The take_while method works very similarly to take; it takes an enumerable collection and returns the first several elements, for as long as each element returns true when passed to the given block. This is NOT like select - once the block returns false for an element, take_while stops looking and returns what it has so far.
- View the objects used in these examples
- View these examples as a runnable ruby script on GitHub.
- Practice this method as an interactive kata on Codewars!
Number List
def prime? number
return true if number < 4
(2...number).each do |factor|
return false if number % factor == 0
end
true
end
@numbers = [1, 0, 3, 2, 5, 4, 7, 6, 9, 8]
# taking until we find an even number:
@numbers.take_while(&:odd?)
#=>
# taking until we find a non-prime number:
@numbers.take_while{|number| prime?(number)}
#=>
Pet Inventory
# taking until we find a pet with low inventory:
@inventory.take_while{|pet| pet.quantity >= 50}.map(&:name)
#=>
# taking until we find the first legless pet:
@inventory.take_while{|pet| pet.legs > 0}.map(&:name)
#=>
Pokey Things
# taking until we see a pokey thing with the letter 'f':
@pokey_things.seek(0)
@pokey_things.take_while{|thing| !thing.include?('f')}.map(&:chomp)
#=>
# taking until a pokey thing has more than 7 letters:
@pokey_things.seek(0)
@pokey_things.take_while{|thing| thing.chomp.length < 7}.map(&:chomp)
#=>
Heroku Log File
# taking until a request uses the POST method:
@requests.take_while{|request| request.method != 'POST'}.map(&:id)
#=>
# taking until a request is successful:
@requests.take_while{|request| request.error?}.map(&:id)
#=>