iOS数据持久化(三)--- CoreData

第1步:首先在创建项目的时候必须把Use Core Data 选上


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1.1 新建的工程就会有一个Coredata.xcdatamodeld文件


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1.2如果忘记选User Core Data,还可以另外创建一个.xcdatamodeld文件


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第2步 创建实体


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2.1创建实体关联的操作对象
/注意/
xcode8.0后 自定义的实体关联的操作对象默认swift语言更改

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2.2然后就会生成四个文件

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第3步:新建一个单例 StudentManager
StudentManager.h文件:

#import <Foundation/Foundation.h>
#import "Student+CoreDataProperties.h"
#import "User.h"
@interface StudentManager : NSObject

@property(nonatomic, strong) User *user;
+(id)shareInstance;
//添加数据
#if 0
-(Student *)insertData:(NSDictionary *)stu;
#else
-(Student *)insertData:(User *)user;
#endif

//删除数据
-(BOOL)deleteDataWithName:(NSString *)name;

//查找数据
-(Student *)qureyDataWithName:(NSString *)name;

//改动数据
-(BOOL)upadateDataWithNewData:(User *)newUser OldName:(NSString *)oldName;

//加载整个存储的数据源
-(NSArray *)loadAllData;
@end

StudentManager.m文件:

#import "StudentManager.h"
#import "AppDelegate.h"
@implementation StudentManager

+(id)shareInstance{
    static StudentManager *studentManager;
    static dispatch_once_t onceTonken;
    dispatch_once(&onceTonken, ^{
        studentManager = [[StudentManager alloc]init];
        
    });
    return studentManager;
}
-(AppDelegate *)delegate{
    return (AppDelegate *)[[UIApplication sharedApplication] delegate];
}

#if 0
#pragma mark --- 添加数据  字典形式
-(Student *)insertData:(NSDictionary *)dict{
    NSError *error;
    NSManagedObjectContext *managerContext = [self delegate].persistentContainer.viewContext;
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Student" inManagedObjectContext:managerContext];
    Student *yonger = [(Student *)[NSManagedObject alloc]initWithEntity:entity insertIntoManagedObjectContext:managerContext];
    
    NSLog(@"++++%@",dict);
    yonger.name = dict[@"name"];
    yonger.age = dict[@"age"] ;
    yonger.phone = dict[@"phone"];
    
    BOOL result = [[self delegate].persistentContainer.viewContext save:&error];
    if (result) {
        return yonger;
    }
    return nil;
}
#else
-(Student *)insertData:(User *)user{
    NSError *error;
    NSManagedObjectContext *managerContext = [self delegate].persistentContainer.viewContext;
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Student" inManagedObjectContext:managerContext];
    Student *yonger = [(Student *)[NSManagedObject alloc]initWithEntity:entity insertIntoManagedObjectContext:managerContext];
    
    NSLog(@"++++%@",user.name);
    yonger.name = user.name;
    yonger.age = user.age ;
    yonger.phone = user.phone;
    
    BOOL result = [[self delegate].persistentContainer.viewContext save:&error];
    if (result) {
        return yonger;
    }
    return nil;
}
#endif
-(NSArray *)loadAllData{
    //创建请求
    NSFetchRequest *request = [[NSFetchRequest alloc]init];
    //设置需要查询的实体对象
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Student" inManagedObjectContext:[self delegate].persistentContainer.viewContext];
    //设置请求实体
    [request setEntity:entity];
    NSError *error = nil;
    NSArray *infos = [[[self delegate].persistentContainer.viewContext executeFetchRequest:request error:&error] mutableCopy];
    if (!error) {
        return infos;
    }
    return nil;
}
//删除 根据姓名删除
-(BOOL)deleteDataWithName:(NSString *)name{ 
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name = %@",name];
    NSFetchRequest *request = [[NSFetchRequest alloc]init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Student" inManagedObjectContext:[self delegate].persistentContainer.viewContext];
    [request setEntity:entity];
    [request setPredicate:predicate];
    [request setFetchLimit:1];
    NSError *error = nil;
    NSArray *infos = [[[self delegate].persistentContainer.viewContext executeFetchRequest:request error:&error] mutableCopy];
    if (infos == nil) {
        return NO;
    }
    for (Student *stu in infos) {
        [[self delegate].persistentContainer.viewContext deleteObject:stu];
        [[self delegate].persistentContainer.viewContext save:&error];
    }
   
    return NO;
}
//查询
-(Student *)qureyDataWithName:(NSString *)name{
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name = %@",name];
    NSFetchRequest *request = [[NSFetchRequest alloc]init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Student" inManagedObjectContext:[self delegate].persistentContainer.viewContext];
    [request setEntity:entity];
    [request setPredicate:predicate];
    [request setFetchLimit:1];
    NSError *error = nil;
    NSArray *infos = [[[self delegate].persistentContainer.viewContext executeFetchRequest:request error:&error] mutableCopy];
    if (infos == nil) {
        NSLog(@"查找不到");
        return nil;
    }
    for (Student *stu in infos) {
        
        return stu;
    }
    return nil;
}
//更新
-(BOOL)upadateDataWithNewData:(User *)newUser OldName:(NSString *)oldName{
    NSError *error;
    //先查找旧数据
    Student *oldstudent = [self qureyDataWithName:oldName];
    oldstudent.name = newUser.name;
    oldstudent.age = newUser.age;
    oldstudent.phone = newUser.phone;
    
    BOOL result = [[self delegate].persistentContainer.viewContext save:&error];
    if (result) {
        NSLog(@"更新成功");
        return YES;
    }
    NSLog(@"修改不成功");
    return NO;
    
}
@end

注解:添加数据用了两种方法,一种是将要操作的数据属性放在字典中进行传送,一种是用一个数据模型user传送。user模型如下,如果要用字典传送就不需要
user.h

#import <Foundation/Foundation.h>
@interface User : NSObject
@property (nonatomic, copy) NSString *age;
@property (nonatomic, copy) NSString *phone;
@property (nonatomic, copy) NSString *name;
@end

user.m

#import "User.h"
@implementation User
/*
  User 可以作为一个数据模型model,如果不用user,我们在保存,查找,删除数据是对数据的传递只能以字典的方式进行,将数据的各个属性挨个保存在dictionary的相应键值中,然后再取出来
 user模型 可避免在传递过程中认为的遗漏数据的某个属性,应为user是以一个数据对象的整体来进行传递的
 #if X
        X=1时执行
 #else 
        X=0时执行
 #endif
 
 */
-(NSString *)name{
    if (!_name) {
        _name = @"";
    }
    return _name;
}

-(NSString *)age{
    if (!_age) {
        _age = @"";
    }
    return _age;
}

-(NSString *)phone{
    if (!_phone) {
        _phone = @"";
    }
    return _phone;
}
@end

源代码见:CoreData增删改查
iOS 数据持久化(四)---SQlite 3

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