Get properties of NSManagedObject as NSDictionary

Question

If I have an NSManagedObject I've fetched from a context, how can I create an NSDictionary out of its dynamic properties without just copying each field into the dictionary explicitly?

If my managed object looks like this, for example:

@implementation Track

@dynamic artist;
@dynamic group;
@dynamic purchase_url;
@dynamic title;
@dynamic file_name;
@dynamic year;

@end

After fetching from the database, in this case, I need an NSDictionary with the same properties set to each of those @dynamic properties.

Could you give more detail about why you want to do this, there may be a better way to achieve what you want. In the meantime, look at NSEntityDescription and attributesByName. — jrturton, Apr 26 '12 at 21:23
Have a look at [this article](http://vladimir.zardina.org/2010/03/serializing-archivingunarchiving-an-nsmanagedobject-graph/). It also covers you for any relations as well. — Alladinian, Apr 26 '12 at 21:23

score 57 · Accepted Answer · edited May 23 '17 at 12:34

57

There is a faster way to convert an NSManagedObject to an NSDictionary (from Matthias Bauch response at https://stackoverflow.com/a/5664745/2294824) :

NSArray *keys = [[[myObject entity] attributesByName] allKeys];
NSDictionary *dict = [myObject dictionaryWithValuesForKeys:keys];

edited May 23 '17 at 12:34

Community

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answered Nov 18 '13 at 02:47

Frédéric

726
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Thanks for this answer,it helps me to wrap up a long standing issue. – Rahul K Rajan Jan 22 '16 at 07:59
is there a reverse for this? NSdictionary to CoreData? – nr5 Feb 12 '16 at 12:47
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Reverse is described in the link from answer: [myObject setValuesForKeysWithDictionary:dict] – Werewolf Aug 23 '16 at 15:20
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This is awesome! I was about to iterate trough keys before seeing this... – Julius Jan 15 '18 at 16:23

Markus · Answer 2 · 2012-04-26T22:01:25.783

You can achieve your approach by following method:

unsigned int count;
objc_property_t *properties = class_copyPropertyList([CoreDataObject class], &count);
NSMutableDictionary *dictionary = [NSMutableDictionary dictionaryWithCapacity:16];

for(int i = 0; i < count; i++) {
    objc_property_t property = properties[i];
    NSString *name = [NSString stringWithCString:property_getName(property) encoding:NSUTF8StringEncoding];
    id obj = [coreDataObjectInstance valueForKey:name];
    if (obj) {
        // Skip properties with nil values (optionally you can use: [dictionary setObject:((obj == nil) ? [NSNull null] : obj) forKey:name]; without any if-statement) 
        [dictionary setObject:obj forKey:name];
    }
}

free(properties);

"CoreDataObject" is the core data object you would like to convert into a NSDictionary while "coreDataObjectInstance" is an instance of this core data object. Keep in mind you have to:

#include <objc/runtime.h>

Furthermore, it would be great if you can give us some more insights what you would like to achieve with this idea, maybe there is a different/better solution.

Hope this helps!

I would like to share with you details about what I may use this in, I want to make an inspector window, so if you selected a row in a table populated with nsmanagedobject subclass, the inspector window will show the properties of this managedObject in three columns tale: property name, property type "string, int..." and prop value what do you think the best way to achieve this scenario?? — AMTourky, Dec 04 '13 at 12:49

score 7 · Answer 3 · answered Oct 31 '13 at 21:11

7

I think this is what you're actually looking for:

NSEntityDescription *trackEntity = [NSEntityDescription entityForName:[Track entityName] inManagedObjectContext:yourMOC];

then you have access to these dictionaries:

[trackEntity propertiesByName];
[trackEntity relationshipsByName];
[trackEntity attributesByName];

each of these dictionaries will have keys corresponding to the property, and the value will be an NSPropertyDescription.

answered Oct 31 '13 at 21:11

bpercevic

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relationshipsByName returns a dictionary of values that are NSRelationshipDescription objects.... – Kendall Helmstetter Gelner Nov 18 '15 at 20:59

score 3 · Answer 4 · answered Aug 02 '19 at 10:19

3

Note: Swift 4.2 update

let keys = Array(YOUR_MANAGED_OBJECT.entity.attributesByName.keys)
let data:[String: Any] = YOUR_MANAGED_OBJECT.dictionaryWithValues(forKeys: keys)

answered Aug 02 '19 at 10:19

ceekay

1,136
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**Swift 5:** `let data = YOUR_MANAGED_OBJECT.dictionaryWithValues(forKeys: YOUR_MANAGED_OBJECT.attributeKeys)` – Daniel Jan 12 '20 at 20:15

Get properties of NSManagedObject as NSDictionary

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