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• Recommendations for an in memory database vs thread safe data structures

  - by yx

  TLDR: What are the pros/cons of using an in-memory database vs locks and concurrent data structures? I am currently working on an application that has many (possibly remote) displays that collect live data from multiple data sources and renders them on screen in real time. One of the other developers have suggested the use of an in memory database instead of doing it the standard way our other systems behaves, which is to use concurrent hashmaps, queues, arrays, and other objects to store the graphical objects and handling them safely with locks if necessary. His argument is that the DB will lessen the need to worry about concurrency since it will handle read/write locks automatically, and also the DB will offer an easier way to structure the data into as many tables as we need instead of having create hashmaps of hashmaps of lists, etc and keeping track of it all. I do not have much DB experience myself so I am asking fellow SO users what experiences they have had and what are the pros & cons of inserting the DB into the system?

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• Can't see or add Website Data Sources in RDLC report in ASP.NET MVC

  - by RobertC

  In the RDLC report, in Design view in Visual Studio 2008, we don't see anything in the Website Data Sources tab and the button to Add New Data Source is grayed out. Only the Refresh button is enabled, and clicking it doesn't do anything. Our business logic layer returns Lists of business objects and the business logic and business object projects are both referenced by the MVC project. This is an MVC app, so there is no App_Code folder. How do we get our business objects to appear in the Website Data Sources list so we can drag and drop fields from the object onto our RDLC report?

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• Performance tuning of a Hibernate+Spring+MySQL project operation that stores images uploaded by user

  - by Umar

  Hi I am working on a web project that is Spring+Hibernate+MySQL based. I am stuck at a point where I have to store images uploaded by a user into the database. Although I have written some code that works well for now, but I believe that things will mess up when the project would go live. Here's my domain class that carries the image bytes: @Entity public class Picture implements java.io.Serializable{ long id; byte[] data; ... // getters and setters } And here's my controller that saves the file on submit: public class PictureUploadFormController extends AbstractBaseFormController{ ... protected ModelAndView onSubmit(HttpServletRequest request, HttpServletResponse response, Object command, BindException errors) throws Exception{ MutlipartFile file; // getting MultipartFile from the command object ... // beginning hibernate transaction ... Picture p=new Picture(); p.setData(file.getBytes()); pictureDAO.makePersistent(p); // this method simply calls getSession().saveOrUpdate(p) // committing hiernate transaction ... } ... } Obviously a bad piece of code. Is there anyway I could use InputStream or Blob to save the data, instead of first loading all the bytes from the user into the memory and then pushing them into the database? I did some research on hibernate's support for Blob, and found this in Hibernate In Action book: java.sql.Blob and java.sql.Clob are the most efficient way to handle large objects in Java. Unfortunately, an instance of Blob or Clob is only useable until the JDBC transaction completes. So if your persistent class defines a property of java.sql.Clob or java.sql.Blob (not a good idea anyway), you’ll be restricted in how instances of the class may be used. In particular, you won’t be able to use instances of that class as detached objects. Furthermore, many JDBC drivers don’t feature working support for java.sql.Blob and java.sql.Clob. Therefore, it makes more sense to map large objects using the binary or text mapping type, assuming retrieval of the entire large object into memory isn’t a performance killer. Note you can find up-to-date design patterns and tips for large object usage on the Hibernate website, with tricks for particular platforms. Now apparently the Blob cannot be used, as it is not a good idea anyway, what else could be used to improve the performance? I couldn't find any up-to-date design pattern or any useful information on Hibernate website. So any help/recommendations from stackoverflowers will be much appreciated. Thanks

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• Enumerable Contains Enumerable

  - by Tim

  For a method I have the following parameter IEnumerable<string> tags and with to query a list of objects, let's call them Post, that contains a property IEnumerable<string> Tags { get; set; }. My question is: How do I use linq to query for objects that contains all the tags from the tags parameter? private List<Post> posts = new List<Post>(); public IEnumerable<Post> GetPostsWithTags(IEnumerable<string> tags) { return ???; }

