iOS中coreData的用法

//
//  ViewController.m
//  coredatademo002
//
//  Created by ganchaobo on 13-6-29.
//  Copyright (c) 2013年 ganchaobo. All rights reserved.
//

#import "ViewController.h"
#import <CoreData/CoreData.h>
#import "Person.h"
@interface ViewController ()

@property(nonatomic,retain) NSManagedObjectContext *context;
@end

@implementation ViewController

#pragma mark -生命周期方法
- (void)viewDidLoad
{
    [super viewDidLoad];
    [self LoadData];

    //[self UdataData];
   // [self addData];
//[self deleteData];
  //  [self searchdata];
    //面向对象操作
    [self addPerson];
    [self searchPerson];
    // Do any additional setup after loading the view, typically from a nib.
}

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

-(void)viewDidUnload{
    [super viewDidUnload];
    self.context=nil;
}
- (void)dealloc
{
    [_context release];
    [super dealloc];
}

#pragma mark-加载数据方式

-(void)LoadData{
    //Nil表是从主bundles中加对应的模型实体
    NSManagedObjectModel *model=[NSManagedObjectModel mergedModelFromBundles:nil];
    for (NSEntityDescription *desc in model.entities) {
        NSLog(@"%@",desc.name);
    }
    //通过模型 和数据库持久化
    NSPersistentStoreCoordinator *storeCoordinator=[[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];
    //持久化到coredata中
    NSString *document= [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    document=[document stringByAppendingPathComponent:@"coredata.db"];
    NSURL *url=[NSURL fileURLWithPath:document];
    NSError *error=nil;
    [storeCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:url options:nil error:&error];
    if(error){
        NSLog(@"打开数据库失败");
        return;
    }

    self.context=[[[NSManagedObjectContext alloc] init] autorelease];
    self.context.persistentStoreCoordinator=storeCoordinator;

}

-(void)addData{

    //把实体对象和实体上下文相关联
    for (int i=; i<; i++) {

    NSManagedObject *obj=[NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:self.context];
        NSString *name=[NSString stringWithFormat:@"gcb%i",i];
        int age=i;
    [obj setValue: name forKey:@"name"];
    [obj setValue:@(age) forKey:@"age"];

    //保存上下文中相关联的对象即可
    }
        [self.context save:nil];

}

-(void)searchdata{
    NSFetchRequest *fetch=[NSFetchRequest fetchRequestWithEntityName:@"Person"];

    //排序
    NSSortDescriptor *sort=[NSSortDescriptor sortDescriptorWithKey:@"age" ascending:NO];
    fetch.sortDescriptors=@[sort];
    //加入查询条件 age>20
//    fetch.predicate=[NSPredicate predicateWithFormat:@"age>%i",20];
    //加入like *c1"
    //fetch.predicate=[NSPredicate predicateWithFormat:@"name like %@",@"*cb1*"];
    NSArray *arr=[self.context executeFetchRequest:fetch error:nil];
    for (NSManagedObject *mode in arr) {
        NSString *name=[mode valueForKey:@"name"];
        int age =[[mode valueForKey:@"age"] intValue];
        NSLog(@"%zi--%@",age,name);
    }
}
//先查询出要修改的数据
-(void)UdataData{
 //要操作那一张表
    NSFetchRequest *Fetch=[NSFetchRequest fetchRequestWithEntityName:@"Person"];
    //先创建排序描述，在排序
    NSSortDescriptor *sort=[NSSortDescriptor sortDescriptorWithKey:@"age" ascending:NO];
    Fetch.sortDescriptors=@[sort];
  //加入查询条件
    Fetch.predicate=[NSPredicate predicateWithFormat:@"age>%i",];
    //把条件加入到上下文进行操作,得到查询集合
    NSArray * arr=[self.context executeFetchRequest:Fetch error:nil];
    for (NSManagedObject *obj in arr) {
    //更改实体的数据
        [obj setValue:@() forKey:@"age"];
    }
    //同步更数据库相关联的数据
    [self.context save:nil];

}

//删除数据， 从数据库中取出来的对象，叫做NSManaedObject对象
-(void)deleteData{
    //要找出上下文中操作的一张表
    NSFetchRequest *FectchRequest=[NSFetchRequest fetchRequestWithEntityName:@"Person"];
    FectchRequest.predicate=[NSPredicate predicateWithFormat:@"age<%i",];
    NSArray *arr=[self.context executeFetchRequest:FectchRequest error:nil];
    for (NSManagedObject *obj in arr) {
        [self.context deleteObject:obj];
    }
    //同步数据库
    [self.context save:nil];
}

#pragma mark-面向对象开发
-(void)addPerson{
    //把要插入的实体和当前上下文相关联
    Person *ps=[NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:self.context];
    ps.name=@"mj__itcast";
    ps.age=@;
    //同步数据和上下文相关联的
    [self.context save:nil];
}
-(void)searchPerson{
    NSFetchRequest *FetchRequest=[NSFetchRequest fetchRequestWithEntityName:@"Person"];
    NSArray *arr=[self.context executeFetchRequest:FetchRequest error:nil];
    for (Person *ps in arr) {
        NSLog(@"name=%@,age=%@",ps.name,ps.age);
    }
}
@end