NSString，NSData，NSFileManager常用方法

一、利用NSString类进行文件路径的处理

文件路径格式：

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

常用方法汇总：

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

- (NSArray *)pathComponents;

2.提取路径的最后一个组成部分，结果：testfile.txt

- (NSString *)lastPathComponent;

3.删除路径的最后一个组成部分，结果：/Users/apple

- (NSString *)stringByDeletingLastPathCpmponent;

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

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

5.去路径最后部分的扩展名，结果：text

- (NSString *)pathExtension;

6.删除路径最后部分的扩展名，结果：/Users/apple/testfile

- (NSString *)stringByDeletingPathExtension;

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

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

二、NSData二进制数据类

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;
        }
}

三、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 *)path1 andPath:(NSString *)path2;

文件是否存在

- (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"];                                                  

将字符串转成NSData类型

NSString *text = @"abcdefg";
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);
}