Arrays are a fundamental data structure of Ruby. Let’s do a quick tour.

Here’s a simple array.

Individual items are accessed with square brackets. Arrays are zero-indexed.

An out-of-bounds access returns nil.

Arrays can mix types.

Concatenation of arrays is done with +, which creates a new array.

An arrays can be appended to, which modifies the original array in place.

The * operator destructures an array.

Arrays can be written in other ways than with square brackets. %w creates arrays from bare words, each one becoming a string.

The delimiter can be changed.

%w is equivalent to single quotes, and %W is equivalent to double quotes.

%i and %I create arrays of symbols