什么是数据持久化?数据的永久存储

为什么要坐数据持久化:存储在内存中的数据,程序关闭,内存释放,数据丢失,这种数据是临时的

数据初九化的本质:数据保存成文件,存储到程序的沙河中

1.沙盒机制

每个应用程序位于文件系统的严格限制部分

每个应用程序只能在为该程序创建的文件系统中读取文件

每个应用程序在IOS系统内都放在了统一的文件夹目录下

沙盒的本质就是一个文件夹,名字是随机分配的.

2.沙盒路径的位置

1.通过Finder查找程序沙盒相对的路径

通过代码查找程序沙盒相对路径

NSString *DocumentPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
    NSLog(@"%@",DocumentPath);

2.沙盒构成

Document                   存储用户数据,需要备份的信息

Library/Caches          存储缓存文件,程序专用的支持文件

Library/Preferences          存储应用程序的偏好设置文件

.app                           程序包(IOS8时,app不存储在沙盒中,有单独的文件夹存储所有程序的app包)

tmp                             存储临时文件,比如:下载的zip包,解压后的再删除

3.获取沙盒目录路径的方法

NSHomeDirectory-------------------->沙盒主路径

NSDocumentDirectory--------------->Document文件夹

NSLibraryDirectory------------------->Library文件夹

NSCachesDirectory------------------>Caches文件夹

NSTemporaryDirectory--------------->tem文件夹

代码

<span style="font-family:SimHei;font-size:18px;">//1.home主目录里面有:Documents,Library,tmp和一个应用程序
    NSLog(@"Home:%@",NSHomeDirectory());
    //2.DocumentsPath路径
    NSString *DocumentsPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
    NSLog(@"DocumentsPath:%@",DocumentsPath);
    //3.Libray
    NSString *librayPath = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES)[0];
    NSLog(@"%@",librayPath);
    //4.temp
    NSLog(@"temp:%@",NSTemporaryDirectory());
    //5.cachesPath
    NSString *cachesPath = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES)[0];
    NSLog(@"cachesPath:%@",cachesPath);
    //6.user
    NSString *user = NSUserName();
    NSLog(@"user:%@",user);</span>

<span style="font-family:SimHei;font-size:18px;">//nsstring写入
    
    //1.写入的路径
    NSString *DocumentPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
    NSLog(@"%@",DocumentPath);
    //2.拼接文件路径
    NSString *filePath = [DocumentPath stringByAppendingString:@"/myText.txt"];
    //3.准备写入的内容
    NSString *content = @"Hello World";
    [content writeToFile:filePath atomically:YES encoding:NSUTF8StringEncoding error:nil];
    //4.读取
    NSString *readString = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:nil];
    NSLog(@"redstring : %@",readString);
    
    
    
    //NSArray
    //1.获取documents路径
    //2.拼接文件路径
    NSString *arrayFile = [DocumentPath stringByAppendingString:@"/array.plist"];
    NSLog(@"arrayPath = %@",arrayFile);
    //3.准备内容
    NSArray * contentArray = @[@"1",@"2",@"3",@"4",@"5",];
    //4.写入
    [contentArray writeToFile:arrayFile atomically:YES];
    //5.读取
    NSArray *readArray = [NSArray arrayWithContentsOfFile:arrayFile];
    NSLog(@"readArray : %@",readArray);
    
    //dictinary
    //1.拼接
    NSString *dictFile = [DocumentPath stringByAppendingString:@"/dict.plist"];
    //2.准备内容
    NSDictionary *dictcontent = @{@"1":@"a",@"2":@"b",@"3":@"c"};
    NSLog(@"%@",dictFile);
    //3.写入
    [dictcontent writeToFile:dictFile atomically:YES];
    //4.读取字典
    NSDictionary *readDict = [NSDictionary dictionaryWithContentsOfFile:dictFile];
    NSLog(@"dict : %@",readDict);</span>

NSFileManager,文件管理,使用detaultManager,创建单利对象

可以创建文件夹

可以创建,移动,复制,删除文件,

可以判断文件是否存在

<span style="font-family:SimHei;font-size:18px;"> //NSFileManager
    //创建文件夹
    //在Documents中创建一个文件夹
    NSString *documentsPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
    //在Documents中创建一个文件夹命名为"个人收藏"
    NSString *path = [documentsPath stringByAppendingString:@"/个人收藏"];
    //创建文件管理(单利),并创建文件夹
    [[NSFileManager defaultManager]createDirectoryAtPath:path withIntermediateDirectories:YES attributes:nil error:nil];
    NSLog(@"DocumentsPath%@",documentsPath);
    //修改文件夹
    NSString *newPath = [documentsPath stringByAppendingString:@"/岛国文化"];
    [[NSFileManager defaultManager]moveItemAtPath:path toPath:newPath error:nil];
    //删除
    [[NSFileManager defaultManager]removeItemAtPath:documentsPath error:nil];
    //判断某个文件是否存在
    //返回值是BOOL,YES存在,NO不存在
    [[NSFileManager defaultManager]fileExistsAtPath:newPath];</span>

