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• Questions about "casting operation" in OOP

  - by rhapsodyn

  When programming, we usually use some type-casting operations. When the casting happens on the objects "on the same level", it feels ok. But when it happens on the ojects "on the different levels"(mainly between father and son), it feels weird. Considering this: Class Son extends Father WhenSon s = (Son)father;, it's absolutely unreasonable. Because a "Son" is not a "Father" anymore, "Son" may grow up with some new properties "Father" doesn't have, the casting operation makes these properties unknown. On the other hand, Father f = (Father)son seems reasonable, but according to LSP "An instance of a derived should be able to replace any instance of its superclass" A "Son" can do anything his "Father" can, so the casting operation seems useless. So can i say that these casting operations are agaisnt OO design principle but necessary?

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• What is the best to format messages for queueing?

  - by Tijmen

  I've been reading up on message queueing lately, and I'd like to implement a simple, extendable, system for my app. While there's a lot of good information on the subject of setting up a MQ system out there, I can't find a lot about the actual implementation. I'm looking for patterns and best practices on how to properly format messages for a queue, and ways to execute the jobs in PHP. Should I use JSON, serialized objects, text, URLs or XML? What information should I send? Is a worker with a switch($job['command']) {} (or something like that) the way to go, or are there any established patterns out there to implement a worker? Help greatly appreciated!

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• Can I have fixed typed ArrayList in C#, just like C++?

  - by Kazoom

  I have an ArrayList which contains fixed type of objects. However everytime I need to extract an object a particular index, I need to typecast it to my user defined type from object type. Is there a way in C# to declare ArrayList of fixed types just like Java and C++, or is there a work around to avoid the typecasting everytime? Edit: I apologize I forgot mentioning that I require the datastructure to be thread-safe, which List is not. Otherwise I would have just used a normal Array. But I want to save myself from the effort of explicitly locking and unlocking while writing the array. So I thought of using ArrayList, synchronize it, but it requires typecasting every time.

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• C++ Multithreaded server help

  - by kisplit

  Hello all, I'm working on a multithreaded server in c++ using boost-asio. Currently a design problem I'm running into deals with erasing a connection. I have a single server instance which holds a vector of connection objects. These connections receive commands which I parse. One command in particular deals with sending data to ALL connections in my vector. Now when a connection disconnects I'm currently erasing this connection from the vector and calling the destructor. It seems like I'm going to run into problems when someone 'SendAll' at the same time someone 'Disconnect'. Could anyone recommend a better design or just point me in the right direction? Any help greatly appreciated. Thanks

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• How to use use external js in typescript

  - by Krishan

  I Generate the Angular JS code through the Typescript code. In one situation, I need to add external JS file to my typescript file and need to access the classes in the js file. I add that js file like this. /// <amd-dependency path="../../vendor/tweenMax.js" /> But still the typescript file can not identify the objects of that javascript file. If someone knows the suitable way, please add your answer. (I'm using min. js file)

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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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• How to provide an API client with 1,000,000 database results?

  - by Chris Dutrow

  What is a good way to provide an API client with 1,000,000 database results? We are cureently using PostgreSQL. A few suggested methods: Paging using Cursors Paging using random numbers ( Add "GREATER THAN ORDER BY " to each query ) Save information to a file and let the client download it Iterate through results, then POST the data to the client server Return only keys to the client, then let the client request the objects from Cloud files like Amazon S3 (still may require paging just to get the file names ). What haven't I thought of that is stupidly simple and way better than any of these options?

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• Getting object coordinates from camera

  - by user566757

  I've implemented a camera in Java using a position vector and three direction vectors so I can use gluLookAt(); moving around in `ghost mode' works fine enough, but I want to add collision detection. I can't seem to figure out how to transform my position vector to coordinates in which OpenGL draws my objects. A rough sketch of my drawing loop is this: glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); camera.setView(); drawer.drawTheScene(); I'm at a loss of how to proceed; looking at the ModelView matrix between calls and my position vector, I haven't found any kind of correlation.

