"fatal error: unexpectedly found nil while unwrapping an Optional value" in Standardized Social Media Sharing Method - swift

Question

I am trying to create a standardized social media sharing method inside my SocialMediaSharingDelegate. Specifying an individual social media service like I do in the facebookShare method works perfectly fine. So to extend this I created an enum with the possible service types and the shareOn method accepts any valid service name to perform sharing.
It seems straight forward. However, when I run the code and click on a button that calls the shareOn method I get a runtime error. The error "fatal error: unexpectedly found nil while unwrapping an Optional value" occurs on the line let serviceViewController... right after the guard statement.
It also works fine if I replace socialMediaService.associatedService() with SLServiceTypeFacebook on that line which is strange because socialMediaService.associatedService() is used without issue in the guard statement.
I can just create separate functions for each service for now but that is not ideal in terms of code reuse.
import Foundation
import UIKit
import Social
enum SocialMediaEnum : String {
case Twitter = "SLServiceTypeTwitter"
case Facebook = "SLServiceTypeFacebook"
// This internal enum function returns the SLServiceType associated with the current enum value
func associatedService() -> String {
var serviceName: String
switch self {
case .Twitter:
serviceName = "SLServiceTypeTwitter"
case .Facebook:
serviceName = "SLServiceTypeFacebook"
}
return serviceName
}
}
class socialMediaSharing : SocialMediaSharingDelegate {
func shareOn(let socialMediaService: SocialMediaEnum, sender: subclassedUIButton?, currentViewController: UIViewController) {
guard SLComposeViewController.isAvailableForServiceType(socialMediaService.associatedService()) else {
let alert = UIAlertController(title: "Accounts", message: "Please login to a Twitter account to tweet.", preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))
currentViewController.presentViewController(alert, animated: true, completion: nil)
return
}
let serviceViewController :SLComposeViewController = SLComposeViewController(forServiceType: socialMediaService.associatedService())
if let imageUrl = sender?.urlString {
if let url:NSURL = NSURL(string: imageUrl as String) {
serviceViewController.addURL(url)
}
}
currentViewController.presentViewController(serviceViewController, animated: true, completion: nil)
}
func facebookShare(sender: subclassedUIButton?, currentViewController: UIViewController) {
guard SLComposeViewController.isAvailableForServiceType(SLServiceTypeFacebook) else {
let alert = UIAlertController(title: "Accounts", message: "Please login to a Facebook account to share.", preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))
currentViewController.presentViewController(alert, animated: true, completion: nil)
return
}
let shareToFacebook :SLComposeViewController = SLComposeViewController(forServiceType: SLServiceTypeFacebook)
if let imageUrl = sender?.urlString {
if let url:NSURL = NSURL(string: imageUrl as String) {
shareToFacebook.addURL(url)
}
}
currentViewController.presentViewController(shareToFacebook, animated: true, completion: nil)
}
}

Answer 1

SLServiceTypeTwitter and SLServiceTypeFacebook are keywords so they should not have quotation marks in the switch statement. The actual values they hold are "com.apple.social.(service name)".