add structure picture

README.md

@@ -26,6 +26,10 @@ pod "ResourcePackage"
 
 ## Usage
 
+
+## Structure
+![Structure](structure.png)
+
 ## Author
 
 [Alfred Gao](http://alfredg.org), [alfredg@alfredg.cn](mailto:alfredg@alfredg.cn)

ResourcePackage/Classes/Sounds.swift

@@ -73,7 +73,7 @@ extension ResourcePackageReader {
     /// 播放音乐
     ///
     /// play music
-    func playMusic(_ key: String, loops: Int = 1, volume: Float = 100) {
+    public func playMusic(_ key: String, loops: Int = 1, volume: Float = 100) {
         stopMusic()
         
         // load music data
@@ -103,7 +103,7 @@ extension ResourcePackageReader {
     /// 停止音乐播放
     ///
     /// stop music
-    func stopMusic() {
+    public func stopMusic() {
         musicPlayer?.stop()
     }