What are the implications of using def
vs. val
in Scala to define a constant, immutable value? I obviously can write the following:
val x = 3;
def y = 4;
var a = x + y; // 7
这两项声明有什么区别? 谁做得更好? 建议采取什么方式? 何时,我会把一人用在另一边?
What are the implications of using def
vs. val
in Scala to define a constant, immutable value? I obviously can write the following:
val x = 3;
def y = 4;
var a = x + y; // 7
这两项声明有什么区别? 谁做得更好? 建议采取什么方式? 何时,我会把一人用在另一边?
Assuming these are class-level declarations:
汇编者将制作<代码>valfinal
,这可导致由考试和测验科采用更为优化的代码。
www.un.org/Depts/DGACM/index_spanish.htm 赢得了标本的储存价值,因此可以节省记忆,但需要每次评估的方法。
就两个世界而言,都成为附庸标,并宣布定型号为val
。
i.e. 而不是
class Foo {
val MyConstant = 42
}
因此:
class Foo {}
object Foo {
val MyConstant = 42
}
<val
一经评估并储存在外地。 <代码>def作为方法实施,每次重新评价,但并不使用记忆空间储存所产生的价值。
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