iOSCoreData数据库：

@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;//操作管理器（增删改查）
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;//被管理的数据模型
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;//持久化协助管理器

  /**
     * 表示要向Person这个表里面插入一条数据
     */
    /*
     参数1：插入的表名
     参数2：托管上下文对象（coreData操作管理器）

     */
    //数据  ->（映射） 对象
    Person *per = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:self.managedObjectContext];
    //设置返回实体对象的属性
    per.name = @"老王";
    per.age = [NSNumber numberWithInt:11];
    per.headImage = [NSData dataWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"1" ofType:@"png"]];

    //保存记录
    [self.managedObjectContext save:nil];

    NSLog(@"%@",NSHomeDirectory());


    //查找数据
    NSFetchRequest *request = [[NSFetchRequest alloc] init];

    //获得表结构实体（把一张表进行实体化）
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Person" inManagedObjectContext:self.managedObjectContext];

    //设置查询的表结构实体（设置查询的是哪张表）
    request.entity = entity;



    /*
    //设置条件查询（谓语）
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name = %@",@"老李"];

    request.predicate = predicate;
     */

    //设置升降序排列
    //YES代表升序，NO代表降序
    NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"age" ascending:YES];

    request.sortDescriptors = @[sort];

    //通过操作管理器发起查询请求
    //resultArr储存搜寻的结果
    NSArray *resultArr = [self.managedObjectContext executeFetchRequest:request error:nil];

    for (Person *per in resultArr) {

        NSLog(@"per.name = %@ per.age = %@",per.name,per.age);

    }


    /*
    for (Person *per in resultArr) {

        NSLog(@"per.name = %@ per.age = %@",per.name,per.age);
        //修改数据（更新）
        per.name = @"老李";

        //保存记录
        [self.managedObjectContext save:nil];

        //删除
        if ([per.age integerValue] == 90) {

            [self.managedObjectContext deleteObject:per];

            //保存记录
            [self.managedObjectContext save:nil];

        }

    }
     */

.M中：
    NSManagedObjectContext *_context;
引入头文件#import "AppDelegate.h"
- (void)loadDataFromCoreData
{
    //coreData查询

    AppDelegate *delegate = [UIApplication sharedApplication].delegate;

    _context = delegate.managedObjectContext;

    NSFetchRequest *request = [[NSFetchRequest alloc]init];

    //从哪个实体中查询数据
    NSEntityDescription *descrip = [NSEntityDescription entityForName:@"CDGoodsModel" inManagedObjectContext:_context];
    //查询规则,where xx = xx
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"cid = %d",_cid];
    [request setEntity:descrip];
    [request setPredicate:predicate];

    NSArray *array = [_context executeFetchRequest:request error:nil];
    [_dataArray addObjectsFromArray:array];
    [_myTable reloadData];
}

数据库删除：
AppDelegate *delegate = [UIApplication sharedApplication].delegate;
        _context = delegate.managedObjectContext;

        for (NSManagedObject *obj in _dataArray)
        {
            [_context deleteObject:obj];
        }
        [_context save:nil];

        [_dataArray removeAllObjects];


数据库插入：CDGoodsModel：表名
   CDGoodsModel *cdModel = [NSEntityDescription insertNewObjectForEntityForName:@"CDGoodsModel" inManagedObjectContext:_context];
            cdModel.imgURL = [NSString stringWithFormat:@"%@",model.imgURL];
            cdModel.price = [NSString stringWithFormat:@"%@",model.price];
            cdModel.discount = [NSString stringWithFormat:@"%@",model.discount];
            cdModel.cid = [NSString stringWithFormat:@"%d",_cid];

            NSError *error = nil;
            if(![_context save:&error])
            {
                NSLog(@"coreData保存数据失败,error=%@",error);
            }else
            {
                [_dataArray addObject:cdModel];
            }

        }

        //刷表
        [_myTable reloadData];

URL 的赋值不可以放到init里