Serialize and Deserialize Objective-C objects into JSON

Question

I need to serialize and deserialize objective-c objects into JSON to store in CouchDB. Do people have any example code for best practice for a general solution? I looked at a few JSON framework and they are stopped at the NSDictionary/NSArray level. i.e. A lot of framework will serialize and deserialize NSDictionary/NSArray into JSON. But I still have to do the work to convert NSDictionary into Objective-C objects.

To make things more complex, my Object A can have reference to an NSArray/NSDictionary of Object Bs.

My question is very similar to this question with addition of the collection requirement.

Instantiating Custom Class from NSDictionary

Answer 1

Finally we can solve this problem easily using JSONModel. This is the best method so far. JSONModel is a library that generically serialize/deserialize your object based on Class. You can even use non-nsobject based for property like int, short and float. It can also cater nested-complex JSON.

Considering this JSON example:

{ "accounting" : [{ "firstName" : "John",                       "lastName"  : "Doe",                     "age"       : 23 },                    { "firstName" : "Mary",                       "lastName"  : "Smith",                     "age"       : 32 }                               ],                               "sales"      : [{ "firstName" : "Sally",                      "lastName"  : "Green",                     "age"       : 27 },                    { "firstName" : "Jim",                        "lastName"  : "Galley",                     "age"       : 41 }                   ]} 

1) Deserialize example. in header file:

#import "JSONModel.h"  @interface Person : JSONModel  @property (nonatomic, strong) NSString *firstName; @property (nonatomic, strong) NSString *lastName; @property (nonatomic, strong) NSNumber *age; @end  @protocol Person;  @interface Department : JSONModel @property (nonatomic, strong) NSMutableArray<Person> *accounting; @property (nonatomic, strong) NSMutableArray<Person> *sales; @end 

in implementation file:

#import "JSONModelLib.h" #import "myJSONClass.h"  NSString *responseJSON = /*from example*/; Department *department = [[Department alloc] initWithString:responseJSON error:&err]; if (!err) {     for (Person *person in department.accounting) {          NSLog(@"%@", person.firstName);         NSLog(@"%@", person.lastName);         NSLog(@"%@", person.age);              }      for (Person *person in department.sales) {          NSLog(@"%@", person.firstName);         NSLog(@"%@", person.lastName);         NSLog(@"%@", person.age);              } } 

2) Serialize Example. In implementation file:

#import "JSONModelLib.h" #import "myJSONClass.h"  Department *department = [[Department alloc] init];  Person *personAcc1 = [[Person alloc] init]; personAcc1.firstName = @"Uee"; personAcc1.lastName = @"Bae"; personAcc1.age = [NSNumber numberWithInt:22]; [department.accounting addOject:personAcc1];  Person *personSales1 = [[Person alloc] init]; personSales1.firstName = @"Sara"; personSales1.lastName = @"Jung"; personSales1.age = [NSNumber numberWithInt:20]; [department.sales addOject:personSales1];  NSLog(@"%@", [department toJSONString]); 

And this is NSLog result from Serialize example:

{ "accounting" : [{ "firstName" : "Uee",                       "lastName"  : "Bae",                     "age"       : 22 }                  ],                               "sales"      : [{ "firstName" : "Sara",                      "lastName"  : "Jung",                     "age"       : 20 }                   ]} 

Answer 2

It sounds like you're looking for a serialization library that can let you convert objects of your own custom classes into JSON, and then reconstitute them back. Serialization of property-list types (NSArray, NSNumber, etc.) already exists in 3rd party libraries, and is even built into OS X 10.7 and iOS 5.

So, I think the answer is basically "no". I asked this exact question a month or two ago on the cocoa-dev mailing list, and the closest I got to a hit was from Mike Abdullah, pointing to an experimental library he'd written:

https://github.com/mikeabdullah/KSPropertyListEncoder

This archives objects to in-memory property lists, but as I said there are already APIs for converting those into JSON.

There's also a commercial app called Objectify that claims to be able to do something similar:

http://tigerbears.com/objectify/

It's possible I'll end up implementing what you're asking for as part of my CouchCocoa library, but I haven't dived into that task yet.

https://github.com/couchbaselabs/CouchCocoa

Answer 3

You can easily add JSON capability to NSObject class with the help of NSDictionary,NSArray and NSJSONSerialization

Serialization:

Just see the example it will be very easy to understand.

Adding JSON Capability to NSObject Class:-

@interface JsonClassEmp : NSObject

@property(strong,nonatomic)NSString *EmpName,*EmpCode;

-(NSDictionary*)GetJsonDict;

@end

@implementation JsonClassEmp

@synthesize EmpName,EmpCode;

//Add all the properties of the class in it.
-(NSDictionary*)GetJsonDict
{
    return [NSDictionary dictionaryWithObjectsAndKeys:EmpName,@"EmpName",EmpCode,@"EmpCode", nil];
}

@end

JSON String Generator:-

In iOS 5, Apple introduced NSJSONSerialization, for parsing JSON strings so by using that we will generate JSON string.

-(NSString*)GetJSON:(id)object
{
    NSError *writeError = nil;

    NSData *jsonData = [NSJSONSerialization dataWithJSONObject:object options:NSJSONWritingPrettyPrinted error:&writeError];

    NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];

    return jsonString;
}

Moving towards Apple’s implementation is always safer to use since you have the guarantee that it will be maintained and kept up to date.

Way to use:-

- (void)viewDidLoad
{
    [super viewDidLoad];

    JsonClassEmp *emp1=[[JsonClassEmp alloc]init];

    [emp1 setEmpName:@"Name1"];

    [emp1 setEmpCode:@"1"];

    JsonClassEmp *emp2=[[JsonClassEmp alloc]init];

    [emp2 setEmpName:@"Name2"];

    [emp2 setEmpCode:@"2"];

    //Add the NSDictionaries of the instances in NSArray
    NSArray *arrEmps_Json=@[emp1.GetJsonDict,emp2.GetJsonDict];

    NSLog(@"JSON Output: %@", [self GetJSON:arrEmps_Json]);

}

Reference

Deserialization:

It's usual way of getting the deserialized data into NSDictionary or NSArray then assign it to class properties.

I am sure using the methods and ideas used above you can serialize & deserialize complex json easily.