How to serialize the following class in objective-c so that it can be used with SBJson?
I get "JSON serialisation not supported for Animal" error when I use this code.
Can someone point out where I am going wrong?
The contents of Animal.h file is as below
#import <UIKit/UIKit.h>
#interface Animal : NSObject<NSCoding> {
NSString *name;
NSString *description;
NSString *imageURL;
}
#property (nonatomic, retain) NSString *name;
#property (nonatomic, retain) NSString *description;
#property (nonatomic, retain) NSString *imageURL;
-(id)initWithName:(NSString *)n description:(NSString *)d url:(NSString *)u;
#end
The contents of Animal.m file is as below
#import "Animal.h"
#implementation Animal
#synthesize name, description, imageURL;
-(id)initWithName:(NSString *)n description:(NSString *)d url:(NSString *)u {
self.name = n;
self.description = d;
self.imageURL = u;
return self;
}
- (id)initWithCoder:(NSCoder *)aDecoder
{
if(self = [super initWithCoder:aDecoder])
{
name = [[aDecoder decodeObjectForKey:#"name"] retain];
description = [[aDecoder decodeObjectForKey:#"description"] retain];
imageURL = [[aDecoder decodeObjectForKey:#"imageURL"] retain];
}
return [self initWithName:name description:description url:imageURL];
}
- (void)encodeWithCoder:(NSCoder *)encoder
{
[super encodeWithCoder:encoder];
[encoder encodeObject:name forKey:#"name"];
[encoder encodeObject:description forKey:#"description"];
[encoder encodeObject:imageURL forKey:#"imageURL"];
}
#end
Make your custom class conform to NSCoding protocol and then serialize it.
For more info, visit the Apple documentation
Also, this link will also help you.
As suggested in this link, archive your custom class to NSData and serialize that as provided in the Apple documentation.
Edit
Make your Animal.m as follows:
#import "Animal.h"
#implementation Animal
#synthesize name, description, imageURL;
-(id)initWithName:(NSString *)n description:(NSString *)d url:(NSString *)u {
self = [super init];
if( self )
{
self.name = n;
self.description = d;
self.imageURL = u;
}
return self;
}
- (id)initWithCoder:(NSCoder *)aDecoder
{
self = [super init];
if( self )
{
self.name = [aDecoder decodeObjectForKey:#"name"];
self.description = [aDecoder decodeObjectForKey:#"description"];
self.imageURL = [aDecoder decodeObjectForKey:#"imageURL"];
}
return self;
}
- (void)encodeWithCoder:(NSCoder *)encoder
{
[encoder encodeObject:name forKey:#"name"];
[encoder encodeObject:description forKey:#"description"];
[encoder encodeObject:imageURL forKey:#"imageURL"];
}
#end
To actually answer your question on how to do it using SBJson: Implement the proxyForJson method. Unless you are serializing an NSArray or NSDictionary you must override this method for serialization to work.
You can see that this is the case by looking at the SBJson source code (in SBJsonWriter.m):
- (NSData*)dataWithObject:(id)object {
...
if ([object isKindOfClass:[NSDictionary class]])
ok = [streamWriter writeObject:object];
else if ([object isKindOfClass:[NSArray class]])
ok = [streamWriter writeArray:object];
else if ([object respondsToSelector:#selector(proxyForJson)])
return [self dataWithObject:[object proxyForJson]];
else {
self.error = #"Not valid type for JSON";
return nil;
}
...
}
}
Implement proxyForJson in Animal.m like this (not tested):
- (NSDictionary*) proxyForJson
{
return [NSDictionary dictionaryWithObjectsAndKeys:self.name, #"name",
self.description, #"description",
self.imageURL, #"imageURL",
nil];
}
This open source project JSONCoding makes the whole process pretty simple, using the new sdk class in conjunction with the NSCoding protocol.
Check the newly introduced NSJSONSerialization class:
NSJSONSerialization class
I think you can check out this if it helps you: Make a Custom Class Serializable
Please check this Property List Programming Guide - Serializing a Property List
and the similar post here:
Make a Custom Class Serializable in Objective-c/iPhone?
Object serialization in XML format using Obj-C / iPhone SDK
See also https://github.com/jsonmodel/jsonmodel
Magical Data Modeling Framework for JSON - allows rapid creation of
smart data models. You can use it in your iOS, macOS, watchOS and tvOS
apps.
