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  • Core Data strategy using in memory cache, or no core data at all?

    - by randombits
    I have a user interface where the user can check off a bunch of items from a tableview, almost like a todo list. The items are populated from a Core Data stack. I need to be able to take all of the items they're clicking through and put them into a "temporary" shopping cart. Once they're in the shopping cart, users can go through the list and remove the items, or just submit them to a server. The thing is, the selected items are temporary just like an internet based shopping cart. It's nothing something that gets persisted once the application closes. Once the view is no longer in display, I can assume that the shopping cart is safe to discard. What's the best way to approach this? Since the user is essentially clicking on instances that map back to a Core Data entity .. should I setup a different persistence store such as in memory and add that store to my managed object context?

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  • Connection between Properties of Entities in Data Oriented Design

    - by sharethis
    I want to start with an example illustrating my question. The following way it is done in the most games. class car { vec3 position; vec3 rotation; mesh model; imge texture; void move(); // modify position and rotation void draw(); // use model, texture, ... }; vector<car> cars; for(auto i = cars.begin(); i != cars.end(); ++i) { i->move(); i->draw(); } Data oriented design means to process the same calculation on the hole batch of data at once. This way it takes more advantage out of the processor cache. struct movedata { vec3 position; vec3 rotation; }; struct drawdata { mesh model; imge texture; }; vector<movedata> movedatas; vector<drawdata> drawdatas; for(auto i = movedatas.begin(); i != movedatas.end(); ++i) { // modify position and rotation } for(auto i = drawdatas.begin(); i != drawdatas.end(); ++i) { // use model, texture, ... } But there comes a point where you need to find other properties according to an entity. For example if the car crashes, I do not need the drawdata and the movedata any more. So I need to delete the entries of this entity in all vectors. The entries are not linked by code. So my question is the following. How are properties of the same entity conceptually linked in a data oriented design?

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  • Help choosing the right data structure

    - by devoured elysium
    I need a data structure with the following requirements: Needs to be able to get elements by index (like a List). I will always just add / remove elements from the end of the structure. I am inclined to use an ArrayList. In this situation, it seems to be O(1) both to read elements (they always are?), remove elements (I only need to remove them at the end of the list) and to add(I only add to the end of the list). There is only the problem that time to time the ArrayList will have a performance penalty when it's completly full and I need to add more elements to it. Is there any other better idea? I don't think of a data structure that'd beat the ArrayList here. Thanks

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  • Store data in Ruby on Rails without Database

    - by snowmaninthesun
    I have a few data values that I need to store on my rails app and wanted to know if there are any alternatives to creating a database table just to do this simple task. Background: I'm writing some analytics and dashboard tools for my ruby on rails app and i'm hoping to speed up the dashboard by caching results that will never change. Right now I pull all users for the last 30 days, and re arange them so I can see the number of new users per day. It works great but takes quite a long time, in reality I should only need to calculate the most recent day and just store the rest of the array somewhere else. Where is the best way to store this array? Creating a database table seems a bit overkill, and i'm not sure that global variables are the correct answer. Is there a best practice for persisting data like this? If anyone has done anything like this before let me know what you did and how it turned out.

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  • Programming DataEntry&Forms: Population of Official Common Data Lists

    - by rlb.usa
    As a programmer of data-entry forms of all kinds, I often find myself making fields for things like Country and State. Consider: Perhaps a list the 50 United States names is an easy thing to find (does one include DC?) , but the countries are not. Nearly every site you find has a differing list with all of the political goings on over the years, and they become outdated quickly. What's the best practice regarding population of these kinds of lists? Is there an official list somewhere that one uses to populate these kinds of formal/official fields? Where do you get this data from, when it's not exactly specified in the specs?

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  • Designing DAOs for data sources other than a database

    - by James P.
    Hi, Until now I've been used to using DAOs to retrieve information from databases. Other sources of data are possible though and I'm wondering if and how the pattern could be applied in general. For example, I'm now working on an application that fetches XML on the web. The XML file could be considered as a data source and the actual fetching is similar in principle to a database request. I'm not quite sure how the DAO could be structured though. Any views on the subject are welcome.

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  • Store image in core data and Retina Display ?

    - by shani
    Hi I have an app that has hundreds of words with 3/4 images for each word. I have 2 versions of each word one for iOS 3 and one for retina display. I wish to save the images as data and connect them to the appropriate word so it will be easy to pull them later. my question is - how do i get the suitable size ? its works great with the @2x wjen you get it from the app file system, but hoe does it supposed to work when i get it from data ? thanks shani

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  • Entity Framework 4 & WCF Data Service: N:M mapping

    - by JJO
    I have three tables in my database: An A table, a B table, and a many-to-many ABMapping table. For simplicity, A and B are keyed with identity columns; ABMapping has just two columns: AId and BId. I built an Entity Framework 4 model from this, and it did correctly identify the N:M mapping between A and B. I then built a WCF Data Service based on this EF model. I'm trying to consume this WCF Data Service. Unfortunately, I can't figure out how to get a mapping between As and Bs to map back to the database. I've tried something like this: A a = new A(); B b = new B(); a.Bs.Add(b); connection.SaveChanges(); But this doesn't seem to have worked. Any clues? What am I missing?

