Question

我有一个班级A，它还定义了对B的隐式转换。

case class A(number:Int) 
case class B(number:Int, tag:String)
implicit def  AtoB(a:A) = B(a.number,"Hello World")

我还有一个检索A的函数，并希望调用一个隐含B参数的函数：

def hello()(implicit b:B)= {....}
def execute = {
    implicit val a:A  = ....
    hello()  //doesnt compile missing implicit parameter b
}

如何在不明确定义B的情况下使此代码正常工作？即

val b:B = a

Answer 1

定义一个这样的函数：

Sub FilnamnRitningar()

Dim varDirectory As Variant
Dim flag As Boolean
Dim i As Integer
Dim strDirectory As String
Dim ws As Worksheet
Dim rng As Range
Dim a As String
Dim o As String
Dim a1 As String
Dim a2 As String

a = Chr(228)
a1 = Chr(229)
o = Chr(246)
a2 = Chr(197)

Set ws = Sheets("Macron")
Set rng = ws.Range("A4:C100")

strDirectory = ("C:\Users\" & Application.VLookup("saljareKonto", rng, 3, False) & "\Dropbox (ATLE Consulting)\ATLE Consulting\Partner\" & Application.VLookup("partnerBolagsnamn", rng, 3, False) & "\Best" & a & "llare\"     & Application.VLookup("kundFulltNamn", rng, 3, False) & "\Ritningar\")
i = 1
flag = True
varDirectory = Dir(strDirectory, vbDirectory)

Range("M153").Select

While flag = True
If varDirectory = "" Then
    flag = False
Else
    Cells(i + 1, 1) = varDirectory
    'returns the next file or directory in the path
    varDirectory = Dir
    i = i + 1
End If

Wend
End Sub

当您拨打implicit def implicitBfromA(implicit a: A): B = a或将其放入hello的配套对象时，请将其放在范围内。

此功能不是隐式转换。它声明，如果范围中已存在类型为B的隐式值，则存在类型B的隐式值。

请注意，要使其正常工作，应该在文件中 A之后定义，或者AtoB应该有明确指定的返回类型：{{1或者你应该在其正文中明确地调用AtoB：implicit def AtoB(a:A): B = B(a.number, "Hello World")

一个完整的工作示例：

AtoB

Scala - 隐式转换为隐式参数

1 个答案: