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• What's the fastest way to determine if a file adheres to a particular class's NSCoding implementatio

  - by Justin Searls

  Given: An application that accesses a directory of files: some plain text, some binary files that adhere to a particular NSCoding implementation, and perhaps other binary files it simply doesn't understand how to process. I want to be able to figure out which of the files in that directory adhere to my NSCoding class, and I'd prefer not to have to fall back on the naïve approach of loading the entirety of each file into memory, attempting to unarchive each. Anyone have an elegant approach or pattern to this problem?

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• [Iphone] - Problem in saving file using NSCoding

  - by Matte Gary

  Hi everybody, I've a problem with Iphone programming... I've a NSMutableArray containing object of type "MyClass". MyClass has some parameters, like NSNumber and NSString. I've followed the Apple Tutorial about coding and decoding object using NSCoding, but when I try to decode the file I've stored, the NSMutableArray contain object of type "MyClass", but with wrong parameters. I think i've done all I've to do (including protocol, including methods like initwithencode etc), but it's still not working... Any suggestions? Thanks a lot! And sorry for my English XD

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• NSCoding and ostream

  - by Stephen Furlani

  Is there a better way to serialize an ObjC object than using /NSKeyedArchive? I need to distribute the object through a C++ std:ostream-like object to put on another computer. The object has over 122 members of various types... for which wants me to [coder encodeObject: (id) forKey: @"blah"]; for all of them... Does anyone have a nice Perl Script that will at least write it out? I don't even know if the objects it contains implement which means this could turn into a huge ugly mess since I can't change the source of the object - I'll have to inherit & add the @interface to it... Or am I being dumb? Apple's guide doesn't help me since archiving to XML won't pass nicely though the ostream. Is there a better way to do this? -S!

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• MPMediaItem - NSCoding problem with MPMediaItemArtwork

  - by z s

  Hi, So MPMediaItem conforms to NSCoding, but it contains a pointer to MPMediaItemArtwork, which doesn't conform to NSCoding. So if I try to archive a MPMediaItem, if that item has some artwork in it, it will not be able to unarchive. I tried to make a category of MPMediaItemArtwork and make it conform to NSCoding, but I can't seem to do that because we don't have access to the actual UIImage that it stores. Does anyone know of any other creative ways to get around this problem? I want to be able to archive an MPMediaItem, even if it means somehow stripping off the artwork object. Is there a way to make a category of a class to strip away certain functionality (instead of just adding more, like we do with categories)? Or any other clever way to achieve this? Thanks.

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• How to persist and load an object which conforms to NSCoding protocol?

  - by mystify

  I have made an class which conforms to the NSCoding protocol and does all the encode and decode stuff. For my app, I simply want to persist an object from that class to the device and the next time when the app launches, I want to load that object back into memory. Basically it's just an class which holds some user input information. For example the user starts writing a text but then quits the app. Next time I want to load that data object. I guess I need NSKeyedArchiver? Is there a good tutorial on this? How do I do that?

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• [iPhone]Objective C, objects which do not conform to NSCoding. How to write them to a file.

  - by Noah

  Hi, I am using an Objective c class, a subclass of NSObject. This class cannot be modified. I have an instance of this class that I wish to write to a file which can be retrieved and later reinstate. The object does not conform to NSCoding. To sum up, I need to save an instance of a class to a file which can be retrieved later, without using any of the NSCoding methods such as NSKeyedArchiving encodeWithCoder ... Using them returns this... NSInvalidArgumentException ...encodeWithCoder:] unrecognised selector sent to instance... Is there any other way I can store this object for later use Thank you

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• Can I do this?? Trying to load an object from within itself.

