grails - Groovy中的分组和总和收集

Question

我有一个对象集合，我想按月份，名称和总数进行分组:

def things = [
    [id:1, name:"fred", total:10, date: "2012-01-01"],
    [id:2, name:"fred", total:10, date: "2012-01-03"],
    [id:3, name:"jane", total:10, date: "2012-01-04"],
    [id:4, name:"fred", total:10, date: "2012-02-11"],
    [id:5, name:"jane", total:10, date: "2012-01-01"],
    [id:6, name:"ted", total:10, date: "2012-03-21"],
    [id:7, name:"ted", total:10, date: "2012-02-09"]
];

我希望输出为:

[
 "fred":[[total:20, month:"January"],[total:10, month:"February"]],
 "jane":[[total:20,month:"January"]],
 "ted" :[[total:10, month:"February"],[total:10, month:"March"]]
]

或类似的规定。使用groovy / grails实现此目的的最佳方法是什么？

Answer 1

以下几行

things.inject([:].withDefault { [:].withDefault { 0 } } ) { 
    map, v -> map[v.name][Date.parse('yyyy-MM-dd', v.date).format('MMMM')] += v.total; map 
}

将为您提供以下结果:

[fred:[January:20, February:10], jane:[January:20], ted:[March:10, February:10]]

(适用于Groovy> = 1.8.7和2.0)