Return file if exists, otherwise return false - swift

Question

I'm trying to make a String extension that searches for a file in my app's directory and either returns that file or returns false if it does not exist. Here's what I have:
extension String {
func doesFileWithNameExist() -> Bool {
let path = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as String
let url = NSURL(fileURLWithPath: path)
let filePath = url.appendingPathComponent(self+".png")?.path
let fileManager = FileManager.default
if fileManager.fileExists(atPath: filePath!) {
return true
} else {
return false
}
}
}
Right now my function just returns a Bool, but I'm wondering if there's a way to just return the file if it exists, otherwise return false. Is there a way to return different value types from a function?

Answer 1

It's highly recommended to use the URL related API. This returns an optional UIImage:
extension String {
func doesFileWithNameExist() -> UIImage? { // maybe better pngImageInDocumentsFolder()
let fileManager = FileManager.default
do {
let url = try fileManager.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
let fullURL = url.appendingPathComponent(self).appendingPathExtension("png")
_ = try fullURL.checkResourceIsReachable()
let data = try Data(contentsOf: fullURL)
return UIImage(data: data)
} catch {
return nil
}
}
}
or using Leo's great reduction (slightly still reduced):
var image: UIImage? {
guard let url = try? FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false).appendingPathComponent(self).appendingPathExtension("‌​png"),
let data = try? Data(contentsOf: url) else { return nil }
return UIImage(data: data)
}

Answer 2

You can return an optional value here, which in Swift is "a thing or nil" – very close to "that file or false." For example, here's a quick tweak to your extension function that returns the path if a file exists there, or nil otherwise:
extension String {
func doesFileWithNameExist() -> String? {
let path = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as String
let url = NSURL(fileURLWithPath: path)
let filePath = url.appendingPathComponent(self+".png")?.path
let fileManager = FileManager.default
if fileManager.fileExists(atPath: filePath!) {
return filePath
} else {
return nil
}
}
}
A quick editorial comment, though: this kind of behavior doesn't seem especially well-suited to a String extension. I'd consider writing an extension on FileManager instead, passing in a string for the file's name. Given the hardcoding of the "png" extension, maybe something with the following signature?
extension FileManager {
func pathToExistingPNGFile(named name: String) -> String? {
// …
}
}