On 04/01/2013, at 08:55, Matthias Wessendorf <
matzew@apache.org> wrote:
> CoreData: API proposal - AGEntityMapper
> Background
> Mapping JSON representations to a "rich" domain model in ObjC is a bit cumbersome. Similar is true when mapping a JSON data/response to a NSMangedObject (and vise versa). There is a base framework for "remote persistence", via the CoreData API, by leveraging a custom NSIncrementalStore -> AFIncrementalStore.
>
> For that,... a similar two-way-mapping is required, as described here.
>
> AeroGear and CoreData
> Our CoreData offerings are leveraging the AFIncrementalStore, therefore (as with other frameworks/libraries) we need a mapping as well. We need to know the name of the entity and we need a NSDictionary that covers the actual JSON/property mapping. It could be done with the vanialla ObjC classes:
>
> // some mappers:
> NSDictionary *task_mapper =
>
>
> [NSDictionary dictionaryWithObjectsAndKeys:@"description",@"desc",@"id",@"myId", nil];
> NSDictionary *project_mapper =
>
>
> [NSDictionary dictionaryWithObjectsAndKeys:@"id",@"myId", nil];
>
>
>
> // create a schema out of the mappers:
> NSDictionary *schema =
>
>
> [NSDictionary dictionaryWithObjectsAndKeys:task_mapper, @"Task", project_mapper, @"Project", nil];
>
>
>
> // pass the schema to the AGCoreDataHelper class, when doing the init...
> Proposal for a custom API
> I'd like to introduce a new wrapper type, called AGEntityMapper:
>
> @interface AGEnityMapper : NSObject
>
>
>
> @property NSString *name;
> @property NSDictionary *mapper;
>
>
>
> -(id) initWithName:(NSString *) name mapper:(NSDictionary *) mapper;
> @end
> This AGEntityMapper would be applied onto the AGCoreDataConfig:
>
> @protocol AGCoreDataConfig <NSObject>
>
>
>
> @property (strong, nonatomic) NSManagedObjectModel *managedObjectModel;
> @property (strong, nonatomic) NSURL *baseURL;
>
>
>
> -(void)applyEntityMappers:(AGEnityMapper *)firstObject, ... NS_REQUIRES_NIL_TERMINATION;
>
>
>
> @end
> The actual code, would look like this:
>
> EnityMapper *taskMapper =
>
>
> [[EnityMapper alloc] initWithName:@"Task"
>
>
> // mapping the properties on the "entity" (NSManagedObject)
>
>
> // to the external representation (e.g. JSON)
>
>
> mapper:@{ @"desc": @"description", @"myId": @"id"}];
>
>
>
> EnityMapper *projectMapper =
>
>
> [[EnityMapper alloc] initWithName:@"Project"
>
>
> // mapping the properties on the "entity" (NSManagedObject)
>
>
> // to the external representation (e.g. JSON)
>
>
> mapper:@{ @"myId": @"id"}];
>
>
>
> AGCoreDataHelper *helper = [[AGCoreDataHelper alloc] initWithConfig:^(id<AGCoreDataConfig> config) {
>
>
>
> [config setBaseURL:[NSURL URLWithString:@"
http://server.com"]];
>
>
>
> [config applyEntityMappers:
>
>
> taskMapper,
>
>
> projectMapper,
>
>
> nil // terminate the varargs.
>
>
> ];
> }];
>
> --
> Matthias Wessendorf
>
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http://matthiaswessendorf.wordpress.com/
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