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 = [ self getManagedContext ];
    
     // 获得 Student 数据表一行数据对应的模型   
    NSEntityDescription * stu =[ NSEntityDescription entityForName : @"Student" inManagedObjectContext :context];
    
    // 实例化 NSFetchRequest 对象，相当于实例化一条 SQL 语句对象
    NSFetchRequest * request  = [[NSFetchRequest alloc ] 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 = [ NSPredicate predicateWithFormat : @"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 = [context executeFetchRequest :request error : nil ];
    
    if (students. count > 0 )
    {
        NSManagedObject * obj =[students lastObject ];
        [obj setValue : @"c#" forKey : @"s_name" ];
    }
    [context save : nil ];
    [ self select ];

}