Database Reference
In-Depth Information
Next, we must deal with the relationships. Just as with the attributes, we
can find out the name of each relationship from the
NSEntityDescription
. By
looping over the resulting
NSDictionary
, we can process each relationship.
However, to make sure we are not in an infinite recursion, we check each
relationship to see whether we should be following it. If we shouldn't follow
it, we simply skip to the next relationship.
if
([relDesc isToMany]) {
NSMutableArray *array = [NSMutableArray array];
for
(NSManagedObject *childMO in [mo valueForKey:key]) {
[array addObject:[self moToDictionary:childMO]];
}
[dict setValue:array forKey:key];
continue
;
}
NSManagedObject *childMO = [mo valueForKey:key];
[dict addEntriesFromDictionary:[self moToDictionary:childMO]];
}
return
dict;
}
From the perspective of the current
NSManagedObject
, there are two types of
relationships: to-one or to-many. If it is a to-one relationship, we grab the
object at the other end of the relationship and turn it into an
NSDictionary
for
inclusion in our
NSMutableDictionary
.
If the relationship is a to-many, we need to iterate over the resulting set and
turn each
NSManagedObject
into an
NSDictionary
and include it in a temporary
array. Once we have iterated over all of the objects in the relationship, we
add the entire array to our master
NSMutableDictionary
using the relationship
name as the key.
Once all of the relationships have been processed, we return the
NSMutableDic-
tionary
to the
-main
so that we can complete the final step.
NSError *error = nil;
NSDictionary *objectStructure = [self moToDictionary:localRecipe];
NSData *data = [NSJSONSerialization dataWithJSONObject:objectStructure
options:0
error:&error];
[self completionBlock](data, error);
}
At the end of the
-main
, we use the
NSJSONSerialization
class to turn the
NSDictionary
structure into a JSON structure. Note that the
PPRExportOperation
does not care
