Simple use of coreData

My personal feeling about coreData technology is that it is troublesome, for beginners? Always use:

The three core classes of coreData:

1. Initialize the NSManagedObjectModel object, load the model file, and read all entity information in the app
2. Initialize the NSPersistentStoreCoordinator object and add a persistence library (SQLite database is used here)
3. Initialize the NSManagedObjectContext object, get the context object to operate the entity, and perform CRUD operations

1. Core creation and insertion;

self.appDelegate=[UIApplication sharedApplication ].delegate;

-(void)insertData{

    NSLog(@" start insertData()");
    
    //1, create a model
    
    //create entity description object
    NSEntityDescription *entityDesription=[NSEntityDescription entityForName:@"Product" inManagedObjectContext:self.appDelegate.managedObjectContext];
    
    //Parameter 1: NSEntityDescription specifies the model
    //Parameter two: (nullable NSManagedObjectContext *) context
    Product *product=[[Product alloc] initWithEntity:entityDesription insertIntoManagedObjectContext:self.appDelegate.managedObjectContext];
    
    //2, attribute assignment
    product.pname=@"Gold";
// int radnom=arc4random()%1000+1;//Random numbers from 1 to 1000
//    product.ccbprice=[NSNumber numberWithInt:radnom];
    
//    [self.arrayData addObject:product];
    // save the data permanently
    [self.appDelegate saveContext];
    
    NSLog(@" end insertData()");
// [self selectData];//Query data

}

operation result:

2016-03-23 22:45:53.813 CoreData2[573:10522] start insertData()

2016-03-23 22:45:53.831 CoreData2[573:10522] end insertData()

2. Query of coreData

Query data: NSFetchRequest

Sort: NSSortDescriptor

#pragma mark //Query data
-(void)selectData{
    
    //1, specify the query object
    //parameter one: query entity
    NSFetchRequest *selectRequest=[[NSFetchRequest alloc] initWithEntityName:@"Product"];
    
// //2, specify the sorting representation object
// //Parameter 1: Sort field
// //Parameter two; whether ascending order yes
//    NSSortDescriptor *sortDesriptor=[[NSSortDescriptor alloc]initWithKey:@"ccbprice" ascending:YES];
//    
// //3, set the order of the request
//    selectRequest.sortDescriptors=@[sortDesriptor];
    
    //4, execute the query
    NSError *error=nil;
    NSArray *selectResouce= [self.appDelegate.managedObjectContext executeFetchRequest:selectRequest error:&error];
    
    
    [self.arrayData addObjectsFromArray:selectResouce];
    
    for (int n=0; n<[self.arrayData count]; n++) {
        
        Product *et=[self.arrayData objectAtIndex:n];
        NSLog(@"%@--",et.pname);
    }}

operation result:

2016-03-23 22: 45: 53.832 CoreData2 [573: 10522 ] Golden--

3. The deletion of coreData All operations of coreData use the context,

After deleting the data, you must save the context, similar to the commit of the database

-(void)delectData{
  
     Product *et=[self.arrayData objectAtIndex:8];

    [self.appDelegate.managedObjectContext deleteObject:et]; //delete data
    
    // save the deleted data
    [self.appDelegate saveContext];
    
    NSLog(@"deleted");
}

operation result:

2016-03-23 22:56:32.481 CoreData2[659:17475] 黄金＋＋--

2016-03-23 22:56:32.483 CoreData2[659:17475] 删除了

4，更新数据

修改第6条的数据

-(void)updataData{ //更新数据
    
    
    Product *et=[self.arrayData objectAtIndex:5];
    
    et.pname=@"百合不是茶";
    
    //保存删除的数据
    [self.appDelegate saveContext];
    
    NSLog(@"end updataData ()");

}

运行前：

2016-03-23 23:01:12.119 CoreData2[692:20232] 黄金--

2016-03-23 23:01:12.120 CoreData2[692:20232] 黄金--

2016-03-23 23:01:12.120 CoreData2[692:20232] 黄金＋＋--

2016-03-23 23:01:12.122 CoreData2[692:20232] 删除了

2016-03-23 23:01:12.124 CoreData2[692:20232] end updataData ()

运行后：

2016-03-23 23:02:07.454 CoreData2[696:20826] 黄金--

2016-03-23 23:02:07.455 CoreData2[696:20826] 黄金--

2016-03-23 23:02:07.455 CoreData2[696:20826] 百合不是茶--

2016-03-23 23:02:07.455 CoreData2[696:20826] 黄金＋＋--

2016-03-23 23:02:07.457 CoreData2[696:20826] 删除了

2016-03-23 23:02:07.458 CoreData2[696:20826] end updataData ()

Simple use of coreData

Guess you like