Generating One Collection from Another

You can use the collect() function to produce a new collection from an existing collection. The resulting one contains the results of evaluating a closure for each element in the original collection.

In the example below, the uppercasedNames collection is a list of the uppercase name property values of all the map entries in the phonebook.

def phonebook = [
                    [name: 'Steve', phone: '[phone]'],
                    [name: 'Joey',  phone: '[phone]'],
                    [name: 'Sara',  phone: '[phone]'],
                    [name: 'Zoe',   phone: '[phone]']   
                 ]
def uppercasedNames = phonebook.collect { it?.name?.toUpperCase() }

You can combine collection functions in a chain to first filter then collect results of only the matching entries. For example, the code below produces a list of the values of the name property of phonebook entries with an Italian phone number.

// First filter phonebook collection, then collect the name values
def italianNames = phonebook.findAll { it?.phone?.startsWith('+39-') }
                            .collect { it?.name }