一、iOS中的沙盒机制

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• iOS应用程序只能对自己创建的文件系统读取文件，这个独立、封闭、安全的空间，叫做沙盒。它一般存放着程序包文件（可执行文件）、图片、音频、视频、plist文件、sqlite数据库以及其他文件。

• 每个应用程序都有自己的独立的存储空间（沙盒）

• 一般来说应用程序之间是不可以互相访问

模拟器沙盒的位置

/User/userName/Library/Application Support/iPhone Simulator

当我们创建应用程序时，在每个沙盒中含有三个文件，分别是Document、Library和temp。

• Document：一般需要持久的数据都放在此目录中，可以在当中添加子文件夹，iTunes备份和恢复的时候，会包括此目录。

• Library：设置程序的默认设置和其他状态信息

• temp：创建临时文件的目录，当iOS设备重启时，文件会被自动清除

获取沙盒目录

• 获取程序的根目录（home）目录

NSString *homePath = NSHomeDirectory()

• 获取Document目录

NSArray  *paths = NSSearchPathDorDirectoriesInDomains(NSDocumentDicrectory,, NSUserDomainMark, YES);                                                                          NSString *docPath = [paths lastObject];

• 获取Library目录

NSArray *paths = NSSearchPathForDirectoriseInDomains(NSLibraryDirectory, NSUserDomainMask, YES);                                                                                  NSString *docPath = [paths lastObject];

• 获取Library中的Cache

NSArray *paths = NSSearchPathForDirectoriseInDomains(NSCachesDirectory, NSUserDomainMask, YES);                                                                                  NSString *docPath = [paths lastObject];

• 获取temp路径

NSString *temp = NSTemporaryDirectory( );

二、NSString类路径的处理方法

文件路径的处理

NSString *path = @"/Uesrs/apple/testfile.txt"

• 常用方法如下

获得组成此路径的各个组成部分，结果：（"/","User","apple","testfile.txt"）

- (NSArray *)pathComponents;

提取路径的最后一个组成部分，结果：testfile.txt

- (NSString *)lastPathComponent;

删除路径的最后一个组成部分，结果：/Users/apple

- (NSString *)stringByDeletingLastPathCpmponent;

将path添加到先邮路径的末尾，结果：/Users/apple/testfile.txt/app.txt

- (NSString *)stringByAppendingPathConmponent:(NSString *)str;

去路径最后部分的扩展名，结果：text

- (NSString *)pathExtension;

删除路径最后部分的扩展名，结果：/Users/apple/testfile

- (NSString *)stringByDeletingPathExtension;

路径最后部分追加扩展名，结果：/User/apple/testfile.txt.jpg

- (NSString *)stringByAppendingPathExtension:(NSString *)str;

三、NSData

• NSData是用来包装数据的

• NSData存储的是二进制数据，屏蔽了数据之间的差异，文本、音频、图像等数据都可用NSData来存储
  

NSData的用法

1.NSString与NSData互相转换

NSData－> NSString                                                                                    NSString *aString = [[NSString alloc] initWithData:adataencoding:NSUTF8StringEncoding];

NSString－>NSData                                                                                     NSString *aString = @"1234abcd";
NSData *aData = [aString dataUsingEncoding: NSUTF8StringEncoding];

将data类型的数据,转成UTF8的数据

+(NSString *)dataToUTF8String:(NSData *)data
{
NSString *buf = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
return [buf autorelease];
}

将string转换为指定编码
+(NSString *)changeDataToEncodinString:(NSData *)data encodin:(NSStringEncoding )encodin{
   NSString *buf = [[[NSString alloc] initWithData:data encoding:encodin] autorelease];
   return buf;
}

2. NSData 与 UIImage
NSData－>UIImage
UIImage *ap_w_picpath = [UIImage p_w_picpathWithData: p_w_picpathData];

//例：从本地文件沙盒中取图片并转换为NSData
NSString *path = [[NSBundle mainBundle] bundlePath];
NSString *name = [NSString stringWithFormat:@"ceshi.png"];
NSString *finalPath = [path stringByAppendingPathComponent:name];
NSData *p_w_picpathData = [NSData dataWithContentsOfFile: finalPath];
UIImage *ap_w_picpath = [UIImage p_w_picpathWithData: p_w_picpathData];

3.NSData与NSArray NSDictionary

+(NSString *)getLocalFilePath:(NSString *) fileName
{
return [NSString stringWithFormat:@"%@/%@%@", NSHomeDirectory(),@“Documents”,fileName];
}

包括将NSData写进Documents目录
从Documents目录读取数据
在进行网络数据通信的时候，经常会遇到NSData类型的数据。在该数据是dictionary结构的情况下，系统没有提供现成的转换成NSDictionary的方法，为此可以通过Category对NSDictionary进行扩展，以支持从NSData到NSDictionary的转换。声明和实现如下：

