Perform map only when not nil?

Question

The following breaks if names is nil. How can I have this map execute only if it's not nil?

self.topics = names.split(",").map do |n|
  Topic.where(name: n.strip).first_or_create!
end

Answer 1

A couple of other options:

Option 1 (checking for result of split when executing map on it):

names_list = names.try(:split, ",")
self.topics = names_list.map do |n|
    Topic.where(name: n.strip).first_or_create!
end if names_list

Option 2 (using try, which will prevent the error):

self.topics = names.try(:split, ",").try(:map) do |n|
    Topic.where(name: n.strip).first_or_create!
end

Answer 2

That depends on what you want topics to become if names is actually nil. The most elegant solution would probably be to substitute an empty string where names is nil:

self.topics = (names || '').split(",").map do |n|
...

But that would assign an empty array to topics. If that's not what you want, you can wrap this with a nil check like this:

if names
  self.topics = ...
end

Or like this:

self.topics = names.split(",").map do |n|
  ...
end if names