• 以前簡(jiǎn)單學(xué)習(xí)過(guò)coredata，但是在公司這么時(shí)間不用了，又感覺(jué)快忘記了，今天就拿點(diǎn)時(shí)間出來(lái)復(fù)習(xí)下coredata
• 本文只是簡(jiǎn)單的復(fù)習(xí)下coredata苫费，涉及到的內(nèi)容也只是數(shù)據(jù)庫(kù)的增刪改查這些基本操作

用coredata必須知道的幾個(gè)概念
/*
 1 、NSManagedObjectContext 管理對(duì)象双抽，上下文百框，持久性存儲(chǔ)模型對(duì)象
 2、NSManagedObjectModel 被管理的數(shù)據(jù)模型牍汹，數(shù)據(jù)結(jié)構(gòu)
 3铐维、NSPersistentStoreCoordinator 連接數(shù)據(jù)庫(kù)的
 4柬泽、NSManagedObject 被管理的數(shù)據(jù)記錄
 5、NSFetchRequest 數(shù)據(jù)請(qǐng)求
 6嫁蛇、NSEntityDescription 表格實(shí)體結(jié)構(gòu)
 */

//
//  ViewController.m
//  CoreData1
//
//  Created by liyang on 16/5/18.
//  Copyright ? 2016年 liyang. All rights reserved.
//

#import "ViewController.h"
#import "AppDelegate.h"
#import <CoreData/CoreData.h>
#import "Person.h"

@interface ViewController ()

/** appdelegate */
@property (nonatomic, strong) AppDelegate *myAppDelegate;
/** 創(chuàng)建一個(gè)上下文的管理對(duì)象 */
@property (nonatomic, strong) NSManagedObjectContext *myContext;
/** 數(shù)據(jù)源數(shù)組 */
@property (nonatomic, strong) NSMutableArray *allDataArray;

@end

@implementation ViewController

/*
 1 锨并、NSManagedObjectContext 管理對(duì)象，上下文睬棚，持久性存儲(chǔ)模型對(duì)象
 2琳疏、NSManagedObjectModel 被管理的數(shù)據(jù)模型，數(shù)據(jù)結(jié)構(gòu)
 3闸拿、NSPersistentStoreCoordinator 連接數(shù)據(jù)庫(kù)的
 4、NSManagedObject 被管理的數(shù)據(jù)記錄
 5书幕、NSFetchRequest 數(shù)據(jù)請(qǐng)求
 6新荤、NSEntityDescription 表格實(shí)體結(jié)構(gòu)
 */

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 初始化
    self.myAppDelegate = [UIApplication sharedApplication].delegate;
    self.myContext = self.myAppDelegate.managedObjectContext;
    self.allDataArray = [NSMutableArray array];
    
    // 刪除所有的數(shù)據(jù)
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
    NSArray *arr = [self.myContext executeFetchRequest:request error:nil];
    for (Person *per in arr) {
        [self.myContext deleteObject:per];
    }
    [self.myAppDelegate saveContext];
}

#pragma mark - 增
- (IBAction)btn1:(id)sender {
    
    // 創(chuàng)建一個(gè)實(shí)體描述對(duì)象
    NSEntityDescription *personDes = [NSEntityDescription entityForName:@"Person" inManagedObjectContext:self.myContext];
    
    // 創(chuàng)建多個(gè)數(shù)據(jù)
    for (int i = 0; i < 10; i++) {
        // 創(chuàng)建一個(gè)Person對(duì)象
        Person *person = [[Person alloc] initWithEntity:personDes insertIntoManagedObjectContext:self.myContext];
        person.name = [NSString stringWithFormat:@"liyang--%d", i];
        person.age = [NSNumber numberWithInt:i];
        [self.myContext insertObject:person];
        
        // 加到數(shù)組中
        [self.allDataArray addObject:person];
    }
    
    [self.myAppDelegate saveContext];
}
#pragma mark - 查
- (IBAction)btn2:(id)sender {
    
    // 查詢(xún)表中數(shù)據(jù)
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
    // 排序
    NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"age" ascending:NO];
    [request setSortDescriptors:@[sort]];
    
    // 按條件查詢(xún)
//    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"age = %@", @23];
//    [request setPredicate:predicate];
    
    NSError *error;
    // 查詢(xún)，注意返回的結(jié)果是數(shù)組
    NSArray *arr = [self.myContext executeFetchRequest:request error:&error];
    if (!error) {
        for (Person *per in arr) {
            NSLog(@" %@, %@", per.age, per.name);
        }
    }
}
#pragma mark - 改
- (IBAction)btn3:(id)sender {
    Person *per = [self.allDataArray objectAtIndex:0];
    if (per) {
        per.name = @"superMan";
        per.age = @1;
        [self.myAppDelegate saveContext];
    }
}

#pragma mark - 刪
- (IBAction)btn4:(id)sender {
    Person *per = [self.allDataArray lastObject];
    if (per) {
        [self.myContext deleteObject:per];
        [self.allDataArray removeObject:per];
        [self.myAppDelegate saveContext];
    }
}

@end

• 在創(chuàng)建工程的時(shí)候記得勾選coredata台汇，不然自己從新建還是挺麻煩的

• 經(jīng)常忘記在表中建的實(shí)體怎么導(dǎo)出苛骨，這其實(shí)就是com+N,選擇coredata，建個(gè)子類(lèi)苟呐，然后全部勾選痒芝，下一步，全部勾選牵素，下一步的事情
  

  創(chuàng)建子類(lèi).png

• 如上圖