昨晚突然有个朋友问起coredata的使用,后来便自己写了个demo看看,发现跟Xcode7使用有些不一样,今天有时间就记下来跟大家分享下。
创建工程时勾选use core data
打开工程时会发现比多一个.xcdatamodeld文件,名字和工程名一致,demo工程名为CoreDataDemo。
选中该文件 点击add Entity 可创建实体,需大写开头,可以理解为model,同时可添加属性,选择属性类型
然后就是Xcode8之后的差异了。
第一个图是之前新建一个file,NSManagedObjectSubclass。
第二个截图是现在Xcode的界面,取消了NSManagedObjectSubclass。
选中创建的Entity,点击导航栏的Editor-->Create NSManagedObjectSubclass,然后按照提示操作下去,会生成四个文件
新建NSManagedObjectSubclass文件
细心的小伙伴可能还会发现AppDelegate跟平时我们创建的有些不同,多了一个coredata操作对象及方法。
//
// AppDelegate.h
// CoreDataDemo
//
// Created by simon on 2017/5/3.
// Copyright © 2017年 simon. All rights reserved.
//
#import
#import
@interface AppDelegate : UIResponder
@property (strong, nonatomic) UIWindow *window;
@property (readonly, strong) NSPersistentContainer *persistentContainer;
- (void)saveContext;
@end
那我们现在来写个增删改查的操作。
#import "ViewController.h"
#import
#import "AppDelegate.h"
#import "Dog+CoreDataClass.h"
@interface ViewController ()
{
AppDelegate *_app;
}
@end
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
_app = (AppDelegate *)[UIApplication sharedApplication].delegate;
[self createBtns];
}
- (void)createBtns{
NSArray *titles = @[@"增",@"删",@"改",@"查"];
for (int i = 0; i < titles.count; i++) {
UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
btn.frame = CGRectMake(30 + i * 60, 100, 40, 40);
[btn setTitle:titles[i] forState:UIControlStateNormal];
[btn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
[btn addTarget:self action:@selector(btnAction:) forControlEvents:UIControlEventTouchUpInside];
btn.tag = i;
[self.view addSubview:btn];
}
}
- (void)btnAction:(UIButton *)btn{
switch (btn.tag) {
case 0:
[self addCoreData];
break;
case 1:
[self deleteCoreData];
break;
case 2:
[self updateCoreData];
break;
case 3:
[self selectCoreData];
break;
default:
break;
}
}
增加一条数据:
- (void)addCoreData{
Dog *dog = [NSEntityDescription insertNewObjectForEntityForName:@"Dog" inManagedObjectContext:_app.persistentContainer.viewContext];
static NSInteger index = 0;
dog.name = [NSString stringWithFormat:@"tom%ld",index++];
dog.sex = @"公";
dog.age = [NSString stringWithFormat:@"%uyears",arc4random() % 15];
[_app saveContext];
}
查询所有数据:
- (void)selectCoreData{
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Dog" inManagedObjectContext:_app.persistentContainer.viewContext];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entity];
NSArray *array = [_app.persistentContainer.viewContext executeFetchRequest :request error:nil];
for (Dog *dog in array) {
NSLog(@"dog name:%@",dog.name);
}
}
如需条件查询可使用 NSPredicate 添加查询条件。
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name=%@",@"tom0"];
request.predicate = predicate;
删除一条数据:
- (void)deleteCoreData{
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Dog" inManagedObjectContext:_app.persistentContainer.viewContext];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
request.entity = entity;
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name=%@",@"tom0"];
request.predicate = predicate;
NSArray *array = [_app.persistentContainer.viewContext executeFetchRequest:request error:nil];
if (array.count) {
for (Dog *dog in array) {
[_app.persistentContainer.viewContext deleteObject:dog];
}
NSLog(@"DELETE SUCCESS!!");
} else
NSLog(@"NOT FOUND DATA");
}
更新某条数据:
- (void)updateCoreData{
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Dog" inManagedObjectContext:_app.persistentContainer.viewContext];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
request.entity = entity;
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name=%@",@"tom0"];
request.predicate = predicate;
NSArray *array = [_app.persistentContainer.viewContext executeFetchRequest:request error:nil];
if (array.count) {
for (Dog *dog in array) {
dog.name = @"jerry8";
}
[_app saveContext];
NSLog(@"UPDATA SUCCESS!!");
} else
NSLog(@"NOT FOUND DATA");
}
顺便问下,用chrome访问,用markdown模式写这些字,chrome崩溃十几次了,输入文字就崩,不知道是不是添加高亮代码块的锅,有没有大神遇到过!(后来这些字都是在文本编辑器写好贴上去的)
参考:http://www.jianshu.com/p/337872d95727