Can you pass a "next" back to the function that called the current function? - ruby-on-rails

Question

I have a series of nested each loops that iterate through a list of cards. These loops call out to other sub-functions that test if certain conditions are met in order to proceed.
def card_handler
cards.each do |card|
#some non-relevant code is here on my end
already_sent?
end
end
def already_sent?
# allows for checking if different emails have been sent on the same card
if list_action == 147
a_s_helper(p1_label)
elsif list_action == 146
a_s_helper(p2_label)
elsif list_action == 145
a_s_helper(p3_label)
end
end
def a_s_helper(label)
if card::card_labels.include? label
# if the card already has the label, I want to log the error and return all the way to the next card in the iteration
puts '\n Order info: \n id: #{id} \n Email already sent'
next
# doesn't work
else
real_id?
end
end
Like I say in my comment in a_s_helper, if the card already has the label, I want to log the error and return all the way to the next card in the iteration. I get an "Invalid next" error from the current setup.
Is there a way to return a next back to the parent function or loop?

Answer 1

next is only valid in the direct context of a loop. Once you call into a method, you are no longer directly in that loop context. You cannot use next to short-circuit the outer loop like this.
You have a couple of options:
Return statuses from your predicate functions (which is what you should do, from a predicate!) and short-circuit the loop based on those, or
Use Ruby's catch...throw construct (which is NOT its raise/rescue exception handler, but is instead something like a block-scoped GOTO statement)
Option 1: Returning statuses. This is the most appropriate method, IMO. Predicate methods (those ending in ?) should conventionally return a boolean and be idempotent (that is, should have no side effects, such as logging a statement). They are conventionally used to ask a yes/no question. Deciding what to do based on that question should ideally be outside of their scope.
def card_handler
cards.each do |card|
#some non-relevant code is here on my end
if already_sent?
puts '\n Order info: \n id: #{id} \n Email already sent'
next
end
end
end
def already_sent?
case list_action
when 145
a_s_helper(p3_label)
when 145
a_s_helper(p2_label)
when 147
a_s_helper(p1_label)
end
end
def a_s_helper(label)
card::card_labels.include? label
end
This causes your helpers to return a true or false value to your loop, which can decide to log a message and go to the next iteration.
Option 2: catch...throw
def card_handler
cards.each do |card|
# Put all your code that should nomally run inside the catch block. If
# the message :email_sent is thrown, then Ruby will zip up the stack and
# resume execution at the end of the block. This will skip any unexecuted
# code in the block, essentially terminating the execution.
catch :email_sent do
already_sent?
end
end
end
def already_sent?
# ...
end
def a_s_helper(label)
# ...
throw :email_sent if card::card_labels.include? label
# ...
end
You may be tempted to use option 2, since it requires less careful control over method construction, but it is perilously close to exceptions as flow control which are widely considered an antipattern (it's essentially a slightly more fancy GOTO, which is notorious for making code difficult to read and debug). If you can simply return a status from your helpers and decide whether or not to continue the loop based on that, you should do so.

Answer 2

I want to show how I ended up implementing the solution I got from #Chris-heald for future people who see this question. I made it a little more compact. This was the code I ended up using:
def card_handler
cards.each do |card|
real_id?
puts "real_id? : #{real_id?}"
next if !(real_id?)
needs_email?
puts "needs_email? : #{needs_email?}"
next if !(needs_email?)
get_email_info
end
end
def needs_email?
case list_action
when 147
!(card::card_labels.include? p1_label::id)
when 146
!(card::card_labels.include? p2_label::id)
when 145
!(card::card_labels.include? p3_label::id)
else
false
end
end
def real_id?
id != 0 ? true : false
end
def get_email_info
#more stuff
end