[GROOVY-4885] groupBy with a list or an array of closures as it's parameter for nested grouping

• Type: New Feature
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.8.1, 1.9-beta-1
• Component/s: groovy-jdk
• Flags: Patch
• Assignee: Guillaume Sauthier
• Reporter: Dinko Srkoc
• Created: 16/Jun/11 07:05
• Updated: 05/Apr/15 14:44
• Resolved: 16/Jun/11 09:01

Description

As described in a thread in the groovy user list here:

http://groovy.329449.n5.nabble.com/a-possibly-useful-collection-method-tp4428105p4428105.html

An implementation of groupBy that receives a list or an array of closures as criteria for grouping would be useful for making nested groupings.

def grouped = [
    [aa: 11, bb: 22, cc: 33],
    [aa: 22, bb: 22, cc: 44],
    [aa: 11, bb: 22, cc: 55],
    [aa: 22, bb: 33, cc: 66],
    [aa: 33, bb: 44, cc: 77]
].groupBy({ it.aa }, { it.bb })

def expected = [
    11:[22:[[aa:11, bb:22, cc:33], [aa:11, bb:22, cc:55]]],
    22:[22:[[aa:22, bb:22, cc:44]], 33:[[aa:22, bb:33, cc:66]]],
    33:[44:[[aa:33, bb:44, cc:77]]]
]

assert grouped[11][22] == [[aa:11, bb:22, cc:33], [aa:11, bb:22, cc:55]]
assert grouped[22][33] == [[aa:22, bb:33, cc:66]]
assert grouped[11][99] == null

groupBy with one closure criterion would behave like the current implementation of groupBy.