Created by Wang, Jerry on Sep 25, 2015

application里一個object extend了一個App:

通過查看source code的實現能發現App是一個trait，繼承了DelayedInit:

scala.DelayedInit

Classes and objects (but note, not traits) inheriting the DelayedInit marker trait will have their initialization code rewritten as follows: code becomes delayedInit(code).

Initialization code comprises all statements and all value definitions that are executed during initialization.

Example:

trait Helper extends DelayedInit { def delayedInit(body: => Unit) = { println(“dummy text, printed before initialization of C”) body // evaluates the initialization code of C } } class C extends Helper { println(“this is the initialization code of C”) } object Test extends App { val c = new C }

Should result in the following being printed:

dummy text, printed before initialization of C this is the initialization code of C

所有帶有App 特質的類，其初始化方法都會被挪到delayedInit方法中。App特質的main方法捕獲到命令行參數，調用delayedInit方法。

要獲取更多Jerry的原創文章，請關注公眾號"汪子熙":

總結

以上是生活随笔為你收集整理的App in Scala的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。