有些同事觉得CoreData是一个看不懂，理解不清的神秘东东，其实ios的本地数据储存是一个sqlite数据库，一个简易的数据库，而这个CoreData是否支持所有储存的数据呢，显然不是的，站在我的角度，我是不支持把一些图片数据保存的CoreData里面，其一，如果保存图片需要把图片转化为Data类型，

    UIImage * image = info[UIImagePickerControllerEditedImage];

    //把Image转化成Data

    self.imageData = UIImagePNGRepresentation(image);

其二，不具有稳定性。下面给大家讲解下CoreData的用法。

1.如果大家现在用Storyboard的，可以在建项目时选择在Use Core Data处打勾。

 

如果你是用纯代码写程序的话，那么你需要手动在AppDelegate里面写上这些代码

.h

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;

@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;

@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;

@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;

- (void)saveContext;

- (NSURL *)applicationDocumentsDirectory;

@end

.m

- (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:@"App_7_addressbook" 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:@"App_7_addressbook.sqlite"];

    

    NSError *error = nil;

    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];

    if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {

                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];

}

这些就是需要建立cordata的根本，不需要你的理解。接下来我们就应该建立一个实体，对cordata不熟悉的技术人员也许疑问为什么简历实体？其实我们储存和获取数据没有对cordata直接操作，而是对实体进行操作。

 

 

 

创建一个model，这就是实体的，然后我们再创建一个实体类：

 

创建意识实体对象，然后生成一个实体类：

 

下面我们就对实体进行操作：

 

@property (strong, nonatomic) NSManagedObjectContext *managedObjectContext;

通过managedObjectContext进行储存操作，

 首先对managedObjectContext进行初始化；

    UIApplication * app = [UIApplication sharedApplication];

    id delegate = [app delegate];

    self.managedObjectContext = [delegate managedObjectContext];

1.然后在保存地方进行往coredata储存，

如：      

self.p.number = self.numberT.text;

self.p.image = self.imageData;

NSError * error;

        if (![self.managedObjectContext save:&error]) {

            NSLog(@"新建保存错误：%@",[error localizedDescription]);

        }

进行保存。

2.在你从coredata获取数据的Controller写，

@property (strong, nonatomic) NSManagedObjectContext *managedObjectContext;

@property(nonatomic,strong)NSFetchedResultsController * fetchedResultsController;

 

这里的fetchedResultsController是从coredata获取数据，

- (void)viewDidLoad {

    [super viewDidLoad];

    

    UIApplication *application = [UIApplication sharedApplication];

    id delegate = application.delegate;

    self.managedObjectContext = [delegate managedObjectContext];

    

    /*********

     通过CoreData获取sqlite中的数据

     *********/

    

    //通过实体名获取请求

    NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:NSStringFromClass([Time class])];

    

    //定义分组和排序规则

    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"timego" ascending:NO];

    

    //把排序和分组规则添加到请求中

    [request setSortDescriptors:@[sortDescriptor]];

    

    //把请求的结果转换成适合tableView显示的数据

    self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil];

    

    

    //执行fetchedResultsController

    NSError *error;

    if ([self.fetchedResultsController performFetch:&error]) {

        NSLog(@"%@", [error localizedDescription]);

    }

    self.fetchedResultsController.delegate = self;

}

这些就是coredata基本简单用法，代码没有过多写，重要核心就是这些了