diff --git a/JSONCodable.xcodeproj/project.pbxproj b/JSONCodable.xcodeproj/project.pbxproj
index 8d4d68e..66474d4 100644
--- a/JSONCodable.xcodeproj/project.pbxproj
+++ b/JSONCodable.xcodeproj/project.pbxproj
@@ -384,7 +384,7 @@
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = macosx;
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
-				SWIFT_VERSION = 3.0;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Debug;
 		};
@@ -427,7 +427,7 @@
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = macosx;
 				SWIFT_OPTIMIZATION_LEVEL = "-Owholemodule";
-				SWIFT_VERSION = 3.0;
+				SWIFT_VERSION = 4.0;
 			};
 			name = Release;
 		};
@@ -483,7 +483,7 @@
 				SDKROOT = iphoneos;
 				SKIP_INSTALL = YES;
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
-				SWIFT_VERSION = 3.0;
+				SWIFT_VERSION = 4.0;
 				TARGETED_DEVICE_FAMILY = "1,2,3,4";
 				TVOS_DEPLOYMENT_TARGET = 9.0;
 				VERSIONING_SYSTEM = "apple-generic";
@@ -538,7 +538,7 @@
 				SDKROOT = iphoneos;
 				SKIP_INSTALL = YES;
 				SWIFT_OPTIMIZATION_LEVEL = "-Owholemodule";
-				SWIFT_VERSION = 3.0;
+				SWIFT_VERSION = 4.0;
 				TARGETED_DEVICE_FAMILY = "1,2,3,4";
 				TVOS_DEPLOYMENT_TARGET = 9.0;
 				VALIDATE_PRODUCT = YES;
@@ -574,7 +574,7 @@
 				ONLY_ACTIVE_ARCH = YES;
 				SUPPORTED_PLATFORMS = "iphoneos macosx appletvos watchos appletvsimulator iphonesimulator watchsimulator";
 				SWIFT_INSTALL_OBJC_HEADER = NO;
-				SWIFT_VERSION = 3.0.1;
+				SWIFT_VERSION = 4.0;
 				TARGETED_DEVICE_FAMILY = "1,2,3,4";
 			};
 			name = Debug;
diff --git a/JSONCodable/JSONDecodable.swift b/JSONCodable/JSONDecodable.swift
index 7c45e56..4d9e81f 100644
--- a/JSONCodable/JSONDecodable.swift
+++ b/JSONCodable/JSONDecodable.swift
@@ -54,12 +54,12 @@ public protocol JSONDecodable {
 
 public extension JSONDecodable {
     /// initialize with top-level Array JSON data 
-    public init(object: [JSONObject]) throws {
+    init(object: [JSONObject]) throws {
         // use empty string key
         try self.init(object:["": object])
     }
 
-    public init?(optional: JSONObject) {
+    init?(optional: JSONObject) {
         do {
             try self.init(object: optional)
         } catch {
@@ -70,7 +70,7 @@ public extension JSONDecodable {
 
 public extension Array where Element: JSONDecodable {
     init(JSONArray: [Any], filtered: Bool = false) throws {
-        self.init(try JSONArray.flatMap {
+        self.init(try JSONArray.compactMap {
             guard let json = $0 as? [String : Any] else {
                 throw JSONDecodableError.dictionaryTypeExpectedError(key: "n/a", elementType: type(of: $0))
             }
@@ -97,11 +97,12 @@ public class JSONDecoder {
     /// Get index from `"[0]"` formatted `String`
     /// returns `nil` if invalid format (i.e. no brackets or contents not an `Int`)
     internal func parseArrayIndex(_ key:String) -> Int? {
-        var chars = key.characters
-        let first = chars.popFirst()
-        let last = chars.popLast()
+        var mkey = key
+        let first = mkey[mkey.startIndex]
+        mkey.remove(at: mkey.startIndex)
+        let last = mkey.popLast()
         if first == "[" && last == "]" {
-            return Int(String(chars))
+            return Int(mkey)
         } else {
             return nil
         }
@@ -228,7 +229,7 @@ public class JSONDecoder {
         guard let array = value as? [JSONObject] else {
             throw JSONDecodableError.arrayTypeExpectedError(key: key, elementType: type(of: value))
         }
-        return try array.flatMap {
+        return try array.compactMap {
             if filter {
                 return try? Element(object: $0)
             } else {
@@ -245,7 +246,7 @@ public class JSONDecoder {
         guard let array = value as? [JSONObject] else {
             throw JSONDecodableError.arrayTypeExpectedError(key: key, elementType: type(of: value))
         }
-        return try array.flatMap {
+        return try array.compactMap {
             if filter {
                 return try? Element(object: $0)
             } else {
@@ -266,10 +267,10 @@ public class JSONDecoder {
         
         for x in array {
             if filter {
-                let nested = x.flatMap { try? Element(object: $0)}
+                let nested = x.compactMap { try? Element(object: $0)}
                 res.append(nested)
             } else {
-                let nested = try x.flatMap { try Element(object: $0)}
+                let nested = try x.compactMap { try Element(object: $0)}
                 res.append(nested)
             }
         }
@@ -300,7 +301,7 @@ public class JSONDecoder {
         guard let array = value as? [Enum.RawValue] else {
             throw JSONDecodableError.arrayTypeExpectedError(key: key, elementType: type(of: value))
         }
-        return array.flatMap { Enum(rawValue: $0) }
+        return array.compactMap { Enum(rawValue: $0) }
     }
     
