objective c - Adding objects To-Many Relationships RLMObject -

i'm starting use realm.io , need add or update to-many relationship rlmobject. imagine have rlmobjects this:

#import <realm/realm.h>  @class person;  // dog model @interface dog : rlmobject @property nsinteger id; @property nsstring *name; @end rlm_array_type(dog) // define rlmarray<dog>  // person model @interface person : rlmobject @property nsstring             *name; @property nsdate               *birthdate; @property rlmarray<dog *><dog> *dogs; @end rlm_array_type(person) // define rlmarray<person> 

dogs rlmobject has primary key (id) , i'm reading json 1 person , various dogs. how can add person , dogs?

i'll loop json person , dogs array. if use above code example, realm warning primary key violation on dogs object:

rlmrealm *realm = [rlmrealm defaultrealm]; dogs *dog = [[dogs alloc] init]; [realm beginwritetransaction];    dog.id = 1;    dog.name = @"lupi";    [realm addorupdateobject:dog];    dog.id = 2;    dog.name = @"rex";    [realm addorupdateobject:dog];  [realm commitwritetransaction];  person *newperson = [[person alloc] init];     [realm beginwritetransaction];         newperson.id = 1;         newperson.name = @"john";         [newperson.dogs addobject:dog];         [realm addorupdateobject:newperson];     [realm commitwritetransaction]; 

if error 'primary key can't changed after object inserted.', reason because you're trying use same object.

dog.id = 1; dog.name = @"lupi"; [realm addorupdateobject:dog];  dog.id = 2; // not allowed. primary key of object saved once can not changed. dog.name = @"rex"; [realm addorupdateobject:dog]; 

realm object not value object. when realm object saved once, changed special object connected database.

so dog.id = 2; means change object saved.

you should create new instance every time when you'd save new objects. following:

dog *dog1 = [[dog alloc] init]; dog1.id = 1; dog1.name = @"lupi"; [realm addorupdateobject:dog1];  dog *dog2 = [[dog alloc] init]; dog2.id = 2; dog2.name = @"rex"; [realm addorupdateobject:dog2];  [realm commitwritetransaction]; 

create objects json

if create new objects json following:

{   "person": {     "id": 1,     "name": "foo",     "birthdate": "1980/10/28",     "dogs": [       {         "id": 1,         "name": "bar"       },       {         "id": 2,         "name": "baz"       }     ]   } } 

you can loop dogs array, create new realm objects every loop.

nsdictionary *json = [nsjsonserialization jsonobjectwithdata:data options:0 error:nil];  nsdictionary *person = json[@"person"];  [realm beginwritetransaction];  person *newperson = [[person alloc] init]; newperson.id = [person[@"id"] integervalue]; newperson.name = person[@"name"];  nsarray *dogs = person[@"dogs"]; (nsdictionary *dog in dogs) {     dog *newdog = [[dog alloc] init];     newdog.id = [dog[@"id"] integervalue];     newdog.name = dog[@"name"];     [realm addorupdateobject:newdog]; }  [realm addorupdateobject:newperson];  [realm commitwritetransaction];