#3 Add appending function to KeyPath using the "+" operator

Sources/KeyPath.swift

@@ -4,7 +4,7 @@ import Foundation
 
 /// Simple struct used to represent multiple segments of a string.
 /// This is a utility used to recursively access values in nested dictionaries.
-public struct KeyPath {
+public struct KeyPath: Hashable {
     public var segments: [String]
 
     public var isEmpty: Bool { return segments.isEmpty }
@@ -41,6 +41,18 @@ extension KeyPath: ExpressibleByStringLiteral {
     }
 }
 
+extension KeyPath: CustomStringConvertible {
+    public var description: String {
+        return segments.joined(separator: ".")
+    }
+}
+
+public extension KeyPath {
+    static func + (lhs: KeyPath, rhs: KeyPath) -> KeyPath {
+        return KeyPath(lhs.description + "." + rhs.description)
+    }
+}
+
 public extension Dictionary where Key == String {
     subscript(keyPath keyPath: KeyPath) -> Any? {
         get {

Tests/KeyPathTests.swift

@@ -74,4 +74,22 @@ final class KeyPathTests : XCTestCase {
         let keyPath = KeyPath(path)
         XCTAssertEqual(keyPath.path, path)
     }
+
+    func test_description_whenSegmentIsEmpty_shouldReturnEmptyString() {
+        XCTAssertEqual(KeyPath(""), "")
+    }
+
+    func test_description_whenSegmentHasOneElement_shouldReturnThatElement() {
+        XCTAssertEqual(KeyPath("element"), "element")
+    }
+
+    func test_description_whenSegmentHasTwoElements_shouldReturnStringSeparatedByPeriod() {
+        XCTAssertEqual(KeyPath("my.name"), "my.name")
+    }
+
+    func test_pathAppending_whenPathIsValid_shouldReturnAppendedPathsUsingPeriod() {
+        let lhs = "this.is.path.start"
+        let rhs = "this.is.path.end"
+        XCTAssertEqual(KeyPath(lhs) + KeyPath(rhs), "this.is.path.start.this.is.path.end")
+    }
 }