This is also the chosen library for the Objective-c Swagger client.
Related
I have a NSMutableArray feed.leagues which has two objects of <MLBLeagueStandings: 0xeb2e4b0>
I want to write it to a file and then read it from the file. This is what I have done:
- (void)encodeWithCoder:(NSCoder *)encoder {
[encoder encodeObject:feed.leagues forKey:#"feed.leagues"];
}
- (id)initWithCoder:(NSCoder *)decoder {
if (self = [super init]) {
self.feed.leagues = [decoder decodeObjectForKey:#"feed.leagues"];
}
return self;
}
-(void)saveJSONToCache:(NSMutableArray*)leaguesArray {
NSString *cachePath = [self cacheJSONPath];
[NSKeyedArchiver archiveRootObject:feed.leagues toFile:cachePath];
NSMutableArray *aArray = [NSKeyedUnarchiver unarchiveObjectWithFile:cachePath];
NSLog(#"aArray is %#", aArray);
}
-(NSString*)cacheJSONPath
{
NSString *documentsDirStandings = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *cacheJSONPath = [NSString stringWithFormat:#"%#/%#_Standings.plist",documentsDirStandings, sport.acronym];
return cacheJSONPath;
}
Your object : MLBLeagueStandings should be serializable and respond to NSCoding protocole :
#interface MLBLeagueStandings : NSObject <NSCoding>{
}
Now in your MLBLeagueStandings class file (.m) add the following methods :
- (id)initWithCoder:(NSCoder *)decoder;
{
self = [super initWithCoder:decoder];
if(self)
{
yourAttribute = [decoder decodeObjectForKey:#"MY_KEY"]
//do this for all your attributes
}
}
- (void)encodeWithCoder:(NSCoder *)encoder;
{
[encoder encodeObject:yourAttribute forKey:#"MY_KEY"];
//do this for all your attributes
}
In fact if you want to write an object to a file (in your case it's an array), all the object contained in this array have to conform to the NSCoding protocole.
Moreover if you want example : here is a good tutorial
Hope it will help you.
NB : if you want to encode/decode primitive type (int, float etc...) use :
[encode encodeInt:intValue forKey:#"KEY"];
(more information on apple doc)
This question already has answers here:
Objective C - How do I use initWithCoder method?
(2 answers)
Closed 9 years ago.
I was reading about initializing the archived objects from a XIB file and found that
- (id)initWithCoder:(NSCoder *)aDecoder
is a way of doing it. But I am not able to get a hang around this. Can someone show me an simple example of how to do this?
Thanks a ton
The NSCoder class is used to archive/unarchive (marshal/unmarshal, serialize/deserialize) of objects.
This is a method to write objects on streams (like files, sockets) and being able to retrieve them later or in a different place.
I would suggest you to read Archiving
You also need to define the following method as follows:
- (void)encodeWithCoder:(NSCoder *)enCoder
{
[super encodeWithCoder:enCoder];
[enCoder encodeObject:instanceVariable forKey:INSTANCEVARIABLE_KEY];
// Similarly for the other instance variables.
....
}
And in the initWithCoder method initialize as follows:
- (id)initWithCoder:(NSCoder *)aDecoder
{
if(self = [super initWithCoder:aDecoder]) {
self.instanceVariable = [aDecoder decodeObjectForKey:INSTANCEVARIABLE_KEY];
// similarly for other instance variables
....
}
return self;
}
You can initialize the object standard way i.e
CustomObject *customObject = [[CustomObject alloc] init];
Example taken from this answer
You can use it in following way:
.h file
#interface Score : NSObject {
NSString *Username;
NSString *TotalPoints;
NSString *LifeRemains;
NSString *ScoreDate;
}
#property (nonatomic, retain) NSString *Username;
#property (nonatomic, retain) NSString *TotalPoints;
#property (nonatomic, retain) NSString *LifeRemains;
#property (nonatomic, retain) NSString *ScoreDate;
in .m file
#synthesize Username, TotalPoints, LifeRemains, ScoreDate;
- (void)encodeWithCoder:(NSCoder *)encoder
{
//Encode properties, other class variables, etc
[encoder encodeObject:self.Username forKey:kScoreUsername];
[encoder encodeObject:self.TotalPoints forKey:kScoreTotalPoints];
[encoder encodeObject:self.LifeRemains forKey:kScoreLifeRemains];
[encoder encodeObject:self.ScoreDate forKey:kScoreDate];
}
- (id)initWithCoder:(NSCoder *)decoder
{
self = [super init];
if( self != nil )
{
//decode properties, other class vars
self.Username = [decoder decodeObjectForKey:kScoreUsername];
self.TotalPoints = [decoder decodeObjectForKey:kScoreTotalPoints];
self.LifeRemains = [decoder decodeObjectForKey:kScoreLifeRemains];
self.ScoreDate = [decoder decodeObjectForKey:kScoreDate];
}
return self;
}
Happy Coding...