  - by Smikey

  Hi all! I have an object which conforms to the NSCoding protocol. The object contains a method to save itself to memory, like so: - (void)saveToFile { NSMutableData *data = [[NSMutableData alloc] init]; NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data]; [archiver encodeObject:self forKey:kDataKey]; [archiver finishEncoding]; [data writeToFile:[self dataFilePath] atomically:YES]; [archiver release]; [data release]; } This works just fine. But I would also like to initialise an empty version of this object and then call its own 'Load' method to load whatever data exists on file into its variables. So I've created the following: - (void)loadFromFile { NSString *filePath = [self dataFilePath]; if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) { NSData *data = [[NSMutableData alloc] initWithContentsOfFile:[self dataFilePath]]; NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data]; self = [unarchiver decodeObjectForKey:kDataKey]; [unarchiver finishDecoding]; } } Now this second method doesn't manage to load any variables. Is this line not possible perhaps? self = [unarchiver decodeObjectForKey:kDataKey]; Ultimately I would like to use the code like this: One viewController takes user entered input, creates an object and saves it to memory using [anObject saveToFile]; And a second viewController creates an empty object, then initialises its values to those stored on file by calling: [emptyObject loadFromFile]; Any suggestions on how to make this work would be hugely appreciated. Thanks :) Michael

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• Saving an NSMutableArray of custom Objects

  - by aahrens

  I have a custom class that is used as a wrapper to an NSMutableArray @interface AllCourses : NSObject { NSMutableArray *arrClasses; } The array above stores Objects of another custom class. @interface Course : NSObject { NSString *className; NSString *classGrade; NSInteger creditHours; } I use the method below to add Course objects to my AllCourses //Adds a new Course to the total Courses -(void) addClass:(Course *)aCourse{ [arrClasses addObject:aCourse]; } What's going to be the best way to save the arrClasses MutableArray in AllCourses so that when my app loads it can keep the saved data the user already entered and populate it?

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• iPhone -- initialization partly by NSKeyedUnarchiver and partly by other means

  - by William Jockusch

  I have an object myObj, which is an instance of a class MyClass. Some of its instance variables always have their initial values passed in by the calling code. Other instance variables will be initialized in one of two ways. For an instanceArray of type NSMutableArray, the possibilities are either instanceArray = [[NSMutableArray alloc]init]; or instanceArray = [someKeyedUnarchiver decodeObjectForKey: kInstanceArrayKey]; The calling code should determine which of the above will be used. Any particular design pattern I should prefer?

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• Are protocols inheritable in Objective-C?

  - by aquaibm

  I saw this in some header file in the framework directory: @interface NSCharacterSet : NSObject <NSCopying, NSMutableCopying, NSCoding> @end @interface NSMutableCharacterSet : NSCharacterSet <NSCopying, NSMutableCopying> @end I thought protocols were inheritable.If I am right about that,There is no need to type <NSCopying, NSMutableCopying> again after "NSMutableCharacterSet : NSCharacterSet".And NSMutableCharacterSet also conforms to NSCoding protocol, right? Than why is Apple typing that again?Am I making mistake?

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• Strange inheritance behaviour in Objective-C

  - by Smikey

  Hi all, I've created a class called SelectableObject like so: #define kNumberKey @"Object" #define kNameKey @"Name" #define kThumbStringKey @"Thumb" #define kMainStringKey @"Main" #import <Foundation/Foundation.h> @interface SelectableObject : NSObject <NSCoding> { int number; NSString *name; NSString *thumbString; NSString *mainString; } @property (nonatomic, assign) int number; @property (nonatomic, retain) NSString *name; @property (nonatomic, retain) NSString *thumbString; @property (nonatomic, retain) NSString *mainString; @end So far so good. And the implementation section conforms to the NSCoding protocol as expected. HOWEVER, when I add a new class which inherits from this class, i.e. #import <Foundation/Foundation.h> #import "SelectableObject.h" @interface Pet : SelectableObject <NSCoding> { } @end I suddenly get the following compiler error in the Selectable object class! SelectableObject.h:16: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'interface' This makes no sense to me. Why is the interface declaration for the SelectableObject class suddenly broken? I also import it in a couple of other classes I've written... Any help would be very much appreciated. Thanks! Michael

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• How to save state of the app when app terminates?

