From 6cc475c603ed4736789f6e46ee0c2c6299373436 Mon Sep 17 00:00:00 2001
From: Sam Warner <sam@goro-des.co.uk>
Date: Sun, 29 Nov 2015 18:23:12 +1100
Subject: [PATCH] adding mapping over Results containing collections

---
 Result/ResultType.swift       | 21 +++++++++++++++++++++
 ResultTests/ResultTests.swift | 12 ++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/Result/ResultType.swift b/Result/ResultType.swift
index f445a32..8db2359 100644
--- a/Result/ResultType.swift
+++ b/Result/ResultType.swift
@@ -64,6 +64,27 @@ public extension ResultType {
 	}
 }
 
+public extension ResultType where Value: CollectionType {
+	/// Returns a new Result by mapping each of `Success`es’ values using `transform`, or re-wrapping `Failure`s’ errors.
+	public func map<U>(@noescape transform: Value.Generator.Element -> U) -> Result<[U], Error> {
+		return flatMap { .Success(transform($0)) }
+	}
+
+	/// Returns the result of applying `transform` to each of `Success`es’ values, or re-wrapping `Failure`’s errors.
+	public func flatMap<U>(@noescape transform: (Value.Generator.Element) -> Result<U, Error>) -> Result<[U], Error> {
+		return analysis(
+			ifSuccess: {
+				$0.map(transform).reduce(.Success([])) { (acc, result) in
+					guard let successes = acc.value, success = result.value else {
+						return acc
+					}
+					return .Success(successes + [success])
+				}
+			},
+			ifFailure: Result<[U], Error>.Failure)
+	}
+}
+
 // MARK: - Operators
 
 infix operator &&& {
diff --git a/ResultTests/ResultTests.swift b/ResultTests/ResultTests.swift
index 2f574ed..bf032de 100644
--- a/ResultTests/ResultTests.swift
+++ b/ResultTests/ResultTests.swift
@@ -16,6 +16,16 @@ final class ResultTests: XCTestCase {
 	func testInitOptionalFailure() {
 		XCTAssert(Result(nil, failWith: error) == failure)
 	}
+	
+	// MARK: Collections
+	
+	func testCollectionMapTransformsSuccesses() {
+		XCTAssertEqual(successCollection.map { $0.characters.count } ?? [], [7, 14])
+	}
+	
+	func testCollectionMapRewrapsFailures() {
+		XCTAssertEqual(failureCollection.map { $0.characters.count } ?? [], [])
+	}
 
 
 	// MARK: Errors
@@ -114,10 +124,12 @@ final class ResultTests: XCTestCase {
 // MARK: - Fixtures
 
 let success = Result<String, NSError>.Success("success")
+let successCollection = Result<[String], NSError>.Success(["success", "anotherSuccess"])
 let error = NSError(domain: "com.antitypical.Result", code: 1, userInfo: nil)
 let error2 = NSError(domain: "com.antitypical.Result", code: 2, userInfo: nil)
 let failure = Result<String, NSError>.Failure(error)
 let failure2 = Result<String, NSError>.Failure(error2)
+let failureCollection = Result<[String], NSError>.Failure(error)
 
 
 // MARK: - Helpers