Question

In a Navigation based app, I’d like to be able to have a “Clone” or “Save As” button on my detailed Product view where a user can create a new Product from one of their existing products they have already entered. In the app, a product has quite a few attribute fields for the user to enter, so I’d like to offer the ability for a user to quickly “Clone” or “Save As” any of their existing products which would automatically copy the attributes of that existing Product over to a new product and allow the user to enter a name for the new Product and save it.

Any help with how to achieve this would be much appreciated. Thanks.

Answer 1

I’m assuming that you are using Core Data, but you don’t specifically mention that. From the context of your question, that seems to make sense.

Copying properties from one object to another can be tricky. I recommend a great book on Core Data by Marcus Zarra. You can find it here http://pragprog.com/titles/mzcd/core-data

In his book, he runs through this through this scenario except in the context of importing and exporting data, but the code should be similar. Here is some code that is available from his book site (above). This copies all properties, including relationships, from one object to another. You must also identify the name of the parent object in order for it to work properly.

This code will not only copy properties, but also relationships, including related objects and their properties. It works quite well.

Hope this helps!

- (void)copyPropertiesFromObject:(NSManagedObject*)oldObject
                    toObject:(NSManagedObject*)newObject
                      parent:(NSString*)parentEntity {

NSString *entityName = [[oldObject entity] name];
NSArray *attKeys = [[[oldObject entity] attributesByName] allKeys];
NSDictionary *attributes = [oldObject dictionaryWithValuesForKeys:attKeys];
[newObject setValuesForKeysWithDictionary:attributes];
//END:copyPropertiesFromObjectProperties

//START:copyPropertiesFromObjectRelationships
id oldDestObject = nil;
id temp = nil;
NSDictionary *relationships = [[oldObject entity] relationshipsByName];
for (NSString *key in [relationships allKeys]) {
    NSRelationshipDescription *desc = [relationships valueForKey:key];
    NSString *destEntityName = [[desc destinationEntity] name];
    if ([destEntityName isEqualToString:parentEntity]) continue;

    if ([desc isToMany]) {
        NSMutableSet *newDestSet = [NSMutableSet set];
        for (oldDestObject in [oldObject valueForKey:key]) {
            temp = [[self lookup] objectForKey:[oldDestObject objectID]];
            if (!temp) {
                temp = [self associateObject:oldDestObject 
                            parent:entityName];
            }
            [newDestSet addObject:temp];
        }
        [newObject setValue:newDestSet forKey:key];
    } else {
        oldDestObject = [oldObject valueForKey:key];
        if (!oldDestObject) continue;
        temp = [[self lookup] objectForKey:[oldDestObject objectID]];
        if (!temp) {
            temp = [self associateObject:oldDestObject 
                                  parent:entityName];
        }
        [newObject setValue:temp forKey:key];
    }
}
}

And this:

- (id)associateObject:(NSManagedObject*)object parent:(NSString*)name {

NSManagedObjectContext *moc = [self mainContext];
NSString *entityName = [[object entity] name];
id temp = nil;

if ([entityName isEqualToString:@"Title"]) {
    temp = [NSEntityDescription insertNewObjectForEntityForName:entityName 
                                     inManagedObjectContext:moc];
    [[self lookup] setObject:temp forKey:[object objectID]];
    [self copyPropertiesFromObject:object toObject:temp parent:name];
    return temp;
}

if ((temp = [self objectOfType:entityName 
                     withName:[object valueForKey:@"name"]])) {
    [[self lookup] setObject:temp forKey:[object objectID]];
    return temp;
}

temp = [NSEntityDescription insertNewObjectForEntityForName:entityName
                                     inManagedObjectContext:moc];
[[self lookup] setObject:temp forKey:[object objectID]];
[self copyPropertiesFromObject:object toObject:temp parent:name];
return temp;
}