Before iOS 5 and OSX 10.7 scalar properties can&#39;t be auto-generated and you had to add setter and getter implementations, which cause some penalty. Auto-generated properties are optimized. I&#39;m not aware of any other penalties.

Scalar and non-scalar properties are represented by the same types in DB, so there will be no change in DB&#39;s size.&amp;nbsp;

You should choose when to use scalar depending on the way you&#39;re going to access these properties. For example, you will need to wrap scalar properties in cocoa object if you&#39;re going to add them to collection (NSArray, NSSet, NSDictionary).





&gt; Core Data has support for many common data types like integers, floats, booleans, and so on. However, by default, the data model editor generates these attributes as `NSNumber` properties in the managed object subclasses. This often results in endless `floatValue`, `boolValue`, `integerValue`, or similar calls on these `NSNumber` objects in the application code.
&gt;
&gt; But we can also just specify those properties with their correct scalar type, e.g. as `int64_t`, `float_t`, or `BOOL`, and it will work with Core Data. Xcode even has a little checkbox in the save dialogue of the `NSManagedObject` generator (“Use scalar properties for primitive data types”) which does this for you.

Source: [objc.io - Data Models and Model Objects][1]


  [1]: http://www.objc.io/issue-4/core-data-models-and-model-objects.html

Is there a way to lock the Android screen via the ADB? 

I find ways to lock the display in an apk, but I want to lock the screen from the PC via ADB, to simulate a display timeout, without having to wait for the timeout. 

Is it possible to do this?

Thanks,
Diane

How to lock Android screen via ADB?

Does anybody know is it possible to open some personal picture when emulator camera starts?

I have an application which is based on image analysis and I would like when I click a button for camera that camera opens not that default Android emulator moving image. I want it to open some image which I set as a default image. So when I choose to take a picture it will show only that image and when I take a take a picture, that image will be saved to gallery, not Android default image.

Android emulator camera custom image

When should I check &quot;use scalar properties for primitive data types&quot; during creating `NSManagedObject` objects? &lt;br/&gt;
What it will cost me (will my data base improve performance or be more lightweight)?

Core Data &quot;use scalar properties for primitive data types&quot; check box

<p>When should I check "use scalar properties for primitive data types" during creating <code>NSManagedObject</code> objects? <br>
What it will cost me (will my data base improve performance or be more lightweight)?</p>


I&#39;ve been using `UIGraphicsBeginImageContextWithOptions()` and I noticed that the last field in that method is a `scalefactor`. And the apple docs says, if I want to set it to 0.0, then it will use the default scale factor of the device&#39;s main screen. Is there a way to get that default scale factor via property or method?

How to get the device&#39;s scale factor?

I&#39;m developing an application in Xcode.

When I try to build, this error comes up:

    ld: in /Users/theodore/Library/Developer/Xcode/DerivedData/Tower-bkpdifuqssebjdgurzmtirbxejnn/Build/Intermediates/Tower.build/Debug/Tower.build/Objects-normal/x86_64/TWRAppDelegate.o, file too small for architecture x86_64
    clang: error: linker command failed with exit code 1 (use -v to see invocation)

Does anyone know what&#39;s wrong?

Xcode linker error: file too small for architecture x86_64

I have stray keychain items on iOS (probably written by old version of app) that I need to delete. Is there an easy way to achieve this?


How to delete all keychain items accessible to an app?

Let say I have a storyboard that contains ```UINavigationController``` as initial view controller. Its root view controller is subclass of ```UITableViewController```, which is ```BasicViewController```. It has ```IBAction``` which is connected to right navigation button of the navigation bar&lt;br /&gt;
&lt;br /&gt;
From there I would like to use the storyboard as a template for other views without having to create additional storyboards. Say these views will have exactly the same interface but with root view controller of class ```SpecificViewController1``` and ```SpecificViewController2``` which are subclasses of ```BasicViewController```.&lt;br /&gt;
Those 2 view controllers would have the same functionality and interface except for the ```IBAction``` method.&lt;br /&gt;
It would be like the following:

    @interface BasicViewController : UITableViewController

    @interface SpecificViewController1 : BasicViewController

    @interface SpecificViewController2 : BasicViewController

Can I do something like that?&lt;br /&gt;
Can I just instantiate the storyboard of ```BasicViewController``` but have root view controller to subclass ```SpecificViewController1``` and ```SpecificViewController2```?&lt;br /&gt;
&lt;br /&gt;
Thanks.


How to use single storyboard uiviewcontroller for multiple subclass

Grouped table views seem to have extra padding on the bottom in iOS 6 (iOS 5 does not have it), but I can&#39;t find any documentation that suggests this is correct / expected behavior.
 
This affects the example projects as well, for instance the `SimpleTableView` project in the `TableViewSuite` example.  I think I had to change the style in the `AppDelegate` to &#39;grouped&#39;, and updated the SDK to iOS 6, but no other changes have been made to the project.
 
