<span style="font-size:18px;">    @property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;  @property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;  @property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;    - (void)saveContext;  - (NSURL *)applicationDocumentsDirectory;</span> 

Person *newPerson = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:self.managedObjectContext];            if (newPerson == nil){          NSLog(@"Failed to create the new person.");          return NO;      }            newPerson.firstName = paramFirstName;      newPerson.lastName = paramLastName;      newPerson.age = [NSNumber numberWithUnsignedInteger:paramAge];      NSError *savingError = nil;            if ([self.managedObjectContext save:&savingError]){          return YES;      } else {          NSLog(@"Failed to save the new person. Error = %@", savingError);      } 

/* Create the fetch request first */      NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];      /* Here is the entity whose contents we want to read */      NSEntityDescription *entity =      [NSEntityDescription       entityForName:@"Person"       inManagedObjectContext:self.managedObjectContext];      /* Tell the request that we want to read the      contents of the Person entity */      [fetchRequest setEntity:entity];      NSError *requestError = nil;      /* And execute the fetch request on the context */      NSArray *persons =      [self.managedObjectContext executeFetchRequest:fetchRequest                                               error:&requestError];      /* Make sure we get the array */      if ([persons count] > 0){          /* Go through the persons array one by one */          NSUInteger counter = 1;          for (Person *thisPerson in persons){              NSLog(@"Person %lu First Name = %@",                    (unsigned long)counter,                     thisPerson.firstName);               NSLog(@"Person %lu Last Name = %@",                     (unsigned long)counter,                     thisPerson.lastName);              NSLog(@"Person %lu Age = %ld",                    (unsigned long)counter,                    (unsigned long)[thisPerson.age unsignedIntegerValue]);              counter++;          }      } else {          NSLog(@"Could not find any Person entities in the context.");       } 

/* Create the fetch request first */      NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];      /* Here is the entity whose contents we want to read */      NSEntityDescription *entity =      [NSEntityDescription       entityForName:@"Person"       inManagedObjectContext:self.managedObjectContext];      /* Tell the request that we want to read the      contents of the Person entity */      [fetchRequest setEntity:entity];      NSError *requestError = nil;      /* And execute the fetch request on the context */      NSArray *persons =      [self.managedObjectContext executeFetchRequest:fetchRequest                                               error:&requestError];      if ([persons count] > 0){          /* Delete the last person in the array */          Person *lastPerson = [persons lastObject];          [self.managedObjectContext deleteObject:lastPerson];          NSError *savingError = nil;          if ([self.managedObjectContext save:&savingError]){              NSLog(@"Successfully deleted the last person in the array.");          } else {              NSLog(@"Failed to delete the last person in the array.");          }      } else {           NSLog(@"Could not find any Person entities in the context.");       }  

<pre code_snippet_id="243955" snippet_file_name="blog_20140319_5_4289257" name="code" class="objc">NSSortDescriptor *ageSort =   [[NSSortDescriptor alloc] initWithKey:@"age"   ascending:YES];   NSSortDescriptor *firstNameSort =   [[NSSortDescriptor alloc] initWithKey:@"firstName"   ascending:YES];   NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:   ageSort,   firstNameSort, nil nil];   fetchRequest.sortDescriptors = sortDescriptors; </pre><p></p>  <pre></pre>  <p></p>  <p style="background-color:rgb(255,255,255); margin:10px auto; padding-top:0px; padding-bottom:0px; font-family:verdana,'ms song',Arial,Helvetica,sans-serif; line-height:19.09090805053711px">  <span style="background-color:rgb(255,255,255)"><span style="font-size:18px"><br>  </span></span></p>  <span style="background-color:rgb(255,255,255)">注意</span><span style="font-size:18px; background-color:rgb(255,255,255)">ascending:YES 属性决定排序顺序</span><span style="background-color:rgb(255,255,255)"><span style="font-size:18px"><br>  <br>  <br>  </span></span><br>