  - by user164589

  Hi guys. I am trying to save the app state by encoding when the app terminates. I've found the solution related this issue. But I don't know how to use. I am really trying to make encoding and decoding like this: http://cocoaheads.byu.edu/wiki/nscoding in CustomObject.h @interface CustomObject : NSObject <NSCoding> { NSArray *someArray; } in CustomObject.m @implementation CustomObject // Other method implementations here - (void) encodeWithCoder:(NSCoder*)encoder { [encoder encodeObject:someArray forKey:@"someArray"]; } - (id) initWithCoder:(NSCoder*)decoder { if (self = [super init]) { someArray = [[decoder decodeObjectForKey:@"someArray"] retain]; } return self; } @end My object to save is another NSArray. Not "someArray" in CustomObject. We call it that "MySaveObject". I want to pass "MySaveObject" to "someArray" in CustomObject. Actually I don't know how to encode "MySaveObject" and to pass to "someArray" in CustomObject. Thanks in advance.

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• Which data persistence options are available on the iPhone?

  - by mystify

  I know already: Core Data, SQLite3, Property List Serialization, NSCoding with NSCoder (encode / decode)... what else?

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• Which are the most useful techniques for faster Bluetooth?

  - by Mike Howard

  Hi. I'm adding peer-to-peer bluetooth using GameKit to an iPhone shoot-em-up, so speed is vital. I'm sending about 40 messages a second each way, most of them with the faster GKSendDataUnreliable, all serializing with NSCoding. In testing between a 3G and 3GS, this is slowing the 3G down a lot more than I'd like. I'm wondering where I should concentrate my efforts to speed it up. How much slower is GKSendDataReliable? For the few packets that have to get there, would it be faster to send a GKSendDataUnreliable and have the peer send an acknowledgement so I can send again if I don't get the Ack within, say, 100ms? How much faster would it be to create the NSData instance using a regular C array rather than archiving with the NSCoding protocol? Is this serialization process (for about a dozen floats) just as slow as you'd expect from an object creation/deallocation overhead, or is something particularly slow happening? I heard that (for example) sending four seperate sets of data is much, much slower, than sending one piece of data four times the size. Would I make a significant saving by sending separate packets of data that wouldn't always go together in the same packet when they happen at the same time? Are there any other bluetooth performance secrets I've missed? Thanks for your help.

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• iPhone: Which are the most useful techniques for faster Bluetooth?

  - by Mike Howard

  Hi. I'm adding peer-to-peer bluetooth using GameKit to an iPhone shoot-em-up, so speed is vital. I'm sending about 40 messages a second each way, most of them with the faster GKSendDataUnreliable, all serializing with NSCoding. In testing between a 3G and 3GS, this is slowing the 3G down a lot more than I'd like. I'm wondering where I should concentrate my efforts to speed it up. How much slower is GKSendDataReliable? For the few packets that have to get there, would it be faster to send a GKSendDataUnreliable and have the peer send an acknowledgement so I can send again if I don't get the Ack within, say, 100ms? How much faster would it be to create the NSData instance using a regular C array rather than archiving with the NSCoding protocol? Is this serialization process (for about a dozen floats) just as slow as you'd expect from an object creation/deallocation overhead, or is something particularly slow happening? I heard that (for example) sending four seperate sets of data is much, much slower, than sending one piece of data four times the size. Would I make a significant saving by sending separate packets of data that wouldn't always go together in the same packet when they happen at the same time? Are there any other bluetooth performance secrets I've missed? Thanks for your help.

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• Write simple data to iphone sandbox?

