iOS开发 - CoreData框架 数据持久化

Core Data

Core Data是iOS5之后才出现的一个框架，它提供了对象-关系映射(ORM)的功能，即能够将OC对象转化成数据，保存在SQLite数据库文件中，也能够将保存在数据库中的数据还原成OC对象。在此数据操作期间，我们不需要编写任何SQL语句，这个有点类似于著名的Hibernate持久化框架，不过功能肯定是没有Hibernate强大的。

传统的数据库要把数据写到数据库，而且要写SQL语句 Core Data 就避免了写SQL语句的麻烦了

CoreData的使用步骤

1.创建模型文件 相当于数据库 
2.添加实体 相当表 
3.创建实体类 相于模型类 
4.生成上下文 关联模型文件生成数据库 
5.保存对象到数据库 
6.从数据库获取对象 
7.更新数据 
8.删除数据

1.创建模型文件 
所谓的创建模型就是间接生成数据库表 

2.添加实体 

3.创建实体类 
以创建员工实体类为例 

生成上下文件 关联模型文件生成数据库

 NSManagedObjectContext  _context = [[NSManagedObjectContext alloc] init];

    // 模型文件 NSManagedObjectModel *model = [NSManagedObjectModel mergedModelFromBundles:nil]; // 持久化存储调度器 NSPersistentStoreCoordinator *store = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model]; NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject]; NSLog(@"%@",doc); NSString *sqlitePath = [doc stringByAppendingPathComponent:@"company.sqlite"]; //数据存储的类型 数据库存储路径 [store addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:[NSURL fileURLWithPath:sqlitePath] options:nil error:nil]; _context.persistentStoreCoordinator = store; 

 

保存对象到数据库

Employee *employee = [NSEntityDescription insertNewObjectForEntityForName:@"Employee" inManagedObjectContext:_context]; employee.name = @"zhangsan"; employee.age = @18; employee.height = @1.89; [_context save:nil]; 

打开CoreData的SQL语句输出开关

    1.打开Product，点击EditScheme... 2.点击Arguments，在ArgumentsPassed On Launch中添加2项 1> -com.apple.CoreData.SQLDebug 2> 1

CoreData实例

生成实体类

#import <Foundation/Foundation.h> #import <CoreData/CoreData.h> @interface Employee : NSManagedObject @property (nonatomic, retain) NSString * name; @property (nonatomic, retain) NSNumber * age; @property (nonatomic, retain) NSNumber * height; @end

#import "Employee.h" @implementation Employee @dynamic name; @dynamic age; @dynamic height; @end

import头文件框架

#import "ViewController.h" #import <CoreData/CoreData.h> #import "Employee.h" @interface ViewController () @property(strong,nonatomic)NSManagedObjectContext *context; @end

CoreData模糊查询

@implementation ViewController #pragma mark 模糊查询 - (IBAction)likeSearcher:(id)sender { // 查询 NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"]; // 过滤 // 1.查询以wang开头员工 NSPredicate *pre = [NSPredicate predicateWithFormat:@"name BEGINSWITH %@",@"wang"]; // 2.以si 结尾 NSPredicate *pre = [NSPredicate predicateWithFormat:@"name ENDSWITH %@",@"si"]; // 3.名字包含 g NSPredicate *pre = [NSPredicate predicateWithFormat:@"name CONTAINS %@",@"g"]; // 4.like 以si结尾 NSPredicate *pre = [NSPredicate predicateWithFormat:@"name like %@",@"li*"]; request.predicate = pre; //读取信息 NSError *error = nil; NSArray *emps = [self.context executeFetchRequest:request error:&error]; if (!error) { NSLog(@"emps: %@",emps); for (Employee *emp in emps) { NSLog(@"%@ %@ %@",emp.name,emp.age,emp.height); } }else{ NSLog(@"%@",error); } } 

CoreData 更新数据

#pragma mark 更新员工信息 - (IBAction)updateEmployee:(id)sender { // 把wangwu的身高更改成 1.7 // 1.查找wangwu NSArray *emps = [self findEmployeeWithName:@"wangwu"]; // 2.更新身高 if (emps.count == 1) { Employee *emp = emps[0]; emp.height = @1.7; } // 3.同步（保存）到数据 [self.context save:nil]; } -(NSArray *)findEmployeeWithName:(NSString *)name{ // 1.查找员工 NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"]; NSPredicate *pre = [NSPredicate predicateWithFormat:@"name=%@",name]; request.predicate = pre; return [self.context executeFetchRequest:request error:nil]; } 

