read

URL is a very common data structure, and can be used for http, file, and other schema.

But I often fell into the pitfalls of using it.

The biggest of all is using the wrong initializer.

Initializations URL(fileURLWithPath:) vs URL(string:)

For local files, always use URL(fileURLWithPath:).

The initialization does 2 things:

1. Encode if needed
2. Append file:// if needed

So for the string path /Document/Space .txt, the initialization will create the URL file:///Document/Space%20.txt.

Use FileManager

Use this for forming URL for local files:

let documentDirectory = try! FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
let fileURL = documentDirectory.appendingPathComponent("secret.txt")

Pitfall: UIActivityViewController

The activityItems can accept a URL to a local file, but they need to be in the format of file://....

If it is not, it will not be sharable 🤔

So do this, if needed:

let fileUrl = URL(fileURLWithPath: url.absoluteString)

Or just don’t ever use URL(string:) for local files.