+ (NSDictionary *)dictionaryWithContentsOfData:(NSData *)data {
   CFPropertyListRef list = CFPropertyListCreateFromXMLData(kCFAllocatorDefault, (CFDataRef)data, kCFPropertyListImmutable, NULL);
   if(list == nil) return nil;
   if ([(id)list isKindOfClass:[NSDictionary class]]) {
        return [(NSDictionary *)list autorelease];
        }
   else {
        CFRelease(list);
        return nil;
        }
}

四、文件管理常用方法

NSFileManager

创建一个文件并写入数据                                                                                    - (BOOL)createFileAtPath:(NSString *)path contents:(NSData *)data attributes:(NSDictionary *)attr;

从一个文件中读取数据                                                                                       - (NSData *)contentsAtPath:(NSString *)path;

scrPath路径上的文件移动到dstPath路径上，注意这里的路径是文件路径而不是目录         - (BOOL)moveItemAtPath:(NSString *)srcPath toPath:(NSString *)dstPath error:(NSError **) error;

scrPath路径上的文件复制到dstPath路径上                                                            - (BOOL)copyItemAtPath:(NSString *)scrPath toPath:(NSString *)dstPath error:(NSError **) error;

比较两个文件的内容是否一样                                                                              - (BOOL)contentsEqualAtPath:(NSString *)path2 andPath:(NSString *)path3;

文件时候存在                                                                                                  - (BOOL)fileExistsAtPath:(NSString *)path;

移除文件                                                                                                        - (BOOL)removeItemAtPath:(NSString *)path error:(NSError **) error;

创建文件管理

NSFileManager *fileManager = [NSFileManager defaultManager];                         NSString *path = [NSHomeDirectory( ) stringByAppendingPathComponent:@"holyBible.txt"];                                                                                                    NSString *text = @"abcdefg";

将字符串转成NSData类型                                                                               NSData *data = [text dataUsingEncoding: NSUTF8StringEncoding];

写入文件                                                                                                      BOOL success = [fileManager createFileAtPath:path contents:data attributes:nil];

创建文件夹

NSString *filePath = [path stringByAppendingPathComponent:@"holyBible.txt"];    NSString *contect = @"abcdefg";                                                                    BOOL success = [fm createFileAtPath:filePath contents:[content dataUsingEncoding: NSUTF8StringEncoding] attributes:nil];

NSFileManager-读取内容                                                                                NSData *fileData = [fileManager contentsAtPath:filePath];                                  NSString *content = [[NSString alloc] initWithData:fileData dataUsingEncoding: NSUTF8StringEncoding];

NSData-读取内容NSString *filePath = [path stringByAppendingPathComponent:@"holyBible.txt"];    NSData *data = [NSData dataWithContentOfFile:filePath];

NSString-读取内容                                                                                        NSString *filePath = [path stringByAppendingPathComponent:@"holyBible.txt"];    NSString *content = [[NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:nil];

移动、复制文件

移动文件（重命名）NSString *toPath = [NSHomeDirectory( ) stringByAppendingPathComponent:@"hellogod/New Testament.txt"];                                                                              [fm createDirectoryAtPath:[toPath stringByDeletingLastPathComponent] withIntermediateDirectories:YES attributes:nil error:nil];                                                  NSError *error;                                                                                            BOOL isSuccess = [fm moveItemAtPath:filePath toPath:toPath error:&error];

复制文件（重命名）                                                                  NSString *copyPath = [NSHomeDirectory( ) stringByAppendingPathComponent:@"备份/Old Testament.txt"];      [fm createDirectoryAtPath:[toPath stringByDeletingLastPathComponent] withIntermediateDirectories:YES attributes:nil error:nil];                                                  BOOL success = [fm copyItemAtPath:toPath toPath:toPath error:nil];

删除文件、获取文件大小

判断文件是否存在和删除文件                                                               if([fm fileExistsAtPath])                                                                                     {                                                                                                                   if ([fm removeItemAtPath:copyPath])                                                                {                                                                                                                  NSLog(@"remove success");                                                                            }                                                                                                                  }

获取文件大小NSFileManager *fileManager = [NSFileManager defaultManager];                         获得文件的属性字典                                                                                        NSDictionary *attrDic = [fileManager attributesOfItemAtpath:sourcePath error:nil]; NSNumber *fileSize = [attrDic objectForKey:NSFileSize];

获取目录文件信息NSFileManager *fileManager = [NSFileManager defaultManager];                        NSString *enuPath = [NSHomeDirectoty( ) stringByAppendingPathComponent:@"Test"];                                                                                                          NSDictionaryEnumerator *dirEnum = [fileManager enumeratorAtPath:enuPath];    NSString *path = nil;                                                                                     while ((path = [dirEnum nextObject]} != nil)                                                        {                                                                                                                 NSLog(@"%@",path);                                                                                        }

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