ios - How to use NSManagedObject without adding it to db? -

i'm having class inherits nsmanagedobject generated using db model:

// .h @interface sketch : nsmanagedobject  @property (nonatomic, retain) nsdate * added; @property (nonatomic, retain) nsstring * board; @property (nonatomic, retain) nsstring * filepath; @property (nonatomic, retain) nsstring * title; @property (nonatomic, retain) nsstring * filename;  @end  // .m @implementation sketch  @dynamic added; @dynamic board; @dynamic filepath; @dynamic title; @dynamic filename;  @end 

i'm using class instances in uitableview. need add instances not stored in db (just show them in list):

sketch sketch = [[sketch alloc] init]; 

but when trying set instance properties

sketch.title = @"test title"; 

i'm getting exception:

-[sketch settitle:]: unrecognized selector sent instance 0x7ff112c13e30 

does mean have to create instance adding them managed context (even if i'm not going store them)?

[nsentitydescription insertnewobjectforentityforname:sketch_entity                                      inmanagedobjectcontext:context]; 

no, can create instances of nsmanagedobject subclasses , add them managed object context later (while i'd suggest not do so). have issue sketch object, not nsmanagedobject , nsmanagedobjectcontext.

the thing should create this:

nsmanagedobjectcontext *moc = ... // managed object context nsentitydescription *entity = [nsentitydescription entityforname:@"sketch"                                           inmanagedobjectcontext:moc]; // note nil context sketch *unassociatedobject =     (sketch *)[[nsmanagedobject alloc] initwithentity:entity                        insertintomanagedobjectcontext:nil]; 

for more details see this answer.