Some finishing on core data (iii)

Some finishing on core data (iii)

The relationship between the four types of core Data stacks and their relationships is as follows:

• Nsmanagedobjectmodel
  
• Nspersistentstore
  
• Nspersistentstorecoordinator
  
• Nsmanagedobjectcontext

Handwritten core Data Stack, the new file inherits NSObject, and in which three objects are initialized in sequence:,, NSManagedObjectContext NSPersistentStoreCoordinator NSManagedObjectModel The specific code is implemented as follows:

1 //CoreDataStack.h2 3 #import<Foundation/Foundation.h>4 #import<CoreData/CoreData.h>5 6 @interfaceCoredatastack:nsobject7 8@property (nonatomic, strong) Nsmanagedobjectcontext *context;9 Ten- (void) Savecontext; One  A @end -  - //COREDATASTACK.M the  - #import "CoreDataStack.h" -  - @interfaceCoredatastack () +  -@property (nonatomic, strong) Nspersistentstorecoordinator *PSC; +@property (nonatomic, strong) Nsmanagedobjectmodel *Managedobjectmodel; A  at @end -  - @implementationCoredatastack -  - @synthesizeManagedobjectmodel =_managedobjectmodel; -  in- (void) Savecontext { -   if(_context) { toNserror *error =Nil; +     if([_context haschanges] && [_context save:&ERROR]) { -NSLog (@"%@", error.localizeddescription); the abort (); *     } $   }Panax Notoginseng } -  the-(Nsurl *) Applicationdocumentsdirectory { +Nsarray *array =[[Nsfilemanager Defaultmanager] urlsfordirectory:nsdocumentdirectory indomains:nsuserdomainmask]; A   returnArray.lastobject; the } +  --(Nsmanagedobjectcontext *) Context { $   if(_context) { $     return_context; -   } -_context =[[Nsmanagedobjectcontext alloc] initwithconcurrencytype:nsmainqueueconcurrencytype]; the [_context setpersistentstorecoordinator:[self PSC]]; -   return_context;Wuyi } the  --(Nspersistentstorecoordinator *) PSC { Wu   if(_PSC) { -     return_PSC; About   } $_PSC =[[Nspersistentstorecoordinator alloc] initwithmanagedobjectmodel:[self Managedobjectmodel]]; -Nsurl *url = [[Self applicationdocumentsdirectory] urlbyappendingpathcomponent:@"Jmdog_walk.sqlite"]; -[_PSC addpersistentstorewithtype:nssqlitestoretype Configuration:nil Url:url options:@{ nsmigratepersistentstoresautomaticallyoption:@1} Error:nil]; -   return_PSC; A } +  the-(Nsmanagedobjectmodel *) Managedobjectmodel { -   if(_managedobjectmodel) { $     return_managedobjectmodel; the   } theNsurl *url = [[NSBundle mainbundle] Urlforresource:@"Jmdog_walk"Withextension:@"MOMD"]; the_managedobjectmodel =[[Nsmanagedobjectmodel alloc] initwithcontentsofurl:url]; the   return_managedobjectmodel; - } in  the @end

The places to be noted are:

1. All global variables are lazy loaded, improving efficiency;
2. Just put it NSManagedObjectContext in the. h to go;
3. Call Addpersistentstorewithtype: Note that the database file is named as the type of the SQLite suffix, otherwise it will be an error;
4. Note that the naming consistency is used in the code JMDog_Walk , and when you build the core data file, you also name the file JMDog_Walk !

Some finishing on core data (iii)