Reading in array of elements from macOS directory

Question

I can read in elements (images or videos) uploaded in Xcode's project this way:

let photos = (1...9).map {
    NSImage(named: NSImage.Name(rawValue: "000\($0)"))
}

or like this:

let videos = (1...100).map { _ in
    Bundle.main.urls(forResourcesWithExtension: "mov", subdirectory: nil)![Int(arc4random_uniform(UInt32(100)))]
}

But how to read in files (as array) from macOS directory using .map method?

/Users/me/Desktop/ArrayOfElements/

Well, how would you go about accessing `/Users/me/Desktop/A/Singe/File.txt`? — Alexander, Mar 26 '18 at 20:12
let url = URL(fileURLWithPath: "/Users/me/Desktop/A/Single/File.txt") — Andy Jazz, Mar 26 '18 at 20:14
Good. Now, how given an `n: Int = 123`, how would you go about accessing `/Users/me/Desktop/A/Single/File123.txt`, using `n`? — Alexander, Mar 26 '18 at 20:15
I mean for the specific case of `n = 123`. How can you put the int `123` in that path, so that you can initialize a `URL` from it? — Alexander, Mar 26 '18 at 20:24
`But if I don't know how many files in my directory...` -> What have you tried to do to figure this out? — Alexander, Mar 26 '18 at 20:24
This directory is Library. There are many files at the moment or a few ones... — Andy Jazz, Mar 26 '18 at 20:33
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/167587/discussion-between-alexander-and-andy). — Alexander, Mar 26 '18 at 21:32

vadian · Accepted Answer · 2020-09-04T11:05:49.377

1

First of all your second way is very expensive, the array of movie URLs is read a hundred times from the bundle. This is more efficient:

let resources = Bundle.main.urls(forResourcesWithExtension: "mov", subdirectory: nil)!
let videos = (1...100).map { _ in
    resources[Int(arc4random_uniform(100))]
}

Reading from /Users/me/Desktop is only possible if the application is not sandboxed, otherwise you can only read form the application container.

To get all files (as [URL]) from a directory use FileManager:

let url = URL(fileURLWithPath: NSHomeDirectory()).appendingPathComponent("Desktop/ArrayOfElements")
do {
    let fileURLs = try FileManager.default.contentsOfDirectory(at: url, includingPropertiesForKeys: nil, options: .skipsHiddenFiles)
    let movieURLs = fileURLs.filter{ $0.pathExtension == "mov" }
    print(movieURLs)
} catch { print(error) }

Rather than using map I recommend to implement an Array extension adding shuffle()

edited Sep 04 '20 at 11:05

answered Mar 26 '18 at 20:19

vadian

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Thank you very much, @vadian. But how can I use `.reversed()` method using FileManager? – Andy Jazz Mar 26 '18 at 20:34
The result is an array. You can use any function array responds to, amongst others `.reverse` – vadian Mar 26 '18 at 20:36
Where to put it? This is unfamiliar syntax for me. – Andy Jazz Mar 26 '18 at 20:37
At the end of the `FileManager` line `...options: [.skipsHiddenFiles]).reversed()` – vadian Mar 26 '18 at 20:41
Damn! Thanks a lot! )) – Andy Jazz Mar 26 '18 at 20:42
could you help me? I have an error after a first loop. – Andy Jazz Mar 27 '18 at 06:58
Thread 1: Fatal error: Index out of range. I have 7 jpeg images in a folder. ArrayOfViews = 20. I published my code as an answer. – Andy Jazz Mar 27 '18 at 07:05
`arc4random_uniform` is zero-based. 7 photos is `arc4random_uniform(6)` – or better `arc4random_uniform(photos.count - 1)` – and you don't need the explicit `UInt32` initializer. – vadian Mar 27 '18 at 07:09
not working with 6, I tried it. Works with 1 only)) Strange. I suppose the error in let image = [NSImage(data: try Data(contentsOf: index))] – Andy Jazz Mar 27 '18 at 07:11
Please delete the answer and ask a new question. Answers shouldn't be misused for subsequent questions. And describe what you are going to accomplish. – vadian Mar 27 '18 at 07:15
https://stackoverflow.com/questions/49506602/random-photos-in-views-fatal-error-index-out-of-range – Andy Jazz Mar 27 '18 at 07:20

Reading in array of elements from macOS directory

1 Answers1