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• Finding the index of a queue that holds a member of a containing object for a given value

  - by Luke Mcneice

  I have a Queue that contains a collection of objects, one of these objects is a class called GlobalMarker that has a member called GlobalIndex. What I want to be able to do is find the index of the queue where the GlobalIndex contains a given value (this will always be unique). Simply using the Contains method shown below returns a bool. How can I obtain the queue index of this match? RealTimeBuffer .OfType<GlobalMarker>() .Select(o => o.GlobalIndex) .Contains(INT_VALUE);

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• "Unable to find any mappings for the given content, keyPath=null" RestKit 0.2

  - by abisson

  So I switched to using RestKit 0.2 and CoreData and I've been having a lot of trouble trying to get the mappings correct... I don't understand why. The JSON Response of my server is like this: { "meta": { "limit": 20, "next": null, "offset": 0, "previous": null, "total_count": 2 }, "objects": [{ "creation_date": "2012-10-15T20:16:47", "description": "", "id": 1, "last_modified": "2012-10-15T20:16:47", "order": 1, "other_names": "", "primary_name": "Mixing", "production_line": "/api/rest/productionlines/1/", "resource_uri": "/api/rest/cells/1/" }, { "creation_date": "2012-10-15T20:16:47", "description": "", "id": 2, "last_modified": "2012-10-15T20:16:47", "order": 2, "other_names": "", "primary_name": "Packaging", "production_line": "/api/rest/productionlines/1/", "resource_uri": "/api/rest/cells/2/" }] } Then in XCode I have: RKObjectManager *objectManager = [RKObjectManager sharedManager]; [AFNetworkActivityIndicatorManager sharedManager].enabled = YES; NSManagedObjectModel *managedObjectModel = [NSManagedObjectModel mergedModelFromBundles:nil]; RKManagedObjectStore *managedObjectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:managedObjectModel]; objectManager.managedObjectStore = managedObjectStore; RKEntityMapping *cellMapping = [RKEntityMapping mappingForEntityForName:@"Cell" inManagedObjectStore:managedObjectStore]; cellMapping.primaryKeyAttribute = @"identifier"; [cellMapping addAttributeMappingsFromDictionary:@{ @"id": @"identifier", @"primary_name": @"primaryName", }]; RKResponseDescriptor *responseCell = [RKResponseDescriptor responseDescriptorWithMapping:cellMapping pathPattern:@"/api/rest/cells/?format=json" keyPath:@"objects" statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)]; [objectManager addResponseDescriptorsFromArray:@[responseCell, responseUser, responseCompany]]; [managedObjectStore createPersistentStoreCoordinator]; NSString *storePath = [RKApplicationDataDirectory() stringByAppendingPathComponent:@"AppDB.sqlite"]; NSString *seedPath = [[NSBundle mainBundle] pathForResource:@"SeedDatabase" ofType:@"sqlite"]; NSError *error; NSPersistentStore *persistentStore = [managedObjectStore addSQLitePersistentStoreAtPath:storePath fromSeedDatabaseAtPath:seedPath withConfiguration:nil options:nil error:&error]; NSAssert(persistentStore, @"Failed to add persistent store with error: %@", error); // Create the managed object contexts [managedObjectStore createManagedObjectContexts]; // Configure a managed object cache to ensure we do not create duplicate objects managedObjectStore.managedObjectCache = [[RKInMemoryManagedObjectCache alloc] initWithManagedObjectContext:managedObjectStore.persistentStoreManagedObjectContext]; My request is: [[RKObjectManager sharedManager] getObjectsAtPath:@"/api/rest/cells/?format=json" parameters:nil success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) { RKLogInfo(@"Load complete: Table should refresh..."); [[NSUserDefaults standardUserDefaults] setObject:[NSDate date] forKey:@"LastUpdatedAt"]; [[NSUserDefaults standardUserDefaults] synchronize]; } failure:^(RKObjectRequestOperation *operation, NSError *error) { RKLogError(@"Load failed with error: %@", error); }]; And I always get the following error: **Error Domain=org.restkit.RestKit.ErrorDomain Code=1001 "Unable to find any mappings for the given content" UserInfo=0x1102d500 {DetailedErrors=(), NSLocalizedDescription=Unable to find any mappings for the given content, keyPath=null}** Thanks a lot!