 

CoreData 删除数据

#pragma mark 删除员工 - (IBAction)deleteEmployee:(id)sender { [self deleteEmployeeWithName:@"lisi"]; } -(void)deleteEmployeeWithName:(NSString *)name{ // 删除zhangsan // 1.查找到zhangsan NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"]; NSPredicate *pre = [NSPredicate predicateWithFormat:@"name=%@",name]; request.predicate = pre; // 2.删除zhangsan NSArray *emps = [self.context executeFetchRequest:request error:nil]; for (Employee *emp in emps) { NSLog(@"删除员工的人 %@",emp.name); [self.context deleteObject:emp]; } // 3.用context同步下数据库 //所有的操作暂时都是在内存里，调用save 同步数据库 [self.context save:nil]; } 

CoreData 查询数据

#pragma mark 读取员工信息 - (IBAction)readEmployee:(id)sender { //创建一个请求对象 （填入要查询的表名-实体类） NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"]; // 过滤查询 // 查找张三 并且身高大于1.8 NSPredicate *pre = [NSPredicate predicateWithFormat:@"name=%@ AND height > %@",@"zhangsan",@(1.8)]; // request.predicate = pre; //排序 以身高进行升序 NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"height" ascending:NO]; // request.sortDescriptors = @[sort]; // 分页查询 总共13条数据 每页显示5条数据 //第一页的数据 request.fetchLimit = 5; request.fetchOffset = 10; //读取信息 NSError *error = nil; NSArray *emps = [self.context executeFetchRequest:request error:&error]; if (!error) { NSLog(@"emps: %@",emps); for (Employee *emp in emps) { NSLog(@"%@ %@ %@",emp.name,emp.age,emp.height); } }else{ NSLog(@"%@",error); } } #pragma mark 添加员工信息 - (IBAction)addEmployee:(id)sender { // 创建员工 Employee *emp1 = [NSEntityDescription insertNewObjectForEntityForName:@"Employee" inManagedObjectContext:self.context]; // 设置员工属性 emp1.name = @"lisi"; emp1.age = @28; emp1.height = @2.10; //保存 - 通过上下文操作 NSError *error = nil; [self.context save:&error]; if (!error) { NSLog(@"success"); }else{ NSLog(@"%@",error); } } 

CoreData 创建上下文

-(void)setupContext{ // 1.上下文 关联Company.xcdatamodeld 模型文件 NSManagedObjectContext *context = [[NSManagedObjectContext alloc] init]; // 关联模型文件 // 创建一个模型对象 // 传一个nil 会把 bundle下的所有模型文件 关联起来 NSManagedObjectModel *model = [NSManagedObjectModel mergedModelFromBundles:nil]; // 持久化存储调度器 NSPersistentStoreCoordinator *store = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model]; // 存储数据库的名字 NSError *error = nil; // 获取docment目录 NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject]; // 数据库保存的路径 NSString *sqlitePath = [doc stringByAppendingPathComponent:@"company.sqlite"]; [store addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:[NSURL fileURLWithPath:sqlitePath] options:nil error:&error]; context.persistentStoreCoordinator = store; self.context = context; } -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{ // 创建员工 for (int i = 0; i < 10; i++) { Employee *emp1 = [NSEntityDescription insertNewObjectForEntityForName:@"Employee" inManagedObjectContext:self.context]; // 设置员工属性 emp1.name = [NSString stringWithFormat:@"wangwu %d",i]; emp1.age = @(28 + i); emp1.height = @2.10; //保存 - 通过上下文操作 NSError *error = nil; [self.context save:&error]; if (!error) { NSLog(@"success"); }else{ NSLog(@"%@",error); } } } @end

调用

- (void)viewDidLoad { [super viewDidLoad]; // 创建一个数据库 company.sqlite // 数据库要一张表 员工表 （name,age,heigt） // 往数据添加员工信息 // CoreData [self setupContext]; }