Database Reference
In-Depth Information
Once we have the data in a JSON structure, we must check whether the top-
level object is an
NSArray
or an
NSDictionary
. Adding this check makes the import
operation more flexible and capable of handling the imported recipes. If the
top-level object is an
NSDictionary
, we know there is a single recipe being
imported and begin the import operation. If the top-level object is an
NSArray
,
we iterate over the array and construct a recipe for each included dictionary.
For each dictionary (whether there are one or many), we construct an
NSManagedObject
and pass both the dictionary and the
NSManagedObject
into
-popu-
lateManagedObject:fromDictionary:
.
- (
void
)populateManagedObject:(NSManagedObject*)mo
fromDictionary:(NSDictionary*)dict
{
NSManagedObjectContext *context = [mo managedObjectContext];
NSEntityDescription *entity = [mo entity];
NSArray *attKeys = [[entity attributesByName] allKeys];
NSDictionary *atttributesDict = [dict dictionaryWithValuesForKeys:attKeys];
[mo setValuesForKeysWithDictionary:atttributesDict];
In the first part of
-populateManagedObject:fromDictionary:
, we want to populate all
the attributes of the
NSManagedObject
. The process is the reverse of what we
accomplished in the
PPRExportOperation
. Here are the steps:
1.
We grab an
NSArray
of all the attribute names for the entity.
2.
We then retrieve an
NSDictionary
from the passed-in
NSDictionary
of only those
attributes and their associated values.
3.
We take the resulting dictionary and hand it off to the
NSManagedObject
via
the
KVC
method
-setValuesForKeysWithDictionary:
.
NSManagedObject* (^createChild)(NSDictionary *childDict,
NSEntityDescription *destEntity,
NSManagedObjectContext *context);
createChild = ^(NSDictionary *childDict, NSEntityDescription *destEntity,
NSManagedObjectContext *context) {
NSManagedObject *destMO = nil;
destMO = [[NSManagedObject alloc] initWithEntity:destEntity
insertIntoManagedObjectContext:context];
[self populateManagedObject:destMO fromDictionary:childDict];
return
destMO;
};
The next step is to create a block to avoid repeating ourselves later in this
method. When we are dealing with the creation of the relationships, we are
