iOS coreData

1、笔者认为core data就是ios内置的一个操作sqlite的框架。

a、首先了解Core data的基本信息

在创建工程的时候，勾选user core data可以直接生成一些操作coreData的方法 创建《Data Model》生成创建表（实体）、属性、联系的文件。创建《NSManagedObject subclass》可直接生成表属性中的get，set方法，在实体文件中 需要注意的地方：（“实体名Dog”也是“表名”）

在使用代码操作coredata框架前，先了解core data中的几个重要对象和重要操作

操作：
a、添加CoreData框架
b、导入#import<CoreData/CoreData.h>

对象：
1、NSManagedObjectContext    管理对象，上下文，持久性存储模型对象
2、NSManagedObjectModel      被管理的数据模型，[数据结构](http://lib.csdn.net/base/31)
3、NSPersistentStoreCoordinator    连接数据库的
4、NSManagedObject    被管理的数据记录
5、NSFetchRequest    数据请求
6、NSEntityDescription    表格实体结构

注意：
tip1：需要知道.xcdatamodel文件编译后为.momd或者.mom文件。
tip2：core data的数据文件生成在沙盒的document文件夹下面。

b、使用core data的个人琢磨步骤
tip1：创建《Data Model》文件（Animations）。
tip2：在Animations中创建一个实体（表）Animate。
tip3：创建《NSManagedObject subclass》文件，生成Animate的属性文件AnimateEntity。
tip4：编写操纵core data框架的oc代码，即entity的管理文件AnimateEntityManager。

下面贴出，笔者实现AnimateEntityManager的代码

#import <Foundation/Foundation.h>
#import "AnimateEntity.h"
@interface AnimateEntityManager : NSObject

@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;

- (void)saveContext;
- (NSURL *)applicationDocumentsDirectory;

//插入数据
- (void)insertCoreData:(NSMutableArray*)dataArray;
//查询
- (NSMutableArray*)selectData:(int)pageSize andOffset:(int)currentPage;
//删除
- (void)deleteData;
//更新
- (void)updateData:(NSString*)newsId withIsLook:(NSString*)islook;

@end

#import "AnimateEntityManager.h"
@import CoreData;

#define TableName @"AnimateEntity"

@implementation AnimateEntityManager

@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;

- (void)saveContext
{
    NSError *error = nil;
    NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
    if (managedObjectContext != nil) {
        if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
            // Replace this implementation with code to handle the error appropriately.
            // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            abort();
        }
    }
}

#pragma mark - Core Data stack

// Returns the managed object context for the application.
// If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application.
- (NSManagedObjectContext *)managedObjectContext
{
    if (_managedObjectContext != nil) {
        return _managedObjectContext;
    }
    
    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (coordinator != nil) {
        _managedObjectContext = [[NSManagedObjectContext alloc] init];
        [_managedObjectContext setPersistentStoreCoordinator:coordinator];
    }
    return _managedObjectContext;
}

// Returns the managed object model for the application.
// If the model doesn't already exist, it is created from the application's model.
- (NSManagedObjectModel *)managedObjectModel
{
    if (_managedObjectModel != nil) {
        return _managedObjectModel;
    }
    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"Animations" withExtension:@"momd"];
    _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
    return _managedObjectModel;
}

// Returns the persistent store coordinator for the application.
// If the coordinator doesn't already exist, it is created and the application's store added to it.
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
    if (_persistentStoreCoordinator != nil) {
        return _persistentStoreCoordinator;
    }
    
    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"Animations.sqlite"];
    
    NSError *error = nil;
    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }
    
    return _persistentStoreCoordinator;
}

#pragma mark - Application's Documents directory

// Returns the URL to the application's Documents directory.获取Documents路径
- (NSURL *)applicationDocumentsDirectory
{
    return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}

//插入数据
- (void)insertCoreData:(NSMutableArray*)dataArray
{
//    NSLog(@"%@",NSHomeDirectory());
    NSManagedObjectContext *context = [self managedObjectContext];
    for (AnimateEntity *entity in dataArray) {
        AnimateEntity *entityInfo = [NSEntityDescription insertNewObjectForEntityForName:TableName inManagedObjectContext:context];
        entityInfo.term = entity.term;
        entityInfo.termUnit = entity.termUnit;
        NSError *error;
        if(![context save:&error])
        {
            NSLog(@"不能保存：%@",[error localizedDescription]);
        }
    }
}

//查询
- (NSMutableArray*)selectData:(int)pageSize andOffset:(int)currentPage
{
    NSManagedObjectContext *context = [self managedObjectContext];
    
    // 限定查询结果的数量
    //setFetchLimit
    // 查询的偏移量
    //setFetchOffset
    
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    
    [fetchRequest setFetchLimit:pageSize];
    [fetchRequest setFetchOffset:currentPage];
    
    NSEntityDescription *entity = [NSEntityDescription entityForName:TableName inManagedObjectContext:context];
    [fetchRequest setEntity:entity];
    NSError *error;
    NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];
    NSMutableArray *resultArray = [NSMutableArray array];
    
    for (AnimateEntity *info in fetchedObjects) {
        NSLog(@"interestBearingtime:%@", info.interestBearingtime);
        NSLog(@"projectName:%@", info.projectName);
        [resultArray addObject:info];
    }
    return resultArray;
}

//删除
-(void)deleteData
{
    NSManagedObjectContext *context = [self managedObjectContext];
    NSEntityDescription *entity = [NSEntityDescription entityForName:TableName inManagedObjectContext:context];
    
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    [request setIncludesPropertyValues:NO];
    [request setEntity:entity];
    NSError *error = nil;
    NSArray *datas = [context executeFetchRequest:request error:&error];
    if (!error && datas && [datas count])
    {
        for (NSManagedObject *obj in datas)
        {
            [context deleteObject:obj];
        }
        if (![context save:&error])
        {
            NSLog(@"error:%@",error);
        }
    }
}
//更新
- (void)updateData:(NSString*)newsId  withIsLook:(NSString*)repaymentMethoud
{
    NSManagedObjectContext *context = [self managedObjectContext];
    
    NSPredicate *predicate = [NSPredicate
                              predicateWithFormat:@"newsid like[cd] %@",newsId];
    
    //首先你需要建立一个request
    NSFetchRequest * request = [[NSFetchRequest alloc] init];
    [request setEntity:[NSEntityDescription entityForName:TableName inManagedObjectContext:context]];
    [request setPredicate:predicate];//这里相当于sqlite中的查询条件，具体格式参考苹果文档
    
    //https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/Predicates/Articles/pCreating.html
    NSError *error = nil;
    NSArray *result = [context executeFetchRequest:request error:&error];//这里获取到的是一个数组，你需要取出你要更新的那个obj
    for (AnimateEntity *info in result) {
        info.repaymentMethoud = repaymentMethoud;
    }
    
    //保存
    if ([context save:&error]) {
        //更新成功
        NSLog(@"更新成功");
    }
}

@end