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  • App in Scala

    Created by Wang, Jerry on Sep 25, 2015

    application里一个object extend了一个App:

    通过查看source code的实现能发现App是一个trait,继承了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


    所有带有App 特质的类,其初始化方法都会被挪到delayedInit方法中。App特质的main方法捕获到命令行参数,调用delayedInit方法。



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  • 原文地址:https://www.cnblogs.com/sap-jerry/p/12418952.html
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