CoreData

表结构：NSEntityDescription

表记录：NSManagedObject

数据库存放方式：NSPersistentStoreCoordinator(持久化存储协调者)

数据库操作：NSManagedObjectContext(被管理的对象上下文)

NSFetchRequest对象（相当于SQL语句）

NSEntityDescription 创建查询实体（相当于设置查询哪个表）

NSSortDescriptor  创建排序描述符，（ascending：是否升序）

delegate.h

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

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

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

- (void)saveContext;

- (NSURL *)applicationDocumentsDirectory;

delegate.m

@synthesize managedObjectContext =_managedObjectContext;

@synthesize managedObjectModel =_managedObjectModel;

@synthesize persistentStoreCoordinator =_persistentStoreCoordinator;

- (void)saveContext

{

   NSError *error =nil;

   NSManagedObjectContext *managedObjectContext =self.managedObjectContext;

   if (managedObjectContext !=nil)

    {

       if ([managedObjectContexthasChanges] && ![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, [erroruserInfo]);

           abort();

        }

       else

           NSLog(@"数据成功插入");

    }

}

- (NSManagedObjectContext *)managedObjectContext

{

    if (_managedObjectContext !=nil) {

        return_managedObjectContext;

    }

    

    NSPersistentStoreCoordinator *coordinator = [selfpersistentStoreCoordinator];

   if (coordinator !=nil) {

        _managedObjectContext = [[NSManagedObjectContextalloc]init];

        [_managedObjectContextsetPersistentStoreCoordinator:coordinator];

    }

    return_managedObjectContext;

}

- (NSManagedObjectModel *)managedObjectModel

{

    if (_managedObjectModel !=nil) {

        return_managedObjectModel;

    }

    NSURL *modelURL = [[NSBundlemainBundle]URLForResource:@"test"withExtension:@"momd"];

    _managedObjectModel = [[NSManagedObjectModelalloc]initWithContentsOfURL:modelURL];

    return_managedObjectModel;

}

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator

{

    if (_persistentStoreCoordinator !=nil) {

        return_persistentStoreCoordinator;

    }

    

    //链接数据库，备数据存储

    NSURL *storeURL = [[selfapplicationDocumentsDirectory]URLByAppendingPathComponent:@"test.sqlite"];

   NSLog(@"%@",storeURL);

    

   NSError *error =nil;

    //持久化存储调度器由托管对象模型初始化

    _persistentStoreCoordinator = [[NSPersistentStoreCoordinatoralloc]initWithManagedObjectModel:[selfmanagedObjectModel]];

    //设置数据存储方式为SQLITE

    if (![_persistentStoreCoordinatoraddPersistentStoreWithType:NSSQLiteStoreTypeconfiguration:nilURL:storeURLoptions:nilerror:&error]) {

    

       NSLog(@"Unresolved error %@, %@", error, [erroruserInfo]);

       abort();

    }    

    

    return_persistentStoreCoordinator;

}

- (NSURL *)applicationDocumentsDirectory

{

    

    

     NSURL *url=[[[NSFileManagerdefaultManager]URLsForDirectory:NSDocumentDirectoryinDomains:NSUserDomainMask]lastObject];

    //NSLog(@"%@",url);

    //NSFileManager *file=[NSFileManager defaultManager];

    //NSLog(@"%@",file);

   

    NSLog(@"%@",[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES)objectAtIndex:0]);

    return url;

}

testView.h

@interface testview :UIViewController

{

   IBOutletUITextField *citytext;

   IBOutletUITextField *provincetext;

   XYZAppDelegate *mydelegate;

    

}

@property(nonatomic,strong)UITextField *citytext;

@property(nonatomic,strong)UITextField *provincetext;

@property(nonatomic,strong)XYZAppDelegate *mydelegate;

-(IBAction)save:(UIButton *)sender;

-(IBAction)read:(UIButton *)sender;

testView.m

- (void)viewDidLoad

{

    [superviewDidLoad];

    self.mydelegate=(XYZAppDelegate *)[[UIApplicationsharedApplication]delegate];

}

-(IBAction)save:(UIButton *)sender

{

    NSManagedObject *object=[NSEntityDescriptioninsertNewObjectForEntityForName:@"Province"inManagedObjectContext:self.mydelegate.managedObjectContext];

    

    [objectsetValue:citytext.textforKey:@"cityname"];

    [objectsetValue:provincetext.textforKey:@"provincename"];

    

    [self.mydelegatesaveContext];

}

-(IBAction)read:(id)sender

{

    NSFetchRequest *fetch=[[NSFetchRequestalloc]init];//相当于sql语句

    NSEntityDescription *object=[NSEntityDescriptionentityForName:@"Province"inManagedObjectContext:self.mydelegate.managedObjectContext];//相当于查询的表

    [fetchsetEntity: object ];

    

    NSSortDescriptor *sort=[[NSSortDescriptoralloc]initWithKey:@"provincename"ascending:NO];//创建排序描述符 scending 是否升序

   NSLog(@"sort:%@",sort);

    

   NSArray *sortarr=[[NSArrayalloc]initWithObjects:sort,nil];

    [fetchsetSortDescriptors:sortarr];

    

   NSError *error;

   NSArray *fetchresult=[self.mydelegate.managedObjectContextexecuteFetchRequest:fetcherror:&error];//获取执行请求结果

    

     for (NSManagedObject *objectin fetchresult) {

//        citytext.text=[object valueForKey:@"cityname"];

//        provincetext.text=[object valueForKey:@"provincename"];

          //NSLog(@"city:%@,province:%@ \n",[object valueForKey:@"cityname"],[object valueForKey:@"provincename"]);

          //NSLog(@"%@",objectid);

    }

    // NSPredicate *pre=[NSPredicate predicateWithFormat:@"%@="];

   // NSLog(@"%@",fetchresult);

    NSLog(@"fetchresult is :%@",fetchresult);

}

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