Investigating revealed that there are `10px` reserved for header and footer views, plus some `20px` that can&#39;t be accounted for.
There are no actual header or footer views (`tableHeaderView` and `tableFooterView` are `nil`, and implementing and returning `nil` for e.g. `viewForFooterInSection` does nothing).
I cannot find any &#39;20&#39; value on the tableView itself, though I may have missed something of course.
 
Adding a zero-size view for the footer does nothing, but adding a `1px` square view causes the extra padding to vanish. e.g.:

    tableView.tableFooterView = [[UIView alloc] initWithFrame:CGRectMake(0,0,1,1)];

It does take up `1px` of height still, so the bottom padding is now `11px`, but this is far less noticeable than 20.  And now setting the `sectionFooterHeight` to 0 will result in only `1px` of bottom-space.
 
My question is: what?  And how can I completely remove it?  This isn&#39;t anything mission-critical, but it is extremely weird, undesirable, and as far as I can tell it&#39;s undocumented. 

Please note - its copy past question from apple dev forum. But I have exactly the same issue and I don&#39;t understand how to solve it too.


Grouped UITableView has 20px of extra padding at the bottom

So, it finally happened. The worst case scenario for any independent iPhone developer occurred. Several users are reporting complete **data loss** after upgrading my app. iCloud Core Data sync is not working. My users are using this app partially to run their businesses. This is a truly *catastrophic failure*.

The only iCloud related thing I changed was to add the key-value store to iCloud. The core data code remained exactly the same, same model version (no migration) etc.

In my tests everything worked beautifully! But to my dismay, users reported that their data was not there anymore when they opened the updated app. 

What could be the reason for this? 

- The *persistent store URL* (an ubiquitous URL) should not have changed. 
- *Merge conflicts* are also unlikely, as this problem should have arisen before the update.
- &lt;strike&gt;Some interference with the new *ubiquitous key-value store* perhaps?&lt;/strike&gt;    
(I have pretty much ruled this out.)

Below please find the code for my managed object model and persistent store. Let me know if you need anything else to assess the problem. 


    - (NSManagedObjectContext *)managedObjectContext {
        
        if (managedObjectContext_ != nil) {
            return managedObjectContext_;
        }
        
        NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
        if (coordinator != nil) {
            managedObjectContext_ = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
    		[managedObjectContext_ performBlockAndWait:^{
    			[managedObjectContext_ setPersistentStoreCoordinator:coordinator];
    			if (useICloud) {
    				[managedObjectContext_ setMergePolicy:NSMergeByPropertyObjectTrumpMergePolicy];
    				[[NSNotificationCenter defaultCenter] addObserver:self
               selector:@selector(mergeiCloud:)
               name:NSPersistentStoreDidImportUbiquitousContentChangesNotification
               object:coordinator];
    			}
    		}];
        }
        return managedObjectContext_;
    }

and 

    - (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
        if (persistentStoreCoordinator_ != nil) {
            return persistentStoreCoordinator_;
        }
    
    	NSMutableDictionary *options = [NSMutableDictionary dictionary];
    	NSURL *storeURL = [[self applicationDocumentsDirectory] 
                URLByAppendingPathComponent:@&quot;SalesCalls.sqlite&quot;];
        
    	[options setObject:[NSNumber numberWithBool:YES] 
                      forKey:NSMigratePersistentStoresAutomaticallyOption];
    	[options setObject:[NSNumber numberWithBool:YES] 
                      forKey:NSInferMappingModelAutomaticallyOption];
    	
    	if (useICloud) {  // this is an internal flag set to YES
    		NSURL *iCloudURL = [[NSFileManager defaultManager] 
                                   URLForUbiquityContainerIdentifier:nil];
    		
    		if (nil!=iCloudURL) {
    			NSString *cloudData = [[iCloudURL path] 
                           stringByAppendingPathComponent:@&quot;data&quot;];
    			iCloudURL = [NSURL fileURLWithPath:cloudData];		
    			
    			[options setObject:@&quot;at.topofmind.salesplus.store&quot; 
                            forKey:NSPersistentStoreUbiquitousContentNameKey];
    			[options setObject:iCloudURL 
                            forKey:NSPersistentStoreUbiquitousContentURLKey];
    			
    			NSURL *nosyncDir = [iCloudURL 
                            URLByAppendingPathComponent:@&quot;data.nosync&quot;];
    			[[NSFileManager defaultManager] createDirectoryAtURL:nosyncDir 
                            withIntermediateDirectories:YES 
                            attributes:nil error:nil];
    
    			storeURL = [nosyncDir 
                            URLByAppendingPathComponent:@&quot;SalesCalls.sqlite&quot;];
    		}
    	}
        
        NSError *error = nil;
        persistentStoreCoordinator_ = [[NSPersistentStoreCoordinator alloc] 
                 initWithManagedObjectModel:[self managedObjectModel]];
    	if (![persistentStoreCoordinator_ 
                      addPersistentStoreWithType:NSSQLiteStoreType
                      configuration:nil URL:storeURL options:options error:&amp;error]) 
       {
    		NSLog(@&quot;Cannot create persistent store coordinator, %@, %@&quot;, 
                            error, [error userInfo]);
    		abort();
        }    
        
        return persistentStoreCoordinator_;
    }

Comments, opinions, wild guesses etc. (and of course solutions!) are all welcome. 

