IOS开发--数据持久化篇文件存储(二)

时间：2016-01-13 23:30:36 阅读：366 评论：0 收藏：0 [点我收藏+]

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前言:个人觉得开发人员最大的悲哀莫过于懂得使用却不明白其中的原理.在代码之前我觉得还是有必要简单阐述下相关的一些知识点. 因为文章或深或浅总有适合的人群.若有朋友发现了其中不正确的观点还望多多指出,不胜感激.

承接上篇博客我们来看看IOS开发中是如何将一个自定义的对象进行归档的
本篇博客将介绍以下几个方面的内容

1)普通的单个对象归档操作
2)拥有继承关系的对象归档
3)同时将多个对象进行归档

1.普通的单个对象归档操作

首先我们来看下最简单的单个对象归档操作
1.自定义一个跟小明一样有名的类(Person)

直接上代码 :

Person.h

 1 #import <Foundation/Foundation.h>
 2 
 3 @interface Person : NSObject<NSCoding>
 4 
 5 /**
 6  *  姓名
 7  */
 8 @property (nonatomic, strong) NSString *name ;
 9 
10 /**
11  *  地址
12  */
13 @property (nonatomic, strong) NSString *address ;
14 
15 /**
16  *  年龄
17  */
18 @property (nonatomic, assign) int age;
19 
20 
21 -(instancetype)initWithName:(NSString *)name address:(NSString *)address age:(int)age;
22 
23 @end

Person.m

 1 #import "Person.h"
 2 
 3 @implementation Person
 4 
 5 -(instancetype)initWithName:(NSString *)name address:(NSString *)address age:(int)age{
 6     if (self = [super init]) {
 7         self.name = name;
 8         self.address = address;
 9         self.age = age;
10     }
11     return self;
12 }
13 
14 //告知编译器,我们需要归档当前对象的哪些属性
15 -(void)encodeWithCoder:(NSCoder *)aCoder{
16     
17     [aCoder encodeObject:self.name forKey:@"name"];
18     [aCoder encodeObject:self.address forKey:@"address"];
19     [aCoder encodeInt: self.age forKey:@"age"];
20 }
21 
22 //告知编译器,解档时对应的属性
23 -(instancetype)initWithCoder:(NSCoder *)aDecoder{
24     
25     self.name = [aDecoder decodeObjectForKey:@"name"];
26     self.address = [aDecoder decodeObjectForKey:@"address"];
27     self.age = [aDecoder decodeIntForKey:@"age"];
28     return self;
29 }
30 
31 @end

控制器代码1:归档

 1 -(void)personArchive{
 2     //创建及初始化对象
 3     Person *p = [[Person alloc] initWithName: @"jack" address:@"Mars" age:20];
 4     
 5     //定义归档路径
 6     NSString *fullPath = [self fullPathWithFileName:@"person.data"];
 7     
 8     //进行归档
 9     [NSKeyedArchiver archiveRootObject:p toFile:fullPath];
10     
11     NSLog(@"对象归档成功");
12 }

控制器代码2:解档

1 -(void)personUnarchive{
2     
3     NSString *fullPath = [self fullPathWithFileName:@"person.data"];
4     
5     Person *p = [NSKeyedUnarchiver unarchiveObjectWithFile:fullPath];
6     
7     NSLog(@"name = %@,address = %@,age = %d",p.name ,p.address ,p.age);
8     
9 }

注: fullPathWithFileName: 方法为便捷获取路径方法,代码如下

1 -(NSString *)fullPathWithFileName:(NSString *)fileName{
2 
3     NSString *documentDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)lastObject];
4     
5     return [documentDir stringByAppendingPathComponent:fileName];
6 
7 }

依次调用我们的归档和解档方法

 [self personArchive];//归档
 [self personUnarchive];//解档

结果如下:

