简介

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。

1.新建工程，记得勾选Use Core Data

2.建立好以后可以看到xxx.xcdatamodeld，在这里可以添加实体和实体的属性。需要注意的是：实体名字必须以大写开头。

3.然后新建一个file，记得是NSManagedObject cubclass

4.勾选自己建立的工程

5、勾选建立的实体

6.我们就可以看到建立好的实体是有4个文件

7.

#import "ViewController.h"

#import "Dog.h"

#import "AppDelegate.h"

#import <CoreData/CoreData.h>

@interface ViewController ()

{

AppDelegate *app;

}

@end

@implementation ViewController

- (void)viewDidLoad {

[super viewDidLoad];

app = [UIApplication sharedApplication].delegate;

[self createButtons];

}

//创建按钮

- (void)createButtons{

NSArray *array = @[@"增", @"删", @"改", @"查"];

for (int i = 0; i < 4; i++) {

UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];

button.frame = CGRectMake(30 + i * 60, 100, 40, 40);

[button setTitle:array[i] forState:UIControlStateNormal];

[button setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];

[button addTarget:self action:@selector(buttonDidClicked:) forControlEvents:UIControlEventTouchUpInside];

button.tag = i;

[self.view addSubview:button];

}

}

- (void)buttonDidClicked:(UIButton *)button{

switch (button.tag) {

case 0:

//add

[self coreDateAdd];

break;

case 1:

//delete

[self coreDataDelete];

break;

case 2:

//update

[self coreDataUpdate];

break;

case 3:

//search

[self coreDataSearch];

break;

default:

break;

}

}

//增

- (void)coreDateAdd{

Dog *dog = [NSEntityDescription insertNewObjectForEntityForName:@"Dog" inManagedObjectContext:app.managedObjectContext];

dog.name = [NSString stringWithFormat:@"汪汪%d", arc4random()%10];

dog.sex = @"公";

dog.age = [NSString stringWithFormat:@"%d", arc4random()%15];

[app.managedObjectContext save:nil];

NSLog(@"add success");

}

//删

- (void)coreDataDelete{

//读取类

NSEntityDescription *entity = [NSEntityDescription entityForName:@"Dog" inManagedObjectContext:app.managedObjectContext];

//建立请求

NSFetchRequest *request = [[NSFetchRequest alloc] init];

[request setEntity:entity];

//设置检索条件

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name=%@", @"汪汪7"];

[request setPredicate:predicate];

NSArray *array = [app.managedObjectContext executeFetchRequest:request error:nil];

if (array.count) {

for (Dog *dog in array) {

[app.managedObjectContext deleteObject:dog];

}

[app.managedObjectContext save:nil];

NSLog(@"delete succeed");

} else{

NSLog(@"no data");

}

}

//改

- (void)coreDataUpdate{

//读取类

NSEntityDescription *entity = [NSEntityDescription entityForName:@"Dog" inManagedObjectContext:app.managedObjectContext];

//建立请求

NSFetchRequest *request = [[NSFetchRequest alloc] init];

[request setEntity:entity];

//设置检索条件

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name!=%@", @"汪汪23"];

[request setPredicate:predicate];

//遍历

NSArray *array = [app.managedObjectContext executeFetchRequest:request error:nil];

if (array.count) {

for (Dog *dog in array) {

dog.name = @"汪汪23";

}

[app.managedObjectContext save:nil];

NSLog(@"update succeed");

} else{

NSLog(@"no result");

}

}

//查

- (void)coreDataSearch{

//读取类

NSEntityDescription *entity = [NSEntityDescription entityForName:@"Dog" inManagedObjectContext:app.managedObjectContext];

//建立请求

NSFetchRequest *request = [[NSFetchRequest alloc] init];

//建立请求的是哪一类

[request setEntity:entity];

//遍历数组

NSArray *array = [app.managedObjectContext executeFetchRequest:request error:nil];

for (Dog *dog in array) {

NSLog(@"%@", dog.name);

}

}

@end