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• How do I find the "concrete class" of a django model baseclass

  - by Mr Shark

  I'm trying to find the actual class of a django-model object, when using model-inheritance. Some code to describe the problem: class Base(models.model): def basemethod(self): ... class Child_1(Base): pass class Child_2(Base): pass If I create various objects of the two Child classes and the create a queryset containing them all: Child_1().save() Child_2().save() (o1, o2) = Base.objects.all() I want to determine if the object is of type Child_1 or Child_2 in basemethod, I can get to the child object via o1.child_1 and o2.child_2 but that reconquers knowledge about the childclasses in the baseclass. I have come up with the following code: def concrete_instance(self): instance = None for subclass in self._meta.get_all_related_objects(): acc_name = subclass.get_accessor_name() try: instance = self.__getattribute__(acc_name) return instance except Exception, e: pass But it feels brittle and I'm not sure of what happens when if I inherit in more levels.

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• Spring.NET & Immediacy CMS (or how to inject to server side controls without using PageHandlerFactor

  - by Simon Rice

  Is there any way to inject dependencies into an Immediacy CMS control using Spring.NET, ideally without having to use to ContextRegistry when initialising the control? Update, with my own answer The issue here is that Immediacy already has a handler defined in web.config that deals with all aspx pages, & so it's not possible add an entry for Spring.NET's PageHandlerFactory in web.config as per a normal webforms app. That rules out making the control implement ISupportsWebDependencyInjection. Furthermore, most of Immediacy's generated pages are aspx pages that don't physically exist on the drive. I have changed the title of the question to reflect this. What I have done to get Dependency Injection working is: Add the usual entries to web.config for Spring.NET as outlined in the documentation, except for the adding the entry to the <httpHandlers> section. In this case I've got my object definitions in Spring.config. Create the following abstract base class that will deal with all of the Dependency Injection work: DIControl.cs public abstract class DIControl : ImmediacyControl { protected virtual string DIName { get { return this.GetType().Name; } } protected override void OnInit(EventArgs e) { if (ContextRegistry.GetContext().GetObject(DIName, this.GetType()) != null) ContextRegistry.GetContext().ConfigureObject(this, DIName); base.OnInit(e); } } For non-immediacy controls, you can make this server side control inherit from Control or whatever subclass of that you like. For any control with which you wish to use with Spring.NET's Inversion of Control container, define it to inherit from DIControl & add the relelvant entry to Spring.config, for example: SampleControl.cs public class SampleControl : DIControl, INamingContainer { public string Text { get; set; } protected string InjectedText { get; set; } public SampleControl() : base() { Text = "Hello world"; } protected override void RenderContents(HtmlTextWriter output) { output.Write(string.Format("{0} {1}", Text, InjectedText)); } } Spring.config <objects xmlns="http://www.springframework.net"> <object id="SampleControl" type="MyProject.SampleControl, MyAssembly"> <property name="InjectedText" value="from Spring.NET" /> </object> </objects> You can optionally override DIName if you wish to name your entry in Spring.config differently from the name of your class. Provided everything's done correctly, you will have the control writing out "Hello world from Spring.NET!" when used in a page. This solution uses Spring.NET's ContextRegistry from within the control, but I would be surprised if there's no way around that for Immediacy at least since the page objects themselves aren't accessible. However, can this be improved at all from a Spring.NET perspective? Is there maybe an Immediacy plugin that already does this that I'm completely unaware of? Or is there an approach that does this in a more elegant way? I'm open to suggestions.

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• Why is django admin not accepting Nullable foreign keys?

