user2782001 - 19 days ago 4

Groovy Question

I want to group by 3 properties but not have each property be it's own nested array. What I want:

`def values=[`

[day:1,month:1,year:1],

[day:1,month:1,year:1],

[day:2,month:1,year:1],

[day:2,month:2,year:1]

];

/*...some code to group by DAY, MONTH, AND YEAR

..desired result is that items with the same day,

month, and year end up in a one level deep subarray

*/

[

[[day:1,month:1,year:1],[day:1,month:1,year:1]],

[[day:2,month:1,year:1]] ,

[[day:2,month:2,year:1]]

];

Using the

Answer

Consider the following use of `inject`

to build up a map whose keys are the appropriate group, and values are the desired lists:

```
def values=[
[day:1,month:1,year:1],
[day:1,month:1,year:1],
[day:2,month:1,year:1],
[day:2,month:2,year:1]
];
def groupMap = [:].withDefault{ key -> [] }
def result = values.inject(groupMap) { val, m ->
val["${m.'day'}${m.'month'}${m.'year'}"] << m
val
}.values()
assert [[day:1, month:1, year:1], [day:1, month:1, year:1]] == result[0]
assert [[day:2, month:1, year:1]] == result[1]
assert [[day:2, month:2, year:1]] == result[2]
```

Source (Stackoverflow)

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