CoreData总结-增删改查操作

#import <CoreData/CoreData.h>
#import "AppDelegate.h"
#import "Classes.h"
#import "Student.h"
- (void)insert
{
    //获得AppDelegate对象得到NSManagedObjectContext的对象
    //    AppDelegate *delegate = [[UIApplication sharedApplication] delegate];
    //    NSManagedObjectContext *context = [delegate managedObjectContext];
    NSManagedObjectContext *context = [self getManagedContext];
    //获得管理对象来管理实体Student，找到实体结构，生成实体对象insertNewObjectForEntityForName方法，区分大小写
    NSManagedObject *stu = [NSEntityDescription insertNewObjectForEntityForName:@"Student" inManagedObjectContext:context];
    //班级实体
    //    NSManagedObject *class1 = [NSEntityDescription insertNewObjectForEntityForName:@"Classes" inManagedObjectContext:context];
    //    [class1 setValue:[NSNumber numberWithInt:1] forKey:@"c_id"];
    //    [class1 setValue:@"classOne" forKey:@"c_name"];
   
    Classes *class1 = [NSEntityDescription insertNewObjectForEntityForName:@"Classes" inManagedObjectContext:context];
    class1.c_id = [NSNumber numberWithInt:2];
    class1.c_name = @"classTwo";
   
    //给实体对象赋值
    [stu setValue:[NSNumber numberWithInt:1] forKey:@"s_id"];
    [stu setValue:@"java" forKey:@"s_name"];

    [stu setValue:class1 forKey:@"Classes"];
   
    Student *stu1 = [NSEntityDescription insertNewObjectForEntityForName:@"Student" inManagedObjectContext:nil];
    stu1.s_id = [NSNumber numberWithInt:2];
    stu1.s_name = @"c++";
   
    //调用Context,保存实体
    NSError *error;
    if([context save:&error]){
        NSLog(@"OK java in");
    }
    else{
        NSLog(@"%@",error);
    }
}

- (NSManagedObjectContext *)getManagedContext
{
    AppDelegate *delegate = [[UIApplication sharedApplication]delegate];
    NSManagedObjectContext *context = [delegate managedObjectContext];
    return context;
}

- (void)select
{
    NSManagedObjectContext *context;
    context = [self getManagedContext];
   
    //查找对象entityForName方法
    NSEntityDescription *stu = [NSEntityDescription entityForName:@"Student" inManagedObjectContext:context];
   
    //构造一个查询对象（查询对象）
    NSFetchRequest *request = [[NSFetchRequest alloc]init];
   
    //设置
    [request setEntity:stu];
   
    //执行查询，返回结果集
    NSArray *resultArray = [context executeFetchRequest:request error:nil];
   
    //遍历结果集
    for(NSManagedObject *entity in resultArray){
        NSLog(@"id = %i,name = %@,class = %@",[[entity valueForKey:@"s_id"] intValue],[entity valueForKey:@"s_name"],[[entity valueForKey:@"classes"] valueForKey:@"c_name"]);
    }
}

- (void)update
{
    //    [self insert];
    //    [self select];
   
    NSManagedObjectContext *context = [self getManagedContext];
    NSEntityDescription *stu = [NSEntityDescription  entityForName:@"Student" inManagedObjectContext:context];
    NSFetchRequest *request = [[NSFetchRequest alloc]init];
    [request setEntity:stu];
   
    //构造查询条件，相当于where语句
    NSPredicate *perdicate = [NSPredicate predicateWithFormat:@"s_id=%d",1];
    [request setPredicate:perdicate];
   
    //*代表任意个字符，含有le的字符
    NSPredicate *p1 = [NSPredicate predicateWithFormat:@"s_name like '*%@'",@"le"];
    //？代表一个字符，第一个字符随意，紧着着含有le的
    NSPredicate *p2 = [NSPredicate predicateWithFormat:@"s_name like '？%@'",@"le"];
    //查询1-10
    NSPredicate *p3 = [NSPredicate predicateWithFormat:@"s_name between{1,10}"];
    //classes.c_name = 'classOne'
    //s_name beginWith 'yang' = =s_name like 'yang*'(开头结尾和包含)ednWith,contains
   
    //执行查询
    NSArray *students = [context executeFetchRequest:request error:nil];
    if (students.count>0) {
        NSManagedObject *obj = [students lastObject];
        [obj setValue:@"ios" forKey:@"s_name"];
       
    }
    [context save:nil];
    [self select];
   
}
- (void)delete
{
    NSManagedObjectContext *context = [self getManagedContext];
    NSEntityDescription *stu = [NSEntityDescription  entityForName:@"Student" inManagedObjectContext:context];
    NSFetchRequest *request = [[NSFetchRequest alloc]init];
    [request setEntity:stu];
   
    //构造查询条件，相当于where语句
    NSPredicate *perdicate = [NSPredicate predicateWithFormat:@"s_id=%d",1];
    [request setPredicate:perdicate];
   
    //执行查询
    NSArray *students = [context executeFetchRequest:request error:nil];
    if (students.count>0) {
       
        [context deleteObject:[students lastObject]];
        [context save:nil];
    }

}

- (void)upDate {
    NSManagedObjectContext * context = [selfgetManagedContext];
    
     //获得Student数据表一行数据对应的模型  
    NSEntityDescription * stu =[ NSEntityDescriptionentityForName:@"Student"inManagedObjectContext:context];
    
    //实例化NSFetchRequest对象，相当于实例化一条SQL语句对象
    NSFetchRequest * request  = [[NSFetchRequestalloc]init];
    
    //设置SQL语句将要操作的数据模型
    [request setEntity:stu];
    
    //构造查询条件，相当于where字句
    NSPredicate * predicate = [NSPredicatepredicateWithFormat:@"s_id=%i",1];
    
    //将查询条件添加到predicate中，相当于sql语句中
    [request setPredicate:predicate];
    
    NSArray* students = [contextexecuteFetchRequest:requesterror:nil];
    
    if(students.count>0)
    {
        NSManagedObject * obj =[studentslastObject];
        [obj setValue:@"c#"forKey:@"s_name"];
    }
    [context save:nil];
    [selfselect];

}