我通常可以找出这些问题，但我只是无法解决这个问题，有什么帮助吗？
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "logout" {
PFUser.logOut() //Log user out
currentUser = PFUser.currentUser()!.username //Reset currentUser variable to nil
}
}
Ld /Users/nickporter/Library/Developer/Xcode/DerivedData/packageTracker-eacmyzjvxkncgxaugoxuxlnmpsgb/Build/Intermediates/packageTracker.build/Debug-iphoneos/packageTracker.build/Objects-normal/armv7/packageTracker normal armv7
cd /Users/nickporter/Developer/packageTracker
export IPHONEOS_DEPLOYMENT_TARGET=8.0
export PATH="/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/bin:/Applications/Xcode.app/Contents/Developer/usr/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin"
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -arch armv7 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS9.0.sdk -L/Users/nickporter/Library/Developer/Xcode/DerivedData/packageTracker-eacmyzjvxkncgxaugoxuxlnmpsgb/Build/Products/Debug-iphoneos -F/Users/nickporter/Library/Developer/Xcode/DerivedData/packageTracker-eacmyzjvxkncgxaugoxuxlnmpsgb/Build/Products/Debug-iphoneos -F/Users/nickporter/Developer/packageTracker/packageTracker -filelist /Users/nickporter/Library/Developer/Xcode/DerivedData/packageTracker-eacmyzjvxkncgxaugoxuxlnmpsgb/Build/Intermediates/packageTracker.build/Debug-iphoneos/packageTracker.build/Objects-normal/armv7/packageTracker.LinkFileList -Xlinker -rpath -Xlinker @executable_path/Frameworks -miphoneos-version-min=8.0 -dead_strip -ObjC -lAFNetworking -lAPTimeZones -lAftership-iOS-SDK -lCSNotificationView -lCTFeedback -lDateTools -lMCSwipeTableViewCell -lMMMaterialDesignSpinner -lMTDates -lNSDate+TimeAgo -lNSTimeZone-CountryCode -lRestKit -lSOCKit -lSVGeocoder -lSVPullToRefresh -lSVPulsingAnnotationView -lSVWebViewController -framework CFNetwork -framework CoreData -framework CoreGraphics -framework CoreLocation -framework MapKit -framework MessageUI -framework MobileCoreServices -framework QuartzCore -framework Security -framework SystemConfiguration -framework UIKit -lAFNetworking -lAPTimeZones -lAftership-iOS-SDK -lCSNotificationView -lCTFeedback -lDateTools -lMCSwipeTableViewCell -lMMMaterialDesignSpinner -lMTDates -lNSDate+TimeAgo -lNSTimeZone-CountryCode -lRestKit -lSOCKit -lSVGeocoder -lSVPullToRefresh -lSVPulsingAnnotationView -lSVWebViewController -framework CFNetwork -framework CoreData -framework CoreGraphics -framework CoreLocation -framework MapKit -framework MessageUI -framework MobileCoreServices -framework QuartzCore -framework Security -framework SystemConfiguration -framework UIKit -fobjc-arc -fobjc-link-runtime -framework MobileCoreServices -framework QuartzCore -framework Accounts -framework Social -lsqlite3 -lz -framework SystemConfiguration -framework Parse -framework Security -framework CoreLocation -framework CoreGraphics -framework CFNetwork -framework AudioToolbox -framework CoreData -lPods-packageTracker -framework Bolts -Xlinker -dependency_info -Xlinker /Users/nickporter/Library/Developer/Xcode/DerivedData/packageTracker-eacmyzjvxkncgxaugoxuxlnmpsgb/Build/Intermediates/packageTracker.build/Debug-iphoneos/packageTracker.build/Objects-normal/armv7/packageTracker_dependency_info.dat -o /Users/nickporter/Library/Developer/Xcode/DerivedData/packageTracker-eacmyzjvxkncgxaugoxuxlnmpsgb/Build/Intermediates/packageTracker.build/Debug-iphoneos/packageTracker.build/Objects-normal/armv7/packageTracker