文件操作

1. 沙盒路径的处理

• 沙盒路径：NSString *homePath = NSHomeDirectory()
• Documents路径：

NSArray *docPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsPath = [docPaths firstObject];

• Library路径：

NSArray *libPaths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES);
NSString *libraryPath = libPaths[0];

• tmp路径：NSString *tmpPath = NSTemporaryDirectory()

2. NSString类路径处理函数的处理

    NSString *path = @"/data/Containers/Data/Application/test.png";
    // 获取路径的各个组成部分
    NSArray *array = [path pathComponents];
    NSLog(@"%@", array);
    // 提取路径最后一个组成部分
    NSString *name = [path lastPathComponent];
    NSLog(@"%@", name);
    // 删除路径的最后一个组成部分
    NSString *string = [path stringByDeletingLastPathComponent];
    NSLog(@"%@", string);
    // 追加
    NSString *addStr = [string stringByAppendingPathComponent:@"name.txt"];
    NSLog(@"%@", addStr);

3. NSData处理

- (void) dataChange: (NSData *) data {
    // NSData -> NSString
    NSString *dataToString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    // NSString -> NSData
    NSData *stringToData = [dataToString dataUsingEncoding:NSUTF8StringEncoding];
    // NSData -> UIImage
    UIImage *image = [UIImage imageWithData:stringToData];
    // UIImage -> NSData
    NSData *data1 = UIImagePNGRepresentation(image);
}

4. NSFileHandle类对文件内容的读取和写入

先获取测试路径和文件

    NSString *docPath = [self getDocumentsPath];
    NSString *testPath = [docPath stringByAppendingPathComponent:@"慕课网"];
    NSString *filePath = [testPath stringByAppendingPathComponent:@"note.txt"];

• 创建文件夹

    NSFileManager *manager = [NSFileManager defaultManager];
    
    BOOL ret = [manager createDirectoryAtPath:testPath
                  withIntermediateDirectories:YES
                                   attributes:nil
                                        error:nil];
    if (ret) {
        NSLog(@"文件夹创建成功");
    } else {
        NSLog(@"失败");
    }

• 创建文件

    NSFileManager *manager = [NSFileManager defaultManager];
    
    BOOL ret = [manager createFileAtPath:filePath
                                contents:nil
                              attributes:nil];

• 写入内容

    NSString *content = @"test for note.";
    
    BOOL ret = [content writeToFile:filePath
                         atomically:YES
                           encoding:NSUTF8StringEncoding
                              error:nil];

• 查看文件是否存在

- (BOOL) fileExist: (NSString *) filePath {
    NSFileManager *manager = [NSFileManager defaultManager];
    if ([manager fileExistsAtPath:filePath]) {
        return YES;
    } else {
        return NO;
    }
}

• 追加内容

    NSFileHandle *fileHandle = [NSFileHandle fileHandleForUpdatingAtPath:filePath]; // 打开文件，准备更新
    [fileHandle seekToEndOfFile]; // 将节点调到文件末尾
    NSString *addContents = @"add to note.";
    NSData *stringToData = [addContents dataUsingEncoding:NSUTF8StringEncoding];
    [fileHandle writeData:stringToData];
    [fileHandle closeFile]; // 关闭文件

• 删除文件

    NSFileManager *manager = [NSFileManager defaultManager];
    BOOL ret = [self fileExist:filePath];
    
    if (ret) {
        BOOL ret2 = [manager removeItemAtPath:filePath error:nil];
        if (ret2) {
            NSLog(@"删除成功");
        } else {
            NSLog(@"删除失败");
        }
    } else {
        NSLog(@"路径不存在");
    }