1.什么是复杂对象

1.在foundation框架内不存在的数据类

2.无法在程序内通过writeToFile类型的方法写入到文件内

3.复杂对象至少包含一个实例对象

复杂对象无法通过writeToFile:方法进行数据持久化,只能通过将复杂对象转换为NSData,通过writeToFile进行数据持久化

将复杂的对象转化为NSData,通过归档;将NSData转换为复杂对象,通过反归档

复杂对象写入文件要遵循NSCoding协议

有两个方法,代码如下:

<span style="font-family:SimHei;font-size:18px;">//进行归档时调用(系统调用)
-(void)encodeWithCoder:(NSCoder *)aCoder
{
    //对属性进行编码
    [aCoder encodeObject:self.name forKey:kName];
    [aCoder encodeObject:self.age forKey:kAge];
}
//进行反归档编码时
-(id)initWithCoder:(NSCoder *)aDecoder
{

    self = [super init];
    //反编码
    if (self)
    {
        self.name = [aDecoder decodeObjectForKey:kName];
    }
    return self;
}</span>

归档/反归档代码如下:

<span style="font-family:SimHei;font-size:18px;">//归档 反归档
    //创建 Person类实例对象
    Person *person1 = [[Person alloc] init];
    person1.name = @"刘杰";
    person1.age = @"39";
    
    Person *person2 = [[Person alloc] init];
    person2.name = @"李士杰";
    person2.age = @"18";
    //归档使用的NSData
    NSMutableData *Person1Data = [NSMutableData data];
    //创建归档工具
    NSKeyedArchiver * archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:Person1Data];
    //进行归档
    [archiver encodeObject:person1 forKey:kPerson1];
    [archiver encodeObject:person2 forKey:kPerson2];

    //完成转换
    [archiver finishEncoding];
    //找到路径
    NSString *docunment = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
    //拼接文件路径
    NSString *personPath = [docunment stringByAppendingString:@"/刘杰.xxoo"];
    //写入文档
    
    [Person1Data writeToFile:personPath atomically:YES];
    NSLog(@"%@",docunment);
    
    //反归档
    //通过文件路径,获取data数据
    NSData * unData = [NSData dataWithContentsOfFile:personPath];
    
    //反归档工具
    NSKeyedUnarchiver *unAechiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:unData];
    
    //反归档
    Person *p1 = [unAechiver decodeObjectForKey:kPerson1];
    Person *p2 = [unAechiver decodeObjectForKey:kPerson2];
    //结束反归档
    [unAechiver finishDecoding];
    
    NSLog(@"name:%@",p1.name);
    NSLog(@"name :%@",p2.name);
</span>

单个归档.反归档

<span style="font-family:SimHei;font-size:18px;">    //获取Documents路径
    NSString *DocumentsPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
    //拼接文件路径
    NSString *filePath = [DocumentsPath stringByAppendingString:@"/PersonArray.plist"];
    //实例一个对象
   
     Person *p1 = [[Person alloc] init];
    p1.name = @"别闹了";
    p1.age = @"1";
    //归档
    [NSKeyedArchiver archiveRootObject:p1 toFile:filePath];
    //反归档
    Person *p2 = [NSKeyedUnarchiver unarchiveObjectWithFile:filePath];
    NSLog(@"name: %@",p2.name);</span>

<span style="font-family:SimHei;font-size:18px;"> //获取Documents路径
    NSString *DocumentsPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
    //拼接文件路径
    NSString *filePath = [DocumentsPath stringByAppendingString:@"/PersonArray.plist"];
    //实例一个对象
    Person *pn1 = [[Person alloc] init];
    pn1.name = @"TOM";
    pn1.age = @"12";
    Person *pn2 = [[Person alloc] init];
    pn2.name = @"KIM";
    pn2.age = @"18";
    
    NSArray *array = @[pn1,pn2];
     //归档
    [NSKeyedArchiver archiveRootObject:array toFile:filePath];
    //反归档
    NSArray *a = [NSKeyedUnarchiver unarchiveObjectWithFile:filePath];
    NSLog(@"%@,%@",[a[0] name],[a[1] name]);</span>

沙盒机制:

简单对象写入文件,只能是NSString,NSArray,NSDictionary,NSData

复杂的对象写入文件,遵守NSCoding协议,实现代理方法

IOS 初级数据持久化-沙盒机制