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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 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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• how to query list in powershell

  - by Varyanica

  add-type -Language CSharpVersion3 -TypeDefinition @" public class pack_code { public pack_code() {} public string code { get; set; } public string type { get; set; } } "@ $a = New-Object pack_code $a.code = "3" $a.type = "5" $b = New-Object pack_code $b.code = "2" $b.type = "5" $c = New-Object pack_code $c.code = "2" $c.type = "5" $d = New-Object pack_code $d.code = "1" $d.type = "1" $codes = New-Object 'System.Collections.Generic.List[object]' $codes.add($a) $codes.add($b) $codes.add($c) $codes.add($d) is there a way to select distinct from $codes and select the objects where type equals 1? How can i use linq with PowerShell?

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• how to access jquery internal data?

  - by Unknown

  As you may or may not be aware as of jQuery 1.7 the whole event system was rewritten from the ground up. The codebase is much faster and with the new .on() method there is a lot of uniformity to wiring up event handlers. One used to be able to access the internal events data and investiate what events are registered on any given element, but recently this internal information has been hidden based on the following scenario... It seems that the "private" data is ALWAYS stored on the .data(jQuery.expando) - For "objects" where the deletion of the object should also delete its caches this makes some sense. In the realm of nodes however, I think we should store these "private" members in a separate (private) cache so that they don't pollute the object returned by $.fn.data()" Although I agree with the above change to hide the internal data, I have found having access to this information can be helpful for debugging and unit testing. What was the new way of getting the internal jquery event object in jQuery 1.7?

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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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• Subsonic foreign key returning collection?

  - by Shaul

  I'm just writing my first "Hello World" program using Subsonic, for which I've thrown together a simple little Customer/Invoice/InvoiceItem/Product database. The connection was successfully made to the DB, and it generated all the right ActiveRecord classes. But for some reason, the Invoice class has a property called Customers, which returns a collection of Customer objects, even though the Invoice table has a CustomerID field which has a foreign key to the Customer table. I would have expected a Customer property returning a single Customer object. I must be doing something wrong - but what?

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• How can I invoke the dialog to set printer options manually?

  - by FromTheMountain

  I'm using WPF and need to let users set some print related options like printer and printer properties (e.g. papertray, landscape/portrait, duplex, etc). I'm aware of the PrintDialog class to get a PrintQueue and PrintTicket object. However I need to create I custom solution and can not show the PrintDialog. I manage to get the available PrintQueue objects and let users select a printer. I'm struggling with the printer properties. My question is: how can I show the dialog in which a user can set the printer properties for the selected PrintQueue (the dialog that is shown when a user clicks on the Properties button in the WPF PrintDialog).

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• Combining XmlSerializer and XmlWriter?

  - by num3ric

  In addition to a list of objects I am serializing to an xml file using C#'s XmlSerializer, I would like to store a few more independent elements (mainly strings from textboxes) in the same xml. public static void SaveBehaviors(ObservableCollection<Param> listParams) { XmlSerializer _paramsSerializer = new XmlSerializer(listParams.GetType()); string path = Environment.GetFolderPath(Environment.SpecialFolder.Desktop); path += "\\test.xml"; using (TextWriter writeFileStream = new StreamWriter(path)) { _paramsSerializer.Serialize(writeFileStream, listParams); using (XmlWriter writer = XmlWriter.Create(writeFileStream)) { writer.WriteStartElement("Foo"); //test entry... writer.WriteAttributeString("Bar", "Some & value"); writer.WriteElementString("Nested", "data"); writer.WriteEndElement(); } } } However, deserializing "test.xml" results in an error because of the added element. I suppose writing in the serialized xml file is prohibited and should be avoided?

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• Objective-c for the iphone: Mystery memory leak

  - by user200341

  My application seems to have 4 memory leaks (on the device, running instruments). The memory leaks seems to come from this code: NSURL *url = [self getUrl:destination]; [destination release]; NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url]; [url release]; [request setHTTPMethod:@"GET"]; [request addValue:@"application/json" forHTTPHeaderField:@"content-type"]; NSURLConnection *connection = [[NSURLConnection alloc]initWithRequest:request delegate:self]; [request release]; [connection release]; I am releasing all my objects as far as I can see but it's still showing this as the source of the 4 memory leaks. This is on the Device running 3.1.3 Is it acceptable to have a few memory leaks in your app or do they all have to go?

