Could someone explain this piece of code of using splat operator with method?
def initialize(talk)
@title, @length = *title_and_length(talk)
end
def title_and_length(talk)
title = talk[/.*(?=\s)/]
str_length = talk.split
if str_length.last.downcase == "talk"
length = LIGHTNING_TALK_LENGTH
elsif str_length.last == "minutes"
length = str_length[-2..-1].join.gsub!("minutes", ' ').to_i
else
fail ArgumentError, "invalid talk length"
end
[title, length]
end
That splat operator is not 'doing' anything here as the returned element is an array. Using the splat operator on a method that does not return an array transforms an assigned variable into an array. Example:
def output(params)
p params
end
Calling without splat operator:
output(1)
=> 1
Calling with splat operator:
*output(1)
[1]
We see if we return the value rather than print it, an error occurs:
def output(params)
params
end
output(1)
=> 1
*output(1)
SyntaxError: (irb): syntax error, unexpected '\n', expecting :: or '[' or '.'
As the splat expects a variable to be assigned to
o = *output(1)
=> [1]
This is how the splat operator expects to be bound to a variable. It takes the 'remaining' elements of an array and attempts to assign them to a variable. So if you remove the splat from the initialize method, you will see the same results. The original author may have included the splat to emphasise the method should be assigned to variables, but that's a guess.
#title_and_lengthdoes/returns, but assuming it returns an array with the title and length that splat operator would be redundant theredef m(n,*pets); pets; end. The method might be calledm(1,"dog","cat","gerbil") #=> ["dog", "cat", "gerbil"]ora = ["dog","cat","gerbil"]; m(1,*a) #=> ["dog", "cat", "gerbil"]. 2.a = [3,4]; b= [5,6]; [1,2,*a,*b,7,8] #=> [1, 2, 3, 4, 5, 6, 7, 8]. In #1, when passing individual objects the splat operator converts them to the arraypetsin the body of the method. When calling the methodm(1,*a)and in #2, the splat operator converts an array to a sequence of its elements.