Interpolation with conditionals - ruby

Question

I want to insert data into a string via interpolation. I want to check if #call.transferred_from is nil, and if so, output #call.transfer_from_other; else output #call.transferred_from.try(:facility_name) along with #call.transferred_from.try(:facility_address).
Here is my code example:
"#{if #call.transferred_from.nil? #call.transfer_from_other else #call.transferred_from.try(:facility_name) #call.transferred_from.try(:facility_address) end}"
Doing this gives me the following error:
syntax error, unexpected keyword_else, expecting keyword_then or ';' or '\n'
I'm not sure where to go. Any help would be appreciated.
Update: 08/04/14
I moved the conditional into a private controller method as follows:
def transfer_from_address
if #call.transferred_from.nil?
#call.transfer_from_other
else
#call.transferred_from.try(:facility_name) + ' ' + #call.transferred_from.try(:facility_address)
end
end
Then I call the following using string interpolation.
#{transfer_from_address}
This seems to work, but I'm not sure that it's proper Ruby.

Answer 1

I know this is not really answering your question, but I'd caution about putting this much logic in an interpolation. While its totally doable, it makes your code very hard to understand.
The fundamental issue I see with your particular issue is you're trying to return 2 things somehow, yet you're just putting both of them next to eachother which is not valid ruby.
Assuming this is in an interpolation you'd want to somehow return them together ..
#{
#call.transferred_from.nil? ?
#call.transfer_from_other :
#call.transferred_from.try(:facility_name) + ' ' + #call.transferred_from.try(:facility_address)
}
I'd really suggest you move this into a variable or a method tho .. and just reference it in the interpolation.
This could look something like:
facility_name_and_address = #call.transferred_from.nil? ? #call.transfer_from_other : #call.transferred_from.try(:facility_name) + ' ' + #call.transferred_from.try(:facility_address)
{
:body => facility_name_and_address
}

Answer 2

If I understand what you are trying to do, I would suggest adding a method to #call which does the job:
class Call
def transfer_text
return transfer_from_other if transferred_from.nil?
"#{transferred_from.try(:facility_name)} #{transferred_from.try(:facility_address)}"
end
end
Then simply calling #call.transfer_text should provide the needed text.
If you want to be more sophisticated, and you don't want trailing white-space in case facility_name or facility_address are nil, you can create a list of them, and join them with white space:
[transferred_from.try(:facility_name), transferred_from.try(:facility_address)].compact.join(' ')
This will make sure spaces will be only between to non-nil elements. If both are nil, and empty string will be the result (rather than a space), and if one is nil, it won't have a leading/trailing space.

Answer 3

why not using
:body => "#{#call.transferred_from.nil? ? #call.transfer_from_other : #call.transferred_from.try(:facility_name) #call.transferred_from.try(:facility_address)"
but anyway I would not use this compact syntax for better maintainability

Answer 4

You just need to put either a semicolon or then right after the condition.
if #call.transferred_from.nil?; #call.transfer_from_other ...
But in your case, there is not much point in putting the entire condition inside a string interpolation. It is better to do the condition outside the string.
By the way, if you fix your first error, then you might encounter the next error:
#call.transferred_from.try(:facility_name) #call.transferred_from.try(:facility_address)
To fix that as well, I think you should do
#call.transferred_from.instance_eval{|e| e.nil? ?
#call.transfer_from_other.to_s :
"#{e.try(:facility_name)} #{e.try(:facility_address)}"
}