[GROOVY-4869] Add ability to 'slice' Map, querying multiple keys at once

• Type: New Feature
• Status: Reopened
• Priority: Major
• Resolution: Unresolved
• Component/s: groovy-jdk
• Flags: Patch
• Assignee: Unassigned
• Reporter: Tim Yates
• Created: 08/Jun/11 04:24
• Updated: 05/Apr/15 14:44

Description

It was brought up on the dev mailing list that you could query multiple list values at once, but not multiple Map values:

Message from groovy-dev by Jon Cox

Groovy currently lets you say:

def    x       =  [100,200,300,400]
assert x[0]    == 100
assert x[2]    == 300
assert x[0,2]  == [100,300]

You can say:

def    y        =  [moo: 100, cow: 200, egg:300 hen:400]
assert y["moo"] == 100
assert y["cow"] == 300

But currently, you cannot slice a Map like this:

assert y["moo","egg"] == [100,300] 

This patch adds that functionality, so you can do (from the unit test)

    void testMapSlice() {
        def m = [ a:1, b:2, c:3 ]
        
        assert m[ 'a', 'b' ] == [ 1, 2 ]
        assert m[ 'a', 'c' ] == [ 1, 3 ]
        assert m[ 'a', 'd', 'c' ] == [ 1, null, 3 ]
    }

Note that the resultant List contains null for keys that were not found. This (I believe) differs from the way that Perl handles this (I believe they are just skipped in perl), but I think that having the null values gives the developer more information.

And they could be filtered out by doing something like:

m[ 'a', 'd', 'c' ].findAll { it }

Hope it's ok!