Iterating through files in a folder with nested fo

问题:

I need to access every file in a folder, including file that exist within nested folders. An example folder might look like this.

animals/
 -k.txt
 -d.jpg
 cat/
   -r.txt
   -z.jpg
   tiger/
      -a.jpg
      -p.pdf
 dog/
   -n.txt
   -f.jpg
 -p.pdf

Say that I wanted to run a process on every file within "animals" that isn't folder. What would be the best way to iterate through the folder "animals" and all of its subfolders to access every file?

Thanks.

回答1:

Use NSDirectoryEnumerator to recursively enumerate files and directories under the directory you want, and ask it to tell you whether it is a file or directory. The following is based on the example listed at the documentation for -[NSFileManager enumeratorAtURL:includingPropertiesForKeys:options:errorHandler:]:

NSFileManager *fileManager = [NSFileManager defaultManager];
NSURL *directoryURL = … // URL pointing to the directory you want to browse
NSArray *keys = [NSArray arrayWithObject:NSURLIsDirectoryKey];

NSDirectoryEnumerator *enumerator = [fileManager
    enumeratorAtURL:directoryURL
    includingPropertiesForKeys:keys
    options:0
    errorHandler:^(NSURL *url, NSError *error) {
        // Handle the error.
        // Return YES if the enumeration should continue after the error.
        return YES;
}];

for (NSURL *url in enumerator) { 
    NSError *error;
    NSNumber *isDirectory = nil;
    if (! [url getResourceValue:&isDirectory forKey:NSURLIsDirectoryKey error:&error]) {
        // handle error
    }
    else if (! [isDirectory boolValue]) {
        // No error and it’s not a directory; do something with the file
    }
}

回答2:

Maybe you can use something like this:

+(void)openEachFileAt:(NSString*)path
{
  NSString* file;
  NSDirectoryEnumerator* enumerator = [[NSFileManager defaultManager] enumeratorAtPath:path];
  while (file = [enumerator nextObject])
  {
     // check if it's a directory
     BOOL isDirectory = NO;
    NSString* fullPath = [path stringByAppendingPathComponent:file];
    [[NSFileManager defaultManager] fileExistsAtPath:fullPath
                                         isDirectory: &isDirectory];
    if (!isDirectory)
    {
      // open your file (fullPath)…
    }
    else
    {
      [self openEachFileAt: fullPath];
    }
  }
}

回答3:

Here is a swift version:

func openEachFileAt(path: String) {
    var file: String

    var subs = NSFileManager.defaultManager().subpathsOfDirectoryAtPath(path, error: nil) as! [String]
    var totalFiles = subs.count
    println(totalFiles)
    for sub in subs {

        if sub.rangeOfString(".DS_Store") != nil {
            //a DS_Store file
        } else if sub.rangeOfString(".xcassets") != nil {
            //a xcassets file
        } else if (sub as NSString).substringWithRange(NSRange(location: 0, length: 4)) == ".git" {
            //a git file
        } else if sub.pathExtension == "swift" {
            //a swift file
        } else if sub.pathExtension == "m" {
            //a objc file
        } else if sub.pathExtension == "h" {
            //a header file
        } else {

        }
        var fullPath = path.stringByAppendingPathComponent(sub)
    }
}

回答4:

This code worked for me.

NSMutableString *allHash;  

  -(NSString*)getIterate:(NSString*)path {

        allHash = [NSMutableString stringWithString:@""];

        NSDirectoryEnumerator *de= [[NSFileManager defaultManager] enumeratorAtPath:path];
        NSString *file;
        BOOL isDirectory;

        for(file in de)
        {

            //first check if it's a file
            NSString* fullPath = [NSString stringWithFormat:@"%@/%@",path,file];

            BOOL fileExistsAtPath = [[NSFileManager defaultManager] fileExistsAtPath:fullPath isDirectory:&isDirectory];
            NSLog(@"Check=>%d",fileExistsAtPath);

            if (!isDirectory) //its a file
            {
                //Do with filepath
            }
            else{ //it's a folder, so recurse
                [self enumerateFolder:fullPath];
            }
        }

        return allHash;


    }

    -(void) enumerateFolder:(NSString*)fileName
    {

        NSDirectoryEnumerator *de= [[NSFileManager defaultManager] enumeratorAtPath:fileName];
        NSString* file;
        BOOL isDirectory;

        for(file in de)
        {
            //first check if it's a file
            BOOL fileExistsAtPath = [[NSFileManager defaultManager] fileExistsAtPath:file isDirectory:&isDirectory];

            if (fileExistsAtPath) {
                if (!isDirectory) //its a file
                { 
                  //Do with file  
                }
                else{ //it's a folder, so recurse

                    [self enumerateFolder:file];
                }
            }
            else printf("\nenumeratefolder No file at path %s",[file UTF8String]);
        }
    }

回答5:

Here's a solution using -subpathsOfDirectoryAtPath:rootPath, with file URLs and modern Objective-C nullability bells & whistles.

typedef void (^FileEnumerationBlock)(NSURL *_Nonnull fileURL);

@interface NSFileManager (Extensions)

- (void)enumerateWithRootDirectoryURL:(nonnull NSURL *)rootURL
                          fileHandler:(FileEnumerationBlock _Nonnull)fileHandler
                                error:(NSError *_Nullable *_Nullable)error;

@end

@implementation NSFileManager (Extensions)

- (void)enumerateWithRootDirectoryURL:(NSURL *)rootURL
                          fileHandler:(FileEnumerationBlock)fileHandler
                                error:(NSError **)error {
    NSString *rootPath = rootURL.path;
    NSAssert(rootPath != nil, @"Invalid root URL %@ (nil path)", rootURL);

    NSArray *subs = [[NSFileManager defaultManager] subpathsOfDirectoryAtPath:rootPath
                                                                        error:error];

    if (!subs) {
        return;
    }

    for (NSString *sub in subs) {
        fileHandler([rootURL URLByAppendingPathComponent:sub]);
    }
}

@end

… and the same in Swift:

func enumerate(rootDirectoryURL rootURL: NSURL, fileHandler:(URL:NSURL)->Void) throws {
    guard let rootPath = rootURL.path else {
        preconditionFailure("Invalid root URL: \(rootURL)")
    }

    let subs = try NSFileManager.defaultManager().subpathsOfDirectoryAtPath(rootPath)
    for sub in subs {
        fileHandler(URL: rootURL.URLByAppendingPathComponent(sub))
    }
}