hcrub · May 3, 2019 21:28 · May 3, 2019 · May 3, 2019
diff --git a/Optional.swift b/Optional.swift
@@ -13,7 +13,7 @@ extension Optional: OptionalType {}
 // The following example shows how you can use the `OptionalType` interface to scope
 // an extension containing an associated type defined as optional. E.g. `InputType??`
 
-interface Validation {
+protocol Validation {
   associatedType InputType
 }
 

diff --git a/Optional.swift b/Optional.swift
@@ -0,0 +1,28 @@
+/// Interface representing an optionally nil value type.
+protocol OptionalType: ExpressibleByNilLiteral {
+    /// The boxed optional type.
+    associatedtype Wrapped
+}
+
+extension Optional: OptionalType {}
+
+// Example
+
+// In this case, we have an extension that returns an optional type.
+// If the associated type is defined as optional, you will return a double optional.
+// The following example shows how you can use the `OptionalType` interface to scope
+// an extension containing an associated type defined as optional. E.g. `InputType??`
+
+interface Validation {
+  associatedType InputType
+}
+
+// Returns `InputType?` 
+extension Validation {
+  func validate() -> InputType? {}
+}
+
+// Returns `InputType?` 
+extension Validation: InputType {
+  func validate() -> InputType {}
+}
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