[Ruby] Differences between count, size, and length

To understand the differences between count, size, and length in Ruby, read these articles:

・count、size、lengthの違い（再考） - うんたらかんたらRuby - Rubyist

・Rubyのsize/length/countの違いは？ - QA@IT

・【Rails】sizeとcountとlengthについて - ゆっくりブログ

That’s all from the Gemba.