java - Groovy GroupBy 变量键集

Question

我正在努力使用 groovy groupBy

我需要支持通过变量键集对数据集进行分组。

我编写了一个测试来解释我的困境，并且希望获得一些帮助来理解如何实现它:

https://groovyconsole.appspot.com/script/5155615986941952

List<Map> people = [
    [
        Sex: "Male",
        Age: 30,
        Job: "Programmer",
        Name: "Boris"
    ],
    [
        Sex: "Female",
        Age: 30,
        Job: "Programmer",
        Name: "Jennifer"
    ],
    [
        Sex: "Male",
        Age: 40,
        Job: "Web Designer",
        Name: "Bob"
    ],
    [
        Sex: "Female",
        Age: 20,
        Job: "Database Admin",
        Name: "Alice"
    ]
]


List results = []
if(people.groupBy({it.Sex}, {it.Age}) != groupBySpecifiedCols(people, ["Sex", "Age"])){
  return "Failed 1"
}

if(people.groupBy({it.Sex}, {it.Age}, {it.Job}) != groupBySpecifiedCols(people, ["Sex", "Age", "Job"])){
  return "Failed 2"
}

def groupBySpecifiedCols(List<Map> data, List<String> columns){
  // IMPLEMENT HERE

  return null
}


return "Success!"​​​​

Answer 1

实际上我想我刚刚解决了这个问题，经过几个小时的挫折后结果很简单:

def groupBySpecifiedCols(List<Map> data, List<String> columns){
  List<Closure> groupByClosures = []
  columns.each{ column ->
    groupByClosures << { it[column] }
  }

  return data.groupBy(groupByClosures)
}

编辑正如评论中指出的，有一种可能更简洁的方法:

def groupBySpecifiedCols(List<Map> data, List<String> columns){
  return data.groupBy(columns.collect{ col -> ((Closure){ it[col] })})
}