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[操作系统]iOS学习之文件管理器(NSFileManager)和文件对接器(NSFileHandle)


1、文件管理器(NSFileManager)

 1> 创建文件夹

  创建所需的方法在头文件的声明:

/* createDirectoryAtPath:withIntermediateDirectories:attributes:error: creates a directory at the specified path. If you pass 'NO' for createIntermediates, the directory must not exist at the time this call is made. Passing 'YES' for 'createIntermediates' will create any necessary intermediate directories. This method returns YES if all directories specified in 'path' were created and attributes were set. Directories are created with attributes specified by the dictionary passed to 'attributes'. If no dictionary is supplied, directories are created according to the umask of the process. This method returns NO if a failure occurs at any stage of the operation. If an error parameter was provided, a presentable NSError will be returned by reference.   This method replaces createDirectoryAtPath:attributes: */ 
// 参数1:创建的文件夹的路径
// 参数2:是否创建媒介的布尔值,一般为YES
// 参数3: 属性,没有就置为nil
// 参数4: 错误信息- (BOOL)createDirectoryAtPath:(NSString *)path withIntermediateDirectories:(BOOL)createIntermediates attributes:(nullable NSDictionary<NSString *, id> *)attributes error:(NSError **)error NS_AVAILABLE(10_5, 2_0);

  实例代码:

  // 创建对象  NSFileManager *manager = [NSFileManager defaultManager];  // 创建路径  NSString *path = NSHomeDirectory();    path = [path stringByAppendingPathComponent:@"test/myApp"];    NSLog(@"%@", path);    NSError *error = nil;    // 创建文件夹  BOOL success = [manager createDirectoryAtPath:path           withIntermediateDirectories:YES                    attributes:nil                      error:&error];  NSLog(@"success = %d,error = %@", success,error);

 2> 向文件夹中添加文件

  内容写入方法在头文件的声明:

// 参数1:要写入内容的文件的文件路径// 参数2:一个BOOL值,一般为YES// 参数3: 编码方式,一般为UTF8// 参数4:错误信息- (BOOL)writeToFile:(NSString *)path atomically:(BOOL)useAuxiliaryFile encoding:(NSStringEncoding)enc error:(NSError **)error;

  实例代码:

  //向文件夹中添加字符串  path = [path stringByAppendingPathComponent:@"zifucuan.txt"];    //初始化一个字符串  NSString *string = @"hello";    BOOL success1 = [string writeToFile:path atomically:YES encoding:NSUTF8StringEncoding error:nil];    if (success1) {        NSLog(@"成功:%@",path);  }else{    NSLog(@"失败");  }

 3> 删除文件夹中文件

  删除文件方法在头文件的声明:

// 参数1:路径// 参数2:错误信息- (BOOL)removeItemAtPath:(NSString *)path error:(NSError **)error NS_AVAILABLE(10_5, 2_0);

  实例代码:

  // 删除path目录下的所有文件  [manager removeItemAtPath:path error:nil];

 4> 文件移动

  文件移动方法在头文件的声明:

// 参数1:要移动的文件路径// 参数2:要移动到的文件路径(目的地)// 参数3:错误信息- (BOOL)moveItemAtPath:(NSString *)srcPath toPath:(NSString *)dstPath error:(NSError **)error NS_AVAILABLE(10_5, 2_0);

  实例代码:

  NSString *documentPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];    // 创建一个文件夹  NSString *copyPath = [documentPath stringByAppendingPathComponent:@"备份/test.txt"];    // stringByDeletingLastPathComponent 删除最后一个路径  [manager createDirectoryAtPath:[copyPath stringByDeletingLastPathComponent]    withIntermediateDirectories:YES            attributes:nil               error:nil];  // 定义一个字符串  NSString *testStr = @"Hello World";    NSData *data = [testStr dataUsingEncoding:NSUTF8StringEncoding];    // 将内容写入文件  [manager createFileAtPath:copyPath           contents:data          attributes:nil];    // 创建一个toPath  NSString *toPath = [documentPath stringByAppendingPathComponent:@"hello/copyTest.txt"];    // 创建一个移动到的文件夹及文件  [manager createDirectoryAtPath:[toPath stringByDeletingLastPathComponent]    withIntermediateDirectories:YES            attributes:nil               error:nil];    BOOL result = [manager moveItemAtPath:copyPath                  toPath:toPath                  error:nil];  NSLog(@"result = %d", result);

 5> 文件copy(拷贝)

  文件copy(拷贝)方法在头文件的声明:

// 参数1:要拷贝的文件路径 
// 参数2:要拷贝到的文件路径(目的地)
// 参数3:错误信息
- (BOOL)copyItemAtPath:(NSString *)srcPath toPath:(NSString *)dstPath error:(NSError **)error NS_AVAILABLE(10_5, 2_0);

  实例代码:

// 路径使用上面的路径[manager copyItemAtPath:copyPath           toPath:toPath           error:nil];

2、文件夹处理器(NSFileHandle)

 1> 使用NSFileHandle向文件夹追加内容

  • 通过fileHandle更新
// 参数为文件路径+ (nullable instancetype)fileHandleForUpdatingAtPath:(NSString *)path;

  • 搜索到文本内容末尾方法
// 搜索到文件内容的末尾- (unsigned long long)seekToEndOfFile;

  • 实例代码:(使用上面的路径)
  // 创建handle对象  NSFileHandle *fileHandle = [NSFileHandle fileHandleForUpdatingAtPath:path];    // 搜索到文本内容末尾  [fileHandle seekToEndOfFile];    NSString *appendStr = @"我是后来的";    NSData *appendData = [appendStr dataUsingEncoding:NSUTF8StringEncoding];    // 将数据写入到对接起  [fileHandle writeData:appendData];    // 关闭对接起  [fileHandle closeFile];

  2> 定位数据

  • 通过fileHandle读取
// 参数为文件路径
+ (nullable instancetype)fileHandleForReadingAtPath:(NSString *)path;

  • 获取文件中可获得的数据(所有数据)
@property (readonly, copy) NSData *availableData;

  • 设置文件的偏移量
// 参数为一个和文件长度有关的数值- (void)seekToFileOffset:(unsigned long long)offset;

  • 从文件的偏移量位置读取到最后
- (NSData *)readDataToEndOfFile;

实例代码:

  // 将“123456”写入file2.txt文件夹中  NSString * content = @"123456";  NSString * filePath2 = [documentPath stringByAppendingPathComponent:@"file2.txt"];  [fileManager createFileAtPath:filePath2 contents:[content dataUsingEncoding:NSUTF8StringEncoding] attributes:nil];    // 通过fileHandle读取  fileHandle = [NSFileHandle fileHandleForReadingAtPath:filePath2];  // 获取数据长度  NSUInteger length = [[fileHandle availableData] length];  // 设置文件的偏移量为文件的一半  [fileHandle seekToFileOffset:length/2.0];  // 从文件的偏移量位置读取到最后  NSData * data = [fileHandle readDataToEndOfFile];  [fileHandle closeFile];  // 打印读取的字符串  NSString * string = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];  NSLog(@"%@",string);