一.可以将oc对象转换成数据保存到sqlite数据库中，也可以将数据库数据还原成oc对象
coredata用的对象结构图如下
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二.实现步骤
第一步 构建模型，并自动创建被管理的实体类。同时构建与之对应的未被管理的实体类
1.构建模型
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2.自动创建被管理的实体类（ NSManagedObject对象）
xcode8 按如下方法创建NSManagedObject subclass
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3.构建与之对应的未被管理的实体类
// Note.h
#import <Foundation/Foundation.h>
@interface Note : NSObject <NSCoding>
@property(nonatomic, strong) NSDate *date;
@property(nonatomic, strong) NSString *content;
- (instancetype)initWithDate:(NSDate *)date content:(NSString *)content;
- (instancetype)init;
@end
// Note.m
#import "Note.h"
@implementation Note
- (instancetype)initWithDate:(NSDate *)date content:(NSString *)content {
self = [super init];
if (self) {
_date = date;
_content = content;
}
return self;
}
- (instancetype)init {
self = [super init];
if (self) {
_date = [[NSDate alloc] init];
_content = @"";
}
return self;
}
#pragma mark--实现NSCoding协议
- (void)encodeWithCoder:(NSCoder *)aCoder {
[aCoder encodeObject:_date forKey:@"date"];
[aCoder encodeObject:_content forKey:@"content"];
}
- (instancetype)initWithCoder:(NSCoder *)aDecoder {
_date = [aDecoder decodeObjectForKey:@"date"];
_content = [aDecoder decodeObjectForKey:@"content"];
return self;
}
@end
第二步：构建持久化操作类（实现上下文，协调器，管理模型三个属性接口，同时实现保存修改接口 saveContext）
// CoreDataDAO.h （(Data Access Objects) 数据访问对象）
#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>
@interface CoreDataDAO : NSObject
//被管理的对象上下文
@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;
//持久化存储协调者
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;
//被管理的对象模型
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;
//保存数据
- (void)saveContext;
@end
// CoreDataDAO.m
#import "CoreDataDAO.h"
@interface CoreDataDAO(filePath)
//获得应用程序沙箱Document目录
- (NSURL *)applicationDocumentsDirectory;
@end
@implementation CoreDataDAO(filePath)
//获得应用程序沙箱Document目录
- (NSURL *)applicationDocumentsDirectory {
return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}
@end
@implementation CoreDataDAO
@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;
#pragma mark - Core Data 堆栈
//返回被管理对象上下文
- (NSManagedObjectContext *)managedObjectContext {
if (_managedObjectContext != nil) {
return _managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (!coordinator) {
return nil;
}
_managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
//1.绑定协调器
[_managedObjectContext setPersistentStoreCoordinator:coordinator];
return _managedObjectContext;
}
//返回持久化存储协调器
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
if (_persistentStoreCoordinator) {
return _persistentStoreCoordinator;
}
//2.绑定数据库
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"CoreDataNotes.sqlite"];
//3.和模型绑定
_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
NSError *error = nil;
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
NSLog(@"加载数据失败");
abort();
}
return _persistentStoreCoordinator;
}
//返回被管理对象模型
- (NSManagedObjectModel *)managedObjectModel {
if (_managedObjectModel != nil) {
return _managedObjectModel;
}
//4.获得当前工程的bundle
NSBundle *frameworkBundle = [NSBundle bundleForClass:[CoreDataDAO class]];
//4.1后缀是momd 不是xcdatamodelid
NSURL *modelURL = [frameworkBundle URLForResource:@"CoreDataNotes" withExtension:@"momd"];
//5.绑定模型原件
_managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return _managedObjectModel;
}
#pragma mark -保存数据
- (void)saveContext {
NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
if (managedObjectContext != nil) {
NSError *error = nil;
//6.有修改保存
if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
NSLog(@"数据保存错误：%@", error.localizedDescription);
abort();
}
}
}
@end
第三步：实现持久化操作类的增删查改
// NoteDAO.h
#import <Foundation/Foundation.h>
#import "Note.h"
#import "CoreDataDAO.h"
@interface NoteDAO : CoreDataDAO
+ (NoteDAO*)sharedInstance;
//查询所有数据
-(NSMutableArray*) findAll;
//有条件查询
-(Note*) findById:(Note*)model;
//插入Note方法
-(int) create:(Note*)model;
//删除Note方法
-(int) remove:(Note*)model;
//修改Note方法
-(int) modify:(Note*)model;
@end
// NoteDAO.m
