IOS - CoreData的使用

本文主要是介绍IOS - CoreData的使用，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

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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
这里写图片描述
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,ANDRODSchool *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