Groovy：如何获得“私有”的价值？ 封闭变量

Question

我的闭包效果很好，但是有时我想获得在闭包中定义的临时变量的最终值。 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

这可能吗？

Answer 1

您可以将状态存储在闭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

如果要控制状态进入的对象，则可以覆盖闭包的委托。 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，没有办法获取变量，因为闭包仅返回一个结果（因此somclosure(2).howDoIGetThis不能工作），并且在闭包实例运行后也无法获取句柄。 ..

我能想到的最好的办法是从Closure返回多个值，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