What does the (unary) * operator do in this Ruby code?
Given the Ruby code
line = "first_name=mickey;last_name=mouse;country=usa"
record = Hash[*line.split(/=|;/)]
I understand everything in the second line apart from the * operator - what is it doing and where is the documentation for this? (as you might guess, searching for this case is proving hard...)
Answer
The * is the splat operator.
It expands an Array into a list of arguments, in this case a list of arguments to the Hash.[] method. (To be more precise, it expands any object that responds to to_ary/to_a, or to_a in Ruby 1.9.)
To illustrate, the following two statements are equal:
method arg1, arg2, arg3
method *[arg1, arg2, arg3]
It can also be used in a different context, to catch all remaining method arguments in a method definition. In that case, it does not expand, but combine:
def method2(*args) # args will hold Array of all arguments
end