Scala中的def vs val vs lazy val评估 [英] `def` vs `val` vs `lazy val` evaluation in Scala

问题描述

我是正确的理解

每次访问

• def都会对其进行评估

• def is evaluated every time it gets accessed

lazy val就会对其求值

val一旦进入执行范围就被评估?

val is evaluated once it gets into the execution scope?

推荐答案

是的，尽管对于第3条，我会说该语句执行时"，因为，例如:

Yes, though for the 3rd one I would say "when that statement is executed", because, for example:

def foo() {
    new {
        val a: Any = sys.error("b is " + b)
        val b: Any = sys.error("a is " + a)
    }
}

这给出了"b is null".永远不会评估b，并且永远不会抛出其错误.但是一旦控制进入该块，它就在范围之内.

This gives "b is null". b is never evaluated and its error is never thrown. But it is in scope as soon as control enters the block.

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