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  • Rails - inheritance hierarchy of classes where a subtype can play two roles

    - by Miquel
    I need to model Owners and Rentees in an application, so you have stuff that is always owned by someone and can be rented for someone else. I first approached this problem with Single Table Inheritance because both types of person will share all attributes, so you would have a model called Person associated to a table people with Owner and Rentee inheriting from Person. The problem is that Single type inheritance discerns subtypes using a field type and therefore a record in the table can represent either an Owner or a Rentee but not both at the same time, while in the real context you can have an Owner which is renting something from another Owner and therefore that person is at the same time an Owner and a Rentee. How would you approach this problem? Would you use separated tables for owners and rentees? Is there any other type of table inheritance in Rails?

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  • C++ Singleton design pattern

    - by Artem Barger
    Recently I've bumped into a realization/implementation of the Singleton design pattern for C++. It has looked like this (I have adopted it from the real life example): // a lot of methods are omitted here class Singleton { public: static Singleton* getInstance( ); ~Singleton( ); private: Singleton( ); static Singleton* instance; }; From this declaration I can deduce that the instance field is initiated on the heap. That means there is a memory allocation. What is completely unclear for me is when exactly the memory is going to be deallocated? Or is there a bug and memory leak? It seems like there is a problem in the implementation. My main question is, how do I implement it in the right way?

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  • Shared data in an ASP.NET application

    - by Barguast
    I have a basic ASP.NET application which is used to request data which is stored on disk. This is loaded from files and sent as the response. I want to be able to store the data loaded from these files in memory to reduce the number of reads from disk. All of the requests will be asking for the same data, so it makes sense to have a single cache of in-memory data which is accessible to all requests. What is the best way to create a single accessible object instance which I can use to store and access this cached data? I've looked into HttpApplication, but apparently a new instance of this is created for parallel requests and so it doesn't fit my needs.

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  • C# LINQ join With Just One Row

    - by Soo
    I'm trying to make a query that grabs a single row from an SQL database and updates it. TableA AId AValue TableB BId AId BValue Ok, so TableA and TableB are linked by AId. I want to select a row in TableB based on AValue using a join. The following query is what I have and only grabs a value from TableB based on AId, I just don't know how to grab a row from TableB using AValue. I know you would need to use a join, but I'm not sure how to accomplish that. var row = DbObject.TableB.Single(x => x.AId == 1) row.BValue = 1; DbObject.SubmitChanges();

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  • Synchronize Azure SQL (cloud) with Azure SQL Emulator (local)?

    - by Sid
    We have an Azure service (web role) that heavily depends on the database. For offline development/testing, we'd like to have the app+db run offline within the emulators. Running the webrole itself within the emulator is straightforward but doing so for the Azure SQL storage isn't so. What is the simplest way to ensure that the cloud Azure SQL database and the emulator/local Azure SQL database are in sync? We can afford some level of staleness for simplicity of sync operation (meaning it's ok for the local copy to be a few hours stale versus mirroring every write as soon as it happens) Thanks

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  • MVC Model architecture

    - by ATT
    I'm getting into CodeIgniter and trying to figure out the good architecture for my models. What kind of models would you create for the following simple example: list page of blog entries: shows part of the entry data, number of comments blog entry page: shows all the entry data, comment list (with part of the comment data) comment page: shows all the comment data I'm trying to get this right so that it's simple and effective. I don't want to load too much information (from the db) on the pages where I don't need them. E.g. should the same entry model handle both multiple entries as well as a single entry? And how should the comments be loaded? I only need the number of comments on the multiple entries (list) page but some of the comment data on the single entry page. How would you handle this?

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  • Entity System and rendering

    - by hayer
    Okey, what I know so far; The entity contains a component(data-storage) which holds information like; - Texture/sprite - Shader - etc And then I have a renderer system which draws all this. But what I don't understand is how the renderer should be designed. Should I have one component for each "visual type". One component without shader, one with shader, etc? Just need some input on whats the "correct way" to do this. Tips and pitfalls to watch out for.

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  • Linq to Sql GroupJoin Paging oddity

    - by OllyA
    I have noticed a strange Sql Translation in a LinqToSql Query I was trying to optimise. If I execute the following Recipients.GroupJoin( RecipientAttributes, x => x.Recipient_Id, y => y.Recipient_Id, (x,y) => new {Recipient = x, Attributes = y}) .Skip(1) .Take(1000) It executes in a single query as expected. However Recipients.GroupJoin( RecipientAttributes, x => x.Recipient_Id, y => y.Recipient_Id, (x,y) => new {Recipient = x, Attributes = y}) .Skip(0) .Take(1000) executes in a separate query for each Attributes selection. Removing the Skip(0) makes no difference either. Can anyone explain this and is there something I can do to get the first page query executing in a single sql statement?