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  • Twin edges - Half edge data structure

    - by Pradeep Kumar
    I have implemented a Half-edge data structure for loading 3d objects. I find that the part of assigning twin/pair edges takes the longest computation time (especially for objects which have hundreds of thousands half edges). The reason is that I use nested loops to accomplish this. Is there a simpler and efficient way of doing this? Below is the code which I've written. HE is the half-edge data structure. hearr is a vector containing all the half edges. vert is the starting vertex and end is the ending vertex. Thanks!! HE *e1,*e2; for(size_t i=0;i<hearr.size();i++){ e1=hearr[i]; for(size_t j=1;j<hearr.size();j++){ e2=hearr[j]; if((e1->vert==e2->end)&&(e2->vert==e1->end)){ e1->twin=e2; e2->twin=e1; } } }

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  • How to copy a structure with pointers to data inside (so to copy pointers and data they point to)?

    - by Kabumbus
    so I have a structure like struct GetResultStructure { int length; char* ptr; }; I need a way to make a full copy of it meaning I need a copy to have a structure with new ptr poinnting on to copy of data I had in original structure. Is It any how possible? I mean any structure I have which contains ptrs will have some fields with its lengths I need a function that would copy my structure coping all ptrs and data they point to by given array of lengthes... Any cool boost function for it? Or any way how to create such function?

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  • The data structure of libev watchers

    - by changchang
    Libev uses three data structures to storage different watchers. Heap: for watchers that sorted by time, such as ev_timer and ev_periodic. Linked list: such as ev_io, ev_signal, ev_child and etc. Array: such as ev_prepare, ev_check, ev_async and etc. There is no doubt about that uses heap to store timer watcher. But what is the criteria of selecting linked list and array? The data structure that stores ev_io watchers seems a little complex. It first is an array that with fd as its index and the element in the array is a linked list of ev_io watcher. It is more convenient to allocate space for array if use linked list as element. Is it the reason? Or just because of the insert or remove operation of ev_io is more frequently and the ev_prepare seems more stable? Or any other reasons?

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  • Where does one get data like Country:(list) State:(list)

    - by rlb.usa
    As a programmer of data-entry forms of all kinds, I often find myself making fields for things like Country: <choose from list>, State: <choose from list>, Race/Ethnicity: <choose from list>. Consider: Perhaps a list the 50 United States names is an easy thing to find (does one include DC?) , but the countries are not. Nearly every site you find has a differing list with all of the political goings on over the years, and they become outdated quickly. What's the best/common practice regarding population of these kinds of lists? Where does this data come from if it's not given in the specs?

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  • Facebook data collection ethical issues

    - by the_great_monkey
    If I have a Facebook app, and my users agree to allow my app to access their information, photos, friends, etc, is it ethical to grab their information when they log in, and then saving it in memory so that the next time he goes to my app, it can load faster? If so, what about when the user logged off? Is the right thing to do to is to delete all the cached information and photos that the user provided? Has Facebook got any way to detect that we're doing this (saving their information, etc)?

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  • Manipulate data for scaling

    - by user1487000
    I have this data: Game 1: 7.0/10.0, Reviewed: 1000 times Game 2: 7.5/10.0, Reviewed: 3000 times Game 3: 8.9/10.0, Reviewed: 140,000 times Game 4: 10.0/10.0 Reviewed: 5 times . . . I want to manipulate this data in a way to make each rating reflective of how many times it has been reviewed. For example Game 3 should have a little heavier weight than than Game 4, since it has been reviewed way more. And Game 2's 7 should be weighted more than Game 1's 7. Is there a proper function to do this scaling? In such a way that ScaledGameRating = OldGameRating * (some exponential function?)

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  • Core Data migration failing with error: Failed to save new store after first pass of migration