I've made a container class to store a single tweet. Its initialized by passing in a dictionary object which is a single tweet.
I then store an array of these 'tweets' which I process through to display in a table.
The project is now finished and I am reviewing everything at the moment and I was wondering is there a better way to do this in the future. Is the memory handled correctly. I declare the string member vars with 'copy' and later in the dealloc I use a 'release' rather than just setting them to 'nil'.
Is my init ok or could that be improved?
Tweet.h
#import
#interface Tweet : NSObject
{
NSString * _userName;
NSString * _tweetText;
NSString * _tweetURL;
}
#property (nonatomic, copy) NSString * userName;
#property (nonatomic, copy) NSString * tweetText;
#property (nonatomic, copy) NSString * tweetURL;
- (id) initWithDict:(NSDictionary *)productsDictionary;
#end
Tweet.m
#implementation Tweet
#synthesize userName = _userName;
#synthesize tweetText = _tweetText;
#synthesize tweetURL = _tweetURL;
- (id) initWithDict:(NSDictionary *)productsDictionary
{
NSDictionary *aDict = [productsDictionary objectForKey:#"user"];
self.userName = [aDict objectForKey:#"screen_name"];
self.tweetText = [productsDictionary objectForKey:#"text"];
NSRange match;
match = [self.tweetText rangeOfString: #"http://"];
if (match.location != NSNotFound)
{
NSString *substring = [self.tweetText substringFromIndex:match.location];
NSRange match2 = [substring rangeOfString: #" "];
if (match2.location == NSNotFound)
{
self.tweetURL = substring;
}
else
{
self.tweetURL = [substring substringToIndex:match2.location];
}
}
else
{
self.tweetURL = nil;
}
return self;
}
-(void) dealloc
{
[self.tweetText release];
[self.tweetURL release];
[self.userName release];
[super dealloc];
}
#end
Many Thanks,
Code
At first sight, I see no inherent flaws here. That looks fine. I would prefer to do:
-(void) dealloc
{
[_tweetText release];
[_tweetURL release];
[_userName release];
[super dealloc];
}
But what you do is good as well.
I am developing iphone application.
I use NSCoder.
MyApplication.h
#define ITEMS_KEY #"items"
#define CATEGORIES_KEY #"categories"
#import <UIKit/UIKit.h>
#interface MyApplicationData : NSObject <NSCoding, NSCopying> {
NSMutableArray* items;
NSMutableArray* categories;
}
#property (nonatomic ,retain) NSMutableArray* items;
#property (nonatomic, retain) NSMutableArray* categories;
#end
Myapplication.m
#import "MyApplicationData.h"
#implementation MyApplicationData
#synthesize items;
#synthesize categories;
#pragma mark NSCoding
- (void)encodeWithCoder:(NSCoder *)aCoder{
[aCoder encodeObject:items forKey:ITEMS_KEY];
[aCoder encodeObject:categories forKey:CATEGORIES_KEY];
}
-(id)initWithCoder:(NSCoder *)aDecoder{
if(self = [super init]){
self.items = [aDecoder decodeObjectForKey:ITEMS_KEY];
self.categories = [aDecoder decodeObjectForKey:CATEGORIES_KEY];
}
return self;
}
#pragma mark -
#pragma mark NSCopying
-(id)copyWithZone:(NSZone *)zone{
MyApplicationData* copy = [[[self class]allocWithZone:zone]init];
items = [self.items copy];
categories = [self.categories copy];
return copy;
}
#end
But warnning.
'NSCoder' may not respond to '-decodeDataObjectForKey'
How to use NSCoder?
Use -decodeObjectForKey: and read the documentation.
