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];}