coreData使用
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
