iOS进阶(数据处理之文件读写)

1.沙盒的定义

每一个iOS程序都会为自己创建一个文件系统目录，这个独立、封闭、安全的空间就叫做沙盒

2.Documents、library(caches/preferences)、tmp

Documents：保存文档信息（例如图片，视频等）的路径信息

Library--caches：存放体积比较大的缓存资源

Library--preferences：保存应用的所有偏好设置（NSUsersDefault）

tmp：保存运行时所需的临时数据

3.获取文件目录

获取当前应用程序的沙盒根目录

NSString *rootPath = NSHomeDirectory();

获取Documents文件目录

NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];

获取caches文件目录

NSString *cachePath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
    NSLog(@"%@",cachePath);

获取preference文件目录

NSString *libPath = [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) lastObject];
    NSLog(@"%@",libPath);
 NSString *cachePath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
    NSLog(@"%@",cachePath)

获取tmp目录   ○

NSString *tmpPath = NSTemporaryDirectory();

4.四种简单对象

NSString/NSArray/NSDictionary/NSData

5.文件处理器（NSFileManager）与文件处理器（NSFileHandle）

NSFileManager

// 在Documents文件夹下,创建一个文件夹(path),在该文件夹下创建一个文件(test.txt),将一个图片对象存入到该文件中,然后在Caches文件夹下创建一个文件夹名为"testDirectroy",将test.txt文件移动到这个文件夹下.
    
    NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    
    NSString *Path = [docPath stringByAppendingPathComponent:@"path"];
    
    NSFileManager *filemanager = [NSFileManager defaultManager];
    
    [filemanager createDirectoryAtPath:Path withIntermediateDirectories:YES attributes:nil error:nil];

    NSString *testPath = [Path stringByAppendingPathComponent:@"test.txt"];
    UIImage *image = [UIImage imageNamed:@"1.jpg"];
    NSData *data = UIImageJPEGRepresentation(image, 1.0);
    
    [data writeToFile:testPath atomically:YES];
    
    NSString *cachePath =[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
    NSString *dirPath = [cachePath stringByAppendingPathComponent:@"testDirectroy"];
    [filemanager createDirectoryAtPath:dirPath withIntermediateDirectories:YES attributes:nil error:nil];
     NSLog(@"dirPath is %@",dirPath);
    
//移动
    NSString *desPath = [dirPath stringByAppendingPathComponent:@"aa.txt"];

    [filemanager moveItemAtPath:testPath toPath:desPath error:nil];

NSFileHandle

对文件内容进行局部修改追加

6.归档与反归档

归档

//创建两个人
    Person *bada = [[Person alloc] initWithName:@"bada" age:@"22" gender:@"男"];
    Person *qiuxiang = [[Person alloc] initWithName:@"qiuxiang" age:@"18" gender:@"女"];
    
    //获取路径
    NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    
    //iOS 中的归档类是NSKeyedArchiver，这个类的作用是将复杂对象转换成NSData对象
    //创建一个可变数据对象
    NSMutableData *mData = [NSMutableData data];
    
    NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:mData];
    //归档时要给归档对象添加标记
    [archiver encodeObject:bada forKey:@"bada"];
    [archiver encodeObject:qiuxiang forKey:@"qiuxiang"];
    
    [archiver finishEncoding];//结束归档，不管还有多少未进行归档的对象，都不会执行归档操作
    //将数据写入文件
    //创建文件路径
    NSString *filePath = [docPath stringByAppendingPathComponent:@"love.png"];//为二进制流文件,什么格式都可以
    [mData writeToFile:filePath atomically:YES];

解档

//获取到存放数据的路径
     NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *filePath = [docPath stringByAppendingPathComponent:@"love.png"];
    
    //获取NSData对象
    NSData *data = [NSData dataWithContentsOfFile:filePath];
    //iOS中的解档类是NSKeyedUnarchiver，他的作用是将NSData对象还原成原本的复杂对象
    NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
    
    //解档
    Person *person = [unarchiver decodeObjectForKey:@"bada"];
    NSLog(@"%@,%@,%@",person.name,person.age,person.gender);