CoreData

CoreData是对sqlite的一次封装。

使用过程

首先新建一个 Data Model
- 添加数据模型（相当于数据库）
- 添加实体对象（相当于一张表）
- 添加实体对象类

//#import "Employee.h"
NS_ASSUME_NONNULL_BEGIN
@interface Employee (CoreDataProperties)
@property (nullable, nonatomic, retain) NSString *name;
@property (nullable, nonatomic, retain) NSNumber *height;
@property (nullable, nonatomic, retain) NSDate *birthday;
@end
NS_ASSUME_NONNULL_END

在viewController中控制

// 1、初始化数据库操作对象
 NSManagedObjectContext *context = [[NSManagedObjectContext alloc] init];
 // 2、指定model模型文件
 NSManagedObjectModel *model = [NSManagedObjectModel mergedModelFromBundles:nil];
 // 3、持久化存储调度器，把数据保存到一个文件，而不是内存
 NSPersistentStoreCoordinator *store = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];
 // 4、告诉Coredata数据库的名字和路径
 NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
 NSString *sqlitePath = [doc stringByAppendingPathComponent:@"company.sqlite"];
 [store addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:[NSURL fileURLWithPath:sqlitePath] options:nil error:nil];
 context.persistentStoreCoordinator = store;

增删改查

- (IBAction)addEmployee:(id)sender
{
    // 创建
//    Employee *emp = [[Employee alloc] init];
    Employee *emp = [NSEntityDescription insertNewObjectForEntityForName:@"Employee" inManagedObjectContext:_context];
    emp.name = @"song";
    emp.height = @1.8;
    emp.birthday = [NSDate date];

    // 存储
    NSError *error = nil;
    [_context save:&error];
    if(error)
    {
        NSLog(@"%@",error);
    }
}

- (IBAction)updataEmployee:(id)sender
{
    // FectchRequest 抓取请求对象
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"];
    // 设置过滤条件
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name = %@",@"song"];
    request.predicate = predicate;
    // 执行请求
    NSArray *fetch = [_context executeFetchRequest:request error:nil];
    for (Employee *emp in fetch) {
        emp.height = @1.9;
    }
    // 存储
    NSError *error = nil;
    [_context save:&error];
    if(error)
    {
        NSLog(@"%@",error);
    }
}

- (IBAction)deleteEmployee:(id)sender
{
    // FectchRequest 抓取请求对象
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"];
    // 设置过滤条件
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name = %@",@"song"];
    request.predicate = predicate;
    // 执行请求
    NSArray *fetch = [_context executeFetchRequest:request error:nil];
    for (Employee *emp in fetch) {
        [_context deleteObject:emp];
    }
    // 存储
    NSError *error = nil;
    [_context save:&error];
    if(error)
    {
        NSLog(@"%@",error);
    }
}

表连接

{
   // 创建两个部门 ios android
    Department *iosDepart = [NSEntityDescription insertNewObjectForEntityForName:@"Department" inManagedObjectContext:_context];
    iosDepart.name = @"ios";
    iosDepart.departNo = @"0001";
    iosDepart.createDate = [NSDate date];

    Department *andrDepart = [NSEntityDescription insertNewObjectForEntityForName:@"Department" inManagedObjectContext:_context];
    andrDepart.name = @"android";
    andrDepart.departNo = @"0002";
    andrDepart.createDate = [NSDate date];

    // 创建两个员工对象 zhangsan属于ios部门 lisi属于android部门
    Employee *zhangsan = [NSEntityDescription insertNewObjectForEntityForName:@"Employee" inManagedObjectContext:_context];
    zhangsan.name = @"zhangsan";
    zhangsan.height = @(1.90);
    zhangsan.birthday = [NSDate date];
    zhangsan.depart = iosDepart;


    Employee *lisi = [NSEntityDescription insertNewObjectForEntityForName:@"Employee" inManagedObjectContext:_context];

    lisi.name = @"lisi";
    lisi.height = @2.0;
    lisi.birthday = [NSDate date];
    lisi.depart = andrDepart;

    // 存储
    NSError *error = nil;
    [_context save:&error];
    if(error)
    {
        NSLog(@"%@",error);
    }
}
- (void)selectEmployee
{
    // 读取ios部门的员工

    // 1.FectchRequest 抓取请求对象
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"];

    // 2.设置过滤条件
    NSPredicate *pre = [NSPredicate predicateWithFormat:@"depart.name = %@",@"android"];
    request.predicate = pre;

    // 4.执行请求
    NSError *error = nil;

    NSArray *emps = [_context executeFetchRequest:request error:&error];
    if (error) {
        NSLog(@"error");
    }

    //NSLog(@"%@",emps);
    //遍历员工
    for (Employee *emp in emps) {
        NSLog(@"名字 %@ 部门 %@",emp.name,emp.depart.name);
    }
}