Groovy：如何獲得“私有”的價值？ 封閉變量

Question

我的閉包效果很好，但是有時我想獲得在閉包中定義的臨時變量的最終值。 例：

def someClosure = {Number input->
  def howDoIGetThis = input + 4
  return 2 * input
}

def normalWay = someClosure(2)
assert normalWay == 4

def myFantasy = someClosure(2).howDoIGetThis
assert myFantasy == 6

這可能嗎？

Answer 1

您可以將狀態存儲在閉包的所有者或委托中。

def howDoIGetThis
def someClosure = {Number input ->
    howDoIGetThis = input + 4
    return input * 2
}

def normalWay = someClosure(2)
assert normalWay == 4

someClosure(2)
def myFantasy = howDoIGetThis
assert myFantasy == 6

如果要控制狀態進入的對象，則可以覆蓋閉包的委托。 例如：

def closureState = [:]
def someClosure = {Number input ->
    delegate.howDoIGetThis = input + 4
    return input * 2
}
someClosure.delegate = closureState

def normalWay = someClosure(2)
assert normalWay == 4

someClosure(2)
def myFantasy = closureState.howDoIGetThis
assert myFantasy == 6

Answer 2

不，沒有辦法獲取變量，因為閉包僅返回一個結果（因此somclosure(2).howDoIGetThis不能工作），並且在閉包實例運行后也無法獲取句柄。 ..

我能想到的最好的辦法是從Closure返回多個值，如下所示：

def someClosure = {Number input->
  def howDoIGetThis = input + 4
  [ 2 * input, howDoIGetThis ]
}

def (normalWay, myFantasy) = someClosure(2)

assert normalWay == 4
assert myFantasy == 6