  - by fuzzygoat

  I want to write a small bit of data from my app to the iphone so I can load it when the app next starts. I am going to write the data using NSCoding, but I don't know what I should be specifying as a path. I understand I would write the data to the application sandbox, just not sure how to specify that. gary

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• Serialize struct with pointers to NSData

  - by leolobato

  Hey guys, I need to add some kind of archiving functionality to a Objective-C Trie implementation (NDTrie on github), but I have very little experience with C and it's data structures. struct trieNode { NSUInteger key; NSUInteger count, size; id object; __strong struct trieNode ** children; __strong struct trieNode * parent; }; @interface NDTrie (Private) - (struct trieNode*)root; @end What I need is to create an NSData with the tree structure from that root - or serialize/deserialize the whole tree some other way (conforming to NSCoding?), but I have no clue how to work with NSData and a C struct containing pointers. Performance on deserializing the resulting object would be crucial, as this is an iPhone project and I will need to load it in the background every time the app starts. What would be the best way to achieve this? Thanks!

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• Updates to NSDictionary attribute in CoreData not saving

  - by sfkaos

  I have created an Entity in CoreData that includes a Transformable attribute type implemented as an NSDictionary. The NSDictionary attribute only contains values of a custom class. The properties of the custom class are all of type NSString. The custom class complies with NSCoding implementing: -(void)encodeWithCoder:(NSCoder*)coder; -(id)initWithCoder:(NSCoder *)coder When saving the Entity for the first time all attributes including the Transformable (NSDictionary) type are properly saved in the DB. When the same Entity is fetched from the DB and updated (including the Transformable attribute) it seems to be updated properly. However, when the app is closed and then reopened fetching the Entity does not show the updated Transformable attribute-type though the rest of the attributes of type NSDate and NSString are up-to-date. The Transformable attribute is the original saved value not the updated value. Is this a problem with KVO or am I missing something else when trying to save an NSDictionary filled with a custom class to CoreData?

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• save and restore state of a tab bar controller

  - by phunehehe

  I have an application that has a UITabBarController with two tabs, each having its own navigation controller. Now I want to store the state of the application when the user closes it, so that when the user relauches the application will show the same place as the last time before it was closed. So, in applicationWillTerminate: I have [NSKeyedArchiver archiveRootObject:tabBarController toFile:@"lastVisitedTab"]; Then, in applicationDidFinishLaunching: I have UITabBarController *last= (UITabBarController *)[NSKeyedUnarchiver unarchiveObjectWithFile:@"lastVisitedTab"]; if (last) tabBarController = [last retain]; I also have an extension to UIImage to make it compliant to NSCoding. However, this doesn't work, as the state is not preserved. The first tab gets selected all the time, and no navigation is preserved either. Can someone tell me what's wrong, or show me how to do it correctly?

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• Should I create subclass NSManagedObject or not?

  - by TP

  Hi, I have spent a few days learning and writing NSCoding and finally got it working. However, it took very long to archive and unarchive the (quite complex) object graph, which is unacceptable. After searching the internet for some time, I think the better way is to use core data. Do you recommend that 1) I should rewrite all my classes as subclasses of NSManagedObject or 2) should I create an instance variable of NSManagedObject in each of my class so that any changes to the class also updates its core data representation? Doing either way will need significant changes to the exiting classes and I think I have to update lots of unit test cases as well if it changes the way the classes are initialized. What do you recommend? I really don't want to head to the wrong approach again... Thanks!

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• save UIImageView state & the save the Entire View

  - by adamprocter

  I have an iPad app where you add photos to a page. I then want to save the photos positions, then add further pages with more photo positions and eventually save all the pagesto be looked at later in a slideshow style. Can anyone advise 1. Saving UIImageView states when moving to new views (or swapping views) - I see this on using NSCoding iPhone - save UIImageView state - but am at a lose - any more examples ? 2. How to save the 'entire' set of view to look at later (like a slideshow) - no idea on where to start with this ? array ? coredata ? Thanks

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• How can we leverage NSAppearance?

