coreData中的NSFetchedResultsController 用法

//回顾一下 core data的用法

//以新建一个项目为例

1.新建项目 选择"Utility Application" -> 选择"Use Core Data"

2.点击proName.xcdatamodeld  ->  Add Entity 增加需要的实体(也就是java中的bean)

3.entity加完之后 选择工程 新建(command+n)  
     ->  选择"Core Data" 中的 "NSManagedObjectsubclass"  
     -> 勾选proName.xcdatamodeld
     -> 勾选entity
     -> create

4. AppDelegate.h 重要的三个属性变量

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

5. AppDelegate.m 中三个重要方法
   (1)
   

    - (NSManagedObjectContext *)managedObjectContext
       {...}

     - (NSManagedObjectModel *)managedObjectModel
       {...}

     - (NSPersistentStoreCoordinator *)persistentStoreCoordinator
       {...}
    

6.纯属查询
   //假设 有一个entity    Department(deptID,deptName)
   //同时 sqlite中已经有数据 我要从中取出所有的department然后放到一个数组中
   (1) DeptViewController.h
        #import <CoreData/CoreData.h>
        #import "AppDelegate.h"
        #import "Department.h"

   (2)

- (AppDelegate*)appDelegate{
    return (AppDelegate*)[UIApplication sharedApplication].delegate;
}

- (void)loadDBData{
    NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:NSStringFromClass([Doctors class])];
    
    // sort by
    NSSortDescriptor *sortID = [[NSSortDescriptor alloc] initWithKey:@"deptId" ascending:YES];
    NSSortDescriptor *sortName  = [[NSSortDescriptor alloc] initWithKey:@"deptName" ascending:YES];
    NSArray *sortArr = [NSArray arrayWithObjects:sortID, sortName, nil];
    [request setSortDescriptors:sortArr];
    
    // where
    NSPredicate *where = [NSPredicate predicateWithFormat:@"deptId == %@", @"0"];
    [request setPredicate:where];

    NSArray *resultArr = [[self appDelegate].managedObjectContext executeFetchRequest:request error:NULL];   //resultArr中的对象全部是Department类型

    self.deptArray = resultArr;
    
    [sortID     release];
    [sortName   release];
    [request    release];
}

7. 删除数据 (先后经过"查询数据"、"删除数据"、"保存数据")

- (void)deleteTable:(Class)tablename{
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *selectionItems = [NSEntityDescription entityForName:NSStringFromClass([tablename class])
                                                      inManagedObjectContext:[self appDelegate].managedObjectContext];
    fetchRequest.entity = selectionItems;
    
    NSMutableArray *items = [[NSMutableArray alloc] initWithArray:[[self appDelegate].managedObjectContext 
                                              executeFetchRequest:fetchRequest 
                                                            error:NULL]];
    while([items count] > 0) {
        id item = [items lastObject];
        [[self appDelegate].managedObjectContext deleteObject:item];
        [items removeObject:item];
    }
    
    [items release];
    [fetchRequest release];
    [[self appDelegate].managedObjectContext save:NULL];
}

8. 添加数据

- (void)insertInManagedObjectContext:(NSManagedObjectContext *)moc withData:(NSDictionary *)data{
    Department *bean = [NSEntityDescription insertNewObjectForEntityForName:NSStringFromClass([Department class])
                                                     inManagedObjectContext:moc];
    
    bean.deptId    = [data valueForKey:@"aId"];
    bean.deptName  = [data valueForKey:@"aName"];

    [moc save:NULL];
}