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  • problem with for xml explicit clause in sql server 2005

    - by harrycode
    I am using for xml explicit clause in sql to send table data as xml from sql to asp.net page. I have created a stored procedure when i run store procedure in sql mgmt studio my xml is same as expected. But when I fetch It in asp.net then Xml returned is broken into two rows if xml exceeds certain character limit. I want result to be in single row. I am unable to figure out why single xml string is broken into two rows. please help

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  • Custom Global Hotkey Win32 C - Problem

    - by UK
    Hello , I am trying to get the user defined global hot key for my application. Here is my application code, user.rc CONTROL "", IDC_MHOTKEY, HOTKEY_CLASS, WS_TABSTOP, 91, 86, 68, 14 function.cpp WORD wHotKey = SendDlgItemMessage(hwnd, IDC_MHOTKEY, HKM_GETHOTKEY, 0, 0); GLOBAL_HOTKEY= wHotKey; RegisterHotKey ( NULL, TURN_OFF_HOTKEY, HIBYTE(LOWORD(wHotKey)) , wHotKey); main.cpp if ( messages.message == WM_HOTKEY && ( HIWORD ( messages.lParam ) == GLOBAL_HOTKEY) ) alert("Coming only for Single Key"); This code works well, Only If the user selects a single key and not working when he selects multiple key combined like CTRL+F8. I know I am doing something wrong here. Really appreciate If someone guide me in a right path.

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  • Call function from object instantiated in one class in another

    - by Dk43
    I have two classes, both of which need to be able to call the same instance of entitymanager class Engine { EntityManager::Entitymanager EManager; } And I need to add an object to a vector contained by this particular instance of Engine. What I want to do is be able to add a bullet spawned by the player to the vector that contains all my entities. class Player : Entity { void SpawnBullet() {Engine::EManager.Add(BULLET);} } The above returns this error: error: object missing in reference to ‘Engine::EManager’ How do I resolve this? Any help or pointers in the right direction would be much appreciated!

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  • How can I find days between different paired rows?

    - by Anthony
    I've been racking my brain about how to do this in one query without PHP code. In a nutshell, I have a table that records email activity. For the sake of this example, here is the data: recipient_id activity date 1 delivered 2011-08-30 1 open 2011-08-31 2 delivered 2011-08-30 3 delivered 2011-08-24 3 open 2011-08-30 3 open 2011-08-31 The goal: I want to display to users a single number that tells how many recipients open their email within 24 hours. E.G. "Users that open their email within 24 hours: 13 Readers" In the case of the sample data, above, the value would be "1". (Recipient one was delivered an email and opened it the next day. Recipient 2 never opened it and recipient 3 waited 5 days.) Can anyone think of a way to express the goal in a single query? Reminder: In order to count, the person must have a 'delivered' tag and at least one 'open' tag. Each 'open' tag only counts once per recipient.

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  • Core Data-Linking one-to-many relationships

    - by Stelmate
    I have a one-to-many relationship where each department has many employees. When I create a new employee object I just link it to the parent department manually by setting the property to the instance of the department I have fetched from my fetch request. However, this seems to be improper because when I try to access the set of employees from the department by simply accessing the .employees property on my department object instance it returns a 0 count. Isn't the fault suppose to fire once I access a property? Am I linking my parent/child objects incorrectly?

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  • Ruby forwarding method calls

    - by JP
    I have an instance of a master class which generates instances of a subclass, these subclasses need to forward some method calls back to the master instance. At the moment I have code looking something like this, but it feels like I should be able to do the same thing more efficiently (maybe with method_missing?) class Master def initalize(mynum) @mynum = mynum end def one_thing(subinstance) "One thing with #{subinstance.var} from #{@mynum}" end def four_things(subinstance) "Four things with #{subinstance.var} from #{@mynum}" end def many_things(times,subinstance) "#{times} things with #{subinstance.var} from #{@mynum}" end def make_a_sub(uniqueness) Subthing.new(uniqueness,self) end class Subthing def initialize(uniqueness,master) @u = uniqueness @master = master end # Here I'm forwarding method calls def one_thing master.one_thing(self) end def four_things master.four_things(self) end def many_things(times) master.many_things(times,self) end end end m = Master.new(42) s = m.make_a_sub("very") s.one_thing === m.one_thing(s) s.many_things(8) === m.many_things(8,s) I hope you can see what's going on here. I would use method_missing, but I'm not sure how to cope with the possibility of some calls having arguments and some not (I can't really rearrange the order of the arguments to the Master methods either) Thanks for reading!