  - by p.g.l.hall

  Here is a simplified version of one of my models: class ImportRule(models.Model): feed = models.ForeignKey(Feed) name = models.CharField(max_length=255) feed_provider_category = models.ForeignKey(FeedProviderCategory, null=True) target_subcategories = models.ManyToManyField(Subcategory) This class manages a rule for importing a list of items from a feed into the database. The admin system won't let me add an ImportRule without selecting a feed_provider_category despite it being declared in the model as nullable. The database (SQLite at the moment) even checks out ok: >>> .schema ... CREATE TABLE "someapp_importrule" ( "id" integer NOT NULL PRIMARY KEY, "feed_id" integer NOT NULL REFERENCES "someapp_feed" ("id"), "name" varchar(255) NOT NULL, "feed_provider_category_id" integer REFERENCES "someapp_feedprovidercategory" ("id"), ); ... I can create the object in the python shell easily enough: f = Feed.objects.get(pk=1) i = ImportRule(name='test', feed=f) i.save() ...but the admin system won't let me edit it, of course. How can I get the admin to let me edit/create objects without specifying that foreign key?

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• An Efficient data structure for Sorted List

  - by holydiver

  I want to save my objects according to a key in the attributes of my object in a sorted fashion. Later on I'll access these objects sequentially from max key to min key. I'll do some search tasks as well. I consider to use either AVL tree or RB Tree. As far as i know they are nearly equivalent in theory(Both have O(logn)). But in practice which one might be better in performance in my situation. And is there a better alternative than those, considering that I'll mostly do insert and sequentially access to the ds.

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• iPhone SDK Nested For Loop performance

  - by Skeep

  Hi All, I have a NSArray of string id and a NSDictionary of NSDictionary objects. I am currently looping through the string id array to match the id value in the NSDictionary. There are around 200 NSDictionary objects and only 5 or so string ID. My current code is such: for (NSString *Str in aArr) { for (NSDictionary *a in apArr) { if ([a objectForKey:@"id"] == Str) { NSLog(@"Found!"); } } } The performance of the above code is really slow and I was wondering if there is a better way to do this?

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• What is the best way to interoperably serialize a message?

  - by iwein

  I'm considering message serialization support for spring-integration. This would be useful for various wire level transports to implement guaranteed delivery, but also to allow interoperability with other messaging systems (e.g. through AMQP). The fundamental problem that arises is that a message containing Java object in it's payload and headers should be converted to a byte[] and/or written to a stream. Java's own serialization is clearly not going to cut it because that is not interoperable. My preference would be to create an interface that allows the user to implement the needed logic for all Objects that take part in serialization. Is this a sensible idea and what would the interface look like? Is there a standard interoperable way to serialize Objects that would make sense in this context?

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• Selecting an element based on class and id in jquery - similar to an SQL query

  - by Ankur

  I want to select an element based on it's class and id, I have seen many similar questions on SO. Most of the users ask why would you ever want to do this - which is not very helpful, trust me, this is the simplest way of solving my UI problem, and it's a very unique and intereting UI related to making generic triple stores easily browsable. At the moment the jQUery looks like this: $(document).ready( function() { $(".predicates").hide(); $(".objects").hide(); $("#subject").click( function() { $("#predId, .predicates").toggle(); // this line } ); $("#predId").click( function() { $("#objId, .objects").toggle(); } ); }); The line I am really interested in is this $("#predId, .predicates").toggle(); how do I get the select to ensure that both #predId and .predicates are true, at the moment it seems that only one or the other has to be true. Is there something like an && operator?

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• Quickly retrieve the subset of properties used in a huge collection in C#

  - by ccornet

  I have a huge Collection (which I can cast as an enumerable using OfType<()) of objects. Each of these objects has a Category property, which is drawn from a list somewhere else in the application. This Collection can reach sizes of hundreds of items, but it is possible that only, say, 6/30 of the possible Categories are actually used. What is the fastest method to find these 6 Categories? The size of the huge Collection discourages me from just iterating across the entire thing and returning all unique values, so is there a faster method of accomplishing this? Ideally I'd collect the categories into a List.

