iOS文件系统---沙盒(sandbox),NSFileManager,NSFileHandle, NSData, 目录，文件

在iOS系统中,每个APP的文件都是独立的, 一个APP大部分处理的文件系统仅限于app的沙盒文件夹.新的APP安装的时候,会产生一系列的文件目录,如下图所示:

下面分开介绍一下:

　　AppName.app: 包含app和响应的资源等

　　Documents: 储存用户产生的数据,这个文件夹里面的数据能够被用户所操作,能够被itune备份.

　　Documents/Inbox:  如果APP允许其他应用打开,这就将其他应用能使用的文件放在这个文件中.

　　Library: 里面有几个文件夹, Cache:存放缓存, Preference:存放一些配置信息, NSUserDefault的信息就放在这个文件夹里面. 这里面放的文件是不让用户直接操作的数据. 

 　 tmp: 临时文件夹,储存一些临时信息,程序退出时会被清除

文件路径:

<pre name="code" class="objc">    //app路径    NSString *appPath = [NSSearchPathForDirectoriesInDomains(NSApplicationDirectory,NSUserDomainMask,YES) objectAtIndex:0];    //Document路径    NSString *documentPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];    //Library路径    NSString *libraryPath = [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) objectAtIndex:0];    //Library/Cache路径    NSString *cachePath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0];    //Library/Preferences路径    NSString *preferencePath = [libraryPath stringByAppendingPathComponent:@"Preferences"];    //tmp路径    NSString *tmpPath = NSTemporaryDirectory();

目录相关操作：

    NSFileManager *fileManager = [NSFileManager defaultManager];    //判断当前的工作目录    NSString *currentPath = [fileManager currentDirectoryPath];    NSLog(@"currentPath = %@",currentPath); //程序启动后默认是跟目录/(程序的主目录)    NSString *documentPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];    //改变当前目录    if ([fileManager changeCurrentDirectoryPath:documentPath]) {        currentPath = [fileManager currentDirectoryPath];    }    //创建目录    NSString *newDirectory = [documentPath stringByAppendingPathComponent:@"newDir"];    if ([fileManager createDirectoryAtPath:newDirectory withIntermediateDirectories:NO attributes:nil error:nil]) {        NSLog(@"create success"); //create success    }    //列出目录的所有内容    NSArray *fileContent = [fileManager contentsOfDirectoryAtPath:documentPath error:nil];    [fileContent enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {        NSLog(@"obj = %@",obj); //obj = newDir 文件名字    }];    //删除目录    if ([fileManager removeItemAtPath:newDirectory error:nil]) {        NSLog(@"delete success");//delete succes    }    //目录或者文件信息    NSDictionary *attribute = [fileManager attributesOfItemAtPath:documentPath error:nil];    NSLog(@"attribute = %@",attribute);    /*     attribute = {     NSFileCreationDate = "2014-11-23 09:48:58 +0000";     NSFileExtensionHidden = 0;     NSFileGroupOwnerAccountID = 20;     NSFileGroupOwnerAccountName = staff;     NSFileModificationDate = "2014-11-29 12:57:01 +0000";     NSFileOwnerAccountID = 501;     NSFilePosixPermissions = 493;     NSFileReferenceCount = 2;     NSFileSize = 68;     NSFileSystemFileNumber = 11768762;     NSFileSystemNumber = 16777218;     NSFileType = NSFileTypeDirectory;     }     */

文件操作：

    //判断一个文件是否存在    NSString *filePath = [documentPath stringByAppendingPathComponent:@"newFile.txt"];    if (![fileManager fileExistsAtPath:filePath]) {        [fileManager createFileAtPath:filePath contents:nil attributes:nil];    }    //列出一个目录中的所有文件    NSURL *bundleURL = [[NSBundle mainBundle] bundleURL];    NSArray *contents = [fileManager contentsOfDirectoryAtURL:bundleURL includingPropertiesForKeys:nil options:NSDirectoryEnumerationSkipsHiddenFiles error:nil];    [contents enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {        NSLog(@"obj = %@",obj);    }];    //写入文件    [@"First Date" writeToFile:filePath atomically:YES encoding:NSUTF8StringEncoding error:nil];    //或者    NSData *data = [@"first data" dataUsingEncoding:NSUTF8StringEncoding];    [data writeToFile:filePath atomically:YES];    //NSFileHandle 取文件操作柄    NSFileHandle *handle = [NSFileHandle fileHandleForReadingAtPath:filePath];    NSMutableData *orignalData = [NSMutableData dataWithData:[handle readDataToEndOfFile]];    [orignalData appendData:data];    [handle closeFile];    handle = [NSFileHandle fileHandleForWritingAtPath:filePath];    [handle writeData:orignalData];    [handle closeFile];        //删除文件    if ([fileManager removeItemAtPath:filePath error:nil]) {        NSLog(@"delete file success");    }