Question

I was looking through some Rails source code and came across

# File vendor/rails/activesupport/lib/active_support/vendor/builder-2.1.2/builder/css.rb, line 129
129:     def target!
130:       @target * ''
131:     end

What does the * ” do? Is that multiplication by an empty string…? And why would you do that.

Answer 1

This is a bizarre syntax. These are equivalent:

>> [1, 2, 3] * 'joiner'
=> "1joiner2joiner3"

>> [1, 2, 3].join 'joiner'
=> "1joiner2joiner3"

so in this case it joins all the entries of @target into one string, with nothing between the entries.

Note: if you do something like [1, 2, 3] * 3 (using an int instead of a str), you’ll get three concatenated copies of the array instead.