Here is the NSCoding protocal methods from my LogEntry object, you can ignore the switch statement and the schema details though, those are from a base class I have written that allows me to keep sane track of changing data formats.
Please note that in addition to using decodeObjectForKey: you also need to make sure you retain/copy the given values as they are autoreleased when received.
- (id)initWithCoder:(NSCoder *)coder {
self = [super initWithCoder:coder];
if (self != nil) {
switch ([schemaVersion intValue]) {
case 2:
filepath = [[coder decodeObjectForKey:#"filepath"] copy];
identifier = [coder decodeInt64ForKey:#"identifier"];
level = [coder decodeIntForKey:#"level"];
lineNumber = [[coder decodeObjectForKey:#"lineNumber"] retain];
message = [[coder decodeObjectForKey:#"message"] retain];
timestamp = [[coder decodeObjectForKey:#"timestamp"] retain];
break;
default:
[self release], self = nil;
break;
}
}
return self;
}
- (void)encodeWithCoder:(NSCoder *)coder {
[coder encodeObject:filepath forKey:#"filepath"];
[coder encodeInt64:identifier forKey:#"identifier"];
[coder encodeInt:level forKey:#"level"];
[coder encodeObject:lineNumber forKey:#"lineNumber"];
[coder encodeObject:message forKey:#"message"];
[coder encodeObject:timestamp forKey:#"timestamp"];
[super encodeWithCoder:coder];
}
I think you should be using -decodeObjectForKey:
I wrote a helper function for using NSCoding. It's a part of VSCore Library. Check it out here:
#interface QuickCoding : NSObject
+ (void)quickEncode:(NSObject<NSCoding>*)object withEncoder:(NSCoder*)encoder;
+ (void)quickDecode:(NSObject<NSCoding>*)object withDecoder:(NSCoder*)decoder;
#end
And the .m file:
#import "QuickCoding.h"
#import "ReflectionHelper.h"
#define QUICK_CODING_HASH #"h4"
#implementation QuickCoding
+ (void)quickEncode:(NSObject<NSCoding>*)object withEncoder:(NSCoder *)encoder{
NSArray *codingKeys = [ReflectionHelper fieldsList:[object class]];
NSUInteger hash = [[codingKeys componentsJoinedByString:#""] hash];
[encoder encodeObject:#(hash) forKey:QUICK_CODING_HASH];
[codingKeys enumerateObjectsUsingBlock:^(NSString *key, __unused NSUInteger idx, __unused BOOL *stop) {
id val = [object valueForKey:key];
if ([val conformsToProtocol:#protocol(NSCoding)]){
[encoder encodeObject:val forKey:key];
}
}];
}
+ (void)quickDecode:(NSObject<NSCoding>*)object withDecoder:(NSCoder *)decoder{
NSArray *codingKeys = [ReflectionHelper fieldsList:[object class]];
NSUInteger hash = [[codingKeys componentsJoinedByString:#""] hash];
NSUInteger decodedHash = [[decoder decodeObjectForKey:QUICK_CODING_HASH] unsignedIntegerValue];
BOOL equalHash = hash == decodedHash;
[codingKeys enumerateObjectsUsingBlock:^(NSString *key, __unused NSUInteger idx, __unused BOOL *stop) {
id val = [decoder decodeObjectForKey:key];
if (equalHash || val){
[object setValue:val forKey:key];
}
}];
}
#end
Full code is here: https://github.com/voipswitch/VSCore/tree/master/VSCore/Storage
I am having an issue in converting a NSObject into NSData. I have a class which inherits NSObject.
When i tried to convert the object of that particular class into NSData as follows :
NSData *dataOnObject = [NSKeyedArchiver archivedDataWithRootObject:classObject];
but it gives out exception stating that -[classObject encodeWithCoder:]: unrecognized selector sent to instance ..
I have also added the object to a newly created array as
NSMutableArray *wrapperedData = [NSMutableArray arrayWithObject: classObject];
NSData *dataOnObject = [NSKeyedArchiver archivedDataWithRootObject:value];
But still , its giving out exception.
So I need to extract the bytes from the object classObject.
Any help would be greatly appreciated ...
awaiting for your reply ...
