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A one-line tree in Groovy

One line Tree in Groovy

The other day, I saw Harold Cooper's One-line tree in Python via autovivication, and wondered if the same thing was possible in Groovy.

The answer is yes! But you need to define the variable tree before you can assign it to the self-referential withDefault closure, hence with Groovy, it's a two-line solution ;-)

Anyway, given:

def tree = { [:].withDefault{ owner.call() } }

We can then do:

users = tree()
users.harold.username = 'hrldcpr'
users.yates.username = 'tim'

And printing this out

println new groovy.json.JsonBuilder( users ).toPrettyString()

gives:

{
    "harold": {
        "username": "hrldcpr"
    },
    "yates": {
        "username": "tim"
    }
}
@crazy4groovy
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crazy4groovy commented Apr 25, 2012

Impressive!

@kingnebby
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kingnebby commented Apr 29, 2013

super dig

@Hubbitus
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Hubbitus commented Nov 19, 2014

All already there ;)

def users = new ConfigObject()

Then using the same:

users.harold.username = 'hrldcpr'
users.yates.username = 'tim'

println new groovy.json.JsonBuilder( users ).toPrettyString()

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