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  • Test massive website

    - by Ant
    My company has just migrated all the code for our website to 3 identical servers on an off-site location. Now it is our job to test them. However, the amount of websites/functionality that we have to test is exorbitant, and multiply that times 3! To check every single link and every single function is a daunting task. We are in the process of manually doing that right now. My question to you guys/girls is this... Is there a way to automate the testing so we don't have to waste our time clicking, waiting, and checking the response, times 3? ;-) Let me know if you need any other info. Thanks!

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  • Is MSDN referencing a system.thread, a worker thread, an io thread or all three?

    - by w0051977
    Please see the warning below taken from the StreamWriter class specification (http://msdn.microsoft.com/en-us/library/system.io.streamwriter.aspx): "Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe." I understand that a W3WC process contains two thread pools i.e. worker threads and I/O threads. A worker thread could contain many threads of its own (if the application creates its own System.Thread instances). Does the warning only relate to System.Threads or does it relate to worker threads and I/O threads as well I.e. as the instance variables of the streamwriter class are not thread safe then does this mean that there would be problems if multiple worker threads access it eg if two users on two different web clients attempt to write to the log file at the same time, then could one lock out the other?

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  • How do I reference a pointer from a different class?

    - by Justagruvn
    First off, I despise singletons with a passion. Though I should probably be trying to use one, I just don't want to. I want to create a data class (that is instantiated only once by a view controller on loading), and then using a different class, message the crap out of that data instance until it is brimming with so much data, it smiles. So, how do I do that? I made a pointer to the instance of the data class when I instantiated it. I'm now over in a separate view controller, action occurs, and I want to update the initial data object. I think I need to reference that object by way of pointer, but I have no idea how to do that. Yes, I've set properties and getters and setters, which seem to work, but only in the initial view controller class. Peace Love applesauce.

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  • Is LocalDB supported by Visual Studio 2010 in Entity Framework 5?

    - by Mathias Lykkegaard Lorenzen
    Is LocalDB supported by Visual Studio 2010 in Entity Framework 5, on .NET 4.0? Or am I doing it wrong? I'm getting a "The network path can't be found" issue when instantiating my model container with a connection string for LocalDB. Here's the connection string: var connectionString = "metadata=res://*/Model.csdl|res://*/Model.ssdl|res://*/Model.msl;provider=System.Data.SqlClient;provider connection string=\"data source=(localdb)\v11.0;initial catalog=fablelane_com_db;integrated security=SSPI;multipleactiveresultsets=True;App=EntityFramework\""; Edit 1 I'm receiving the following error when connecting, more specifically: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server). Edit 2 I just figured out that changing to Visual Studio 11 beta doesn't work either. Still receiving the same error-message.

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  • Need guidance for my first Android application: how many activities should I use?

    - by jul
    Hi, I'm starting Android doing an application for searching restaurants, and some guidance would be welcome! On the first screen I'd like to have a search field with a submit button (I get the data from a web service), and below a list with the results of the search. When clicking on one of the items of the list it will show a screen with the restaurant details as well as a map showing its location. My questions are: Can I do everything in one single activity or should I do an activity for the search, one for the result list, one for the restaurant description, and another for the map? Would doing one single activity make the application more responsive? How can I use a list and a map within a normal activity (without ListActivity and MapActivity)? Any help, pointer, example application or sample code is very appreciated! Thank you Jul

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  • NSInvalidArgumentException – App terminates while i'm trying to copy a captured video to documents f

    - by ChrNis
    I'd like to try the wisdom of the crowds..because i'm frustrated right now. Thanks in advance. So here is my code: - (void)imagePickerController:(UIImagePickerController *)ipc didFinishPickingMediaWithInfo:(NSDictionary *)info{ NSLog(@"info: %@",info); NSString *newFilename = [NSString stringWithFormat:@"%@/%@.mov", [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"], [NSString stringWithFormat:@"%d", (long)[[NSDate date] timeIntervalSince1970]]]; NSLog(@"newFilename: %@",newFilename); NSFileManager *filemgr = [NSFileManager defaultManager]; NSError *err; if ([filemgr copyItemAtPath:[info objectForKey:@"UIImagePickerControllerMediaURL"] toPath:newFilename error:&err] == YES) NSLog (@"Move successful"); else NSLog (@"Move failed"); and this is the log: 2010-05-16 18:19:01.975 erlkoenig[7099:307] info: { UIImagePickerControllerMediaType = "public.movie"; UIImagePickerControllerMediaURL = "file://localhost/private/var/mobile/Applications/BE25F9B5-2D08-4B59-8B62-D04DF7BB7E5B/tmp/-Tmp-/capture-T0x108cb0.tmp.8M81HU/capturedvideo.MOV"; } newFilename: /var/mobile/Applications/BE25F9B5-2D08-4B59-8B62-D04DF7BB7E5B/Documents/1274026741.mov [NSURL fileSystemRepresentation]: unrecognized selector sent to instance 0x1c1f90 *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSURL fileSystemRepresentation]: unrecognized selector sent to instance 0x1c1f90

