A collection of some useful Ruby methods and (partly) dirty tricks.

tricks.rb

# Initilize an array containing plucked property of each hash in array
array_of_hashes = [] << array_of_hashes.map(&:hash_property)

# Generate a random alphanumeric string, with a fixed length
[*('a'..'z'), *('0'..'9')].sample(15).join

# Find average of list of intergers, read from STDIN
avg, n = 0.0, 1.0
arr = STDIN.read.split("\n").map(&:to_i)
arr.each { |i| avg = (n - 1) / n * avg + i / n; n += 1.0 }
avg # => Average