IOS数据持久化之Core Data(二) - 单表操作

上篇我们简要介绍了Core Data的框架，我们对Core Data有了一个基本的认识，这些都是理论上的，下面我们做一个Demo,执行一些简单的增、删、改、查等操作。

首先我们新建一个Project,在创建的时候勾选"Use Core Data"复选框，

创建完成以后如下：

系统自动为我们创建了一个与工程同名的Data Model,打开该Model,新建一个Entity，设置Entity的Name,添加Entity的Attributes,如下图：

由于我们在创建Project的时候勾选了"Use Core Data",所以系统已经自动为我们生成了Core Date增、删、改、查的对象，首先我们看看系统自动创建好的Core Data对象,对象说明看注释，截图如下：

下面我们需要做的就是完成对数据的增、删、改、查，首先我们新建一个Student类，字段参照我们创建的Student Entity中的Attributes，代码如下：

#import <Foundation/Foundation.h>

@interface Student : NSObject

@property(nonatomic,strong)NSString *no;
@property(nonatomic,strong)NSString *studentName;
@property(nonatomic,retain)NSNumber *age;
@property(nonatomic,retain)NSNumber *sex;

@end
           

#import "Student.h"

@implementation Student

@synthesize  age;
@synthesize no;
@synthesize studentName;
@synthesize sex;

@end
           

然后我们在界面上添加四个方法，分别是数据的添加、修改、删除、查询，代码如下：

添加数据：

#pragma mark 保存数据
-(BOOL)SaveData:(Student *)stu{
    BOOL result = YES;
    NSManagedObjectContext *context =[self managedObjectContext];
    Student *student =[NSEntityDescription insertNewObjectForEntityForName:TableName inManagedObjectContext:context];

    student.no =stu.no;
    student.age = stu.age;
    student.studentName = stu.studentName;
    student.sex = stu.sex;
    
    NSError *error = nil;
    if([context save:&error]){
        result = YES;
        NSLog(@"保存数据成功");
    }else{
        result = NO;
        NSLog(@"保存数据失败");
    }
    
    return result;
}
           

修改数据：

-(BOOL)UpdateData:(NSString *)no StudentName:(NSString *)newName{
    BOOL result = YES;
    
    NSManagedObjectContext *context =[self managedObjectContext];
    
    NSPredicate *predicate =[NSPredicate predicateWithFormat:@" no like[cd] '123'"];
    
    NSFetchRequest *fetchRequest =[[NSFetchRequest alloc] init];
    NSEntityDescription *entity =[NSEntityDescription entityForName:TableName inManagedObjectContext:context];
    [fetchRequest setEntity:entity];
    [fetchRequest setPredicate:predicate];
    
    NSError *error = nil;
    NSArray *resultArr =[context executeFetchRequest:fetchRequest error:&error];
    for(Student *stu in resultArr){
        stu.studentName = newName;
    }
    if([context save:&error]){
        result = YES;
        NSLog(@"更新成功");
        
    }else{
        result = NO;
        NSLog(@"更新失败");
    }
    return result;
}
           

删除数据：

-(BOOL)DeleteData:(NSString *)no{
    BOOL result =  YES;
    
    NSManagedObjectContext *context =[self managedObjectContext];
    NSEntityDescription *entity =[NSEntityDescription entityForName:TableName inManagedObjectContext:context];
    NSPredicate *predicate =[NSPredicate predicateWithFormat:@"no like[cd] '%@'",no];
    NSFetchRequest *fetchRequest =[[NSFetchRequest alloc] init];
    //[fetchRequest setIncludesPropertyValues:NO];
    
    [fetchRequest setEntity:entity];
    [fetchRequest setPredicate:predicate];
    
    NSError *error = nil;
    
    NSArray *array =[context executeFetchRequest:fetchRequest error:&error];
    if(!error && array && [array count])
    {
        for(NSManagedObject *obj in array){
            [context deleteObject:obj];
        }
        if([context save:&error]){
            result = YES;
        }else{
            result = NO;
        }
    }
    return result;
}
           

查询：

-(NSArray *)SelectData:(int)pagesize RecordOffset:(int)currentPage{
    NSManagedObjectContext *context =[self managedObjectContext];
    NSFetchRequest *fetchRequest =[[NSFetchRequest alloc] init];
    [fetchRequest setFetchLimit:pagesize];
    [fetchRequest setFetchOffset:currentPage];
    
    NSEntityDescription *entity =[NSEntityDescription entityForName:TableName inManagedObjectContext:context];
    [fetchRequest setEntity:entity];
    NSError *error = nil;
    NSArray *array =[context executeFetchRequest:fetchRequest error:&error];
    return array;
}
           

示例代码下载

参考：

1、https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CoreData/Articles/cdTechnologyOverview.html#//apple_ref/doc/uid/TP40009296-SW1

2、https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/Predicates/Articles/pCreating.html