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  • The Advancement of Technology That Lead to Websites Being One of the Most Important Business Assets

    Twenty years ago the world was a very different place. Most companies were still using paper based filing systems and people saw computers as being complicated and expensive. Businesses had storage rooms and large filing cabinets full of alphabetically and chronologically ordered documents and letters. Due to the efforts of large corporations, technology has advanced in a way that most people would have never imagined. What would have taken up a full warehouse worth of space can now be stored digitally in a device that is smaller than a book and it can be searched through in a matter of seconds.

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  • Java: Superclass to construct a subclass on certain conditions, possible?

    - by ramihope
    I have this condition public class A { public action() { System.out.println("Action done in A"); } } public class B extends A { public action() { System.out.println("Action done in B"); } } when I create an instance of B, the action will do just actions in B, as it overrides the action of the superclass. the problem is that in my project, the super class A is already used too many times, and I am looking for a way that under certain conditions, when i create an instance of A it makes a check and if it is true, replace itself with B. public class A { public A() { if ([condition]) { this = new B(); } } public action() { System.out.println("Action done in A"); } } A a = new A(); a.action(); // expect to see "Action done in B"... is this possible in some way?

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  • I need to get past my permissions to recover data

    - by adsmz
    Due to some mishaps, I am unable to boot into Kubuntu at all. However, my data is still on the hard drive. I managed to get one of the other two computers to which I have access to read the disk by booting into a liveCD session of kubuntu. The only storage medium to which I have access is a 30 GB data stick. Here's where the trouble starts: In music alone, I have to back up about 60 GB. Obviously this is going to have to be split into chunks and moved over to the second spare PC until I can reinstall Kubuntu on my laptop. All of the data that needs backed up is behind a permissions wall, so while I can view it, I can't interact with it directly. I know copying and moving through the terminal can get around this with sudo cp or sudo mv, but is there a way to first compress multiple folders in a single archive, then move it? (While we're on the subject, what compression method would be best for large volumes of music in MP3, WAV, and OGG format?)

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  • What do C# Table Adapters actually return?

    - by Raven Dreamer
    I'm working on an application that manipulates SQL tables in a windows form application. Up until now, I've only been using the pre-generated Fill queries, and self-made update and delete queries (which return nothing). I am interested in storing the value of a single value from a single column (an 'nchar(15)' name), and though I have easily written the SQL code to return that value to the application, I have no idea what it will be returned as. SELECT [Contact First Name] FROM ContactSkillSet WHERE [Contact ID] = @CurrentID Can the result be stored directly as a string? Do I need to cast it? Invoke a toString method?

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  • Django GenericRelation doesn't save related object's id - is this a bug or am I doing it wrong?

    - by pinkeen
    I have a model with a generic relation (call it A), when creating an instance of this object I pass an instance of another model (call it B) as the initializer of the content_object field (via kwargs of the constructor). If I don't save B before creating A then when saving A the content_object_id is saved to the db as NULL. If I save B before passing it to the constructor of A then everything's allright. It's not logical. I assumed that the ID of the related object (B) is fetched when doing A.save() and it should throw some kind of an exception if B isn't saved yet but it just fails silently. I don't like the current solution (saving B beforhand) because we don't know yet if I will be always willing to keep the object, not just scrap it, and there are performance considerations - what if I will add some another data and save it once more shortly after. class BaseNodeData(models.Model): ... extnodedata_content_type = models.ForeignKey(ContentType, null=True) extnodedata_object_id = models.PositiveIntegerField(null=True) extnodedata = generic.GenericForeignKey(ct_field='extnodedata_content_type', fk_field='extnodedata_object_id') class MarkupNodeData(models.Model): raw_content = models.TextField() Suppose we do: markup = MarkupNodeData(raw_content='...') base = BaseNodeData(..., extnodedata=markup) markup.save() base.save() # both records are inserted to the DB but base is stored with extnodedata_object_id=NULL markup = MarkupNodeData(raw_content='...') base = BaseNodeData(..., extnodedata=markup) base.save() markup.save() # no exception is thrown and everything is the same as above markup = MarkupNodeData(raw_content='...') markup.save() base = BaseNodeData(..., extnodedata=markup) base.save() # this works as expected Of course I can do it this way, but it doesn't change anything: base = BaseNodeData(...) base.extnodedata = markup My question is - is this a bug in django which I should report or maybe I'm doing something wrong. Docs on GenericRelations aren't exactly verbose.

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