Groovy : Map
Groovy has a very bad documentation, but it's also so powerfull.
Play with Map
def empty = [:] assert empty.size() == 0 //keys are Strings by default assert [key:'value'] == ['key':'value'] //you must use parentheses if a variable should become a key def myVar = "theKey" def myMap = [(myVar):'someValue'] assert myMap['theKey'] == 'someValue' //you can use array-style notation or bean-style notation to access and set entries def map = [:] //array-style map['a'] = 1 assert map['a'] == 1 //bean-style map.b = 2 assert map.b == 2 //using a default value in case the key is not available def someMap = [a:1,b:2] assert someMap.get('a', -1) == 1 assert someMap.get('c', -1) == -1 assert someMap.get('c') == -1 //TAKE CARE! assert someMap.get('d') == null //iterating over a map with each() -> "it" is an entry with properties key and value def iterationMap = [a:1,b:2,c:3] def keyList = [] iterationMap.each { keyList << it.key } assert keyList.contains('a') assert keyList.contains('b') assert keyList.contains('c') //or split the entry into key and value directly iterationMap.each { key, value -> keyList << key} assert keyList.size() == 6 //get all keys of a map def keys = [a:1].keySet() assert keys.size() == 1 assert keys.contains('a') assert ['a'] as Set == [a:1].keySet() assert ['a'] == [a:1].keySet().toList() //you can use findAll with maps, too def books = [ 'Graeme Rocher':'The Definitive Guide to Grails', 'Dierk Koenig':'Groovy in Action'] def subMap = books.findAll { key, value -> key == 'Graeme Rocher'} assert subMap.size() == 1 assert subMap.'Graeme Rocher' == 'The Definitive Guide to Grails' //and collect... collect does a transformation with each entry def list = books.collect { key, value -> (key == 'Dierk Koenig')? 'GINA' : value } assert list.join(',') == 'GINA,The Definitive Guide to Grails'
