[英]A better way to test the value of an Option?
I often find myself with an Option[T]
for some type T
and wish to test the value of the option against some value. 对于某些类型的
T
,我经常发现自己有一个Option[T]
,并且希望根据某个值来测试该选项的值。 For example: 例如:
val opt = Some("oxbow")
if (opt.isDefined && opt.get == "lakes")
//do something
The following code is equivalent and removes the requirement to test the existence of the value of the option 以下代码是等效的,并删除了测试选项值是否存在的要求
if (opt.map(_ == "lakes").getOrElse(false))
//do something
However this seems less readable to me. 然而,这对我来说似乎不太可读。 Other possibilities are:
其他可能性是:
if (opt.filter(_ == "lakes").isDefined)
if (opt.find(_ == "lakes").isDefined) //uses implicit conversion to Iterable
But I don't think these clearly express the intent either which would be better as: 但我不认为这些明确表达了更好的意图:
if (opt.isDefinedAnd(_ == "lakes"))
Has anyone got a better way of doing this test? 有没有人有更好的方法来做这个测试?
How about 怎么样
if (opt == Some("lakes"))
This expresses the intent clearly and is straight forward. 这清楚地表达了意图并且是直截了当的。
对于Scala 2.11,您可以使用Some(foo).contains(bar)
Walter Chang FTW,但这是另一个尴尬的选择:
Some(2) exists (_ == 2)
val opt = Some("oxbow")
opt match {
case Some("lakes") => //Doing something
case _ => //If it doesn't match
}
You can use for-comprehension as well: 您也可以使用for-understanding:
for {val v <- opt if v == "lakes"}
// do smth with v
I think pattern matching could also be used. 我认为也可以使用模式匹配。 That way you extract the interesting value directly:
这样你直接提取有趣的值:
val opt = Some("oxbow")
opt match {
case Some(value) => println(value) //Doing something
}
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