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• How to build boost foreach cycle

  - by Ockonal

  Hi guys! I have some abstract class called IClass (has pure virtual function). There are some classes which inherit IClass: CFirst, CSecond. I want to add objects of classes which inherit into boost::ptr_vector: class IClass { virtual void someFunc() = 0; }; class CFirst : public IClass { }; class CSecond : public IClass { }; boost::ptr_vector<IClass> objectsList; objectsList.push_back(new CFirst()); objectsList.push_back(new CSecond()); And now my goal is to call function (which is declarated in IClass) from all objects in objectsList. I'd prefer to use BOOST_FOREACH: foreach(IClass tempObj, objectsList) { tempObj.someFunc(); } The problem is that IClass - abstract class, so I can't make instance of it for the foreach-cycle. What should I do?

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• Django Grouping Query

  - by Matt

  I have the following (simplified) models: class Donation(models.Model): entry_date = models.DateTimeField() class Category(models.Model): name = models.CharField() class Item(models.Model): donation = models.ForeignKey(Donation) category = models.ForeignKey(Category) I'm trying to display the total number of items, per category, grouped by the donation year. I've tried this: Donation.objects.extra(select={'year': "django_date_trunc('year', %s.entry_date)" % Donation._meta.db_table}).values('year', 'item__category__name').annotate(items=Sum('item__quantity')) But I get a Field Error on item__category__name. I've also tried: Item.objects.extra(select={"year": "django_date_trunc('year', entry_date)"}, tables=["donations_donation"]).values("year", "category__name").annotate(items=Sum("quantity")).order_by() Which generally gets me what I want, but the item quantity count is multiplied by the number of donation records. Any ideas? Basically I want to display this: 2010 - Category 1: 10 items - Category 2: 17 items 2009 - Category 1: 5 items - Category 3: 8 items

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• R: Using sapply on vector of POSIXct

  - by Chris

  I have what may be a very simple question. I want to process a column of POSIXct objects from a dataframe and generate a vector of datetime strings. I tried to use the following sapply call dt <- sapply(df$datetime, function(x) format(x,"%Y-%m-%dT%H:%M:%S")) but to no avail. I keep getting the following error Error in prettyNum(.Internal(format(x, trim, digits, nsmall, width, 3L, : invalid 'trim' argument When I apply this function to a single POSIXct object from the column, I have no problem. So I'm stumped at the moment about what the problem is. Do I need to do something special with POSIXct objects?

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• Jackrabbit: How to obtain list of DavResources by given url?

  - by kilonet

  Using Jackrabbit WebDAV library, how can I get list of all resources as DavResources objects?

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• Ruby efficient way of building an array from an array of arrays

  - by randombits

  I have an array of ActiveRecord objects, each one which has its own respective errors array. I want to flatten it all out and get only the unique values into one array. So the top level array might look like: foo0 = Foo.new foo1 = Foo.new foo2 = Foo.new foo3 = Foo.new arr = [foo0, foo1, foo2, foo3] Each one of those objects could potentially have an array of errors, and I'd like to get just the unique message out of them and put them in another array, say called error_arr. How would you do it the "Ruby" way?

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• Accessing FacesContext from Web Service

  - by scriptmonster

  I'm developing a Web Service which will be called by clients which are written by me. In the web service I need to use application-wide objects which eases the load of application on the system. I have implemented my application-wide objects as shown in this question. I can use my object in a jsf page with no problem as follows. MyObject mo = (MyObject) FacesContext.getCurrentInstance().getExternalContext().getApplicationMap().get("MyObjectsName"); But when it comes to use it in a Web Service Request FacesContext.getCurrentInstance() returns null. Is there any way to use the FacesContext in a web service.

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• ACCESS 2003 Excel 2003 : VBA for opening Excel file from Access and copying a pictre from excel the

  - by Justin

  So I have an excel workbook that has a nice global map of shaperange objects. With some very simple code I can change the colors, group and ungroup collections of countries into arrays, etc...and it works pretty well. However, I would like to bring this into Access. So I could copy and paste all the shapes into an access form manually, but then they become pictures and I cannot change the colors of the countries (shaperange objects) to have the map act interactively as I can in excel. So I am thinking that I know how to use excel functions from access, and how to open excel from access. Is there a way to copy an object from excel (I know the file name and the shape name that i mean to copy everytime), and bringing it back to access to paste on a form? Atypical, I know, all my Access questions are. Thanks!

