Multiple assignment using a Map's value instead of a variable with Groovy

Question

In Groovy, I have a function that returns a triple. I'd like to:

put the first value returned in a Map for an arbitrary key and
assign the two other values to variables.

I can do:

Map m = [:]
(day, month, year) = "12 February 2014".split(" ");
m["day"] = day;

But I would like to get rid of the variable day, like this:

Map m = [:]
(m["day"], month, year) = "12 February 2014".split(" ");

For some reason it seems to be not possible. This is what the compiler alerts me about:

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
/web/com/139223923319646/main.groovy: 2: expecting ')', found ',' @ line 2, column 10.
   (m["day"], month, year) = "12 February 2014".split(" ");
            ^

Would you guys be able to either help me or explain to me why this syntax cannot be used?

See the bottom of this page groovy.codehaus.org/Multiple+Assignment - they don't exactly say why, other than only use with 'simple variables, which means you map is not a 'simple' object. Someone more Groovy-savvy, (like maybe Tim Yates!) might be able to fill in the blanks. — mikemil
– mikemil, Commented Feb 12, 2014 at 21:52

tim_yates · Accepted Answer · 2014-02-12 21:48:55Z

2

You can do this:

def dstr = "12 February 2014"
def m = [['day', 'month', 'year'], dstr.split( " " )].transpose()
                                                     .collectEntries()

To get

assert m == [ day:'12', month:'February', year:'2014' ]

But I'm not sure that's what you want...

answered Feb 12, 2014 at 21:48

tim_yates

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grantmcconnaughey · Accepted Answer · 2014-02-12 21:45:19Z

2

This is not possible unfortunately, according to the multiple assignment Groovy documentation.

Currently only simple variables may be the target of multiple assignment expressions, e.g. if you have a person class with firstname and lastname fields, you can't currently do this:
(p.firstname, p.lastname) = "My name".split()

Your first example is the best way to do this currently.

answered Feb 12, 2014 at 21:45

grantmcconnaughey

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1 Comment

ccjmne Over a year ago

Oops, it seems that I just couldn't find that information myself! Sorry about that, and thank you for your reply ;)

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