scala 禁止“丢弃的非单位值”警告
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Suppress "discarded non-Unit value" warning
提问by Robin Green
I have added the scalac command line argument -Ywarn-value-discardto my build because this would have caught a subtle bug that I just found in my code. However, I now get some warnings for "discarded non-Unit value" that are about intentional discards, not bugs. How do I suppress those warnings?
我已将 scalac 命令行参数添加-Ywarn-value-discard到我的构建中，因为这会捕获我刚刚在我的代码中发现的一个微妙的错误。但是，我现在收到一些关于“丢弃的非单位值”的警告，这些警告是关于故意丢弃的，而不是错误。我如何抑制这些警告？
回答by Régis Jean-Gilles
You suppress these warning by explictly returning unit (that is ()).
By example turn this:
您可以通过显式返回 unit（即()）来抑制这些警告。举个例子：
def method1() = {
println("Hello")
"Bye"
}
def method2() {
method1() // Returns "Bye", which is implicitly discarded
}
into:
进入：
def method1() = {
println("Hello")
"Bye"
}
def method2() {
method1()
() // Explicitly return unit
}
回答by Todd Owen
According to this answer, you can also use the syntax val _, i.e.
根据这个答案，您还可以使用语法val _，即
def method2(): Unit = {
val _ = method1()
}
But there is some dispute over whether this or the answer by @Régis is the preferred style.
但是对于这个或@Régis 的答案是否是首选风格存在一些争议。
回答by floating cat
Now you can suppress value-discard warning via type ascription to Unitin Scala 2.13.
现在，你可以通过抑制类型归属价值丢弃警告，Unit在斯卡拉2.13。
This is an example:
这是一个例子：
def suppressValueDiscard(): Unit =
"": Unit
