Length vs Size vs Count

.length#

  • Calculates length

.size#

  • Alias of length

.count#

  • Rule of thumb, don't use .count to get size/length when possible.
  • .count usually meant to be used with a block or an argument and will return the number of matches in an Enumerable:
arr = [1, 1, 2, 3, 5, 6, 8]
arr.count(&:even?) # => 3
arr.count(1) # => 2

size vs length vs length() vs count#

[38] pry(main)> temp = [1,2,3]
=> [1, 2, 3]
[39] pry(main)> temp.size
=> 3
[40] pry(main)> temp.length
=> 3
# () is optional in Ruby
[41] pry(main)> temp.length()
=> 3
[42] pry(main)> temp.count
=> 3

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