CoreData

CoreData的使用：

第一步：创建一个 DataDemo.xcdatamodel 文件，在其中建一个实体名字为 Entity1 ，实体中建两个字段 id 和 name。
第二步：为项目添加 CoreData.framework 框架，然后在 .pch 中加入 #import <coredata/coredata.h>
第三步：在 app delegate 中定义 core data 的相关对象（同时完成它们的初始化工作）
.h 文件：

1 #import <coredata/coredata.h>
2 @private NSManagedObjectModel *managedObjectModel;    NSManagedObjectContext *managedObjectContext;    NSPersistentStoreCoordinator *persistentStoreCoordinator;
3 @property (nonatomic, retain, readonly) NSManagedObjectModel *managedObjectModel;
4 @property (nonatomic, retain, readonly) NSManagedObjectContext *managedObjectContext;
5 @property (nonatomic, retain, readonly) NSPersistentStoreCoordinator *persistentStoreCoordinator;
6 - (NSString*) applicationDocumentsDirectory;
7 - (void) saveContext;

.m 文件：

 

 1 @synthesize managedObjectModel;
 2 @synthesize managedObjectContext;
 3 @synthesize persistentStoreCoordinator;
 4 - (void)dealloc {    
 5     [managedObjectModel release];    
 6     [managedObjectContext release];    
 7     [persistentStoreCoordinator release];    
 8     [super dealloc];
 9 }
10 - (NSString*)applicationDocumentsDirectory{     
11     //return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];    
12     NSArray *paths =  NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
13    //判断document目录下是否存在文件夹，如果为0则置为nil
14     NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;    
15     return basePath;    
16     //return [NSURL URLWithString:basePath];
17 }
18 - (void)saveContext{       
19     NSError *error = nil;      
20     NSManagedObjectContext *objectContext = self.managedObjectContext;      
21     if (objectContext != nil){             
22     　　if ([objectContext hasChanges] && ![objectContext save:&error])               {       
23     　　NSLog(@"Unresolved error %@, %@", error, [error userInfo]);                      
24     　　abort();           
25     　　}      
26 　　}
27 }
28 - (NSManagedObjectContext *)managedObjectContext{    
29 　　if (managedObjectContext != nil) {        
30 　　　　return managedObjectContext;    
31 　　}    
32 　　NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];    
33 　　if (coordinator != nil) {        
34 　　　　managedObjectContext = [[NSManagedObjectContext alloc] init];        
35 　　　　[managedObjectContext setPersistentStoreCoordinator:coordinator];    
36 　　}    
37 　　return managedObjectContext;
38 }
39 - (NSManagedObjectModel *)managedObjectModel{    
40 　　if (managedObjectModel != nil) {        
41 　　return managedObjectModel;    
42 　　}    
43 　　//从本地所有 xcdatamodel 文件中获得这个 CoreData 的数据模板    
44 　　managedObjectModel = [[NSManagedObjectModel mergedModelFromBundles:nil] retain];    
45 　　return managedObjectModel;
46 }
47 - (NSPersistentStoreCoordinator *)persistentStoreCoordinator{    
48 　　if (persistentStoreCoordinator != nil) {        
49 　　　　return persistentStoreCoordinator;    
50 　　}    
51 　　//数据库名为TestDB.sqlite    
52 　　NSURL *storeUrl = [NSURL fileURLWithPath:[[self applicationDocumentsDirectory] stringByAppendingPathComponent:@"TestDB.sqlite"]];    
53 　　NSError *error;    
54 　　persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];    
55 　　if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:nil error:&error]) {        
56 　　　　NSAssert(0, @"persistentStoreCoordinator init failed!");    
57 　　}    
58 　　return persistentStoreCoordinator;
59 }
60 - (void)applicationWillTerminate:(UIApplication *)application{    
61 　　NSError *error;    
62 　　if (managedObjectContext != nil) {        
63 　　　　if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {            
64 　　　　NSAssert(0, @"save changes failed when terminage application!");        
65 　　　　}    
66 　　}
67 }