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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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• Are MongoDB and CouchDB perfect substitutes?

  - by raoulsson

  I haven't got my hands dirty yet with neither CouchDB nor MongoDB but I would like to do so soon... I also have read a bit about both systems and it looks to me like they cover the same cases... Or am I missing a key distinguishing feature? I would like to use a document based storage instead of a traditional RDBMS in my next project. I also need the datastore to handle large binary objects (images and videos) automatically replicate itself to physically separate nodes rendering the need of an additional RDBMS superfluous Are both equally well suited for these requirements? Thanks!

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• Pass structured data from C++ app to ASP.NET web service.

  - by Odrade

  I have Visual C++ application that needs to communicate with a ASP.NET web service. Specifically, the app needs to pass structured data (e.g. objects that contain lists of structures, etc) as a parameter to one of the service methods. The C++ application is already generating an xml document that contains this data. The document is generating using an xml library, so it should always well-formed. What is a good method for passing this data to the web service? I'm thinking about passing the document to the web service as a string parameter, then deserializing to a .NET object based on an xsd. But, I hear that passing an xml doc as a string parameter is not recommended. So, my questions: What are the pitfalls associated with sending the document as a string parameter, assuming that the document itself is always well-formed? Assuming the above is a bad idea, what are some good alternate approaches?

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• C++ Variable declarable in function body, but not class member?

  - by anon

  I want to create a C++ class with the following type: It can be declared inside of a function. It can be declared inside of a member function. It can not be declared as a class member. The use of this: think "Root" objects for a GC. Is this possible in C++? In particular, I'm using g++. Willing to switch to clang. Either templates or macro solution fine. Thanks!

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• jQuery after show() assumes that display:inline is :hidden. Why?

  - by Janis Veinbergs

  With jQuery 1.4.2, :hidden filter is not filtering out elements that were hidden, but i've made then visible by calling show(). Filter assumes it is still hidden. Is this bug or am i missing something? Consider the following code: $("td.ms-authoringcontrols > span[id*='_ParallelApprovers']:hidden:first").css("display") "none" $("td.ms-authoringcontrols > span[id*='_ParallelApprovers']:hidden:first").show() Object $("td.ms-authoringcontrols > span[id*='_ParallelApprovers']:hidden:first").css("display") "inline" // ?? Let me scratch my head... $("td.ms-authoringcontrols > span[id*='_ParallelApprovers']:hidden:first").is(":hidden") true //element with "display:inline", visible in browser, but yet it is hidden Instead of "inline", you would expect "none", because :hidden filter was used. What it does is from an array of objects it selects first hidden element. Each time i call these lines of code, i expect them to select next hidden element (not the one i just showed).

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• android exit application completely and go to main applications screen

  - by Totti

  i know that this question is asked many times, but really i can't understand the answer, i want to set button, when user click it i want to exit the application (also the carbage collector should remove the objects), and after exiting i want to go to the screen where the user found the application icon on mobile. for exit i don't know what to do for going to the screen where to find the application icon i tried like this Intent intent = new Intent(Intent.ACTION_MAIN); intent.addCategory(Intent.CATEGORY_HOME); intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); startActivity(intent); but doesn't work

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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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• Does anyone else think instance variables are problematic in database-backed applications?

  - by Ben Aston

  It occurs to me that state control in languages like C# is not well supported. By this, I mean, it is left upto the programmer to manage the state of in-memory objects. A common use-case is that instance variables in the domain-model are copies of information residing in persistent storage (i.e. the database). Clearly this violates the single point of authority principle, and "synchronisation" has to be managed by the developer. I envisage a system where instead of instance variables, we have simple public access/mutator methods marked with attributes that link them to the database, and where reads and writes are mediated by a framework that decides whether to hit the database. Does such a system exist? Am I completely missing the point, or is there some truth to this idea?

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