The rows in the listing have alternating background colors. The Rails helper method called does this by setting the CSS class of each row to either bg-green-50 or bg-white, automatically toggling between the two style names on successive lines.
It mentions a helper method, but doesn’t say what that is. It took me a bit to read the code and realized it’s referring to the
cycle('bg-green-50', 'bg-white') line.
cycle in the quoted text, “The Rails helper method called cycle does this by setting the CSS class…” to make it clea