[英]How to make two function parameters as implicit
Assume we have Object that takes function as parameter of apply
method: 假设我们有Object作为
apply
方法的参数:
object Wrapper {
def apply(block: TypeA => String) = {
TypeA a = ...
block(a)
}
}
TypeA
is domain type of application. TypeA
是域类型的应用程序。
Now when I define inline block I can define TypeA
parameter as implicit: 现在,当我定义内联块时,我可以将
TypeA
参数定义为隐式:
Wrapper { implicit a => functionThatUseImplicitA() }
But what if block
parameter is not Function1
, but Function2
? 但是如果
block
参数不是Function1
,而是Function2
呢? How can I define both parameters as implicit? 如何将两个参数定义为隐式?
object Wrapper2 {
def apply(block: (TypeA, TypeB) => String) = {
TypeA a = ...
TypeB b = ...
block(a, b)
}
}
This one does not work: 这个不起作用:
Wrapper { implicit (a, b) => functionThatUseImplicitAB() }
The only workaround is define them as vals: 唯一的解决方法是将它们定义为val:
Wrapper { (a, b) =>
implicit val ia = a
implicit val ib = b
functionThatUseImplicitAB()
}
Thanks! 谢谢!
According to the SLS 6.23 Anonymous Functions implicit
keyword is allowed only for single argument functions: 根据SLS 6.23,匿名函数
implicit
关键字仅允许用于单个参数函数:
Expr ::= (Bindings | [‘ implicit ’] id | ‘_’) ‘=>’ Expr
ResultExpr ::= (Bindings | ([‘ implicit ’] id | ‘_’) ‘:’ CompoundType) ‘=>’ Block
So you can't make two function parameters as implicit. 所以你不能把两个函数参数作为隐式。
This is the one of reasons to use curried functions: 这是使用curried函数的原因之一:
object Wrapper {
def apply(block: TypeA => TypeB => String) = ???
}
Wrapper { implicit a => implicit b =>
functionThatUseImplicitAB()
}
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