Updated static cantMap(value:toType:)->NSError method on NSError to r…

…eturn an error that is more debugger friendly (prints a helpful, human-readable description), and that conforms to standard practices with regard to the 'domain' property.

ConcurrencyTests/PromiseTests.swift

@@ -187,7 +187,7 @@ class PromiseTests: QuickSpec {
  expect(mappedFuture.isComplete).toEventually(beTrue())
  expect(mappedFuture.succeeded).toEventually(beFalse())
  expect(mappedFuture.failed).toEventually(beTrue())
- expect(item(mappedFuture.error, isA: NSError.self, and: {$0.domain == "Could not map value (3) to type String."})).toEventually(beTrue())
+ expect(item(mappedFuture.error, isA: NSError.self, and:{ $0.description == "Concurrency: Could not map value (3) to type String." })).toEventually(beTrue())
  expect(mappedFuture.value).toEventually(beNil())
  }
  }

Source/ConcurrencyHelpers.swift

@@ -8,8 +8,38 @@ import Foundation
 
 extension NSError {
  static func cantMap<T,Q>(value:T, toType: Q.Type) -> NSError {
+ return CantMapError(value: value, toType: toType)
+ }
+}
+
+fileprivate class CantMapError<Q,T>: NSError {
+
+ private var descriptionString: String
+
+ init(value: T, toType: Q.Type) {
  let typeString = String(describing: type(of: Q.self)).replacingOccurrences(of: ".Type", with: "")
- let description = "Could not map value (\(value)) to type \(typeString)."
- return NSError(domain: description, code: 0, userInfo: nil)
+ let description = "Concurrency: Could not map value (\(value)) to type \(typeString)."
+ self.descriptionString = description
+
+ super.init(domain: "com.concurrency.map", code: 0, userInfo: ["description" : description])
+ }
+
+ required init?(coder aDecoder: NSCoder) {
+ self.descriptionString = "Mapping Error"
+
+ super.init(coder: aDecoder)
+
+ if let unarchivedDescription = self.userInfo["description"] as? String {
+ self.descriptionString = unarchivedDescription
+ }
+ }
+
+ override var description: String {
+ return descriptionString
+ }
+
+ public static func ==(lhs: CantMapError, rhs: CantMapError) -> Bool {
+ return lhs.description == rhs.description
  }
+
 }