> On 11 Mar 2015, at 00:24, Bill Cheeseman <[email protected]> wrote:
>
> I'm using Xcode 6.2 and Swift 1.1.
>
> 1. The following statement reports the error "'NSURL?' does not have a member
> named 'path'" even though executableURL has a trailing exclamation point to
> unwrap it. The caret identifying the location of the error is placed under
> the exclamation point.
>
> for thisApp in NSWorkspace.sharedWorkspace().runningApplications {
> let thisPath = thisApp.executableURL!.path // ERROR
> }
>
> If I change executableURL to bundleURL, the error goes away. Yet
> executableURL and bundleURL are declared identically according to the
> NSRunningApplication reference document. As far as I know, bundleURL and
> executableURL both satisfy fileURL.
>
> The error also goes away if I assign thisApp to a local variable and
> expressly downcast it to NSRunningApplication, as shown below. Why would I
> need to do that with executableURL, when it isn't necessary with bundleURL?
>
> for thisApp in NSWorkspace.sharedWorkspace().runningApplications {
> let myAppAndIMeanIt = thisApp as NSRunningApplication
> let thisPath = myAppAndIMeanIt.executableURL!.path // NO ERROR
> }
>
> Is this a Swift bug?
>
No, one of yours again - although I don't really understand what's going on
with the plethora of optionals it's pretty easy, using something I've
recommended dozens of times, to gain insight into what the compiler thinks it's
doing by, as usual, splitting the line up into two assignments and using opt
option+click to see what type it has guessed things are.
In the first case if you split out thisApp.executableURL into its own line you
will find it's of type 'NSURL?!'. I actually don't know entirely what that
means, an implicitly unwrapped optional to an optional. I suppose it's means
it's possibly something which is possibly an NSURL with an implicit guarantee
that it's not nothing at all. Anyway your '!' before '.path' just unwraps the
implicitly unwrapped optional bit. Yes I know it's implicitly unwrapped already
but I believe the '!' just unwraps it from implicitly unwrapped optional to
optional NSURL to really unwrapped, ie optional NSURL. So you need two '!!',
one for the '!' and one for the '?'.
let thisPath = thisApp.executableURL!!.path
I tried to move the ugliness around a bit, you can do
for thisApp in NSWorkspace.sharedWorkspace().runningApplications as [
NSRunningAppliction ]
{
let thisPath = thisApp.executableURL!.path
}
except in 6.3 now you can't do that, you have to have 'as!', so it isn't much
nicer although possibly more consistent
Why does this happen with executableURL and not bundleURL, I don't really know.
Both those properties are defined on both NSBundle and NSRunningApplication
however the bundleURL is non-optional on both of them and the executableURL is
optional on NSRunningApplication but not on NSBundle. Since runningApplications
returns an [ AnyObject ] I assume there's one level of optionality in err ...
something and then another one in executableURL because it might be optional,
or not.
Amusing crash of the day whilst trying to work this out
import Cocoa
for thisApp in NSWorkspace.sharedWorkspace().runningApplications
{
//let pp = thisApp as! NSRunningApplication
let tt = thisApp.bundleURL!.path
}
works fine. However if you uncomment the commented line, which does nothing but
set an unused variable, the line below crashes with EXC_i386_INVOP. That's 6.3,
in 6.2 you have to remove the '!' in the commented line after the 'as', however
you still get the same crash.
All this to work around nil, a concept I've always rather liked.
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