     // [Enum]?
@@ -311,7 +312,7 @@ public class JSONDecoder {
         guard let array = value as? [Enum.RawValue] else {
             throw JSONDecodableError.arrayTypeExpectedError(key: key, elementType: type(of: value))
         }
-        return array.flatMap { Enum(rawValue: $0) }
+        return array.compactMap { Enum(rawValue: $0) }
     }
     
     // [String:JSONCompatible]
diff --git a/JSONCodable/JSONEncodable+Mirror.swift b/JSONCodable/JSONEncodable+Mirror.swift
index 45d53eb..0dfbb60 100644
--- a/JSONCodable/JSONEncodable+Mirror.swift
+++ b/JSONCodable/JSONEncodable+Mirror.swift
@@ -12,7 +12,7 @@ public extension Mirror {
      
      - returns: array of Tuples containing the label and value for each property
      */
-    public func getAllProperties() -> [(label: String?, value: Any)] {
+    func getAllProperties() -> [(label: String?, value: Any)] {
         var children: [(label: String?, value: Any)] = []
         for element in self.children {
             children.append(element)
diff --git a/JSONCodable/JSONEncodable.swift b/JSONCodable/JSONEncodable.swift
index 4e62ec4..596f210 100644
--- a/JSONCodable/JSONEncodable.swift
+++ b/JSONCodable/JSONEncodable.swift
@@ -54,8 +54,8 @@ public extension JSONEncodable {
         let mirror = Mirror(reflecting: self)
 
         #if !swift(>=3.0)
-            guard let style = mirror.displayStyle where style == .Struct || style == .Class else {
-            throw JSONEncodableError.IncompatibleTypeError(elementType: self.dynamicType)
+            guard let style = mirror.displayStyle, (style == .Struct || style == .Class) else {
+                throw JSONEncodableError.IncompatibleTypeError(elementType: type(of: self))
             }
         #else
 
@@ -105,7 +105,7 @@ public extension JSONEncodable {
 public extension Array { //where Element: JSONEncodable {
     private var wrapped: [Any] { return self.map{$0} }
 
-    public func toJSON() throws -> Any {
+    func toJSON() throws -> Any {
         var results: [Any] = []
         for item in self.wrapped {
             if let item = item as? JSONEncodable {
@@ -122,7 +122,7 @@ public extension Array { //where Element: JSONEncodable {
 // Dictionary convenience methods
 
 public extension Dictionary {//where Key: String, Value: JSONEncodable {
-    public func toJSON() throws -> Any {
+    func toJSON() throws -> Any {
         var result: [String: Any] = [:]
         for (k, item) in self {
             if let item = item as? JSONEncodable {
@@ -246,7 +246,7 @@ public class JSONEncoder {
 
     // [Enum]
     public func encode<Enum: RawRepresentable>(_ value: [Enum], key: String) throws {
-        let result = try value.flatMap {
+        let result = try value.compactMap {
             try ($0.rawValue as? JSONCompatible)?.toJSON()
         }
         object = update(object: object, keys: key.components(separatedBy: "."), value: result)
@@ -257,7 +257,7 @@ public class JSONEncoder {
         guard let actual = value else {
             return
         }
-        let result = try actual.flatMap {
+        let result = try actual.compactMap {
             try ($0.rawValue as? JSONCompatible)?.toJSON()
         }
         object = update(object: object, keys: key.components(separatedBy: "."), value: result)
diff --git a/JSONCodable/JSONString.swift b/JSONCodable/JSONString.swift
index 88ee3c8..c45115e 100644
--- a/JSONCodable/JSONString.swift
+++ b/JSONCodable/JSONString.swift
@@ -9,7 +9,7 @@
 import Foundation
 
 public extension JSONEncodable {
-    public func toJSONString() throws -> String {
+    func toJSONString() throws -> String {
         switch self {
         case let str as String:
             return escapeJSONString(str)
@@ -45,7 +45,7 @@ private func escapeJSONString(_ str: String) -> String {
 }
 
 public extension Optional where Wrapped: JSONEncodable {
-    public func toJSONString() throws -> String {
+    func toJSONString() throws -> String {
         switch self {
         case let .some(jsonEncodable):
             return try jsonEncodable.toJSONString()
diff --git a/JSONCodableTests/EncodeNestingTests.swift b/JSONCodableTests/EncodeNestingTests.swift
index 3c5e66c..b61e15c 100644
--- a/JSONCodableTests/EncodeNestingTests.swift
+++ b/JSONCodableTests/EncodeNestingTests.swift
@@ -28,6 +28,15 @@ class EncodeNestingTests: XCTestCase {
                 XCTFail()
                 return
         }
-        XCTAssert(String(describing:json1) == String(describing:propertyItemArray), "failed to convert to \(propertyItemArray)")
+        
+        XCTAssert(propertyItemArray.isEqual(to: json1), "failed to convert to \(propertyItemArray)")
     }
 }
+
+private extension JSONObject {
+    
+    func isEqual(to obj: JSONObject) -> Bool {
+        (self as NSDictionary).isEqual(to: obj)
+    }
+        
+}