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• How to keep historic details of modification in a database (Audit trail)?

  - by mada

  I'm a J2EE developer & we are using hibernate mapping with a PostgreSQL database. We have to keep track of any changes occurs in the database, in others words all previous & current values of any field should be saved. Each field can be any type (bytea, int, char...) With a simple table it is easy but we a graph of objects 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?

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• Composite Views and View Controllers

  - by BillyK

  Hi, I'm somewhat new to Android and am in the process of designing an application with a couple fairly complex views. One of the views is intended to involve a complex view displaying information associated with model objects and segregated into several different views; the navigation of which is meant to be achieved using sliding effects (i.e. sliding one's finger across the screen to traverse from one screen to the next, etc). The view itself will be used to host multiple sets of views for varying types of model objects, but with a general structure that is reused between them all. As a rough example, the view might come up to display information about a person (the model object), displaying several details views: a view for general information, a view displaying a list of hobbies, and a view displaying a list of other individuals associated with their social network. The same general view, when given a model object representing a particular car would give several different views: A general view with details, A view containing photo images for that vehicle, a view representing locations which it could be purchased from, and a view providing a list of related cars. (NOTE: This is not the real data involved, but is representative of the general intent for the view). The subviews will NOT cover the entire screen real-estate and other features within the view should be both visible and able to be interacted with by the user. The idea here is that there is a general view structure that is reusable and which will manage a set of subviews dynamically generated based upon the type of model object handed to the view. I'm trying to determine the appropriate way to leverage the Android framework in order to best achieve this without violating the integrity of the framework. Basically, I'm trying to determine how to componentize this larger view into reusable units (i.e. general view, model-specific sub-view controllers, and individual detail views). To be more specific, I'm trying to determine if this view is best designed as a composite of several custom View classes or a composite of several Activity classes. I've seen several examples of custom composite views, but they typically are used to compose simple views without complex controllers and without attention to the general Activity lifecycle (i.e. storing and retrieving data related to the model objects, as appropriate). On the other hand, the only real example I've seen regarding a view comprised of a composite of Activities is the TabActivity itself, and that isn't customizable in the fashion that would be necessary for this. Does anyone have any suggestions as to the appropriate way to structure my view to achieve the application framework I'm looking for? Views? Activities? Something else? Any guidance would be appreciated. Thanks in advance.

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• How do you deal with the conflict between ActiveSupport::JSON and the JSON gem?

  - by Luke Francl

  I am stumped with this problem. ActiveSupport::JSON defines to_json on various core objects and so does the JSON gem. However, the implementation is not the same -- the ActiveSupport version takes arguments and the JSON gem version doesn't. I installed a gem that required the JSON gem and my app broke. The issue is that I'm using to_json in a controller that returns a list of objects, but I want to control which attributes are returned. When code anywhere in my system does require 'json' I get this error message: TypeError: wrong argument type Hash (expected Data) I tried a couple of things that I read online to fix it, but nothing worked. I ended up re-writing the gem to use ActiveSupport::JSON.decode instead of JSON.parse. This works but it's not sustainable...I can't be forking gems every time I want to use a gem that requires the JSON gem. Update: The best solution of this problem is to upgrade to Rails 2.3 or higher, which fixed it.

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• Android: Deciding between SurfaceView and OpenGL (GLSurfaceView)

  - by Rich

  Is there a way to decide up front based on the expected complexity of a game/app in the planning phase whether to use regular Canvas drawing in a SurfaceView or to go with OpenGL? I've been playing around with a Canvas and only need 2D movement, and on a fairly new phone I'm getting pretty decent performance with a bunch of primitive objects and a few bitmaps running around the screen on a solid background. Is it fair to say that if I'm going to be drawing background images and increasing the number of objects being moved and drawn on top of them that I should go straight to OpenGL?

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