Iterate through files in a folder and its subfolde

问题:

I'm quite new to programming a Swift and I'm trying to iterate through the files in a folder. I took a look at the answer here and tried to translate it to Swift syntax, but didn't succeed.

let fileManager = NSFileManager.defaultManager()
let enumerator:NSDirectoryEnumerator = fileManager.enumeratorAtPath(folderPath)

for element in enumerator {
    //do something
}

the error I get is:

Type 'NSDirectoryEnumerator' does not conform to protocol 'SequenceType'

My aim is to look at all the subfolders and files contained into the main folder and find all the files with a certain extension to then do something with them.

回答1:

Use the nextObject() method of enumerator:

while let element = enumerator?.nextObject() as? String {
    if element.hasSuffix("ext") { // checks the extension
    }
}

回答2:

Nowadays (early 2017) it's highly recommended to use the – more versatile – URL related API

let fileManager = FileManager.default

do {
    let resourceKeys : [URLResourceKey] = [.creationDateKey, .isDirectoryKey]
    let documentsURL = try fileManager.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
    let enumerator = FileManager.default.enumerator(at: documentsURL,
                            includingPropertiesForKeys: resourceKeys,
                                               options: [.skipsHiddenFiles], errorHandler: { (url, error) -> Bool in
                                                        print("directoryEnumerator error at \(url): ", error)
                                                        return true
    })!

    for case let fileURL as URL in enumerator {
        let resourceValues = try fileURL.resourceValues(forKeys: Set(resourceKeys))
        print(fileURL.path, resourceValues.creationDate!, resourceValues.isDirectory!)
    }
} catch {
    print(error)
}

回答3:

I couldn't get pNre's solution to work at all; the while loop just never received anything. However, I did come across this solution which works for me (in Xcode 6 beta 6, so perhaps things have changed since pNre posted the above answer?):

for url in enumerator!.allObjects {
    print("\((url as! NSURL).path!)")
}

回答4:

In case that you are getting the

'NSDirectoryEnumerator?' does not have a member named 'nextObject' error

the while loop should be:

while let element = enumerator?.nextObject() as? String {
  // do things with element
}

It has something to do with optional chaining

回答5:

Swift 3

let fd = FileManager.default
fd.enumerator(atPath: "/Library/FileSystems")?.forEach({ (e) in
    if let e = e as? String, let url = URL(string: e) {
        print(url.pathExtension)
    }
})

回答6:

returns all files in a directory

Swift 3

let fileNames = try! FileManager.default.contentsOfDirectory(atPath: "/Volumes/Seagate/Path/")

for fileName in fileNames {

    print(fileName)

}

回答7:

Swift3 + absolute urls

extension FileManager {
    func listFiles(path: String) -> [URL] {
        let baseurl: URL = URL(fileURLWithPath: path)
        var urls = [URL]()
        enumerator(atPath: path)?.forEach({ (e) in
            guard let s = e as? String else { return }
            let relativeURL = URL(fileURLWithPath: s, relativeTo: baseurl)
            let url = relativeURL.absoluteURL
            urls.append(url)
        })
        return urls
    }
}

Based on code from @user3441734

回答8:

SWIFT 3.0

Returns all files with extension in the Directory passed & its subdirectories

func extractAllFile(atPath path: String, withExtension fileExtension:String) -> [String] {
    let pathURL = NSURL(fileURLWithPath: path, isDirectory: true)
    var allFiles: [String] = []
    let fileManager = FileManager.default
    let pathString = path.replacingOccurrences(of: "file:", with: "")
    if let enumerator = fileManager.enumerator(atPath: pathString) {
        for file in enumerator {
            if #available(iOS 9.0, *) {
                if let path = NSURL(fileURLWithPath: file as! String, relativeTo: pathURL as URL).path, path.hasSuffix(".\(fileExtension)"){
                    let fileNameArray = (path as NSString).lastPathComponent.components(separatedBy: ".")
                    allFiles.append(fileNameArray.first!)
                }
            } else {
                // Fallback on earlier versions
                print("Not available, #available iOS 9.0 & above")
            }
        }
    }
    return allFiles
}

回答9:

Updating for Swift 3:

let fileManager = FileManager()     // let fileManager = NSFileManager.defaultManager()
let en=fileManager.enumerator(atPath: the_path)   // let enumerator:NSDirectoryEnumerator = fileManager.enumeratorAtPath(folderPath)

while let element = en?.nextObject() as? String {
    if element.hasSuffix("ext") {
        // do something with the_path/*.ext ....
    }
}

回答10:

Adding to vadian's response -- the Apple docs mention that Path-based URLs are simpler in some ways, however file reference URLs have the advantage that the reference remains valid if the file is moved or renamed while your app is running.

From the documentation for "Accessing Files and Directories":

"Path-based URLs are easier to manipulate, easier to debug, and are generally preferred by classes such as NSFileManager. An advantage of file reference URLs is that they are less fragile than path-based URLs while your app is running. If the user moves a file in the Finder, any path-based URLs that refer to the file immediately become invalid and must be updated to the new path. However, as long as the file moved to another location on the same disk, its unique ID does not change and any file reference URLs remain valid."

https://developer.apple.com/library/content/documentation/FileManagement/Conceptual/FileSystemProgrammingGuide/AccessingFilesandDirectories/AccessingFilesandDirectories.html

回答11:

If you want to categorically check whether an element is a file or a subdirectory:

let enumerator = FileManager.default.enumerator(atPath: contentsPath);
while let element = enumerator?.nextObject() as? String {             
   if(enumerator?.fileAttributes?[FileAttributeKey.type] as! FileAttributeType == FileAttributeType.typeRegular){
                //this is a file
   }
   else if(enumerator?.fileAttributes?[FileAttributeKey.type] as! FileAttributeType == FileAttributeType.typeDirectory){ 
                //this is a sub-directory
    }
}

回答12:

Recently struggled with this when handling an array of urls, whether they be a directory or not (eg. drag and drop). Ended up with this extension in swift 4, may be of use

extension Sequence where Iterator.Element == URL {

    var handleDir: [URL] {
        var files: [URL] = []
        self.forEach { u in
            guard u.hasDirectoryPath else { return files.append(u.resolvingSymlinksInPath()) }
            guard let dir = FileManager.default.enumerator(at: u.resolvingSymlinksInPath(), includingPropertiesForKeys: nil) else { return }
            for case let url as URL in dir {
                files.append(url.resolvingSymlinksInPath())
            }
        }
        return files
    }
}

回答13:

Avoid reference URLs, while they do have some advantages as stated above, they eat system resources and if you’re enumerating a large filesystem (not that large actually) your app will hit a system wall quickly and get shutdown by macOS.