#import <CoreData/CoreData.h>
#import "NoteDAO.h"
#import "NoteManagedObject+CoreDataClass.h"
@interface NoteDAO()
@property (nonatomic,strong) NSDateFormatter *dateFormatter;//日期格式化
@end
@implementation NoteDAO
static NoteDAO *sharedSingleton = nil;
+ (NoteDAO *)sharedInstance {
static dispatch_once_t once;
dispatch_once(&once, ^{
sharedSingleton = [[self alloc] init];
//初始化DateFormatter
sharedSingleton.dateFormatter = [[NSDateFormatter alloc] init];
[sharedSingleton.dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
});
return sharedSingleton;
}
//查询所有数据
- (NSMutableArray *)findAll
{
NSMutableArray *result = nil;
NSManagedObjectContext *cxt = [self managedObjectContext];
//1.构建fetchRequest （数据提取请求类）
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Note" inManagedObjectContext:cxt];
//1.1 请求实体
fetchRequest.entity = entity;
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:TRUE];
NSArray *sortDescriptors = @[sortDescriptor];
//1.2 请求排序
fetchRequest.sortDescriptors = sortDescriptors;
NSError *error = nil;
//2.请求返回结果集
NSArray *listData = [cxt executeFetchRequest:fetchRequest error:&error];
if (!error) {
NSMutableArray *resListData = [[NSMutableArray alloc] init];
//3.获取被管理的实体对象ManagedObject（a.ManagedObject是模型自动创建被管理的类，note是自己创建的未被管理，两者一一对应。b.a.ManagedObject只在数据持久层使用，note也可以在表示层）
for (NoteManagedObject *mo in listData) {
Note *note = [[Note alloc] initWithDate:mo.date content:mo.content];
[resListData addObject:note];
}
result = resListData;
}
return result;
}
//有条件查询（按照主键查询数据方法）
- (Note *)findById:(Note *)model
{
Note * result = nil;
NSManagedObjectContext *cxt = [self managedObjectContext];
//1.构建fetchRequest （数据提取请求类）
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Note" inManagedObjectContext:cxt];
//1.1实体
fetchRequest.entity = entity;
//1.2 设置查询条件
fetchRequest.predicate = [NSPredicate predicateWithFormat: @"date = %@",model.date];
NSError *error = nil;
//2.请求返回结果集
NSArray *listData = [cxt executeFetchRequest:fetchRequest error:&error];
//3.获取被管理的实体对象ManagedObject，建立与之对应的未被管理的实体类
if (error == nil && [listData count] > 0) {
NoteManagedObject *mo = [listData lastObject];
Note *note = [[Note alloc] initWithDate:mo.date content:mo.content];
result = note;
}
return result;
}
//插入Note方法
- (int)create:(Note *)model
{
NSManagedObjectContext *cxt = [self managedObjectContext];
//1.创建一个被管理的note对象
NoteManagedObject *note = [NSEntityDescription insertNewObjectForEntityForName:@"Note" inManagedObjectContext:cxt];
note.date = model.date;
//1.1或者用如下方法设置
// [note setValue:model.date forKey:@"date"];
note.content = model.content;
//2.保存数据，同步到持久化数据文件中
[self saveContext];
return 0;
}
//删除Note方法
- (int)remove:(Note *)model
{
NSManagedObjectContext *cxt = [self managedObjectContext];
//1.构建fetchRequest （数据提取请求类）
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Note" inManagedObjectContext:cxt];
//1.1实体
[request setEntity:entityDescription];
//1.2 设置删除条件
request.predicate = [NSPredicate predicateWithFormat: @"date = %@", model.date];
NSError *error = nil;
//2.查出要删除的实体（所以和查询很像），再删除
NSArray *listData = [cxt executeFetchRequest:request error:&error];
if (error == nil && [listData count] > 0) {
NoteManagedObject *note = [listData lastObject];
//3.删除
[self.managedObjectContext deleteObject:note];
//4.保存修改数据
[self saveContext];
}
return 0;
}
//修改Note方法
- (int)modify:(Note *)model {
NSManagedObjectContext *cxt = [self managedObjectContext];
//1.构建fetchRequest （数据提取请求类）
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Note" inManagedObjectContext:cxt];
//1.1实体
[request setEntity:entityDescription];
//1.2 设置修改条件
NSPredicate *predicate = [NSPredicate predicateWithFormat: @"date = %@", model.date];
[request setPredicate:predicate];
NSError *error = nil;
//2.查出要修改的实体（所以和查询很像），再修改
NSArray *listData = [cxt executeFetchRequest:request error:&error];
if (error == nil && [listData count] > 0) {
//3.修改
NoteManagedObject *note = [listData lastObject];
note.content = model.content;
//4.保存修改数据
[self saveContext];
}
return 0;
}
@end
ps:coreData绑定的数据库存在如下文件里面（需要第三方工具查看）
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