认识cocoa Data在ios开发中的环境情况。
Core Data简单使用的样例。可以使用模板中的master—detail 这种控制器组合可以轻松完毕。
主要的文件夹框架：
对应的Core Data中的基本对象都会自己主动生成。
masterController.md的代码：
//// MasterViewController.m// Tasks//// Created by 朱敏 on 15/8/24.// Copyright (c) 2015年 helinyu. All rights reserved.//#import "MasterViewController.h"#import "DetailViewController.h"#import "TaskEntryViewController.h"@interface MasterViewController ()@end@implementation MasterViewController- (void)awakeFromNib { [super awakeFromNib];}- (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. self.navigationItem.leftBarButtonItem = self.editButtonItem; UIBarButtonItem *addButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(insertNewObject:)]; self.navigationItem.rightBarButtonItem = addButton;}- (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated.}- (void)insertNewObject:(id)sender { TaskEntryViewController *tevc = [[TaskEntryViewController alloc]init]; tevc.managedObjectContext = self.managedObjectContext; [self presentViewController:tevc animated:YES completion:nil];// NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];// NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity];// NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];// // // If appropriate, configure the new managed object.// // Normally you should use accessor methods, but using KVC here avoids the need to add a custom class to the template.// [newManagedObject setValue:[NSDate date] forKey:@"timeStamp"];// // // Save the context.// NSError *error = nil;// if (![context 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 - Segues- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender { if ([[segue identifier] isEqualToString:@"showDetail"]) { NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow]; NSManagedObject *object = [[self fetchedResultsController] objectAtIndexPath:indexPath]; [[segue destinationViewController] setDetailItem:object]; }}#pragma mark - Table View- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return [[self.fetchedResultsController sections] count];}- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { id sectionInfo = [self.fetchedResultsController sections][section]; return [sectionInfo numberOfObjects];}- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell" forIndexPath:indexPath]; [self configureCell:cell atIndexPath:indexPath]; return cell;}- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath { // Return NO if you do not want the specified item to be editable. return YES;}- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath { if (editingStyle == UITableViewCellEditingStyleDelete) { NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext]; [context deleteObject:[self.fetchedResultsController objectAtIndexPath:indexPath]]; NSError *error = nil; if (![context 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(); } }}- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath { NSManagedObject *object = [self.fetchedResultsController objectAtIndexPath:indexPath]; cell.textLabel.text = [[object valueForKey:@"taskText"] description]; cell.detailTextLabel.text = [[object valueForKey:@"timeStamp"] description];}#pragma mark - Fetched results controller- (NSFetchedResultsController *)fetchedResultsController{ if (_fetchedResultsController != nil) { return _fetchedResultsController; } NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; // Edit the entity name as appropriate.// NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:self.managedObjectContext]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Task" inManagedObjectContext:self.managedObjectContext]; [fetchRequest setEntity:entity]; // Set the batch size to a suitable number. [fetchRequest setFetchBatchSize:20]; // Edit the sort key as appropriate. NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"timeStamp" ascending:NO]; NSArray *sortDescriptors = @[sortDescriptor]; [fetchRequest setSortDescriptors:sortDescriptors]; // Edit the section name key path and cache name if appropriate. // nil for section name key path means "no sections". NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:@"Master"]; aFetchedResultsController.delegate = self; self.fetchedResultsController = aFetchedResultsController; NSError *error = nil; if (![self.fetchedResultsController performFetch:&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(); } return _fetchedResultsController;} #pragma mark NSFetchedResultsControllerDelegate- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller{ [self.tableView beginUpdates];}- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id )sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type{ switch(type) { case NSFetchedResultsChangeInsert: [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade]; break; case NSFetchedResultsChangeDelete: [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade]; break; default: return; }}- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath{ UITableView *tableView = self.tableView; switch(type) { case NSFetchedResultsChangeInsert: [tableView insertRowsAtIndexPaths:@[newIndexPath] withRowAnimation:UITableViewRowAnimationFade]; break; case NSFetchedResultsChangeDelete: [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade]; break; case NSFetchedResultsChangeUpdate: [self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath]; break; case NSFetchedResultsChangeMove: [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade]; [tableView insertRowsAtIndexPaths:@[newIndexPath] withRowAnimation:UITableViewRowAnimationFade]; break; }}- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller{ [self.tableView endUpdates];}/*// Implementing the above methods to update the table view in response to individual changes may have performance implications if a large number of changes are made simultaneously. If this proves to be an issue, you can instead just implement controllerDidChangeContent: which notifies the delegate that all section and object changes have been processed. - (void)controllerDidChangeContent:(NSFetchedResultsController *)controller{ // In the simplest, most efficient, case, reload the table view. [self.tableView reloadData];} */@end detail中的代码没有什么改动，创建之后就能够生成，这个我们就无论了 TaskEntryViewController.m文件的代码：
//// TaskEntryViewController.m// Tasks//// Created by 朱敏 on 15/8/24.// Copyright (c) 2015年 helinyu. All rights reserved.//#import "TaskEntryViewController.h"@interface TaskEntryViewController ()@end@implementation TaskEntryViewController- (void)viewDidLoad { [super viewDidLoad]; // NSSet self.tf = [[UITextField alloc]initWithFrame:CGRectMake(65, 20, 200, 20)]; [self.tf setBackgroundColor:[UIColor lightGrayColor]]; [self.tf setDelegate:self ]; [self.view addSubview:self.tf]; UILabel *lb1 = [[UILabel alloc]initWithFrame:CGRectMake(5, 20, 60, 20)]; [lb1 setText:@"Task"]; [self.view addSubview:lb1];}- (BOOL)textFieldShouldReturn:(UITextField *)textField{ NSManagedObjectContext *context = self.managedObjectContext; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Task" inManagedObjectContext:context]; NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context]; [newManagedObject setValue:[NSDate date] forKey:@"timeStamp"]; [newManagedObject setValue:[self.tf text] forKey:@"taskText"]; NSError *error = nil; if (![context save:&error]) { NSLog(@"Unresolved error %@,%@",error,[error userInfo]); abort(); } [self dismissViewControllerAnimated:YES completion:nil]; return YES;}@end 对应的storyBoard的改变的界面： 