CoreData简单使用

一. 你可以在创建项目的时候勾选CoreData的勾勾，这样创建出来的项目在AppDelegate.h和m文件中会自动生成CoreData的一些方法，以及回自动生成.xcdatamodeld文件
二.或者自己创建.xcdatamodeld文件，倒入CoreData.framework文件，自定义创建一个继承与NSObject的类讲CoreData一些必备方法写入，调用.h／m文件如下
1.创建数据模型

#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>

@interface CoreDateTwo : NSObject
@property (nonatomic, strong) NSString *coreDataName;

@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;
- (void)saveContext;
- (NSURL *)applicationDocumentsDirectory;

//单例使用
+(instancetype)share;
- (void)createTest;
@end

#import "CoreDateTwo.h"
#import "Failedone.h"
#import "FailedTwo.h"

@implementation CoreDateTwo

@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;

- (NSManagedObjectModel *)managedObjectModel {
    // The managed object model for the application. It is a fatal error for the application not to be able to find and load its model.
    if (_managedObjectModel != nil) {
        return _managedObjectModel;
    }
    //    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"TestCoreDate2" withExtension:@"momd"];

    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:_coreDataName withExtension:@"momd"];

    _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
    return _managedObjectModel;
}

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {

    if (_persistentStoreCoordinator != nil) {
        return _persistentStoreCoordinator;
    }
    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    //    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"TestCoreDate2.sqlite"];
    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:[NSString stringWithFormat:@"%@.sqlite",_coreDataName]];

    NSError *error = nil;
    NSString *failureReason = @"There was an error creating or loading the application's saved data.";
    if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {

        NSMutableDictionary *dict = [NSMutableDictionary dictionary];
        dict[NSLocalizedDescriptionKey] = @"Failed to initialize the application's saved data";
        dict[NSLocalizedFailureReasonErrorKey] = failureReason;
        dict[NSUnderlyingErrorKey] = error;
        error = [NSError errorWithDomain:@"YOUR_ERROR_DOMAIN" code:9999 userInfo:dict];

        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    return _persistentStoreCoordinator;
}

- (NSManagedObjectContext *)managedObjectContext {
    // Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.)
    if (_managedObjectContext != nil) {
        return _managedObjectContext;
    }

    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (!coordinator) {
        return nil;
    }
    _managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
    [_managedObjectContext setPersistentStoreCoordinator:coordinator];

    return _managedObjectContext;
}

- (NSURL *)applicationDocumentsDirectory {

    return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}

- (void)saveContext {
    NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
    if (managedObjectContext != nil) {
        NSError *error = nil;
        if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            abort();
        }
    }
}

+(instancetype)share{
    static CoreDateTwo *shareObject;
    static dispatch_once_t one;
    dispatch_once(&one,^{
        shareObject = [[CoreDateTwo alloc] init];
    });
    return shareObject;
}
-(void)createTest{
    NSManagedObjectContext *context = [self managedObjectContext];
    Failedone *failedBankInfo = [NSEntityDescription insertNewObjectForEntityForName:@"Failedone"inManagedObjectContext:context];
    failedBankInfo.title = @"Testville";
    failedBankInfo.number = [NSNumber numberWithInt:16];
    FailedTwo *failedBankDetails = [NSEntityDescription insertNewObjectForEntityForName:@"FailedTwo"inManagedObjectContext:context];
    failedBankDetails.title = @"failedBankDetail";
    failedBankDetails.one = failedBankInfo;
    failedBankInfo.two = failedBankDetails;
    NSError *error;
    if (![context save:&error]) {
        NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
    }

    // Test listing all FailedBankInfos from the store
//这里我们创建一个叫做fetch request的新方法，你可以将一个fetch request看做Sql中的select语句，我们调用entityForName方法来获取一个指向FailedBankInfo的指针，之后使用setEntity方法来告诉我们的fetch request我们想要的是哪一种的实体。 
     NSEntityDescription *entity = [NSEntityDescription entityForName:@"Failedone"inManagedObjectContext:context];
    [fetchRequest setEntity:entity];
    NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];
    for (Failedone *info in fetchedObjects) {
        NSLog(@"Name: %@", info.title);
        FailedTwo *details = info.two;
        NSLog(@"Zip: %@", details.title);

    }
}
@end