ios深度解析之coreData

coreData数据持久化 是对SQLite的升级优化, 这里有几个非常重要的类:

1.NSManagerObjectModel(被管理对象的模型, 实体) 

2.NSEntityDescription (创建实体描述, 实体名必须跟类名相同)

3,NSFetchRequest (从实体中查询)

4.NSManagedObjectContext(被管理对象上下文, 临时数据库(添加, 查询,修改,删除数据))

5.NSPrisistenStoreCoordinator(持久化存储助理 , 数据库的连接器)

6.创建表步骤:

(1) ctrl +  n新建



(2)选中所建项目



(3)选中项目 添加数据



(4)在工程里自动会生成.h和.m文件

7.环境搭建上下文

#pragma mark - 添加数据
- (IBAction)tianjia:(UIButton *)sender {

// 创建实体描述
NSEntityDescription *studentED = [NSEntityDescription entityForName:@"Student" inManagedObjectContext:self.managerContext];

for (int i = 0; i < 10; i++) {
// 根据实体描述创建对象
Student *student = [[Student alloc] initWithEntity:studentED insertIntoManagedObjectContext:self.managerContext];

// 给实体赋值
student.name = [NSString stringWithFormat:@"毛毛%d号", i];
student.age = [NSNumber numberWithInt: 18 + i*5];
student.sex = [NSString stringWithFormat:@"女"];
}

// 数据同步
NSError *error = nil;
[self.managerContext save:&error];
if (!error) {

NSLog(@"存储成功");
}

}

#pragma mark - 查询数据
- (IBAction)chaXun:(UIButton *)sender {

// 从实体中查询
NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Student"];

// 创建实体描述
NSEntityDescription *studetED = [NSEntityDescription entityForName:@"Student" inManagedObjectContext:self.managerContext];

// 设置查询实体
request.entity = studetED;

// 设置排序 yes升序 no降序
NSSortDescriptor *sort = [[NSSortDescriptor alloc] initWithKey:@"age" ascending:YES];
request.sortDescriptors = @[sort];

//根据条件查询
// NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name = %@", @"毛毛7号"];

// 模糊查询 包含
// NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name CONTAINS%@", @"7"];

// NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name LIKE %@", @"毛毛*号"];

// request.predicate = predicate;

// 数组接收查询数据
NSArray *array = [self.managerContext executeFetchRequest:request error:nil];

// 遍历数组 取出数据打印
for (Student *student in array) {

NSLog(@"姓名:%@, 年纪:%@, 性别:%@", student.name, student.age, student.sex);
}

}

#pragma mark - 修改数据
- (IBAction)xiuGai:(UIButton *)sender {

// 从实体中修改
NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Student"];

// 创建实体描述
NSEntityDescription *StudentED = [NSEntityDescription entityForName:@"Student" inManagedObjectContext:self.managerContext];

// 设置修改的实体
request.entity = StudentED;

// 根据条件修改
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name = %@", @"毛毛1号"];
request.predicate = predicate;

// 数据接收修改数据
NSArray *array = [self.managerContext executeFetchRequest:request error:nil];

if (array.count > 0) {
Student *student = array.lastObject;
student.name = @"军军";
student.age = @1;
student.sex = @"男";

// 同步数据
if ([self.managerContext save:nil]) {

NSLog(@"修改成功");
} else {

NSLog(@"修改失败");
}
} else {
NSLog(@"没有对应的实体");
}

}

#pragma mark - 删除数据
- (IBAction)shanChu:(UIButton *)sender {

// 从实体中删除
NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Student"];

// 创建实体描述
NSEntityDescription *StudentED = [NSEntityDescription entityForName:@"Student" inManagedObjectContext:self.managerContext];

// 设置删除的实体
request.entity = StudentED;

// 根据条件删除
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"sex = %@", @"女"];

request.predicate = predicate;

// 数据接收删除数据
NSArray *array = [self.managerContext executeFetchRequest:request error:nil];

if (array.count > 0) {
// 遍历数组
for (Student *stu in array) {
// 删除数据
[self.managerContext deleteObject:stu];

// 同步数据
if ([self.managerContext save:nil]) {

NSLog(@"删除成功");
} else {

NSLog(@"删除失败");
}
}

}else {
NSLog(@"没事这个实体");
}

}

#pragma mark - 被管理对象上下的懒加载方法
- (NSManagedObjectContext *)managerContext
{
if (! _managerContext) {

// 获取apdelegate当中的被管理对象上下文
_managerContext = ((AppDelegate *)[UIApplication sharedApplication].delegate).managedObjectContext;

}

return _managerContext;

}