NSFetchedResultController与UITableView

 1 #import "AppDelegate.h"
 2 #import "Book.h"
 3 @interface AppDelegate ()
 4 @end
 5 @implementation AppDelegate
 6 -(void)addBookWithTitle:(NSString *)title andAuthor:(NSString *)author andPrice:(NSNumber *)price
 7 {
 8     Book *book = [NSEntityDescription insertNewObjectForEntityForName:NSStringFromClass([Book class]) inManagedObjectContext:self.managedObjectContext];
 9     book.title = title;
10     book.author = author;
11     book.price = price;
12 }
13 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
14     //如果不想每次执行时测试数据都重新插入一遍，可以使用偏好设置，如果已经存在了，就不再进行插入了。
15     NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
16     BOOL isInserted = [userDefaults boolForKey:@"inInserted"];
17     if (!isInserted)
18     {
19         //插入数据
20         [self addBookWithTitle:@"*文*" andAuthor:@"徐" andPrice:@10000.1];
21         [self addBookWithTitle:@"西游记" andAuthor:@"吴承恩" andPrice:@20.5];
22         [self addBookWithTitle:@"水浒传" andAuthor:@"施耐庵" andPrice:@5.1];
23         [self addBookWithTitle:@"三国演义" andAuthor:@"罗贯中" andPrice:@10.2];
24         [self addBookWithTitle:@"史记" andAuthor:@"司马迁" andPrice:@45.3];
25         [self addBookWithTitle:@"资治通鉴" andAuthor:@"司马光" andPrice:@56.5];
26         [self saveContext];
27         //保存偏好设置
28         [userDefaults setBool:YES forKey:@"inInserted"];
29         //自动步更新
30         [userDefaults synchronize];
31     }
32     return YES;
33 }

  1 #import "BookTableViewController.h"
  2 #import "Book.h"
  3 #import "AppDelegate.h"
  4 @interface BookTableViewController ()<NSFetchedResultsControllerDelegate>
  5 @property(strong,nonatomic)NSFetchedResultsController *fetchedRC;
  6 @property(strong,nonatomic)NSManagedObjectContext *managedObjectContext;
  7 @end
  8 
  9 @implementation BookTableViewController
 10 
 11 - (void)viewDidLoad {
 12     [super viewDidLoad];
 13     //获取应用代理
 14     AppDelegate *delegate = [[UIApplication sharedApplication]delegate];
 15     //本次案例需要对CoreData的内容进行修改，涉及到managedObjectContext，但是magagedObjetContext属于Appdelegate的属性，此处使用协议获取创建新的managedObjectContext;
 16     self.managedObjectContext = delegate.managedObjectContext;
 17     //使用fetchedRC获取数据
 18     NSError *error = nil;
 19     [self.fetchedRC performFetch:&error];
 20     if (error) {
 21         NSLog(@"NSFetchedResultsController获取数据失败");
 22     }
 23 }
 24 -(NSFetchedResultsController *)fetchedRC
 25 {
 26     //判断fetchRC是否存在，如果不存在则创建新的，否则直接返回
 27     if (!_fetchedRC) {
 28         //使用NSFetchRequest进行获取数据
 29         NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:NSStringFromClass([Book class])];
 30         request.fetchBatchSize = 20;
 31         //设置以某个字段进行排序，此案例以：price价格大小进行排序
 32         NSSortDescriptor *priceSort = [NSSortDescriptor sortDescriptorWithKey:@"price" ascending:YES];
 33         //对获取的数据进行排序
 34         [request setSortDescriptors:@[priceSort]];
 35         //创建新的fetchedRC
 36         _fetchedRC = [[NSFetchedResultsController alloc]initWithFetchRequest:request managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil];
 37         _fetchedRC.delegate = self;
 38     }
 39     return _fetchedRC;
 40 }
 41 
 42 #pragma mark - Table view data source
 43 //设置tableView的分组数
 44 - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
 45 {
 46     //分组的数据取决于创建sectionNameKeyPath的设置；
 47     return self.fetchedRC.sections.count;
 48 }
 49 //设置tableView每组有多少行
 50 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
 51     id sectionsInfo = [self.fetchedRC.sections objectAtIndex:section];
 52     return [sectionsInfo numberOfObjects];
 53 }
 54 //自定义方法，设置单元格的显示内容
 55 -(void)configCell:(UITableViewCell *)cell andIndexPath:(NSIndexPath *)indexPath
 56 {
 57     //获取选中的对象
 58     Book *book = [self.fetchedRC objectAtIndexPath:indexPath];
 59     cell.textLabel.text = [NSString stringWithFormat:@"%@ %@",book.title,book.author];
 60     cell.detailTextLabel.text = [NSString stringWithFormat:@"%@",book.price];
 61 }
 62 -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
 63 {
 64     //1.根据reuseindentifier先到对象池中去找重用的单元格
 65     static NSString *reuseIndetifier = @"bookCell";
 66     UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:reuseIndetifier];
 67     //2.如果没有找到需要自己创建单元格对象
 68     if (cell == nil) {
 69         cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:reuseIndetifier];
 70     }
 71     //3.设置单元格对象的内容
 72     [self configCell:cell andIndexPath:indexPath];
 73     return cell;
 74 }
 75 // Override to support conditional editing of the table view.
 76 - (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath {
 77     // Return NO if you do not want the specified item to be editable.
 78     return YES;
 79 }
 80 // Override to support editing the table view.
 81 - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
 82     if (editingStyle == UITableViewCellEditingStyleDelete)
 83     {
 84         Book *book = [self.fetchedRC objectAtIndexPath:indexPath];
 85         //1.先删除CoreData中的相应数据
 86         [self.managedObjectContext deleteObject:book];
 87         //插入新的记录
 88         AppDelegate *delegate = [[UIApplication sharedApplication]delegate];
 89         [delegate addBookWithTitle:@"唐诗三百首" andAuthor:@"李白等" andPrice:@12.3];
 90         book.price = @([book.price doubleValue]+10);
 91         NSError *error = nil;
 92         [self.managedObjectContext save:&error];
 93         if(error) {
 94             NSLog(@"失败");
 95         }
 96     } else if (editingStyle == UITableViewCellEditingStyleInsert)
 97     {
 98     }
 99 }
100 #pragma mark - NSFetchedResultsController代理方法
101 -(void)controllerWillChangeContent:(NSFetchedResultsController *)controller
102 {
103     [self.tableView beginUpdates];
104 }
105 -(void)controllerDidChangeContent:(NSFetchedResultsController *)controller
106 {
107     [self.tableView endUpdates];
108 }
109 /**
110  * 以下方法共进行了两项操作：
111     1.判断操作的类型
112     2.对修改的数据、或新插入的数据位置进行局部刷新
113  */
114 -(void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath
115 {
116     if (type == NSFetchedResultsChangeDelete)//删除操作
117     {
118         [self.tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
119     }
120     else if (type == NSFetchedResultsChangeInsert)//插入操作
121     {
122         [self.tableView insertRowsAtIndexPaths:@[newIndexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
123     }
124     else if (type == NSFetchedResultsChangeUpdate)//更新操作
125     {
126         //首先获取cell;
127         UITableViewCell *cell = [self.fetchedRC objectAtIndexPath:indexPath];
128         //调用configCell方法
129         [self configCell:cell andIndexPath:indexPath];
130         //重新加载指定行
131         [self.tableView reloadRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
132     }
133 }
134 @end