The collect/map methods take an enumerable collection, runs each item through the given block, and returns a new array of the results.
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Number List
@numbers = [1, 0, 3, 2, 5, 4, 7, 6, 9, 8]
# all numbers multiplied by two:
@numbers.map{|number| number * 2}
#=> [2, 0, 6, 4, 10, 8, 14, 12, 18, 16]
# the even status for all numbers:
@numbers.map(&:even?)
#=> [false, true, false, true, false, true, false, true, false, true]
Pet Inventory
# leg counts for all pets:
@inventory.map(&:legs)
#=> [4, 4, 0, 8, 6, 2, 0]
# leg totals for each pet type:
@inventory.map{|pet| pet.legs * pet.quantity}
#=> [400, 200, 0, 8, 60000, 4, 0]
Pokey Things
# letter counts for all pokey things:
@pokey_things.seek(0)
@pokey_things.map{|thing| thing.chomp.size}
#=> [6, 4, 5, 41]
# all pokey things, capitalized:
@pokey_things.seek(0)
@pokey_things.map(&:chomp).map(&:capitalize)
#=> ["Cactus", "Pole", "Knife", "Cactus holding poles with knives attached"]
Heroku Log File
# request methods for all heroku requests:
@requests.map(&:method)
#=> ["GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "POST", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET", "GET"]
# total response times for all heroku requests:
@requests.map{|request| request.connect + request.service}
#=> [1459, 1642, 17, 2, 1, 1, 3, 0, 1008, 1, 2, 1015, 994, 1371, 18, 10, 2, 17, 2, 2, 1, 60, 3, 912, 1, 5, 697, 3, 863, 1318, 696]