shortcut for creating a Map from a List in groovy?

I've recently came across the need to do exactly that: converting a list into a map. This question was posted before Groovy version 1.7.9 came out, so the method collectEntries didn't exist yet. It works exactly as the collectMap method that was proposed:

Map rowToMap(row) {    row.columns.collectEntries{[it.name, it.val]}}

If for some reason you are stuck with an older Groovy version, the inject method can also be used (as proposed here). This is a slightly modified version that takes only one expression inside the closure (just for the sake of character saving!):

Map rowToMap(row) {    row.columns.inject([:]) {map, col -> map << [(col.name): col.val]}}

The + operator can also be used instead of the <<.

Check out "inject". Real functional programming wonks call it "fold".

columns.inject([:]) { memo, entry ->    memo[entry.name] = entry.val    return memo}

And, while you're at it, you probably want to define methods as Categories instead of right on the metaClass. That way, you can define it once for all Collections:

class PropertyMapCategory {    static Map mapProperty(Collection c, String keyParam, String valParam) {        return c.inject([:]) { memo, entry ->            memo[entry[keyParam]] = entry[valParam]            return memo        }    }}

Example usage:

use(PropertyMapCategory) {    println columns.mapProperty('name', 'val')}

Was the groupBy method not available when this question was asked?