method

sample

rails latest stable - Class: Array

sample(n=nil)

public

Backport of Array#sample based on Marc-Andre Lafortune’s github.com/marcandre/backports/ Returns a random element or n random elements from the array. If the array is empty and n is nil, returns nil. If n is passed and its value is less than 0, it raises an ArgumentError exception. If the value of n is equal or greater than 0 it returns [].

[1,2,3,4,5,6].sample     # => 4
[1,2,3,4,5,6].sample(3)  # => [2, 4, 5]
[1,2,3,4,5,6].sample(-3) # => ArgumentError: negative array size
           [].sample     # => nil
           [].sample(3)  # => []

# File activesupport/lib/active_support/core_ext/array/random_access.rb, line 13
  def sample(n=nil)
    return self[Kernel.rand(size)] if n.nil?
    n = n.to_int
  rescue Exception => e
    raise TypeError, "Coercion error: #{n.inspect}.to_int => Integer failed:\n(#{e.message})"
  else
    raise TypeError, "Coercion error: obj.to_int did NOT return an Integer (was #{n.class})" unless n.kind_of? Integer
    raise ArgumentError, "negative array size" if n < 0
    n = size if n > size
    result = Array.new(self)
    n.times do |i|
      r = i + Kernel.rand(size - i)
      result[i], result[r] = result[r], result[i]
    end
    result[n..size] = []
    result
  end

1Note

return random element

korin · May 31, 2011

>> a = [1,2,3]
>> a.sample
2

the same as

>> a[rand(a.length - 1)]
1

sample

Method deprecated or moved

1Note

return random element

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