coreData

#import "ViewController.h"
#import "Husband.h"
#import "Wife.h"
@interface ViewController ()

@end

@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
#pragma mark - 上下文
    // 从应用程序包中加载模型文件
    NSManagedObjectModel *model = [NSManagedObjectModel mergedModelFromBundles:nil];
    // 传入模型对象，初始化NSPersistentStoreCoordinator
    NSPersistentStoreCoordinator *psc = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];
    // 初始化上下文
    NSManagedObjectContext *context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
    // 设置上下文的persistentStoreCoordinator属性
    context.persistentStoreCoordinator = psc;
#pragma mark - 持久化存储库
    // 构建SQLite数据库文件的路径
    NSString *filePath = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"model.data"];
    // 将数据库路径转成URL
    NSURL *url = [NSURL fileURLWithPath:filePath];
    // 添加持久化存储库，这里使用SQLite作为存储库
    NSError *error = nil;
    NSPersistentStore *store = [psc addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:url options:nil error:&error];
    // 判断数据库是否添加成功
    if (store == nil) {
        [NSException raise:@"添加数据库错误" format:@"%@", [error localizedDescription]];
    }

@end

#pragma mark - 添加数据
    // 创建一个Husband实体对象，传入上下文
    Husband *husband = [NSEntityDescription insertNewObjectForEntityForName:@"Husband" inManagedObjectContext:context];
    // 通过键值编码的方式设置Husband的name属性
    [husband setValue:@"jack" forKey:@"name"];
    // 通过coredata生成的实体类来创建一个Wife实体对象，传入上下文
    Wife *wife = [NSEntityDescription insertNewObjectForEntityForName:@"Wife" inManagedObjectContext:context];
    // 通过setter方法设置属性
    wife.name = @"rose";
    // 设置Husband和Wife之间的关联关系（一方关联，另一方自动关联）
    wife.husband = husband;
    // 利用上下文对象，将数据同步到持久化存储库
    BOOL success = [context save:&error];
    if (!success) {
        [NSException raise:@"访问数据库错误" format:@"%@", [error localizedDescription]];
    }

#pragma mark - 删除数据
    // 初始化一个查询请求
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    // 设置要查询的实体
    request.entity = [NSEntityDescription entityForName:@"Husband" inManagedObjectContext:context];
    // 设置条件过滤(搜索name等于jack2的实体)
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name == %@", @"jack2"];
    request.predicate = predicate;
    // 执行请求,返回一个数组
    NSArray *objs = [context executeFetchRequest:request1 error:&error];
    if (error) {
        [NSException raise:@"查询错误" format:@"%@", [error localizedDescription]];
    }

#pragma mark - 查询数据
    // 初始化一个查询请求
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    // 设置要查询的实体
    request.entity = [NSEntityDescription entityForName:@"Husband" inManagedObjectContext:context];
    // 设置排序（按照name降序）
    NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"name" ascending:NO];
    request.sortDescriptors = [NSArray arrayWithObject:sort];
    // 设置条件过滤(搜索name中包含字符串"ja"的记录)
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name like %@", @"*ja*"];
    request.predicate = predicate;
    // 执行请求,返回一个数组
    NSArray *objs = [context executeFetchRequest:request error:&error];
    if (error) {
        [NSException raise:@"查询错误" format:@"%@", [error localizedDescription]];
    }
    // 遍历数据
    for (NSManagedObject *obj in objs) {
        NSLog(@"name = %@", [obj valueForKey:@"name"]);
        // 实体属性中包含另一个实体，不需要再次设置查询请求，Core Data会根据关联关系查询到关联的实体信息
        NSLog(@"wife = %@", [[obj valueForKey:@"wife"] valueForKey:@"name"]);
    }

转载于：宏创学院