iOS_SN_CoreDate(一)封装使用

看过一篇封装CoreData的文章挺不错，有基本使用封装，但是没有写怎么与tableView结合使用，我自己用的过程有些小波折，自己做了一个demo，大家可以看源码一些基本使用应该不难了，

原文：http://blog.csdn.net/pengyuan_d/article/details/40657225?utm_source=tuicool&utm_medium=referral

（1）创建一个Data Model文件，命名为MyModel.xcdatamodeld

（2）创建Users表，添加如图的字段

（3）创建NSManagedObject subclass表实体文件

（4）在Users.m文件中，覆写description方法

CoreDataDBHelper.h

#import <Foundation/Foundation.h>

#import <CoreData/CoreData.h>  

// 本地文件存储的路径

#define PATH [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/sqlite.db"]  

#define MODEL_NAME @"MyModel"  

@interface CoreDataDBHelper : NSObject

{

    // 1.数据模型对象

    NSManagedObjectModel *_managedObjectModel;  

    // 2.创建本地持久文件对象

    NSPersistentStoreCoordinator *_persistentStoreCoordinator;  

    // 3.管理数据对象

    NSManagedObjectContext *_managedObjectContext;

}  

// 设计成单例模式

+ (CoreDataDBHelper *)shareCoreDataDBHelper;  

// 添加数据的方法

- (BOOL)insertDataWithModelName:(NSString *)modelName

          setAttributWithDic:(NSDictionary *)params;  

// 查看

/*

    modelName           :实体对象类的名字

    predicateString     :谓词条件

    identifers          :排序字段集合

    ascending           :是否升序

 */

- (NSArray *)selectDataWithModelName:(NSString *)modelName

                     predicateString:(NSString *)predicateString

                                sort:(NSArray *)identifers

                           ascending:(BOOL)ascending;  

// 修改

- (BOOL)updateDataWithModelName:(NSString *)modelName

                predicateString:(NSString *)predicateString

             setAttributWithDic:(NSDictionary *)params;  

// 删除

- (BOOL)deleteDataWithModelName:(NSString *)modelName

                predicateString:(NSString *)predicateString;  

@end

CoreDataDBHelper.m


#import "CoreDataDBHelper.h"  

@implementation CoreDataDBHelper  

- (instancetype)init

{

    self = [super init];

    if (self)

    {

        // 1.数据模型对象

        NSURL *modelUrl = [[NSBundle mainBundle] URLForResource:MODEL_NAME withExtension:@"momd"];

        _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelUrl];  

        // 2.创建本地持久文件对象

        _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:_managedObjectModel];

        // 设置本地数据的保存位置

        NSURL *fileUrl = [NSURL fileURLWithPath:PATH];  

        [_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:fileUrl options:nil error:nil];  

        // 3.管理数据对象

        _managedObjectContext = [[NSManagedObjectContext alloc] init];

        [_managedObjectContext setPersistentStoreCoordinator:_persistentStoreCoordinator];

    }

    return self;

}  

// 设计成单例模式

+ (CoreDataDBHelper *)shareCoreDataDBHelper

{

    static CoreDataDBHelper *coreDataDBHelper = nil;

    static dispatch_once_t onceToken;

    dispatch_once(&onceToken, ^{

        coreDataDBHelper = [[CoreDataDBHelper alloc] init];

    });  

    return coreDataDBHelper;

}  

// 添加数据的方法

/*

    params : @{

                  @"name":@"张三"，

                  @"age":@20

             }

 */

- (BOOL)insertDataWithModelName:(NSString *)modelName

             setAttributWithDic:(NSDictionary *)params

{

    NSEntityDescription *entity = [NSEntityDescription insertNewObjectForEntityForName:modelName inManagedObjectContext:_managedObjectContext];  

    // 遍历参数字典

    for (NSString *key in params)

    {

        SEL selector = [self selWithKeyName:key];

        if ([entity respondsToSelector:selector])

        {

            [entity performSelector:selector withObject:params[key]];

        }

    }

    [_managedObjectContext insertObject:entity];  

    // 保存到本地

    return [_managedObjectContext save:nil];

}  

// 查看

/*

 modelName           :实体对象类的名字

 predicateString     :谓词条件

 identifers          :排序字段集合

 ascending           :是否升序

 */

- (NSArray *)selectDataWithModelName:(NSString *)modelName

                     predicateString:(NSString *)predicateString

                                sort:(NSArray *)identifers

                           ascending:(BOOL)ascending

{

    // 1.创建实体对象

    NSEntityDescription *entity = [NSEntityDescription entityForName:modelName inManagedObjectContext:_managedObjectContext];  

    // 2.创建一个查询对象

    NSFetchRequest *request = [[NSFetchRequest alloc] init];

    // 告诉查询对象你要查询的数据类型

    [request setEntity:entity];  

    // 添加查询条件

    if (predicateString != nil || [predicateString isEqualToString:@""])

    {

        NSPredicate *predicate = [NSPredicate predicateWithFormat:predicateString];

        [request setPredicate:predicate];

    }  

    // 3.设置排序

    NSMutableArray *sortDescriptors = [NSMutableArray array];

    for (NSString *identifer in identifers)

    {

        // 创建排序对象

        NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:identifer ascending:ascending];

        // 把排序对象添加到数组中

        [sortDescriptors addObject:sortDescriptor];

    }

    // 把排序对象设置到查询对象里面

    [request setSortDescriptors:sortDescriptors];  

    // 3.开始查询

    return [_managedObjectContext executeFetchRequest:request error:nil];

}  

// 修改

- (BOOL)updateDataWithModelName:(NSString *)modelName

                predicateString:(NSString *)predicateString

             setAttributWithDic:(NSDictionary *)params

{

    // 获取所有需要修改实体对象

    NSArray *entitys = [self selectDataWithModelName:modelName predicateString:predicateString sort:nil ascending:NO];  

    // 遍历所有的实体对象

    for (NSEntityDescription *entity in entitys)

    {

        // 修改对象的属性

        for (NSString *key in params)

        {

            SEL selector = [self selWithKeyName:key];

            if ([entity respondsToSelector:selector])

            {

                [entity performSelector:selector withObject:params[key]];

            }

        }

    }  

    return [_managedObjectContext save:nil];  

}  

// 删除

- (BOOL)deleteDataWithModelName:(NSString *)modelName

                predicateString:(NSString *)predicateString

{

    // 获取所有需要修改实体对象

    NSArray *entitys = [self selectDataWithModelName:modelName predicateString:predicateString sort:nil ascending:NO];  

    // 遍历所有的实体对象

    for (NSEntityDescription *entity in entitys)

    {

        // 删除对象

        [_managedObjectContext deleteObject:entity];  

    }  

    return [_managedObjectContext save:nil];

}  

// 通过一个字符串反回一个set方法

- (SEL)selWithKeyName:(NSString *)keyName

{

    NSString *first = [[keyName substringToIndex:1] uppercaseString];

    NSString *end = [keyName substringFromIndex:1];

    NSString *selString = [NSString stringWithFormat:@"set%@%@:",first,end];

    return NSSelectorFromString(selString);

}  

@end

本文GitHub地址https://github.com/zhangkiwi/iOS_SN_CoreData

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