IOS - CoreData的使用

今天学习了CoreData的使用，在这里做一下笔记也为了方便以后的查询。

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（Android上面常用的框架XUtils里面的dbUtils也是使用的这种方式去管理数据），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。

CoreData使用到的关键词组

测试代码：

#import "ViewController.h"
#import <CoreData/CoreData.h>
#import "Person.h"
#import "School.h"

@interface ViewController (){
    //上下文对象
    NSManagedObjectContext *_context;
}

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    //初始化上下文对象
    _context = [[NSManagedObjectContext alloc] init];
    //上下文关联数据库

    //model模型文件
    NSManagedObjectModel *model = [NSManagedObjectModel mergedModelFromBundles:nil];

    //持续化可存储调度器
    NSPersistentStoreCoordinator *store = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];
    //数据库保存路径
    NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *sqlitePath = [doc stringByAppendingPathComponent:@"person.db"];
    NSLog(@"sqlitePath :%@",sqlitePath);
    //告诉CoreData数据库的名字和路径
    [store addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:[NSURL fileURLWithPath:sqlitePath] options:nil error:nil];
    _context.persistentStoreCoordinator = store;
}

#pragma mark 保存数据
- (IBAction)Save:(id)sender {
    //保存表关联数据
    //创建两个学校 IOS,ANDROD
    School *iosSchool = [NSEntityDescription insertNewObjectForEntityForName:@"School" inManagedObjectContext:_context];
    iosSchool.name = @"IOS学校";
    iosSchool.num = @"1001";
    iosSchool.createData = [NSDate date];

    //创建android实体类
    School *androidSchool = [NSEntityDescription insertNewObjectForEntityForName:@"School" inManagedObjectContext:_context];
    androidSchool.name = @"android学校";
    androidSchool.num = @"1002";
    androidSchool.createData = [NSDate date];

    //创建两个人 张三属于IOS学校，李四数据Android学校

    for(int i = 0 ; i < 15 ; i++){
        Person *iosPerson = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:_context];
        iosPerson.name = [NSString stringWithFormat:@"张三 %d",i];
        iosPerson.height = @(1.50 + i);
        iosPerson.birthday = [NSDate date];
        iosPerson.school = iosSchool;
    }

    Person *androidPerson = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:_context];
    androidPerson.name = @"李四";
    androidPerson.height = @1.85;
    androidPerson.birthday = [NSDate date];
    androidPerson.school = androidSchool;

    [_context save:nil];

//    //通过NSEntityDescription的insert方法去获得一个关联对象
//    Person *mPerson = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:_context];
//    //为获取的对象去添加属性
//    mPerson.name = @"王五";
//    mPerson.height = @1.79;
//    mPerson.birthday = [NSDate date];
//
//    //调用_context的save方法去保存数据
//    [_context save:nil];
}

#pragma mark 读取数据
- (IBAction)Read:(id)sender {
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Person"];

    request.fetchOffset = 0;
    request.fetchLimit = 6;

    request.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"height" ascending:YES]];

    //BEGINSWITH 以什么开头
    //ENDSWITH 以什么结尾
    //CONTAINS 包含
    request.predicate = [NSPredicate predicateWithFormat:@"name CONTAINS %@",@"1"];

    //使用like
    //张三 1*  以张三 1开头
    //*张三 1 以张三 1结尾
    request.predicate = [NSPredicate predicateWithFormat:@"name like %@",@"张三 1*"];

    NSArray *array = [_context executeFetchRequest:request error:nil];
    for(Person *mPerson in array){
        NSLog(@"姓名 ： %@,身高 : %@,学校 ： %@",mPerson.name,mPerson.height,mPerson.school.name);
    }

//    //FetchRequest 抓取请求对象
//    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
//
//    //限定抓取条件
//    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name = %@",@"李四"];
//    request.predicate = predicate;
//
//    //排序
//    NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"height" ascending:YES];
//    request.sortDescriptors = @[sort];
//
//    //执行抓取请求
//    NSArray *requestArray = [_context executeFetchRequest:request error:nil];
//    for(Person *mPerson in requestArray){
//        NSLog(@"姓名 ： %@ ，身高 ：%@ ， 生日 ：%@",mPerson.name,mPerson.height,mPerson.birthday);
//    }
}

#pragma mark 更新数据
- (IBAction)update:(id)sender {
    //首先获取需要更新的NSManagedObject对象
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
    request.predicate = [NSPredicate predicateWithFormat:@"name = %@",@"王五"];
    //得到查询的数据
    NSArray *array = [_context executeFetchRequest:request error:nil];
    //更改查询到的数据
    for(Person *mPerson in array){
       mPerson.name = @"李六";
       mPerson.height = @1.99;

    }
    //保存
    [_context save:nil];

}

#pragma mark 删除数据
- (IBAction)delete:(id)sender {
    //删除数据同样需要首先获得需要删除的NSManagedObject对象
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
//    request.predicate = [NSPredicate predicateWithFormat:@"name = %@",@"李六"];
    NSArray *array = [_context executeFetchRequest:request error:nil];
    //获取到数据之后调用deleteObject去删除NSManagedObject对象
    for(Person *mPerson in array){
        [_context deleteObject:mPerson];
    }
    //保存更改
    [_context save:nil];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

具体参照李明杰老师博客：http://blog.csdn.net/q199109106q/article/details/8563438/#t4

demo地址:http://download.csdn.net/detail/u011068996/8808331