Today’s Ruby Tuesday is on Enumerable#find a.k.a. Enumerable#detect.

Enumerable#find takes a predicate as a block and returns the first item for which the predicate returns true. If the predicate doesn’t return true for any of the items in the enumeration, nil is returned.

[1, 2, 3, 4, 5, 6, 7, 8, 9].find {|x| x > 5}
# => 6
[1, 2, 3, 4, 5, 6, 7, 8, 9].find {|x| x > 15}
# => nil

Enumerable#find can also take a “callable” as an argument, which will be called to if no item matches the predicate, and use that result as the return value of Enumerable#find.

[1, 2, 3, 4, 5, 6, 7, 8, 9].find(-> {:oops}) {|x| x > 15}
# => :oops
[1, 2, 3, 4, 5, 6, 7, 8, 9].find(-> {:oops}) {|x| x > 5}
# => 6
[1, 2, 3, 4, 5, 6, 7, 8, 9].find(-> {[true, false].sample}) {|x| x > 15}
# => false
[1, 2, 3, 4, 5, 6, 7, 8, 9].find(-> {[true, false].sample}) {|x| x > 15}
# => true
[1, 2, 3, 4, 5, 6, 7, 8, 9].find(-> {[true, false].sample}) {|x| x > 15}
# => false

–Proctor