diff --git a/.DS_Store b/.DS_Store
index a1a605e..a49e7ea 100644
Binary files a/.DS_Store and b/.DS_Store differ
diff --git a/README.md b/README.md
index e7d2aec..f30e0d4 100644
--- a/README.md
+++ b/README.md
@@ -5,7 +5,7 @@
 [![GitHub license](https://img.shields.io/badge/License-BSD%203--Clause-blue.svg)](https://github.com/shogo4405/Logboard/blob/master/LICENSE.md)
 
 * Simple logging framework for your framework project.
-* [API Documentation](https://shogo4405.github.io/Logboard/)
+* [API Documentation](https://shogo4405.github.io/Logboard/documentation/logboard/)
 
 ## Usage
 ```swift
@@ -32,7 +32,7 @@ source 'https://github.com/CocoaPods/Specs.git'
 use_frameworks!
 
 def import_pods
-pod 'Logboard', '~> 2.3.0'
+pod 'Logboard', '~> 2.3.1'
 end
 
 target 'Your Target'  do
@@ -42,7 +42,7 @@ end
 ```
 ### Carthage
 ```
-github "shogo4405/Logboard" ~> 2.3.0
+github "shogo4405/Logboard" ~> 2.3.1
 ```
 
 ## Appenders
diff --git a/Sources/Logboard/ConsoleAppender.swift b/Sources/Logboard/ConsoleAppender.swift
index 5527a29..7492473 100644
--- a/Sources/Logboard/ConsoleAppender.swift
+++ b/Sources/Logboard/ConsoleAppender.swift
@@ -2,6 +2,10 @@ import Foundation
 
 /// The ConsoleAppender class can output your xcode console with print function.
 public class ConsoleAppender: LBLoggerAppender {
+    /// Creates a ConsoleAppender instance.
+    public init() {
+    }
+
     public func append(_ logboard: LBLogger, level: LBLogger.Level, message: [Any], file: StaticString, function: StaticString, line: Int) {
         print(LBLogger.dateFormatter.string(from: Date()), "[\(level)]", "[\(logboard.identifier)]", "[\(filename(file.description)):\(line)]", function, ">", message.map({ String(describing: $0) }).joined(separator: ""))
     }
diff --git a/Sources/Logboard/MultiAppender.swift b/Sources/Logboard/MultiAppender.swift
index 811b9ef..cc12aa3 100644
--- a/Sources/Logboard/MultiAppender.swift
+++ b/Sources/Logboard/MultiAppender.swift
@@ -12,6 +12,10 @@ public class MultiAppender: LBLoggerAppender {
     /// The appenders.
     public var appenders: [LBLoggerAppender] = []
 
+    /// Creates a MultIAppender instance.
+    public init() {
+    }
+
     public func append(_ logboard: LBLogger, level: LBLogger.Level, message: [Any], file: StaticString, function: StaticString, line: Int) {
         for appender in appenders {
             appender.append(logboard, level: level, message: message, file: file, function: function, line: line)
diff --git a/Sources/Logboard/NullAppender.swift b/Sources/Logboard/NullAppender.swift
index fb93058..f669ac4 100644
--- a/Sources/Logboard/NullAppender.swift
+++ b/Sources/Logboard/NullAppender.swift
@@ -2,6 +2,8 @@ import Foundation
 
 /// The NullAppender class does output no message.
 public class NullAppender: LBLoggerAppender {
+    public static let shared = NullAppender()
+
     public func append(_ logboard: LBLogger, level: LBLogger.Level, message: [Any], file: StaticString, function: StaticString, line: Int) {
     }
 
diff --git a/Sources/Logboard/SocketAppender.swift b/Sources/Logboard/SocketAppender.swift
index 6f7b179..fd6ec82 100644
--- a/Sources/Logboard/SocketAppender.swift
+++ b/Sources/Logboard/SocketAppender.swift
@@ -4,6 +4,10 @@ import Foundation
 public class SocketAppender: LBLoggerAppender {
     private var socket: NetSocket = NetSocket()
 
+    /// Creates a SocketAppende instance.
+    public init() {
+    }
+
     /// Connects the Logboard Console service.
     public func connect(_ name: String, port: Int) {
         socket.connect(withName: name, port: port)