iOS进阶学习-CoreData

@interface ViewController ()
// 声明属性（管理对象上下文,sqlite中是声明一个存储路径的属性）
@property (nonatomic, strong) NSManagedObjectContext *managedObjectContext;

@end

@implementation ViewController
// 懒加载
- (NSManagedObjectContext *)managedObjectContext
{
    // 因为在AppDelegaate中已经实现过了，所以在这里从AppDelegate中去获取
    if (_managedObjectContext == nil) {
        // 获取AppDelegate对象，用系统的单例方法创建
        AppDelegate *appDelegate = [UIApplication sharedApplication].delegate;
        _managedObjectContext = appDelegate.managedObjectContext;
    }
    return _managedObjectContext;
}

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

- (NSURL *)applicationDocumentsDirectory {
    // 打印CoreData的存储路径（sqlite的dbPath字符串路径）URL类型
    return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}
#pragma mark - 获取管理对象
- (NSManagedObjectModel *)managedObjectModel {
    if (_managedObjectModel != nil) {
        return _managedObjectModel;
    }
    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"UISenior_4_1CoreData" withExtension:@"momd"];
    _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
    return _managedObjectModel;
}
#pragma mark - 数据库持久化协调器
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
    if (_persistentStoreCoordinator != nil) {
        return _persistentStoreCoordinator;
    }
    
    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"UISenior_4_1CoreData.sqlite"];
    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]) {
        // Report any error we got.
        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;
}

#pragma mark - 获取数据库上下文
- (NSManagedObjectContext *)managedObjectContext {
    
    if (_managedObjectContext != nil) {
        return _managedObjectContext;
    }
    
    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (!coordinator) {
        return nil;
    }
    _managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
    [_managedObjectContext setPersistentStoreCoordinator:coordinator];
    return _managedObjectContext;
}

#pragma mark - 添加数据
- (void)addPerson
{
    // 添加的步骤
    // 1.创建person实体对象，然后告诉managedObjectContext,让他做好准备,将这个对象添加到数据库中
    Person *per = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:self.managedObjectContext];
    // 2.给对象属性赋值
    per.personName = @"MBBoy";
    per.personGender = @"Unknow";
    per.personAge = @10;
    // 3.将per对象存入数据库
    BOOL result = [_managedObjectContext save:nil];
    // 4.判断是否插入成功
    if (result) {
        NSLog(@"添加数据成功");
    }else {
        NSLog(@"添加数据失败");
    }
    
}

#pragma mark - 更改数据
- (void)updatePerson
{
    // 1.实例化查询请求类
    NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
    // 2.设置查询条件
    fetchRequest.predicate = [NSPredicate predicateWithFormat:@"personName = ‘MBBoy‘"];
    // 3.由context根据更新条件的请求去具体进行更新操作
    NSArray *resultArray = [_managedObjectContext executeFetchRequest:fetchRequest error:nil];
    // 4.遍历搜索出来的结果
    for (Person *per in resultArray) {
        per.personName = @"Root";
        per.personGender = @"animal";
        per.personAge = @89;
    }
    BOOL result = [_managedObjectContext save:nil];
    // 6.判断结果
    if (result) {
        NSLog(@"更新数据成功");
    }else {
        NSLog(@"更新数据失败");
    }
}

#pragma mark - 删除数据
- (void)deletePerson
{
    // 1.实体化请求类（查询）
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
    // 2.找到删除的条件(根据什么进行删除)(NSPredicate)
    request.predicate = [NSPredicate predicateWithFormat:@"personName = ‘MBBoy‘"];
    // 3.由context根据删除条件的请求去具体进行删除操作
    NSArray *resultArray = [_managedObjectContext executeFetchRequest:request error:nil];
    // 4.遍历搜索出来的结果
    for (Person *per in resultArray) {
        // 删除查询到的相关的人
        [_managedObjectContext deleteObject:per];
    }
    // 5.进行删除结果的判断
    BOOL result = [_managedObjectContext save:nil];
    // 6.判断结果
    if (result) {
        NSLog(@"删除数据成功");
    }else {
        NSLog(@"删除数据失败");
    }
}

#pragma mark - 查询相关信息
- (void)selectAllPerson
{
    // 1.实例化查询请求
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"personName LIKE ‘*R*‘"];
    request.predicate = predicate;
    NSArray *resultArray = [_managedObjectContext executeFetchRequest:request error:nil];
    for (Person *per in resultArray) {
        NSLog(@"name = %@, gender = %@, age = %@", per.personName, per.personGender, per.personAge);
    }
   
}