Ruby’s splat operator, written *, unwraps an array or an array-convertible object into a bare list of elements. In a method call, it expands an array into separate arguments: names = ["David", "Black"]; combine_names(*names) passes two arguments rather than one array. section 7.4.2
The distinction is easiest to see when constructing arrays. [*array] copies the array’s elements into a new array, while [array] creates a nested array containing array as one item. The star therefore has an unarraying, or bracket-removing, effect. section 7.4.2
The same syntax also appears in parameter lists:
- A starred parameter such as *c collects remaining arguments into an array. section 2.4.2
- Required parameters before and after the splat receive values before the catch-all parameter does. section 2.4.2
- When no arguments remain, the catch-all parameter becomes an empty array; too few required arguments still raise an ArgumentError. section 2.4.2
Mixed required and catch-all parameters
def mixed_args(a,b,*c,d)\n puts "Arguments:"\n p a,b,c,d\nend\nmixed_args(1,2,3,4,5)\n# 1\n# 2\n# [3, 4]\n# 5\n\nRuby assigns the required arguments at both ends first, then places the middle values in c. section 2.4.2
