CoreData-二次封装（三）

衔接上两篇讲到的CoreData的使用，本篇主要介绍在实际开发中CoreData要进行二次封装，易扩展也方便使用。

创建一个继承自NSObject的类文件

1. .h文件的接口

#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>
#import "Student+CoreDataProperties.h"
@interface CoreDataManager : NSObject
// 放在.H 文件中，增删改查时让外部进行调用
@property(nonatomic,strong)NSManagedObjectContext *context;
+ (instancetype)shareManager;
- (BOOL)insertDataWithEntityName:(NSString *)entityName andDictionary:(NSDictionary *)dict;
- (NSArray *)selectRecordWithEntityName:(NSString *)entityName andPredicateString:(NSString *)predicateString andSortWithKeyArr:(NSArray *)sortKeyArr andAscending:(BOOL)ascending;
- (BOOL)deleteDataWithEntityName:(NSString *)entityName predicateString:(NSString *)predicateString;
- (BOOL)updateRecordWithEntityName:(NSString *)entityName andPredicateString:(NSString *)predicateString andSetAttributeDict:(NSDictionary*)dict;
@end

2. .m文件中的实现

#import "CoreDataManager.h"
@interface CoreDataManager()
@property(nonatomic,readwrite,strong)NSManagedObjectModel *objModel;
@property(nonatomic,readwrite,strong)NSPersistentStoreCoordinator *persistentCoordinator;
@end
@implementation CoreDataManager
static CoreDataManager *instance;
+(instancetype)shareManager{
    
    if(instance == nil){
        instance = [[super alloc] init];
    }
    return instance;
}
+(instancetype)allocWithZone:(struct _NSZone *)zone{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        instance = [super allocWithZone:zone ];
    });
    return instance;
}
-(id)copyWithZone:(NSZone *)zone{
    return instance;
}
-(id)mutableCopyWithZone:(NSZone *)zone{
    return instance;
}
#pragma mark: 注意和创建的.xcdatamodeld 文件名保持一致
- (NSManagedObjectModel *)objModel{
    if (!_objModel) {
        //      Model  保持和xcdatamodeld 文件名一致，不然modelUrl 为nil
        NSURL *modelUrl = [[NSBundle mainBundle] URLForResource:@"Model" withExtension:@"momd"];
        _objModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelUrl];
        
    }
    return _objModel;
}
#pragma mark: 根据项目情况自己命名要保存的数据库文件名字
- (NSPersistentStoreCoordinator *)persistentCoordinator{
    if (!_persistentCoordinator) {
        //        创建coordinator
        _persistentCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:self.objModel];
        //        指定数据库文件
        NSString *urlStr = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"myCoreData.sqlite"];
        NSURL *url = [NSURL fileURLWithPath:urlStr];
        NSError *error;
        [_persistentCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:url options:nil error:&error];
        if (error) {
            NSLog(@"创建持久化容器失败 %@",error);
        }
    }
    return _persistentCoordinator;
}
- (NSManagedObjectContext *)context{
    if (!_context) {
        _context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
        _context.persistentStoreCoordinator = self.persistentCoordinator;
    }
    return _context;
}
#pragma mark : 增删改查方法封装
// 可以根据具体的实体对象进行封装 就不用调用performSelector了
// 添加数据 -- 需要模型名  表名 字典数据 只能通过字典一个一个添加
- (BOOL)insertDataWithEntityName:(NSString *)entityName andDictionary:(NSDictionary *)dict {
   
//    获取实体对象
    NSManagedObject *entity = [NSEntityDescription insertNewObjectForEntityForName:entityName inManagedObjectContext:self.context];
   
// 遍历参数字典
    for (NSString *key in dict) {
//        使用kvc 赋值
//        注意key要和表中字段名保持一致，不区分大小写，但查找不到key值会崩溃
        [entity setValue:dict[key] forKey:key];
    }
    NSError *error;
    [self.context save:&error];
    if (error) {
        NSLog(@"%@",error);
        return NO;
    }else{
        return YES;
    }
    
}
- (BOOL)deleteDataWithEntityName:(NSString *)entityName predicateString:(NSString *)predicateString{
    //    获取要删除的记录
  NSArray *result = [self selectRecordWithEntityName:entityName andPredicateString:predicateString andSortWithKeyArr:nil andAscending:YES];
    for (NSManagedObject *obj in result) {
        [self.context deleteObject:obj];
    }
    NSError *error;
    [self.context save:&error];
    if (error) {
        return NO;
    }
    return  YES;
}
- (BOOL)updateRecordWithEntityName:(NSString *)entityName andPredicateString:(NSString *)predicateString andSetAttributeDict:(NSDictionary*)dict{
    
    NSArray *result = [self selectRecordWithEntityName:entityName andPredicateString:predicateString andSortWithKeyArr:nil andAscending:YES];
    for (NSManagedObject *obj in result) {
        
        for (NSString *key in dict) {
//            注意属性名和实体表的字段名要保持一致，不然会崩(但不区分大小写)
//              如果要修改的字段名，表中没有会崩溃
            [obj setValue:dict[key] forKey:key];
        }
        
    }
    NSError *error;
    [self.context save:&error];
    if (error) {
        return NO;
    }
    return YES;
}
// 返回的数据记得转模型
- (NSArray *)selectRecordWithEntityName:(NSString *)entityName andPredicateString:(NSString *)predicateString andSortWithKeyArr:(NSArray *)sortKeyArr andAscending:(BOOL)ascending{
    
    //    获取实体对象
    NSEntityDescription *entity = [NSEntityDescription entityForName:entityName inManagedObjectContext:self.context];
    
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    [request setEntity:entity];
//    创建查询条件
    if (predicateString != nil) {
         NSPredicate *predicate = [NSPredicate predicateWithFormat:predicateString];
        //    添加查询条件
        request.predicate = predicate;
    }
//    设置排序
    NSMutableArray *sortDescriptors = [NSMutableArray array];
    for (NSString *sortKey in sortKeyArr) {
        // 创建排序对象
        NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:sortKey ascending:ascending];
        // 把排序对象添加到数组中
        [sortDescriptors addObject:sortDescriptor];
        
    }
    request.sortDescriptors = sortDescriptors;
    NSArray *arr = [self.context executeFetchRequest:request error:nil];
    
    return arr;
}
@end