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=0; i<10; 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",5];
//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:@(50) 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",50];
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=@28;
//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