Groovy/Grails : 如何将多个key组合成groupBy？

Question

我有一个列表，我想按所有三个键进行分组，我指的是 How to group a list of list。

def given  = [
  [Country:'Japan',Flag:'Yes',Event:'New Year'],
  [Country:'china',Flag:'No',Event:'Spring Festival'],
  [Country:'uk',Flag:'No',Event:'National Holiday'],
  [Country:'us',Flag:'Yes',Event:'Labour Day'],
  [Country:'us',Flag:'Yes',Event:'New Year'],
  [Country:'uk',Flag:'Yes',Event:'Memorial Day']
]

我们可以分组：

 def mapped = given.groupBy {
      [(it["Country"]) : it["Flag"] ] }

如何按 [(it["Country"]) : it["Flag"] : it["Event"] ] 分组？

预期结果：[['Japan':['Yes':[NewYear]]]:[['Country':'Japan', 'Flag':'Yes', 'Event':'New Year']]，..

Answer 1

given.groupBy( { it.Country }, { it.Flag }, { it.Event } )

一个以 3 个闭包作为参数的方法。

Answer 2

这个有什么用，不懂。 @dmahapatro 的解决方案提供了更易于处理的结果。在您的示例中，您只想将递归映射作为分组依据的键。我最怀疑这会很好地处理实际的分组情况。

def given  = [
[Country:'Japan',Flag:'Yes',Event:'New Year'],
[Country:'china',Flag:'No',Event:'Spring Festival'],
[Country:'uk',Flag:'No',Event:'National Holiday'],
[Country:'us',Flag:'Yes',Event:'Labour Day'],
[Country:'us',Flag:'Yes',Event:'New Year'],
[Country:'uk',Flag:'Yes',Event:'Memorial Day']
]

println given.groupBy{ [(it.Country): [(it.Flag): [it.Event]]] }.inspect()
//=> [['Japan':['Yes':['New Year']]]:[['Country':'Japan', 'Flag':'Yes', 'Event':'New Year']], ...

Groovy/Grails : 如何将多个key组合成groupBy？

Groovy/Grails : How to groupBy multiple keys combined?

grails

groovy

functional-programming