iOS开发-文件管理之多的是你不知道的事（一）

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一、iOS中的沙盒机制

• iOS应用程序仅仅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（可运行文件）、图片、音频、视频、plist文件、sqlite数据库以及其它文件。

• 每一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能够互相訪问

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，在每一个沙盒中含有三个文件，各自是Document、Library和temp。

• Document：一般须要持久的数据都放在此文件夹中，能够在其中加入子文件夹。iTunes备份和恢复的时候，会包含此文件夹。

• Library：设置程序的默认设置和其它状态信息

• temp：创建暂时文件的文件夹，当iOS设备重新启动时，文件会被自己主动清除

获取沙盒文件夹

• 获取程序的根文件夹（home）文件夹

NSString *homePath = NSHomeDirectory()

• 获取Document文件夹

NSArray  *paths = NSSearchPathDorDirectoriesInDomains(NSDocumentDicrectory,NSUserDomainMark,YES);                                                                           

NSString *docPath = [paths lastObject];

• 获取Library文件夹

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"

• 经常用法例如以下

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加入到先邮路径的末尾，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 *aimage = [UIImage imageWithData: imageData];
 
//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 *imageData = [NSData dataWithContentsOfFile: finalPath];
UIImage *aimage = [UIImage imageWithData: imageData];

3.NSData与NSArray  NSDictionary

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

包含将NSData写进Documents文件夹
从Documents文件夹读取数据
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，

为此能够通过Category对NSDictionary进行扩展。以支持从NSData到NSDictionary的转换。

声明和实现例如以下：
 
+ (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、文件管理经常用法

NSFileManager

创建一个文件并写入数据                                                                                    

- (BOOL)createFileAtPath:(NSString *)path contents:(NSData *)data attributes:(NSDictionary *)attr;

从一个文件里读取数据                                                                                       

- (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文件夹          

- (BOOL)moveItemAtPath:(NSString *)srcPath toPath:(NSString *)dstPath error:(NSError **) error;

scrPath路径上的文件拷贝到dstPath路径上                                                            

- (BOOL)copyItemAtPath:(NSString *)scrPath toPath:(NSString *)dstPath error:(NSError **) error;

比較两个文件的内容是否一样                                                                               

- (BOOL)contentsEqualAtPath:(NSString *)path1 andPath:(NSString *)path2;

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、拷贝文件                                                                                             

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];

拷贝文件（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

推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];   

获取文件夹文件信息                                                                                            

NSFileManager *fileManager = [NSFileManager defaultManager];                         

NSString *enuPath = 

[NSHomeDirectoty( ) stringByAppendingPathComponent:@"Test"];                                                                                                           NSDictionaryEnumerator *dirEnum = [fileManager enumeratorAtPath:enuPath];     

NSString *path = nil;                                                                                      

while ((path = [dirEnum nextObject]} != nil)                                                        

{                                                                                                                  NSLog(@"%@",path);                                                                                        

}

郝萌主倾心贡献，尊重作者的劳动成果。请勿转载。

假设文章对您有所帮助。欢迎给作者捐赠。支持郝萌主，捐赠数额任意。重在心意^_^ 

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