Cannot get completion result when removing file using NSFileManager in Swift

Question

I'm trying to remove a video that the user recorded and now has decided to delete. I have both a file URL and then obviously a path too.

I have tried using the removal methods of the NSFileManager class for both the file and the path, but I'm having trouble getting a completion result to confirm whether the file has actually been deleted or not.

Here is an example of how I'm trying to remove the file in Swift:

let deleted = try! NSFileManager.defaultManager().removeItemAtURL(self.fileURL)

This will give me a warning of Constant 'deleted' inferred to have type '()', which may be unexpected

Using removeItemAtPath produces the same warning. If I run the code, deleted simply logs as ()

If I look at the method signatures for these two methods it's clear that they do not return a result, but take for example the documentation for the removeItemAtURL method: true if the item was removed successfully or if URL was nil. Returns false if an error occurred. If the delegate aborts the operation for a file, this method returns true. However, if the delegate aborts the operation for a directory, this method returns false. true if the item was removed successfully or if URL was nil. Returns false if an error occurred. If the delegate aborts the operation for a file, this method returns true. However, if the delegate aborts the operation for a directory, this method returns false.

It also mentions taking an error parameter but doesn't have one. And then finally in the last sentence it says: Returns YES if the item was removed successfully or if URL was nil.

As a last resort I figured I could just become the delegate for NSFileManager , but it's delegate protocol does not offer any completion methods.

How can I properly remove a file or path and then verify that it has actually been deleted?

Answer 1

You're right that in Swift it returns Void (I believe the docs include the return value description for when you have Objective-C or Both turned on, as opposed to just Swift -- they've got a lot of work to do updating the docs).

If you continue reading the documentation for that function, you'll see a section titled "Handling Errors in Swift", which says:

In Swift, this method returns Void and is marked with the throws keyword to indicate that it throws an error in cases of failure.

You call this method in a try expression and handle any errors in the catch clauses of a do statement, as described in Error Handling in The Swift Programming Language (Swift 2.1) and Error Handling in Using Swift with Cocoa and Objective-C (Swift 2.1).

So wrap your call in a try/catch and handle the error if there is one. If there wasn't an error, it succeeded.