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--- ios-labs-s14:advanced-core [2014/02/25 15:47]
mbarboi created
+++ ios-labs-s14:advanced-core [2014/02/26 10:28] (current)
mbarboi
@@ Line 6: / Line 6: @@
 Implementing CoreData into your application:
   -Add CoreData framework
-  -Import CoreData
+  -Import CoreData Headers
+  -Add methods to AppDelegate
+Adding CoreData Accessors:
+====Adding CoreData Methods====
+  *Add the following code to AppDelegate.h right before //@end//
+<code>
+@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;
+@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;
+@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;
+- (void)saveContext;
+- (NSURL *)applicationDocumentsDirectory;
+</code>
+  *Add the following code to AppDelegate.m immediately after //@implementation//
+<code>
+@synthesize managedObjectContext = _managedObjectContext;
+@synthesize managedObjectModel = _managedObjectModel;
+@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;
+</code>
+  *Add the following code to AppDelegate.m right before //@end//
+<code>
+- (void)saveContext
+{
+    NSError *error = nil;
+    NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
+    if (managedObjectContext != nil) {
+        if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
+            // Replace this implementation with code to handle the error appropriately.
+            // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
+            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
+            abort();
+        }
+    }
+}
+#pragma mark - Core Data stack
+// Returns the managed object context for the application.
+// If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application.
+- (NSManagedObjectContext *)managedObjectContext
+{
+    if (_managedObjectContext != nil) {
+        return _managedObjectContext;
+    }
+    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
+    if (coordinator != nil) {
+        _managedObjectContext = [[NSManagedObjectContext alloc] init];
+        [_managedObjectContext setPersistentStoreCoordinator:coordinator];
+    }
+    return _managedObjectContext;
+}
+// Returns the managed object model for the application.
+// If the model doesn't already exist, it is created from the application's model.
+- (NSManagedObjectModel *)managedObjectModel
+{
+    if (_managedObjectModel != nil) {
+        return _managedObjectModel;
+    }
+    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"Model" withExtension:@"momd"];
+    _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
+    return _managedObjectModel;
+}
+// Returns the persistent store coordinator for the application.
+// If the coordinator doesn't already exist, it is created and the application's store added to it.
+- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
+{
+    if (_persistentStoreCoordinator != nil) {
+        return _persistentStoreCoordinator;
+    }
+    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"_.sqlite"];
+    NSError *error = nil;
+    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
+    if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
+        /*
+         Replace this implementation with code to handle the error appropriately.
+         abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
+         Typical reasons for an error here include:
+         * The persistent store is not accessible;
+         * The schema for the persistent store is incompatible with current managed object model.
+         Check the error message to determine what the actual problem was.
+         If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory.
+         If you encounter schema incompatibility errors during development, you can reduce their frequency by:
+         * Simply deleting the existing store:
+         [[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil]
+         * Performing automatic lightweight migration by passing the following dictionary as the options parameter:
+         @{NSMigratePersistentStoresAutomaticallyOption:@YES, NSInferMappingModelAutomaticallyOption:@YES}
+         Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details.
+         */
+        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
+        abort();
+    }
+    return _persistentStoreCoordinator;
+}
+#pragma mark - Application's Documents directory
+// Returns the URL to the application's Documents directory.
+- (NSURL *)applicationDocumentsDirectory
+{
+    return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
+}
+</code>
+===CoreData Vocabulary===
+  -Persistent Store Coordinator- As the name suggest it is a coordinator , that coordinates between manage object context and low level file saved in our data base (Sqlite file)
+  -ManagedObjectContext- You can think of a managed object context as an intelligent scratch pad. When you fetch objects from a persistent store, you bring temporary copies onto the scratch pad . You can then modify those objects however you like. Unless you actually save those changes, however, the persistent store remains unaltered.
+  -NSManageObject Model- A managed object model is an instance of the NSManagedObjectModel class. It describes a schema (contains definitions) for objects (also called entities )—that you use in your application. Filename is  *.xcmodeld
+  -Properties (of entity )- An entity’s properties are its attributes and relationships. Amongst other features, each property has a name and a type.

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