[GROOVY-1635] Improve docs for Collection.groupBy and add new Collection.collate(Closure) [Small breaking change]

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.0
• Fix Version/s: 1.5.2
• Assignee: Paul King
• Reporter: Marc Palmer
• Created: 03/Jan/07 14:20
• Updated: 23/Dec/07 12:25
• Resolved: 23/Dec/07 00:41

Description

The documentation for Collection.groupBy is a little ambiguous in that it does not make it absolutely clear that the return value is a Map of keys pointing to values that are ArrayLists.

A new method, Collection.collate(Closure) would be a nice addition, to allow collation of a collection of objects into a map keyed on some value provided by a closure, without returning a List for every value. This might be implemented so:

java.util.Map collate(Closure collator) {
    def result = [:]
    this.each() {
         result[collator.call(it)] = it
    }
}