code like crazy just to take whats on the screen and throw it on paper. How are people doing this? Does anyone have a recommended 3rd party for allowing printing of largish datagrids? Thanks

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  • Zend Studio 7.1 PHPUnit Test Case wizard does not populate "Element to Test"

    - by Mike
    When I follow the instructions in ZS documentation to create a phpunit test case, the wizard returns no objects to select on the "Element to Test" line. Selecting "browse" provides an empty dialog box. The PHPUnit path in my preferences shows "/Applications/zend/zs710/plugins/com.zend.php.phpunit_7.1.0.v20091120-0900/resources/library/". What else can I check to see why I cannot create a test case? I'm new to ZS and PHP, so I have no idea how to troubleshoot this. Thanks.

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  • ASP.NET MVC 2 Model object validation

    - by Jimmy
    Hey guys, I'm trying to validate a model object outside of the context of ModelState within a controller, I currently have a parser that creates model objects from an excel file and I want to be able to report how many entries were added to the database and how many failed, is there a way to validate a model object on its data annotations outside of model binding? I'm looking for something similar to the rails model method of model.valid? or a way for me to implement that myself. My current solution is just manually checking if a few key fields are present but this duplicates requirements between my model class and its metadata, there has to be a better way to hook into the model validation checking that is done by mvc 2. Thanks

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  • Reference variable to an object instantiated/initialized in another class in Java

    - by Alex
    The reason I'm asking is because I'm getting NullPointerException. I now this is very easy but I'm pretty new programming and find this a bit confusing. So say I have initialized an object in a class and want to access that same object from another class. Like now for instance I'm working on a small Chess game, in my model Game class I have an instance of Board, an object. Board, in turn, has an array of Squares. Square[][]. Game has board, board has Square[][]. Now if I want to access the Square[][] through the object board (in Game) of type Board. Do I just declare a variable with the same name and type or do I have to initialize it again? Board board OR Board board = new Board(); Note, I have already initialized board in the class Game so if I do it again, won't they be two totally different Board objects?

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  • How can this be done with (N)Hibernate?

    - by Vilx-
    I'm creating a windows forms application with NHibernate. It's an MDI application, so there is no limit to how many forms the user can have open at the same time (probably many). For most forms I want to have an "OK" and a "Cancel" button. Both close the form, but "OK" also saves the modified data to the DB. The forms can be pretty complex, and the modifications are likely to touch a whole graph of objects, adding some, deleting some, and changing some more. It would be good if the changes could be automatically detected and persisted as needed, without the need to manually keep track of each of them. What would be a good way to do this? Extra information: I can make whatever DB schema I want. I'm using MSSQL 2008 and currently have decided for GUID primary keys (with guid.comb generator) and a TIMESTAMP column for optimistic concurrency. I tried to simply set FlushMode of a NHibernate ISession to Never, doing all modifications as needed, and then calling Flush() if the user clicked OK. But that didn't work.

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  • Sorting 1000-2000 elements with many cache misses

    - by Soylent Graham
    I have an array of 1000-2000 elements which are pointers to objects. I want to keep my array sorted and obviously I want to do this as quick as possible. They are sorted by a member and not allocated contiguously so assume a cache miss whenever I access the sort-by member. Currently I'm sorting on-demand rather than on-add, but because of the cache misses and [presumably] non-inlining of the member access the inner loop of my quick sort is slow. I'm doing tests and trying things now, (and see what the actual bottleneck is) but can anyone recommend a good alternative to speeding this up? Should I do an insert-sort instead of quicksorting on-demand, or should I try and change my model to make the elements contigious and reduce cache misses? OR, is there a sort algorithm I've not come accross which is good for data that is going to cache miss?

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  • Examples of both beautiful and ugly java code?

    - by tputkonen
    I would like to demonstrate how difficult it is for a layman to identify high quality code from flawed code. I'm thinking of doing this with the help of two java methods. Both of the methods should look like they do the same, pretty simple thing. However one of them should have several kind of flaws, for example: iteration with array off by one error string concatenations causing lots of objects to be created (as opposed to StringBuffer in the "good" code, which looks more complicated) possibly null pointer exception (but it should not be trivial to spot) Those are just some examples, all kinds of other issues including bugs and performance related structures are highly appreciated. Methods should be around 10-20 lines of length, and the task they do should be something simple - preferably printing something in an iteration.

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