  - by Brad Allred

  I was reading the Cocoa documentation and stumbled across some new features in the 10.9 API. From the docs I gather that the NSAppearance class and a related protocol NSAppearanceCustomization Appear to be a means of customizing the appearance of NSView and its descendants. An NSAppearance object represents a file that specifies a standard or custom appearance that applies to a subset of UI elements in an app. An app can contain multiple appearance files and—because NSAppearance conforms to NSCoding—you can use Interface Builder to assign UI elements to an appearance. Typically, you customize a window by using Xcode to create an appearance file that contains the views you want to customize and the custom art that should be applied to them. Xcode transforms the file’s art content into a runtime format that AppKit can draw when the specified views are displayed. Well that all sounds neat and promising, but nowhere in the documentation can I find what an appearance file is or how to make one. Google searches are coming up empty other than for the thin documentation I have already read. I do see that UIKit has a similar sounding UIAppearance class, but from what I can tell this is not a straight port of the UIKit class. Does anybody know how to make this magic "appearance file" and what exactly we can do with it?

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• iPhone - User Defaults and UIImages

  - by Staros

  Hello, I've been developing an iPhone app for the last few months. Recently I wanted to up performance and cache a few of the images that are used in the UI. The images are downloaded randomly from the web by the user so I can't add specific images to the project. I'm also already using NSUserDefaults to save other info within the app. So now I'm attempting to save a dictionary of UIImages to my NSUserDefaults object and get... -[UIImage encodeWithCoder:]: unrecognized selector sent to instance I then decided to subclass UIImage with a class named UISaveableImage and implement NSCoding. So now I'm at... @implementation UISaveableImage -(void)encodeWithCoder:(NSCoder *)encoder { [encoder encodeObject:super forKey:@"image"]; } -(id)initWithCoder:(NSCoder *)decoder { if (self=[super init]){ super = [decoder decodeObjectForKey:@"image"]; } return self; } @end which isn't any better than where I started. If I was able to convert an UIImage to NSData I would be good, but all I can find are function like UIImagePNGRepresentation which require me to know what type of image this was. Something that UIImage doesn't allow me to do. Thoughts? I feel like I might have wandered down the wrong path...

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• How to serialize object containing NSData?

  - by AO

  I'm trying to serialize an object containing a number of data fields...where one of the fields is of datatype NSData which won't serialize. I've followed instructions at http://www.isolated.se but my code (see below) results in the error "[NSConcreteData data]: unrecognized selector sent to instance...". How do I serialize my object? Header file: @interface Donkey : NSObject<NSCoding> { NSString* s; NSData* d; } @property (nonatomic, retain) NSString* s; @property (nonatomic, retain) NSData* d; - (NSData*) serialize; @end Implementation file: @implementation Donkey @synthesize s, d; static NSString* const KEY_S = @"string"; static NSString* const KEY_D = @"data"; - (void) encodeWithCoder:(NSCoder*)coder { [coder encodeObject:self.s forKey:KEY_S]; [coder encodeObject:self.d forKey:KEY_D]; } - (id) initWithCoder:(NSCoder*)coder; { if(self = [super init]) { self.s = [coder decodeObjectForKey:KEY_STRING]; self.d [coder decodeObjectForKey:KEY_DATA]; } return self; } - (NSData*) serialize { return [NSKeyedArchiver archivedDataWithRootObject:self]; } @end

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• Storing arrays in NSUserDefaultsController

  - by neoneye

  Currently I use NSUserDefaults and I'm interested in using NSUserDefaultsController, so that I get notifications when things change. Below is my current code. items = /* NSArray of MYItem's */; NSData* data = [NSKeyedArchiver archivedDataWithRootObject:items]; [[NSUserDefaults standardUserDefaults] setObject:data forKey:kMYItems]; How should I rework my code to store items in NSUserDefaultsController ? Is NSKeyedArchiver the smartest way to store arrays? @interface MYItem : NSObject <NSCoding> { NSString* name; NSString* path; } @property (copy) NSString* name; @property (copy) NSString* path; @end @implementation MYItem @synthesize name, path; -(void)encodeWithCoder:(NSCoder*)coder { [coder encodeObject:name forKey:@"name"]; [coder encodeObject:path forKey:@"path"]; } -(id)initWithCoder:(NSCoder*)coder { [super init]; [self setName:[coder decodeObjectForKey:@"name"]]; [self setPath:[coder decodeObjectForKey:@"path"]]; return self; } @end

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