You must implement for your own object such as:
- (void)encodeWithCoder:(NSCoder *)aCoder
{
[aCoder encodeObject:self.name forKey:#"name"];
[aCoder encodeInt:self.age forKey:#"age"];
[aCoder encodeObject:self.email forKey:#"email"];
[aCoder encodeObject:self.password forKey:#"password"];
}
BOOL success = [NSKeyedArchiver archiveRootObject:person toFile:archiveFilePath];
and:
- (id)initWithCoder:(NSCoder *)aDecoder
{
if (self = [super init]) {
self.name = [aDecoder decodeObjectForKey:#"name"];
self.age = [aDecoder decodeIntForKey:#"age"];
self.email = [aDecoder decodeObjectForKey:#"email"];
self.password = [aDecoder decodeObjectForKey:#"password"];
}
return self;
}
Person *unarchivePerson = [NSKeyedUnarchiver unarchiveObjectWithFile:archiveFilePath];
You need to implement encodeWithCoder: on your custom class, serializing all of its attributes using the NSCoder passed into it. If its attributes include any more custom classes, they'll need encodeWithCoder: implementing too.
Instead of
NSData *dataOnObject = [NSKeyedArchiver archivedDataWithRootObject:classObject];
it should be
NSData *dataOnObject = [[NSUserDefaults standardUserDefaults] objectForKey:#"someKey"];
But that's just for reading data in that's already been saved. If you want to save an object as NSData then you have this:
[[NSUserDefaults standardUserDefaults] setObject:[NSKeyedArchiver archivedDataWithRootObject:classObject] forKey:#"someKey"];
But that's not all. Your classObject has to implement the NSCoding protocol and have the two methods encodeWithCoder: and initWithCoder: since it's not an NS object in order for it to work.
you can only archive objects that support the NSCoding protocol
You can convert any object to NSData with the NSCoding protocol.
You can find sample code to do this here:
http://samsoff.es/posts/archiving-objective-c-objects-with-nscoding
This is a example of custom object converted to NSData (so it can be then saved into user defaults)
Create the following files:
Catalog.h
#interface Catalog : NSObject
#property (nonatomic, assign) int pk;
#property (nonatomic, copy) NSString *catalogName;
#property (nonatomic, copy) NSString *catalogDescription;
#property (nonatomic, assign) int catalogEdition;
#property (nonatomic, assign) int catalogTotalPages;
- (void)encodeWithCoder:(NSCoder *)aCoder;
- (id)initWithCoder:(NSCoder *)aDecoder;
#end
Catalog.m
#import <Foundation/Foundation.h>
#import "Catalog.h"
#implementation Catalog
- (void)encodeWithCoder:(NSCoder *)aCoder {
[aCoder encodeObject:self.catalogName forKey:#"catalogName"];
[aCoder encodeObject:self.catalogDescription forKey:#"catalogDescription"];
[aCoder encodeInt:self.catalogEdition forKey:#"catalogEdition"];
[aCoder encodeInt:self.catalogTotalPages forKey:#"catalogTotalPages"];
}
- (id)initWithCoder:(NSCoder *)aDecoder
{
if (self = [super init]) {
self.catalogName = [aDecoder decodeObjectForKey:#"catalogName"];
self.catalogDescription = [aDecoder decodeObjectForKey:#"catalogDescription"];
self.catalogEdition = [aDecoder decodeIntForKey:#"catalogEdition"];
self.catalogTotalPages = [aDecoder decodeIntForKey:#"catalogTotalPages"];
}
return self;
}
#end
Finally in your controller include header files
#import "Catalog.h"
And add this code to use your object (in this case im saving into user defaults)
Catalog *catalog = [[Catalog alloc] init];
catalog.catalogName = #"catalogName";
catalog.catalogDescription = #"catalogName";
catalog.catalogEdition = 1;
NOTE: in this line of code is where the actual data passing is taking place
//archiving object to nsdata
NSData *encodedObject = [NSKeyedArchiver archivedDataWithRootObject:catalog];
[[NSUserDefaults standardUserDefaults] setObject:encodedObject forKey:#"keyName"];
[[NSUserDefaults standardUserDefaults] synchronize];
In case you want to get your object back from NSData
NSData *nsData = [[NSUserDefaults standardUserDefaults] objectForKey:#"keyName"];
//unarchiving object to nsdata
Catalog *selectedCatalog = [NSKeyedUnarchiver unarchiveObjectWithData: nsData];
Hope this helps!