技术分享

至此我们已经实现了简单的单个对象的归档和解档操作,下面我们来看下继承关系下的对象的归档解档操作

2.拥有继承关系的对象归档和解档

定义一个Student类继承自Person类,代码如下

Student.h

 1 #import "Person.h"
 2 
 3 @interface Student : Person
 4 
 5 /**
 6  *  学校名称
 7  */
 8 @property (nonatomic, strong) NSString *schoolName;
 9 
10 -(instancetype)initWithName:(NSString *)name address:(NSString *)address age:(int)age schoolName:(NSString *)schoolName;
11 
12 @end

Student.m

 1 #import "Student.h"
 2 
 3 @implementation Student
 4 
 5 -(instancetype)initWithName:(NSString *)name address:(NSString *)address age:(int)age schoolName:(NSString *)schoolName{
 6     if (self = [super initWithName:name address:address age:age]) {
 7         self.schoolName =schoolName;
 8     }
 9     return self;
10 }
11 
12 
13 -(void)encodeWithCoder:(NSCoder *)aCoder{
14     
15     [super encodeWithCoder:aCoder];
16     
17     [aCoder encodeObject:self.schoolName forKey:@"schoolName"];
18 }
19 
20 -(instancetype)initWithCoder:(NSCoder *)aDecoder
21 {
22     self = [super initWithCoder:aDecoder];
23     self.schoolName = [aDecoder decodeObjectForKey:@"schoolName"];
24     return self;
25 }
26 @end

控制器方法1:归档

 1 -(void)studentArchive{
 2 
 3     Student *stu = [[Student alloc] initWithName:@"小明" address:@"走廊" age:10 schoolName:@"剑桥大学"];
 4     
 5     NSString *fullpath = [self fullPathWithFileName:@"stu.data"];
 6     
 7     [NSKeyedArchiver archiveRootObject:stu toFile:fullpath];
 8     
 9     NSLog(@"归档成功");
10 }

控制器方法2:解档

1 -(void)studentUnarchive{
2     
3     NSString *fullpath = [self fullPathWithFileName:@"stu.data"];
4     Student *stu = [NSKeyedUnarchiver unarchiveObjectWithFile:fullpath];
5     NSLog(@"name = %@,age = %d,address = %@,schoolName = %@",stu.name,stu.age ,stu.address,stu.schoolName);
6 }

依次调用上述两个方法,运行结果如下

技术分享

3.同时将多个对象归档

演示代码如下:

1.归档

 1 -(void)multipleArchive{
 2     
 3     Student *s0 = [[Student alloc]initWithName:@"name0" address:@"address0" age:10 schoolName:@"schoolName0"];
 4     Student *s1 = [[Student alloc]initWithName:@"name1" address:@"address1" age:20 schoolName:@"schoolName1"];
 5    
 6     
 7     NSMutableData *data = [NSMutableData data];
 8     NSKeyedArchiver *archive = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
 9     
10     [archive encodeObject:s0 forKey:@"student0"];
11     [archive encodeObject:s1 forKey:@"student1"];
12     
13     [archive finishEncoding];
14     
15     NSString *fullpath = [self fullPathWithFileName:@"multiple.data"];
16     
17     [data writeToFile:fullpath atomically:YES];
18     
19     NSLog(@"多对象归档成功");
20 
21 }

02.解档:

 1 -(void)multipleUnArchive{
 2     
 3     NSString *fullpath = [self fullPathWithFileName:@"multiple.data"];
 4     NSData *data = [NSData dataWithContentsOfFile:fullpath];
 5     NSKeyedUnarchiver *unArchive = [[NSKeyedUnarchiver alloc]initForReadingWithData:data];
 6     Student *stu0 = [unArchive decodeObjectForKey:@"student0"];
 7     Student *stu1 = [unArchive decodeObjectForKey:@"student1"];
 8     [unArchive finishDecoding];
 9     NSLog(@"name = %@,age = %d,address = %@,schoolName = %@",stu0.name,stu0.age,stu0.address,stu0.schoolName);
10     NSLog(@"name = %@,age = %d,address = %@,schoolName = %@",stu1.name,stu1.age,stu1.address,stu1.schoolName);
11 
12 }