为什么使用Convenience Initializer修复我的问题？

Please have a look at the two versions of the Renderer class. Renderer1's initializer executes successfully. Renderer2's initializer crashes on the call to super.init. The init(overlay:) initializer referenced in the crash message is declared by MKOverlayRenderer which is 3 levels up the class hierarchy.Please have a look at the two versions of the R