**UPDATE:** 

One of my customers lost all his data and after reinstalling and resetting everything (rebooting device, etc.) he could not sync with iCloud any more. The symbol simply does not show up in the Settings.

More iCloud Core Data synching woes

I&#39;m new to iOS. I&#39;ve been trying to make an application that will store an image captured from the camera into `CoreData`. I now know how to store data like `NSString`s, `NSDate` and other type but struggling to store an image. I&#39;ve read so many articles saying you must write it to the disk and write to a file, but I can&#39;t seem to understand it.

The following code is the one i used to store other data to core data.


    - (IBAction)submitReportButton:(id)sender
    {
        UrbanRangerAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
        
        managedObjectContext = [appDelegate managedObjectContext];
        
        NSEntityDescription *entity = [NSEntityDescription entityForName:@&quot;PotholesDB&quot; inManagedObjectContext:appDelegate.managedObjectContext];
        NSManagedObject *newPothole = [[NSManagedObject alloc]initWithEntity:entity insertIntoManagedObjectContext:managedObjectContext];
        
           
        [newPothole setValue:self.relevantBody.text forKey:@&quot;relevantBody&quot;];
        [newPothole setValue:self.subjectReport.text forKey:@&quot;subjectReport&quot;];
        [newPothole setValue:self.detailReport.text forKey:@&quot;detailReport&quot;];
    //    [newPothole setValue:self.imageView forKey:@&quot;photo&quot;];
    
        NSDate *now = [NSDate date];
        //NSLog(@&quot;now : %@&quot;, now);
        NSString *strDate = [[NSString alloc] initWithFormat:@&quot;%@&quot;, now];
        NSArray *arr = [strDate componentsSeparatedByString:@&quot; &quot;];
        NSString *str;
        str = [arr objectAtIndex:0];
        NSLog(@&quot;now : %@&quot;, str);
        
        [newPothole setValue:now forKey:@&quot;photoDate&quot;];
        [newPothole setValue:self.latitudeLabel.text forKey:@&quot;latitude&quot;];
        [newPothole setValue:self.longitudeLabel.text forKey:@&quot;longitude&quot;];
        [newPothole setValue:self.addressLabel.text forKey:@&quot;streetName&quot;];
        [newPothole setValue:streeNameLocation forKey:@&quot;location&quot;];
        
        
        NSError *error;
        [managedObjectContext save:&amp;error];
        
        UIAlertView *ll = [[UIAlertView alloc] initWithTitle:@&quot;Saving&quot; message:@&quot;Saved data&quot; delegate:nil cancelButtonTitle:@&quot;OK&quot; otherButtonTitles:nil];
        
        [ll show];
    } 

How to store an image in core data

I&#39;m preparing an update for a Core Data based app for fixes with iOS 7. I use Xcode 5 and iOS 7 SDK GM. However I realized a different behavior of the persistent store (which is a `UIManagedDocument`): Prior to iOS 7 builds there was only one file `persistentStore` in the documents folder (sometimes there was a second one `persistentStore-journal`).

In iOS 7 builds (clean installation) there are now three files for the persistent store:

 - `persistentStore`
 - `persistentStore-wal` and
 - `persistentStore-shm`

Did Apple change the journal mode by default to WAL now? I wonder if there is an impact on my app (think of users how update from the last version)? Would it be best to disable WAL - and if so, how can I do this with iOS 7/`UIManagedDocument`?

Core Data and iOS 7: Different behavior of persistent store

I use Xcode for iOS development. I have some entity (for example, User), and I need to set unique constraint for his name, but I can&#39;t find how I can do it through visual editor. Is it possible to do it through GUI? Or it&#39;s possible through code only? I will be glad to get some screenshot.


How to add unique constraints for some fields in Core Data

**Update for Xcode 8:**

In Xcode 8, one needs to go to the Core Data Model Editor and Show the File Inspector. Near the bottom is an option for code generation. Select Swift.

**Edit**: I found the solution to generate a Swift model from Core Data entity:

On Xcode:

*Editor &gt; Create NSManagedOjbect &gt; Click button &quot;Next&quot; &gt; Click button &quot;Next&quot; &gt; Select &quot;Swift&quot; Langage &gt; Click button &quot;Create&quot;*

---

I tried Swift langage by creating a new Swift project on Xcode 6 beta using Core Data.

When I generate my models from my Core Data&#39;s entities, Xcode creates Objective-C models.

Is there a way to generate Swift model rather than Obejctive-C model with Core Data ?

Thanks !


Content Type	Original Author	Original Content on Stackoverflow
Question	rowwingman	View Question on Stackoverflow
Solution 1 - Objective C	Evgeny Shurakov	View Answer on Stackoverflow
Solution 2 - Objective C	Perry	View Answer on Stackoverflow

Core Data "use scalar properties for primitive data types" check box

Objective C Problem Overview

Objective C Solutions

Solution 1 - Objective C

Solution 2 - Objective C

Android emulator camera custom image

How to lock Android screen via ADB?

Attributions