flatPred

This is a function that makes optionals in preconditions a little less painful:

import UIKit

extension Optional {
/// Thanks to http://www.russbishop.net/improving-optionals for how to get
the "Wrapped" type
    func flatPred(_ f: (Wrapped) -> Bool) -> Bool {
      return self.flatMap(f) ?? false
    }
 }

 var dict = ["hello":"there", "you":"🐨s"]


 //
 // Use these to verify it's the same as the precondition with flatmap ?? false
 //

 var str:String? = dict["🐨s"] //fails as nil
 //var str:String? = dict["you"]    //fails as non-there
 //var str:String? = dict["hello"]  //succeeds

 //precondition( str.flatMap{$0 == "there"} ?? false , "It's not there!")

 print("Normal vanilla")

 precondition( str.flatPred{ $0 == "there"}, "It's really not there!")

 print("naming left to you, I dislike flatApply and flatPred")

langford/flatPred

flatPred