We have method:
def sum(x, y, z)
x + y + z
end
and array
arr = [1,2,3]
How can one pass the array to sum method? Actually I need something like:
pseudo
sum(arr.each {|i| i})
without changing method, and it to work if sum would accept splat, so please do not offer sum(arr[0], arr[1], arr[2])
You can use the splat operator * Doing so will automatically assign each value in array to the corresponding named parameter.
sum(*arr)
#=> The above will automagically do
#=> x = arr[0]
#=> y = arr[1]
#=> z = arr[2]
ArgumentError will be raised if more elements are passed.
sum's parameters with Method#parameters:method(:sum).parameters #=> [[:req, :x], [:req, :y], [:req, :z]]. Note you first need to convert the symbol :sum to a method with Object#method.
arr will be ignored, if present" - an ArgumentError is raised if the number of arguments don't match.
As a global method, you could create a sum method that will accept both numbers and arrays using the * operator:
def sum *numbers
numbers.flatten.inject :+
end
it will accept:
sum 1,2,3,4
sum [1,2,3,4]
sum [1,2,3,4],[3,4],8,9
The *numbers is an array containing all the arguments passed to the sum method (except a block, which the method doesn't accept). That's what the * operator does.
The #inject method is a really handy shortcut to be used on enumerable objects.