a2/bwobjectmapping

Small library that parse JSON and map it to any object, works with NSManagedObject.

BWObjectMapping

Small library that parse JSON and map it to any object, works with NSManagedObject.

Example object interface

@interface User : NSObject

@property (nonatomic, strong) NSNumber *userID;
@property (nonatomic, strong) NSString *firstName;
@property (nonatomic, strong) NSDate *createdAt;

@end

Mapping

[BWObjectMapping mappingForObject:[User class] block:^(BWObjectMapping *mapping) {
	[mapping mapPrimaryKeyAttribute:@"id" toAttribute:@"userID"];
	[mapping mapKeyPath:@"first_name" toAttribute:@"firstName"];
	[mapping mapAttributeFromArray:@[@"name"]];
	[mapping mapAttributeFromDictionary:@{@"created_at" : @"createdAt"}];    
  
	[[BWObjectMapper shared] registerMapping:mapping withRootKeyPath:@"user"];
}];

At the last line we register the mapping and give a root key path. You don't need to have one, but if not the mapper will not be able to guess which mapping class to use.

Object creation

[[BWObjectMapper shared] objectWithBlock:^id(Class objectClass, NSString *primaryKey, id primaryKeyValue, id JSON) {
	return [[objectClass alloc] init];
}];

The json

{
	"user": [{
		"id": 1,
		"first_name": "Bruno",
		"created_at": "2012-08-10T06:12:28Z"
	}]
}

Default parsing date format is Rails format.

Map json to object

NSArray *objects = [[BWObjectMapper shared] objectsFromJSON:JSON];

Because the JSON contain a root key path, the mapping automatically discover.

All mapping methods

- (NSArray *)objectsFromJSON:(id)JSON withMapping:(BWObjectMapping *)mapping;

- (NSArray *)objectsFromJSON:(id)JSON withObjectClass:(Class)objectClass;

- (NSArray *)objectsFromJSON:(id)JSON;

- (id)objectFromJSON:(id)JSON withMapping:(BWObjectMapping *)mapping;

- (id)objectFromJSON:(id)JSON withMapping:(BWObjectMapping *)mapping existingObject:(id)object;

- (id)objectFromJSON:(id)JSON withObjectClass:(Class)objectClass;

- (id)objectFromJSON:(id)JSON withObjectClass:(Class)objectClass existingObject:(id)object;

- (id)objectFromJSON:(id)JSON;

- (id)objectFromJSON:(id)JSON existingObject:(id)object;

Note about date format

If you don't use Rails date format you have two options:

1. Specify global date format

   [objectMapping mapKeyPath:@"created_at" toAttribute:@"createdAt" dateFormat:@""];

2. Custom date format on each attribute.

   [[BWObjectMapper shared] setDefaultDateFormat:@""];

Handling relation

Let's suppose you have a JSON like this:

{
    "model": "HB20",
    "year": "2013",
    "engine": {
        "type": "v8"
    },
    "wheels": [
        {
            "id": "123123123",
            "type": "16"
        },
        {
            "id": "1234",
            "type": "17"
        }
    ]
}

• First define your models:

@interface Car : NSObject

@property (nonatomic, copy)   NSString *model;
@property (nonatomic, copy)   NSString *year;
@property (nonatomic, strong) Engine   *engine;
@property (nonatomic, strong) NSArray  *wheels;

@end

@interface Engine : NSObject

@property (nonatomic, copy) NSString *type;

@end

@interface Wheel : NSObject

@property (nonatomic, copy) NSString *identifier;
@property (nonatomic, copy) NSString *size;

@end

• After this what you need to do is define their mappings in somewhere like this:

#import "MappingProvider.h"
#import "Car.h"
#import "Engine.h"
#import "Wheel.h"

@implementation MappingProvider

+ (BWObjectMapping *)carMapping
{
    return [BWObjectMapping mappingForObject:[Car class] block:^(BWObjectMapping *mapping) {
        [mapping mapAttributeFromArray:@[@"model", @"year"]];
        [mapping hasOneWithRelationMapping:[self engineMapping] fromKeyPath:@"engine"];
        [mapping hasManyWithRelationMapping:[self wheelMapping] fromKeyPath:@"wheels"];
    }];
}

+ (BWObjectMapping *)engineMapping
{
    return [BWObjectMapping mappingForObject:[Engine class] block:^(BWObjectMapping *mapping) {
        [mapping mapAttributeFromArray:@[@"type"]];
    }];
}

+ (BWObjectMapping *)wheelMapping
{
    return [BWObjectMapping mappingForObject:[Wheel class] block:^(BWObjectMapping *mapping) {
        [mapping mapAttributeFromArray:@[@"size"]];
        [mapping mapAttributeFromDictionary:@{
            @"id": @"identifier"
         }];
    }];
}

• And to instanciate the root object you can do this:

Car *car = [[BWObjectMapper shared] objectFromJSON:carJSON withMapping:[MappingProvider carMapping]];

Installation

Copy BWObjectMapper dir into your project.

Or with Cocoapods

pod 'BWObjectMapper', :git => "https://github.com/brunow/BWObjectMapper.git", :tag => "0.2.0"

ARC

BWObjectMapper is ARC only.

Thanks

Big thanks to lucasmedeirosleite that added hasMany and hasOne relation.

Contact

Bruno Wernimont

• Twitter - @brunowernimont