CoreData入门

本文作为笔者自己的备忘录，由浅至深的记录学习过程

一：添加库

二：添加CoreDataHelper类

.h文件

//
//  CoreDataHelper.h
//  CoreDate学习
//
//  Created by 王一 on 2016/11/28.
//  Copyright © 2016年 wangyi. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>

@interface CoreDataHelper : NSObject

@property(nonatomic,strong,readonly)NSManagedObjectContext *context;
@property(nonatomic,strong,readonly)NSManagedObjectModel *model;
@property(nonatomic,strong,readonly)NSPersistentStoreCoordinator *coordinator;
@property(nonatomic,strong,readonly)NSPersistentStore   *store;

-(void)setupCoreData;
-(void)saveContext;

@end

.m文件

//
//  CoreDataHelper.m
//  CoreDate学习
//
//  Created by 王一 on 2016/11/28.
//  Copyright © 2016年 wangyi. All rights reserved.
//
#define debug 1
#import "CoreDataHelper.h"

@implementation CoreDataHelper

#pragma mark - FILES
//存储文件名
NSString *storeFilename = @"2016121.sqlite";

#pragma mark - PATHS
//程序文档目录路径
-(NSString *)applicationDocumentsDirectory{
    if (debug == 1) {
        NSLog(@"Running %@ '%@'",self.class,NSStringFromSelector(_cmd));
    }
    return [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
}

//向应用程序文档目录中添加名为Stores的子目录
-(NSURL *)applicationStoresDirectory{
    if (debug == 1) {
        NSLog(@"Running %@ '%@'",self.class,NSStringFromSelector(_cmd));
    }
    NSURL *storesDirectory = [[NSURL fileURLWithPath:[self applicationDocumentsDirectory]] URLByAppendingPathComponent:@"Stores"];
    NSFileManager *fileManager = [NSFileManager defaultManager];
    if (![fileManager fileExistsAtPath:[storesDirectory path]]) {
        NSError *error = nil;
        if ([fileManager createDirectoryAtURL:storesDirectory withIntermediateDirectories:YES attributes:nil error:&error]) {
            if (debug == 1) {
                NSLog(@"Successfully created Stores directory");
            }
        }else{
            NSLog(@"FAILED to create Stores directory: %@",error);
        }
    }
    return storesDirectory;
}

//存储区的文件名添加到Store目录的路径中
-(NSURL *)storeURL{
    if (debug == 1) {
        NSLog(@"Running %@ '%@'",self.class,NSStringFromSelector(_cmd));
    }
    return [[self applicationStoresDirectory] URLByAppendingPathComponent:storeFilename];
}

#pragma mark - SETUP
//初始化Core Data三个方法
-(id)init{
    if (debug == 1) {
        NSLog(@"Running %@ '%@'",self.class,NSStringFromSelector(_cmd));
    }
    self = [super init];
    if (self == nil) {
        return nil;
    }
    _model = [NSManagedObjectModel mergedModelFromBundles:nil];
    _coordinator = [[NSPersistentStoreCoordinator alloc]initWithManagedObjectModel:_model];
    _context = [[NSManagedObjectContext alloc]initWithConcurrencyType:NSMainQueueConcurrencyType];
    [_context setPersistentStoreCoordinator:_coordinator];
    return self;
}

-(void)loadStore{
    if (debug == 1) {
        NSLog(@"Running %@ '%@'",self.class,NSStringFromSelector(_cmd));
    }
    if (_store) {
        return;
    }
    
    NSDictionary *options = @{
                              NSMigratePersistentStoresAutomaticallyOption:@YES,
                              NSInferMappingModelAutomaticallyOption:@YES,
                              NSSQLitePragmasOption: @{@"journal_mode": @"DELETE"}
                              };
    
    NSError *error = nil;
    _store = [_coordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:[self storeURL] options:options error:&error];
    if (_store == nil) {
        NSLog(@"Failed to add store.Error:%@",error);
        abort();
    }else{
        if (debug == 1) {
            NSLog(@"Successfully added store: %@",_store);
        }
    }
}

-(void)setupCoreData{
    if (debug == 1) {
        NSLog(@"Running %@ '%@'",self.class,NSStringFromSelector(_cmd));
    }
    [self loadStore];
}

#pragma mark - SAVING

-(void)saveContext{
    if (debug == 1) {
        NSLog(@"Running %@ '%@'",self.class,NSStringFromSelector(_cmd));
    }
    if ([_context hasChanges]) {
        NSError *error = nil;
        if ([_context save:&error]) {
            NSLog(@"_context SAVED changes to persistent store");
        }else{
            NSLog(@"Failed to save _context: %@",error);
        }
    }else{
        NSLog(@"SKIPPED _context save,there are no changes!");
    }
}
@end

三：添加、删除、排序、筛选的一些简单操作

注意：排序和筛选很少会写代码，用的是Xcode请求模板，功能强大，简单，这里只是为了记录

    //插入数据
    NSArray *namesArray = [NSArray arrayWithObjects:@"a王一", @"a刘洋", @"c陈攀科", @"b韩熙", @"e赵密柱", @"f王楠侠", @"g沈建", @"h付晓奎", nil];
    for (NSString *nameString in namesArray) {
        Item *itemArray = [NSEntityDescription insertNewObjectForEntityForName:@"Item" inManagedObjectContext:_coreDataHelper.context];
        itemArray.name = nameString;
        NSLog(@"%@",itemArray.name);
    }

    //获取数据
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Item"];
    NSArray *array = [_coreDataHelper.context executeFetchRequest:request error:nil];
    for (Item *itemArray in array) {
        NSLog(@"itemArray = %@",itemArray.name);
    }

    //排序
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Item"];
    NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"name" ascending:YES];
    [request setSortDescriptors:[NSArray arrayWithObject:sort]];
    NSArray *array = [_coreDataHelper.context executeFetchRequest:request error:nil];
    for (Item *itemArray in array) {
        NSLog(@"itemArray = %@",itemArray.name);
    }

    //查找筛选 前50条
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Item"];
    NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"name" ascending:YES];
    [request setSortDescriptors:[NSArray arrayWithObject:sort]];
    [request setFetchLimit:50];
    NSPredicate *filer = [NSPredicate predicateWithFormat:@"name != %@",@"一"];
    [request setPredicate:filer];
    NSArray *array = [_coreDataHelper.context executeFetchRequest:request error:nil];
    for (Item *itemArray in array) {
        NSLog(@"itemArray = %@",itemArray.name);
    }