Update README.md

DavinAhn · DavinAhn · commit 941b42dc8136 · 2017-01-19T11:35:42.000+09:00
diff --git a/README.md b/README.md
@@ -6,6 +6,8 @@ Calling native code from Javascript in iOS likes JavascriptInterface in Android.
 - Swift 3
 - iOS8+
 
+(based on WKJavaScriptController 1.1.0+)
+
 ## Installation
 This library is distributed by [CocoaPods](https://cocoapods.org).
 
@@ -38,6 +40,7 @@ $ pod install
 import WKJavaScriptController
 
 // Create protocol.
+// '@objc' keyword is required. because method call is based on ObjC.
 @objc protocol JavaScriptInterface {
     func onSubmit(_ dictonary: [String: AnyObject])
     func onSubmit(_ email: String, firstName: String, lastName: String, address1: String, address2: String, zipCode: JSInt, phoneNumber: String)
@@ -92,4 +95,11 @@ native.onSubmit({
 	'last_name': 'Ahn',
 	'mail': 'davin.ahn@ridi.com',
 });
-```
+```
+
+## Limitations
+- Can not receive native return in JavaScript.
+- Method argument length is up to 10.
+- Allowed types for argument types are NSNumber, NSString, NSDate, NSArray, NSDictionary, and NSNull(If pass undefined in JavaScript).
+- If Value Types of Swift(Bool, Int32, Int, Float, Double, ...) used in argument is not wrapped in NSArray or NSDictionary, then it must be replaced with JSBool, JSInt or JSFloat.
+(In ObjC, Value types of Swift is replaced by NSNumber.)