第四步：在相关的 viewcontroller 中操作数据，基本的 core data 操作代码如下：

 1 　　NSError *error; 
 2　　 testSQLiteAppDelegate *app = (testSQLiteAppDelegate*)[[UIApplication sharedApplication] delegate]; 
 3 　　NSManagedObjectContext *context = app.managedObjectContext;  
 4 　　//1、插入 
 5 　　NSManagedObject *newManagedObject  = nil; 
 6 　　newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:@"Entity1" inManagedObjectContext:context]; 
 7 　　[newManagedObject setValue:[NSNumber numberWithInt:1] forKey:@"id"]; 
 8 　　[newManagedObject setValue:@"i love you" forKey:@"name"]; 
 9 　　if (![context save:&error]){    
10 　　　　NSLog (@"The error is: %@", [error userInfo]); 
11 　　} else {    
12 　　　　NSLog (@"The newManagedObject's id is: %@", [newManagedObject valueForKey:@"id"]); 
13 　　}
14  //2、查询 
15 　　NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; 
16 　　NSEntityDescription *entity = [NSEntityDescription entityForName:@"Entity1" inManagedObjectContext:context]; 
17 　　NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"id" ascending:YES]; 
18 　　NSSortDescriptor *sortDescriptor2 = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES]; 
19 　　NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor1, sortDescriptor2, nil]; 
20 　　[fetchRequest setSortDescriptors:sortDescriptors]; 
21 　　[fetchRequest setEntity:entity]; [fetchRequest setFetchBatchSize:20]; 
22 　　NSArray *objects = [context executeFetchRequest: fetchRequest error:&error]; 
23 　　if (objects == nil) {     
24 　　　　NSLog(@"There was an error!"); 
25 　　} else {    
26 　　　　for (NSManagedObject *oneObject in objects)    {      
27 　　　　　　 NSLog(@"%@",[oneObject valueForKey:@"name"]);    
28 　　　　}         
29 　　}
30  //3、删除 
31 　　[context deleteObject:[objects objectAtIndex:0]];
32 　　 if (![context save:&error]) {     
33  　　　　exit(-1); 
34 　　}

这里更详细的补充一点关于 core data 的操作代码：
1、条件过滤:选择 cid=1 的数据

 

1 - (NSFetchedResultsController*) fetchedResultsController {        
2 　　NSPredicate *predicate = [NSPredicate predicateWithFormat:@"cid=1"];        
3 　　[fetchRequest setPredicate:predicate]; 
4 }

2、通用代码，在 viewcontroller 里面会用到：
TestViewController.h 的代码：

 

1 @interface TestViewController : UITableViewController <NSFetchedResultsControllerDelegate>{        
2 　　NSFetchedResultsController *fetchedResultsController;    
3 　　NSManagedObjectContext *managedObjectContext;      
4 }  
5 @property (nonatomic, retain) NSFetchedResultsController *fetchedResultsController;
6 @property (nonatomic, retain) NSManagedObjectContext *managedObjectContext;  
7 - (void)configureCell:(UITableViewCell *)cell withCategory:(Category *)category;
8 @end

TestViewController.m 的代码：
 

 1 -(NSFetchedResultsController *)fetchedResultsController {
 2         if (fetchedResultsController != nil){
 3             return fetchedResultsController;
 4         }
 5         NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
 6         NSEntityDescription *entity = [NSEntityDescription entityForName:@"Category" inManagedObjectContext managedObjectContext];
 7         [fetchRequest setEntity:entity];
 8         NSSortDescriptor *nameDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES];
 9         NSArray *arraySortDescriptor = [[NSArray alloc] initWithObjects:nameDescriptor, nil];
10         [fetchRequest setSortDescriptors:arraySortDescriptor];
11         NSPredicate *predicate = [NSPredicate predicateWithFormat:cidString];
12         [fetchRequest setPredicate:predicate];
13         NSFetchedResultsController *frController =  [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:@"name" cacheName:@"Root"];
14         frController.delegate = self;
15         self.fetchedResultsController = frController;
16         [frController release];
17         [fetchRequest release];
18         [nameDescriptor release];
19         return fetchedResultsController;
20     }
21     - (void)controllerWillChangeContent:(NSFetchedResultsController *) {
22         [self.tableView beginUpdates];
23     }
24     - (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject   atIndexPath:(NSIndexPath *)indexPath forChangeType: (NSFetchedResultsChangeType)type   newIndexPath:(NSIndexPath *)newIndexPath   {          UITableView *tableView = self.tableView;
25         switch (type) {
26             case NSFetchedResultsChangeInsert:
27                 [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
28                 break;
29             case NSFetchedResultsChangeDelete:[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
30                 break;
31             case NSFetchedResultsChangeMove:[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
32                 [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
33                 break;
34             case NSFetchedResultsChangeUpdate:
35             [self configureCell:[tableView cellForRowAtIndexPath:indexPath] withCategory:anObject];
36                 break;
37             default:
38             break;
39         }
40     }
41     - (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
42         switch(type) {
43             case NSFetchedResultsChangeInsert:[self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
44                 break;
45             case NSFetchedResultsChangeDelete:[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
46                 break;
47         }
48     }
49     - (void) controllerDidChangeContent:(NSFetchedResultsController *)controller {
50         [self.tableView endUpdates];
51     }

 

posted @ 2013-12-16 20:35  激情为梦想而生  阅读(213)  评论(0)  编辑  收藏  举报