    - by unforgiven
    In the past I had already implemented successfully automatic migration from version 1 of my data model to version 2. Now, using SDK 3.1.3, migrating from version 2 to version 3 fails with the following error: Unresolved error Error Domain=NSCocoaErrorDomain Code=134110 UserInfo=0x5363360 "Operation could not be completed. (Cocoa error 134110.)", { NSUnderlyingError = Error Domain=NSCocoaErrorDomain Code=256 UserInfo=0x53622b0 "Operation could not be completed. (Cocoa error 256.)"; reason = "Failed to save new store after first pass of migration."; } I have tried automatic migration using NSMigratePersistentStoresAutomaticallyOption and NSInferMappingModelAutomaticallyOption and also migration using only NSMigratePersistentStoresAutomaticallyOption, providing a mapping model from v2 to v3. I see the above error logged, and no object is available in the application. However, if I quit the application and reopen it, everything is in place and working. The Core Data methods I am using are the following ones - (NSManagedObjectModel *)managedObjectModel { if (managedObjectModel != nil) { return managedObjectModel; } NSString *path = [[NSBundle mainBundle] pathForResource:@"MYAPP" ofType:@"momd"]; NSURL *momURL = [NSURL fileURLWithPath:path]; managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:momURL]; return managedObjectModel; } - (NSManagedObjectContext *) managedObjectContext { if (managedObjectContext != nil) { return managedObjectContext; } NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator]; if (coordinator != nil) { managedObjectContext = [[NSManagedObjectContext alloc] init]; [managedObjectContext setPersistentStoreCoordinator: coordinator]; } return managedObjectContext; } - (NSPersistentStoreCoordinator *)persistentStoreCoordinator { if (persistentStoreCoordinator != nil) { return persistentStoreCoordinator; } NSURL *storeUrl = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"MYAPP.sqlite"]]; NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil]; NSError *error = nil; persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: [self managedObjectModel]]; if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:options error:&error]) { // Handle error NSLog(@"Unresolved error %@, %@", error, [error userInfo]); } return persistentStoreCoordinator; } In the simulator, I see that this generates a MYAPP~.sqlite files and a MYAPP.sqlite file. I tried to remove the MYAPP~.sqlite file, but BOOL oldExists = [[NSFileManager defaultManager] fileExistsAtPath: [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"MYAPP~.sqlite"]]; always returns NO. Any clue? Am I doing something wrong? Thank you in advance.

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  • Migration Core Data error code 134130

    - by magichero
    I want to do migration with 2 core database. I have read apple developer document. For the first database, I add some attributes (string, integer and date properties) to new version database. And follow all steps, I have done migration successfully with the first once. But the second database, I also add attributes (string, integer, date, transformable and binary-data properties) to new version database. And follow all steps (like the first database) but system return an error (134130). Here is the code: if (persistentStoreCoordinator_) { PMReleaseSafely(persistentStoreCoordinator_); } // Notify NSNotificationCenter *nc = [NSNotificationCenter defaultCenter]; [nc postNotificationName:GCalWillMigrationNotification object:self]; // NSString *sourceStoreType = NSSQLiteStoreType; NSString *dataStorePath = [PMUtility dataStorePathForName:GCalDBWarehousePersistentStoreName]; NSURL *storeURL = [NSURL fileURLWithPath:dataStorePath]; BOOL storeExists = [[NSFileManager defaultManager] fileExistsAtPath:dataStorePath]; // NSError *error = nil; NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil]; persistentStoreCoordinator_ = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:self.managedObjectModel]; [persistentStoreCoordinator_ addPersistentStoreWithType:sourceStoreType configuration:nil URL:storeURL options:options error:&error]; if (error != nil) { abort(); } error is not nil and below is log: Error Domain=NSCocoaErrorDomain Code=134130 "The operation couldn\u2019t be completed. (Cocoa error 134130.)" UserInfo=0x856f790 {URL=file://localhost/Users/greensun/Library/Application%20Support/iPhone%20Simulator/5.0/Applications/D10712DE-D9FE-411A-8182-C4F58C60EC6D/Library/Application%20Support/Promise%20Mail/GCalDBWarehouse.sqlite, metadata={type = immutable dict, count = 7, entries = 2 : {contents = "NSStoreModelVersionIdentifiers"} = {type = immutable, count = 1, values = ( 0 : {contents = ""} )} 4 : {contents = "NSPersistenceFrameworkVersion"} = {value = +386, type = kCFNumberSInt64Type} 6 : {contents = "NSStoreModelVersionHashes"} = {type = immutable dict, count = 2, entries = 0 : {contents = "SyncEvent"} = {length = 32, capacity = 32, bytes = 0xfdae355f55c13fbd0344415fea26c8bb ... 4c1721aadd4122aa} 1 : {contents = "ImportEvent"} = {length = 32, capacity = 32, bytes = 0x7676888f0d7eaff4d1f844343028ce02 ... 040af6cbe8c5fd01} } 7 : {contents = "NSStoreUUID"} = {contents = "51678BAC-CCFB-4D00-AF5C-8FA1BEDA6440"} 8 : {contents = "NSStoreType"} = {contents = "SQLite"} 9 : {contents = "_NSAutoVacuumLevel"} = {contents = "2"} 10 : {contents = "NSStoreModelVersionHashesVersion"} = {value = +3, type = kCFNumberSInt32Type} }, reason=Can't find model for source store} I try a lot of solutions but it does not work. I just add more attributes to 2 new version database, and succeed in migrating once. Thanks for reading and your help.

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  • localization with core data

    - by Tristan
    Hi there, Does anyone have any recommendations with localization of core data? My application will have information that will sometimes be the same in both langauges, such as a person's photo, or different such as the person's biography. From what I understand, it's possible to localize the field names (http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CoreData/Articles/cdUsingMOM.html#//apple_ref/doc/uid/TP40005190-SW13), but what's the best course of action for field values? Thanks! Tristan

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